Hardy Geraniums are one of most versatile an adaptable perennials for our area. Available in many colors and habits, they can be useful in sun and shade, moist and dry, as a single specimen, as companion plants and as ground covers. These are not to be confused with the Pelargoniums which are the house plant, container and bedding plant “geraniums” which are not hardy outdoor plants in Colorado. The name “geranium” is derived from a Greek word meaning little crane, hens the common name “cranesbill” which refers to the appearance of the seed heads. The majority of the species of geraniums are native to the northern and mountain regions of Eurasia and North and South America although some are found in South Africa, India, Indonesia etc. Most grow in grasslands, meadows, roadsides and open woodlands. Therefore the natural habitat for most hardy geraniums seems to be sunny and moist or part-shade and moist or dry.
Japanese Beetle is one of the most damaging insect pests in the Eastern and Midwestern US, but until recently, Coloradans were spared that challenge. It entered the US in 1916, but took until 2003 before a population was established in Colorado. This first infestation was in the Palisade area on the Western Slope. Even though eradication efforts were mostly successful there, established populations have been found since 2005 in Pueblo, southern Denver, Englewood, at DU and at Denver Botanic Gardens. Smaller populations are being seen now in Boulder and Jefferson County.
Most of our native plains plants and shrubs including:
Desert Four O’Clock
Sulfur Flower (Eriogonums)
There has been a lot of interest at our nursery, and in current plant-breeding programs for smaller shrubs. Most of the old-time favorite shrubs are very large. Most lilacs, viburnums, honeysuckles, forsythias, privets, elderberries, serviceberries, butterfly bushes and hibiscus are 6’-12’ high and often as wide. These are great to provide screening and big masses of color along fences or the back of the border.
Nolo Bait is not a poison. It is a parasite that only affects grasshoppers and Mormon Crickets. It will not harm people, pets, wildlife or beneficial insects. It is most effective on small grasshoppers. In 3-4 weeks up to 50% of the grasshopper population will die. In addition, their eggs will be infected for the following season, and because grasshoppers are cannibalistic, they spread the disease. Put out shallow trays of the bran bait in small quantities. Wind, rain and contact with soil organisms can reduce bait available to grasshoppers.
Ducks, chickens, turkeys and guinea fowl can significantly reduce grasshopper populations. They must be fenced and put inside a safe structure every night to protect them from predators. They will also eat some plants, like vegetables.
Corn Gluten: made from corn it functions as an organic weed-and-feed. It works by keeping all seeds from germinating. Once a plant (or weed) begins to grow the Corn Gluten will not harm it. Very effective when used twice a year, in October and February. The effect lasts 6 months. The feed part is the 9% nitrogen fertilizing effect which thickens grass and stimulates the growth of all plants.
20% Vinegar: this natural acid will burn plant tissues it is sprayed on. Best to apply in bright sunlight and hot days. Spray thoroughly. Very effective on annuals; perennials may need more than one application. Be careful not to overspray on desirable plants as it is non-selective. Repeated use can acidify soils which in our alkaline soils is not usually a problem except for alkaline-loving plants like lilac.
Cotinus, known as Smoketree, is a genus of woody plants appreciated for their “smoky” flower plumes and for their leaf color, especially in autumn. Michael Dirr in his famous Manual of Woody Landscape Plants says “…it may be the best of all American shrub/trees for intensity of color.” Two species and many selections and hybrids offer leaf colors ranging from rich blue-green, maroon red, purple-red and yellow-gold; and the fall colors are even more vibrant. With the current passion for new plants, it is curious that Smoketree is not seen more often in our western landscapes.
Lavenders are great xeriscape perennials for Colorado, which bloom in the heat and dry of July and August. They are native to the rocky hillsides of the Mediterranean region. Here as well, they like good drainage, full sun, our alkaline soil and dry, loamy humus. Lavenders are aromatic herbs with gray foliage, the leaves as well as the flowers being strongly fragrant.
After last November’s 77 degree cold plunge to 13 degrees below zero, most roses suffered die-back, some died to the ground and some died completely. But there were roses that had only minimal damage and some that will bounce back with a good show of vigorous growth and generous flowering this year. Here are some observations and conclusions about growing sustainable roses in Colorado.
Roses are cane shrubs, similar to blackberries and raspberries. Their wood has a pithy center and is not as hard or as strong as a lilac. Consequently roses are more vulnerable to insects, diseases, desiccation and cold, but another consequence is that they can grow and regrow much faster than woody shrubs like lilac and viburnum.
