FALL GARDEN CARE
In the ‘Old Normal’, by now, we would expect to have had some light frosts and maybe some killing frost in the Denver-Boulder area. And some rain, and even snow. And lots of leaves would have fallen from the trees and shrubs. Most of us with irrigation systems would have had them blown out and turned off. But this long extension of summer heat and drought is definitely not the Normal we used to rely on. As gardeners, we have to adapt. Here are some suggestions for fall garden maintenance under these new conditions.
PLANTING
Perennials, Trees & Shrubs: This fall we have a great opportunity to continue planting! We’ve had some of our best successes with transplanting hardy roses, shrubs, trees and perennials in October. There is enough time for new plants to establish before the soil freezes. Do mulch your new plantings (see mulching section below), and water thoroughly and frequently while daytime temperatures remain above 40 degrees and the soil has not yet frozen. We still have a lot of really great plants in great condition, and nearly all of them are on sale! See our Fall Sale details below.
Bulbs: It’s Prime Time for planting bulbs for next spring’s flowers! See the list of our bulbs for 2024 here.
Garlic: Plant garlic cloves from mid-October (now!) through mid-November. Here is our Garlic Planting Guide.
WATERING
Many plants in our gardens have bloomed and gone to seed. Both of those activities take a lot of energy, and lack of water after all that work can weaken plants and make them more vulnerable to drying winter winds and cold. A surprising fact is that more plants die over the winter here from dehydration than from cold. Also, temperatures can plummet very suddenly and drastically in autumn, giving plants no time to adjust. Being well-hydrated gives plants a better chance of surviving these polar vortex events.
During the growing season, the best way to water plants here is to
water infrequently – once a week for conventional ornamentals, less often for more xeric plants
water slowly –so that the soil can absorb all the water and none of it runs off the surface, and
water deeply – so that the soil is moist 6” below the surface.
The most reliable way to gauge whether you’ve watered enough is to water for a set duration (start with a half hour), wait 15 minutes, then dig a small hole 6 to 8 inches deep, in or near the root zone , and feel the soil with your finger(s). If the soil is moist at that depth, you’ve watered deeply enough. If the soil is soggy or the hole is filled with water, you have overwatered. If it’s still dry 6 inches down, water for another 15 minutes, and again if necessary, until the soil is moist at a sufficient depth. Total up the durations of each watering period, and you’ll know how to set your timer or irrigation clock.
Winter watering is important too, as our winters are often dry and windy. Be sure to mark your calendar with winter watering reminders! All evergreens (conifers and ‘broad-leafed’) and all fall-planted plants should be watered twice a month in winter. Give the whole garden a deep watering at least once a month. Choose a day when there is little snow cover and daytime temperatures will be at least 40 degrees. Water in the late morning to give the moisture to soak in before nightfall. The Mile High City has more sunny days than Miami, accompanied by cold and strong wind, all of which stress plants.
Please note that there is no ‘one size fits all’ instruction for watering (or anything else about gardening). Most seedlings need frequent watering until their root systems are deep enough to stay moist. New plantings need frequent watering while they are establishing. In the hottest part of the summer (usually July), you’ll probably need to water twice as often as usual.
And it’s important to distinguish between the needs of plants in different settings as well as plants that come from different environments. So woodland or streambank plants may need more water, while steppe or desert plants will need less. North or east-facing gardens will usually need less water than south and west-facing gardens. Soil composition will have a big impact on how often you need to water, and so will the topography; slopes dry out faster than level ground. It’s very important to know the water requirements of your plants and group them in your garden by their water needs.
If this hot, dry fall is an indication of the autumn weather to come as this decade unfolds, we will need to make some changes in what plants we grow and how we water them. I think we still need to shut off irrigation systems sooner, rather than later, to avoid costly repairs. Assess your garden’s performance under this fall’s conditions and think about replacing plants that struggled because of the heat and lack of rain. Perhaps it’s time to develop a way to collect, store and distribute water through Permaculture and ‘rain harvesting’ practices. Perhaps it’s time to convert part of your garden to native, dryland plants (our specialty) that thrive in adversity and add to natural habitat for pollinators, birds and other beneficial wildlife. Just a thought……..
WEED AND INSECT CONTROL
It’s not too late to apply Corn Gluten to your turf areas to feed the grass while reducing weeds. Corn gluten is a natural product that interrupts the germination of seeds, and at the same time provides slow-release nitrogen fertilizer from an organic source. We recommend applying in spring and fall. Read more about Corn Gluten here.
Japanese Beetles have retreated underground, at last! One way you can hit them while they’re down is to apply Grub Gone to lawn areas and around ornamental grasses