In our American communities, one of the responsibilities of home-ownership is to keep the ground covered. Bare earth, like weeds, indicates lack of care. So then, how do we cover the ground? The cheapest, fastest, and easiest way is to roll out bluegrass sod. “Instant” landscapes can be accomplished with a supervised construction crew that knows little about plants. And as long as water was plentiful, bluegrass was the unquestioned solution.
The 2017 Plant Select shrub introduction is a woody plant with a tongue-twister of a name, a long history of survival at the old Cheyenne Horticultural Station, and has a heart-warming story of two great local plantsmen who brought it out of obscurity into Colorado gardens.
Cotoneaster racemiflora soongorica or Sungari Redbead Cotoneaster is a very tough and beautiful shrub, having survived over 40 years of neglect at the closed and unwatered Cheyenne High Plains Horticultural Research Station. It grows 6′-8′ high and wide with arching branches. The dark green leaves that are gray-white underneath, are attractive in themselves, and the flattened clusters of white, Hawthorn-like flowers are some of the showiest of all cotoneasters. They attract bees and other pollinators. Following the flowers are showy red fruits, a quarter of an inch or more in diameter. These berries are not messy and are popular with garden birds. They cluster along the thin branches, appearing as ropes of beads — hence the common name.
Overview: The Good News: 100,000 insect species; only 200 pests. We do not need neonics or any toxic pesticide to grow plants well. The solution is human attention, biodiversity, nutrient-dense soils, application of nontoxic management, and tolerance.
The Bad News: Most people and most nurseries don’t know the good news. They believe the chemical companies that we need to fear and attack insects and fungi as enemies.
More Good News: The concern of ordinary citizens who call nurseries and businesses and ask them if they are using systemic neonic poisons in their plants, is having a powerful effect. These companies now know we care and will buy plants that are neonic-free if we can. This could get them to change.
For many people, pruning is the maintenance job they most fear and dread. And it is good to be wary, because a tree that is badly pruned can dominate a landscape with its ugliness for years, can be more prone to breakage and disease, and can have a much shorter life.
Tree and shrub pruning have four basic aspects: the practical or aesthetic interests of the owners, the biology of how trees “heal”, the physics of what makes a branch strong or weak, and the art of how to create beautiful forms.
Most of us think of gooseberries as the small, green, sour fruits in a gooseberry pie. I remember, as a kid, thinking that they were only fit for a goose. But now I have had the pleasure of eating several varieties that are delicious, right off the bush, when fully ripe. Europeans have had a couple centuries to cultivate and breed Ribes uva-crispa (grossularia) which is the European Gooseberry.
Pyrethrum is one of the best known botanical insecticides, effective against a wide variety of insect pests and generally considered safe to use. Is it really safe? To answer any question about pyrethrum it must first be explained that what is referred to as “pyrethrum” can be many different products. There is pyrethrum, the raw flowers; pyrethrins,the extracts from the flowers; and pyrethroids, synthetic pyrethrum. In addition many other insecticides and enhancers are often added to formulations which are called “pyrethrum”.
At our nursery it is not unusual for people to ask us for plants that “bloom all the time”. And we have to admit that most perennial plants only have one sexual cycle per season, and that for a garden to have truly continuous bloom, we must include spring-blooming plants, summer-blooming plants and fall-blooming plants.
In addition, there are a few other important issues to mention regarding the quest for long-blooming perennials. One is that “long-blooming” should be included in the larger subject of “long seasonal interest” which can include foliage color, interesting textures, contrasting forms, evergreen and ever-silver, sculptural elements, fall color, and attractive fruits, seeds and bark. It is also relevant that long-blooming can sometimes mean short-lived because the plants’ strategy to produce a lot of flowers resulting in a lot of seed, can exhaust the plants.
You might think a nurseryman would have a collector’s garden with rare and choice specimens of every kind, but with only one or two of everything. My garden didn’t turn out that way. I chose minimal watering, only 5-7 times a year, with plants anybody could grow organically, and with strict limits to time and money spent on maintenance. After 29 years, the original xeriscape at Harlequin’s Gardens Nursery turned out to be a naturalized garden. There are natives and unusual plants in this garden, but it is dominated by good or useful “weeds” that make big splashes of color or create a living mulch and thrive with little care. And it changes without my permission, though, of course, I am the gardener, so I get to have some influence.
Diffuse Knapweed, Centaurea diffusa is a relative of the cottage garden flower, Bachelor’s Button and a native of southern Europe and the Ukraine. I used to think that Bindweed was a bad weed, but that was before Diffuse Knapweed moved into north Boulder and has taken over several acres all around me. It is classified as a biennial that can be a short-lived perennial. I am beginning to think that if it is mowed and flowers little, it is perennial, but if it grows to a mature plant producing thousands of seed, then it is a biennial or annual.
Pruning is one of the most misunderstood aspects of gardening. Those of us who are more gentle and sensitive may not want to cut into a living tree or shrub at all, leaving the pruning to nature. Others who identify with aggressive measures see control as the goal and prune as if they were beating back the jungle. However all externally applied concepts should be relinquished in preference to an approach which begins with the needs and repair systems of the plants themselves. What’s wrong with the let-it-be approach? Nothing if you don’t mind the tree/shrub having half as long to live and finding broken branches hanging and fallen after big storms. Dead branches in particular should not be left too long because they are entries into the tree for decay and diseases; the bark, like our skin, is a protective organ. And what is wrong with hacking back a shrub or tree that is overgrown? Nothing if you don’t mind the tree/shrub living half as long because the stress caused by this approach weakens the plant and makes it vulnerable to decay, diseases and insect damage; nothing is wrong if you don’t mind the forest of sucker growth that follows overpruning; no problem, if you don’t mind your wife being mad at you for years every time she looks at its tortured form.
This tough native xeriscape shrub is seldom given credit for being a broadleaf evergreen, but in the duldrums of dry summer and in the winter, these plants are very useful. I especially like to see it piercing through the white snow in its green, bold, formal, sharp rosette. The stilleto-like leaves are 1’-2 1/2’ long and rosettes increase from the rhizomatous roots. In the garden these off-sets can be cut off with a spade if the plant needs to be kept from spreading. The very sharp leaves are difficult to weed around so I use a dense groundcover around mine (Sedum spurium ‘Bronze Carpet’ makes a nice contrast). This very sharpness which the plant has developed to keep from being browsed to death, can be employed to protect other more delicate plants, like a clump of species tulips, from the deer and rabbits. These yuccas are also useful for traffic management, so best kept a good distance from walks and entryways.
Waterwise Shade Trees 40—75′
- Populus acuminata-Lanceleaf Cottonwood
- Salix amygdaloides-Peachleaf Willow
- Celtis occidentalis-Western Hackberry
- Fraxinus pennsylvanica-Green Ash
- Pinus ponderosa-Ponderosa Pine
- Pinus flexilis-Limber Pine
- Pinus contorta var. latifolia-Lodgepole Pine
- Pseudotsuga manziesii var. glauca- Rocky Mt. Douglas Fir
We are continuing to profile noxious weeds in order that we all get to know them. Although not the most fun aspect of gardening, it is important that we help to control their spread so as to avoid impacting our native plant and animal populations, and in some cases, helping to reduce the spread of weeds into our own gardens. An added benefit of learning to recognize weeds is that any plant that appears in our garden that we do not recognize to be a weed, may be left to grow. Wonderful wildflowers and other desirables can thus windfall their way into our gardens.
Pesticides were never a good idea. They were designed to make money from petroleum, not to benefit the public good. Pesticides, fungicides and herbicides are poisons that were developed to kill life. Not only has this approach poisoned our earth and ourselves, it has failed to control Nature. Our soils are less productive, and weeds and pests have adapted by becoming resistant. Stronger poisons are not the answer.
In the last 20 years, the new “nicotine” pesticides (neonicotinoids) have become the industry standards because they are less toxic to people and animals than the old organophophate pesticides, and that is good. But the neonicotinoids (neonics) are even more toxic to insects; they last 3 months to 5 years; all parts of the plants are poison, and the poison goes into our water.
I have been an arborist for 35 years and spent a lot of my life studying trees and so I have these comments on When to Prune Trees:
- Yes, wounds close more quickly when pruned in spring
- Yes, for certain pest problems like Dutch Elm disease, it is important not to prune when the beetles are flying and best not to prune fireblight in the early spring.
- And trees without leaves do have a clearer view of the branching, but climbing into the branches gives a far better view and pruning with the leaves on helps determine thinning density as well as judging weight on a branch.
- Alex Shigo, often called the Father of Modern Arboriculture, wrote that pruning can be done anytime unless a tree is stressed, in which case it is better not to prune when a tree is putting on leaves or dropping leaves.
- Summer is a good time to prune fruit and other trees when you are trying make or keep them smaller.
- Fall is the best time to prune for fireblight, after the leaves have started turning color and before the leaves fall off. This is the time when you won’t spread the fireblight on your tools, so you don’t have to disinfect after every cut.
- Cytospera canker disease should be pruned out in dry weather, which usually is not spring.
- The most important factor is not the timing; it is the accuracy of making a pruning cut that neither cuts off the branch collar, nor leaves a stub. Then wounds will close most quickly.
- I asked Dr. Shigo if it is harmful to prune Maple and Birch in early spring when they bleed. He told me it is not harmful. And it seems to me that it doesn’t bleed for more than a few days.
The opportunity of winter sun in Colorado for heat and light to grow plants in a greenhouse
- cold and sunny
- short season
- energy from coal and petroleum are expensive and atmosphere-polluting
- greenhouse captures free energy
- greenhouse is a tool to produce food and
- is a cheerful winter room
- protects plants from deer, raccoons, hail and grasshoppers.8) efficient use of water
Plants have evolved to time their seed germination, flowering and fruit/seed formation within particular temperature ranges (often regulated by day length). Their distribution geographically is also limited by high and low temperatures. Extreme conditions affect plant performance, survival and reproduction. In 2012, in the Denver-Boulder area, we had record-setting high temperatures: We tied the all-time high of 105 degrees Fahrenheit, and June was the hottest on record. We endured 73 days over 90 degrees and 13 days of 100 degrees or more (in the last 140 years, there have been only 83 days of 100 degree temperatures in the Denver area). And because drought accompanied the heat, 62 of Colorado’s 64 counties were declared crop disaster areas by the US Secretary of Agriculture.
One spring day, my wife Eve and I were taking a walk along a stream when suddenly Eve picked up the sweet scent of something unusual. I sniffed the air and recognized a distinctly grapey aroma, and we realized that near us was a wild grape growing up a tree. It was the native Vitis riparia, the Riverbank Grape. In my 20s I had helped extract the seeds from the very small and abundant fruits to make a wild grape pie, that clings in my memory as one of the best pies I have ever eaten.
What is the big deal about heirloom tomatoes? Hasn’t modern science brought us big improvements with hybrids that are bigger fruiting, higher yielding, resistant to many diseases and low in acid and high in vitamins? Yes, there are many hybrids that do boast these benefits. However the varieties that have earned the designation of “heirloom” have been treasured and saved through many years of growing and eating. Presumably they have endured for two main reasons: the success of the plants through many varying seasons and locations, and the big reason, FLAVOR. It was probably in reference to heirloom tomatoes that the song was written “Only two things that money can’t buy: true love and home-grown tomatoes.” There is something about that genuine tomato flavor that has made the tomato America’s most popular vegetable, and the tomatoes in the supermarkets don’t even come close.
When I first moved to rural north Boulder, I saw the ten acre short grass prairie next to my land as “empty”. Almost nothing that grew there was over a foot tall. Where I came from in Eastern Iowa, we would call that “barren”. However in the last 20 years in Colorado, my tastes and perspective have changed. In Iowa, the weeds as well as the herbaceous perennials spring 2′-6′ high each year, then die back to the ground to hide in their roots under the plant debris and snow until spring. In sunny, dry Colorado, there are many natives as well as well-adapted foreigners from high desert and steppe regions that stay evergreen to make up for a shorter growing season and that stay short in accordance with leaner soils and fierce climate changes, wind and hail.
Many fruits can be grown successfully here on the Front Range of Colorado. At one time, there were commercial apple orchards in Boulder and Fort Collins, commercial sour cherry orchards and canneries between Loveland and Fort Collins and commercial raspberry production in various places. Cheap shipping, more reliable weather and harvests in other regions, and a raspberry disease chased these operations to other states. However there is great potential here for the home gardener to grow tree- and bush-ripened fruit that is delicious, organic, fresh and economical.
In the mile-high, sunny and dry west, silver is more valuable in the garden than gold. Gold and variegated foliage effects may be a gardener’s delight in the moist, shady and cloudy east and northwest, but here many of those leaves burn while silver leaves reflect heat and ultraviolet rays. The silver color of plant leaves is caused by fine hairs, microscopic scales or a waxy substance. These structural adaptations improve the drought tolerance of plants by cooling and by reducing water loss through transpiration.
Plant Select is a program to identify, promote and distribute little known, but great plants that are successful in Colorado and the Intermountain West. It is a cooperative venture of the Denver Botanic Gardens and Colorado State University, along with many nursery and landscape professionals. The program is more than ten years old and has brought to public view both natives and other well-adapted plants. Several plants are chosen each year and introduced through colorful brochures, the Plant Select web site and through various demonstration gardens, which can be found at www.plantselect.org/demonstrationgardens.
In the last issue I discussed three vines recommended by Jim Knopf for serving the special needs of the Boulder-Dushanbe Teahouse arbors. These vines were Clematis tangutica, Bokaravine Fleeceflower, and Riverbank Grape. Because the legs supporting the arbors are 12’-15’ tall, only the most cold-hardy and vigorous vines could be used.
There are several native artemisias that are naturally well-adapted to our soils and climate, drought-tolerant, and useful in our landscapes. These silver-leafed shrubs make great contrasts with green foliage and great foils for flowers of any color. They are now classified under three genuses: Seriphidium, Oligosporas and Artemisia.
(Just this PDF – should we turn it into a regular page?)
Even if the economy doesn’t drive us to foraging in the wild, there are some native fruits that are good to know, to eat and to grow at home.
Wild Plum, Prunus americana, is blooming all over Boulder and much of the Front Range as I write. It is easy to identify with its early spring clouds of white blossoms and waves of sweet perfume that carry across the yard or the ditch. It is quite happy in a ditch where it gets a little extra water, and is not at its best in very dry conditions where it will grow more as a shrub than a tree.
by Mikl Brawner
Plants have many important functions, like making leaves, making flowers and seeds, growing, storing starches in the roots etc, but we humans are usually unaware of the vital function of transpiration.
It is estimated that 98% of a plants energy is used in the work of transpiration. How does this process work? and why is it so essential to a plant?
Parsley is not merely a garnish. Besides its wide-ranging multicultural culinary uses, it has, like many culinary herbs, significant nutritional and medicinal values and important roles in the garden. And in Ancient Greece, parsley was used to crown heroes. Every part of the plant is useful.
Parsley (Petroselinum crispum) is an attractive, very cold-hardy biennial herb in the Apiaceae (bee-flower) family. It is available in flat-leaf and curled-leaf forms, both of which have rich, glossy green serrated leaves on slender stalks. In the first year, parsley continually produces a mass of foliage, which can be freely harvested as needed.
I enjoyed the article by Renee Galeano-Popp in the fall 2016 Aquilegia, but I would like to take exception to her statement that in terms of alternate hosts of gooseberries and currants that “just about any Ribes species will do.”
Currants and gooseberries have been increasing in popularity among gardeners because their fruits are high in immune-building phytochemicals, because they take up less space than a fruit tree, are easier to pick the fruit, are productive even with late freezes and recent introductions are better flavored and less resistant to diseases.
Tomatoes are claimed to be the most popular garden vegetable. More than 35 million gardeners in the US grow their own tomatoes. And with world production at 170 million tons, they have become the world’s most popular fruit, surpassing bananas, apples and oranges. Some people believe the reason is the versatility in ways to eat them, some say it is the flavor or the beauty. But one thing is for sure: you can’t buy a tomato that tastes as good as a ripe one fresh from the garden. As the Guy Clark song goes: “Only two things that money can’t buy; and that’s true love and homegrown tumatuhs.” The poor taste and lack of sugar in commercial tomatoes is both the result of breeding for uniformly red fruit and the fact that they are picked green so they don’t bruise in shipping.
WATER: Most vegetables need a consistent, generous supply of water. Use drip irrigation, or use overhead sprinkler early in the day.
SOIL: Organic matter (humus) feeds vital soil organisms that feed plants, improves soil texture, moisture-retention, & aeration. We recommend incorporating compost to a depth of ~8”. Note: Almost all of our soil amendments are produced locally.
Plants are one of the most successful life forms. In fact, we could say that they are the most successful life form, because plants are self-sufficient. They can live without eating other beings because they can make their own food. Only plants, phytoplankton, algae and cyanobacteria can synthesize food from sunlight, carbon dioxide, minerals and water.
At the same time, plants have a serious limitation: they are rooted to the earth, so they can’t run away from pests and they can’t pursue another plant in order to have sex. But are plants helpless. Oh, no. They have developed chemical warfare and chemical magnetism to protect themselves from predators and attract allies.
Native Plants In Harlequin’s Gardens Display Gardens
You are sipping smoky Russian Caravan tea on the patio of an elaborate teahouse, talking and laughing with your friends. The rich pinks, bright reds, fresh whites and warm yellows of hundreds of roses fill your view and the heady redolence of their perfumes fills the air. A brisk stream is flowing nearby. Are you in Samarkand? Tashkent? No, this scene is in Boulder, Colorado at the Boulder-Dushanbe Teahouse. Now, at the fourth anniversary of the completion of the teahouse and the planting of the rose garden, an exuberance of roses is anticipated for May and June and plenty of flowers until frost. These roses are not the hybrid teas and floribundas that have been popular in the 80-100 years of recent history; these are wild species roses, heirloom roses from the 13th through the 19th centuries, plus modern shrub roses from the Canadian breeding program, David Austin roses and others. These varieties were chosen for their cold-hardiness, disease-resistance, fragrance and general ability to thrive in Colorado.
What group of plants has the longest proven record of success in Colorado for enduring the radical ups and downs of our weather, including droughts? Our native plants, of course. And if we give them similar conditions to what they have in nature, they will succeed with little care. Here are a few of my favorite native plants that have thrived in my xeriscape garden for the past 10-15 years.
Liatris punctata, the Dotted Gayfeather stores its energy in a thick taproot that helps it produce flowers even after a dry summer. The tufts of rough, narrow leaves are little-noticed until they shoot up their thin flower spikes to 10”-16”, and burst into bloom with lavender-violet “feathers” in August or September. They are especially dramatic in groups of four to ten plants, and they can continue to bloom for a month or more. Liatris punctata is native to the foothills and plains of Boulder County, and unlike cultivated varieties, needs no supplemental water once established.
In general, shade trees are not very tolerant of drought. Some people have gotten the idea that since trees have big root systems, they are less vulnerable to dry conditions. Unfortunately this is not true. Truly xeric trees that are native to arid regions are usually small, more like big shrubs. Even in our semi-arid region, photos from a hundred years ago, show very open and unshaded areas where we now have our urban forests. Most shade trees come from forested areas with much more rainfall and deeper, richer soils. On top of that, our trees are often made to grow in very confined areas in heavily compacted soils. So even under normal circumstances, big trees have a hard life here in Colorado. Therefore, during a drought, we must take extra care to make sure they survive by deeply watering at least once a month. If you multiply the diameter of a tree in inches times 10, you will get the recommended gallons of water required per watering. This water should be applied, not next to the trunk, but in a wide band around the drip line.
Lilacs were brought to America by the earliest settlers and have been very popular landscape shrubs ever since for good reasons. Lilacs are tough, drought tolerant, usually healthy, long-lived, have masses of beautiful flowers and most of them have a delicious fragrance. In dry Colorado air, you have to stick your nose in most flowers to get the smell, but lilacs carry their rich perfume for quite a distance. Like most young boys, I was more interested in bugs than flowers, but my earliest memory of a flower was lying on a grassy hill next to a lilac hedge in full bloom, soothing my spring fever in the sweet, heady fragrance of the common lilac. This powerful aroma is one of the main attractions to lilac and one of the reasons why people forgive other garden qualities like the huge size and habit of suckering.
In fact, the tendency to sucker and the ease of transplanting are primary reasons for the rapid spread of lilacs across America. By the 1650s, lilacs were growing all over the colonies, and later they were carried west by the pioneers. I recently pruned some lilacs that were planted by miners in the rocky foothills above Boulder. I can just imagine some rough traveler, burning with gold fever and the Colorado sun, sharing his canteen with a lilac sucker.
Lilacs are natives of colder regions of southeastern Europe and northern regions of China and Korea. What we call Common Lilac, Syringa vulgaris, came from Romania, Yugoslavia and Bulgaria. The species comes in purple and white, is long blooming and is one of the most fragrant. It will grow to 12—15′ and can spread to make wide clumps, making a good screen. Because they are native to limestone areas, they prosper in our alkaline soils. And their hardiness makes them enduring in Colorado: books say to zone 4, but local growers say zone 3 or even 2 and to 10,000′.
Another reason lilacs are so popular is that they have been hybridized so much that there are many colors and forms to choose from. From Syringa vulgaris were bred at least 1500 cultivars. Starting in the 1880s, Victor Lemoine of France began selecting and hybridizing lilacs. It was a family enterprise with Victor as the leader, Madame Lemoine climbing ladders to do the actual cross pollinating and their son Emile taking over the business. They achieved 214 successful varieties, and both Victor and Madame Lemoine have great lilacs names after them. These are what we now call the French Lilacs. Since Lemoine, there have been many lilac breeders, several from the United States including Father John Fiala who wrote the great reference Lilacs: The Genus Syringa.
Some successful Syringa vulgaris cultivars available in our area are: ‘Albert Holden’ has deep violet blossoms with a silver reverse and good fragrance and grows to only 7—8′. ‘Arch McKean’ which has magenta flowers and very little suckering, growing to 7—8′. ‘Beauty of Moscow’ (’Krasavitsa Moskvy’) with double white fragrant blossoms growing to 10—12′.(”one of the finest lilacs in commerce.” Fiala); ‘President Grevy’ has excellent double blue flowers in immense panicles.
‘Edith Cavell’ is rated “excellent” with double white, very showy flowers. ‘Monge’ is a single deep purple that is “outstandingly showy” and grows to 10—12′. This one is thriving at the neglected Cheyenne Station. ‘Sensation’ is very striking with its purple flowers edged with white. ‘Marie Frances’ has true soft pink flowers that are very fragrant.
Besides Syringa vulgaris, there are 22 other species, all from Asia. Some of these are not garden worthy, several were used in breeding great new hybrids and some make good shrubs in themselves. Syringa laciniata is sometimes available. It is quite beautiful with its cut leaves and its lavender blossoms. It is an annual bloomer, is long-flowering and suckers very little.
Syringa meyeri is compact and the variety ‘Palabin’ is available locally. It grows to 5′, needs little pruning and likes loose soils. It has deep purple buds and lavender-blue flowers and succeeds in dry conditions.
Syringa microphylla ‘Superba’ has small leaves, as its name implies. It is slow growing to 6—8′ and is wide spreading with small clusters of dark pink flowers that are sweetly fragrant. This is a lilac that will make a few blooms again in summer and fall. This is a real treat.
Syringa oblata is occasionally available and although it is an early bloomer, it is less susceptible to freezing than S. vulgaris and so is fairly reliable. The flowers are pale purple and the fall color is wine red. The variety dilatata is a superior form with very fragrant purple flowers and the variety ‘Cheyenne’ is extremely fragrant.
Syringa x hyacinthiflora is a cross between Syringa oblata and S. vulgaris. These hybrids bloom a week to 10 days before the French Vulgaris Hybrids. The fragrant flowers can be white, lavender or purple and the fall color is wine red. They are successful large, dense shrubs for Colorado, growing to 10—12′, and can be used as hedges since their leaves and flowers form all the way to the lower branches. They are hardy to 9000′. However since they bloom early, avoid planting them in a frost pocket or next to a tall wall or house where the flowers can be coaxed to open early only to be frozen. A few that are available locally are ‘Mount Baker’ with very fragrant, pure white flowers, ‘Assissippi’ which is the earliest with fragrant lavender flowers, and ‘Pocahontas’ with deep violet fragrant flowers.
Syringa patula is a late blooming species from the mountains of South Korea. The selection ‘Miss Kim’ is fabulous for its compact form and its very fragrant ice-blue-lavender flowers. It has burgundy fall color and prefers a well-drained soil.
Syringa x prestoniae are a series of hybrids from crossing Syringa villosa and S. reflexa. Isabella Preston was the Canadian hybridizer of these prolific bloomers. They flower about 10-14 days later than S. vulgaris and have a spicy “oriental” fragrance. They are very hardy to zone 2 and can grow to 9000′ or 10,000′. They do not sucker and so can be pruned into small multi-stemmed trees. Some varieties that are available locally are: ‘Isabella’ with lavender flowers, ‘James Macfarlane’ with pink flowers, ‘Miss Canada’ with deep pink flowers only growing to 6—9′ and ‘Minuet’ with purple flowers growing to 6—9′.
Another lilac species that is a favorite in Colorado is Syringa reticulata, the Japanese Tree Lilac. It grows to 15—5′, blooming with white flowers in very late spring. The variety ‘Ivory Silk’ has a more compact form and the same cinnamon-brown peeling bark. The fragrance is like privet, that is, not delicious. It is hardy to zone 4 and 6500′.
The best culture for lilacs is fertile, well-drained soil with plenty of organic matter in full sun. The Common Purple and Common White seem to do just fine in my lean gravelly soil with almost no organic matter, but for the hybrids, for longer bloom, bigger and more flowers higher fertility is necessary. Father Fiala says commercial fertilizer is no substitute for two year old manure and compost, because they provide tilth, hold moisture and feed the soil microorganisms. The worst conditions for lilacs are “wet feet”, shade and subsoil. If heavy wet clay is all there is, Father Fiala says to build a 3′ high mound with gravel, top soil, manure and compost; and plant at the top of the mound. Another option is to plant near the top of a slope; never near the bottom. Syringa vulgaris and its offspring are the most tolerant lilacs for heavy clay, but not if it is soggy.
The best pruning for lilacs is to remove the dead, broken and very old. Also take out many of the suckers, but leave the biggest ones if they aren’t too crowded. Once the shrub is mature, remove a fourth to a third of the oldest wood every year. And prune the tallest branches down 10%-20% to a side branch leading out. This should be done soon after blooming so next year’s buds are not removed.
When a lilac has not been blooming well or has gotten very old with little care, it can often be rejuvenated if the roots are sound. First scratch in some composted manure into the top 2″ of the soil, and then mulch 3″ deep. Then cut out the oldest canes, or if it has too much dead, cut the whole shrub to the ground in the early spring before it leafs out. This will either renew it or if the roots are rotten, it may not survive the operation. Do not cut a weak lilac to the ground in the summer, because that would likely kill it.
There is not universal agreement as to the value of dead-heading the spent flowers, but Father Fiala and the Arnold Arboretum believe it is worth the trouble if it is done immediately after blooming. This will save energy that will result in better blooming and health. This can be a big job, but I have found removing even half the spent flowers is helpful.
Lilacs are generally healthy if they get decent drainage, some pruning and some organic matter. But they can have a few problems. In Colorado, a warm February and March followed by a frigid April or May can freeze the buds or flowers and ruin the floral show for a whole year. Another problem can be powdery mildew, turning the leaves almost white. If the plant is strong, this will cause no real harm; just rake up the diseased leaves. Some varieties like Syringa meyeri, S. microphylla, S. reticulata, ‘Mme. Lemoine’ and ‘Pocahontas’ are resistant to mildew. You can control the mildew with a non-toxic spray of horticultural oil and baking soda, one tablespoon each in a gallon of water, or there is a new product related to baking soda called Green Cure. One other possible problem is lilac borer which can tunnel into the wood to weaken or kill stems. This should not be a problem if the plant has good vitality. I have heard “painting” the lower trunks with wood ash and water repels them.
Like every plant, lilac has its strengths and weaknesses, but far more strengths. It is truly a sustainable shrub for Colorado, being both tough and drought tolerant. Enjoy the great variety of forms, flower colors and fragrances. And by planting the early, middle and late bloomers, you can enjoy a long season of flowers. I recommend that you go to the nurseries in the spring when they are in bloom so you can smell and see, and cultivate those that really speak to you. No nursery can carry more than a fraction of even the best varieties. Two mail order lilac nurseries are Heard Gardens in Iowa and Wedge Nursery in Minnesota.
Here are a few Father Fiala identifies as some of the top varieties that are not available locally, as far as I know: ‘Flower City’, ‘Dwight D. Eisenhower’, ‘Avalanche’, ‘Violetta’, ‘Blue Danube’, ‘Mechta’, ‘Larksong’, ‘Marechal Foch’, ‘Paul Thirion’, ‘Edith Braun’, ‘Sarah Sands’, ‘Etna’.
We gardeners are always looking for tough plants. And those of us who are pursuing the elusive “sustainable garden” are searching for Colorado-adapted plants that do well with little or no care. But that is not enough. A sustainable garden is one where there is a balanced ecosystem of plants that can change as conditions change, to favor first one species and then another, but no plant should take over the entire space. Those dominating plants are the ones I call real weeds: the garden bullies.
Many gardeners would agree that it is better to wish all your life for a plant you can’t grow, than to have a plant your whole life you wish you could get rid of. So in this article I’m going to warn you about some plants that are often bullies in the garden. These plants are dangerous because they flower and look pretty enough in the beginning, but just give them room and a little time and LOOK OUT!! Some of them can be valuable plants in harsh conditions where little else will survive or where they are isolated, but some are invasive in Nature, and some are such thugs that putting them in the garden is like inviting the Hell’s Angels to your dinner party.
“You can join the fight to save the honeybees by planting a pollinator-supporting garden.” This is a recommendation made by a Penn. State Master Gardener program. Is this weird? Not at all. The European Parliament has approved creating bee “recovery zones” across the Continent. These recovery zones will provide bees with nectar and pollen in areas that are free from pesticides. Why is it a big deal that honeybee populations around the world are declining? One reason is that one third of the human diet comes from plants that are pollinated by honeybees. Another reason is that honeybees may be the “canary in the coal mine”; just the first to show that there is a problem that hasn’t yet surfaced in other pollinators and other beings.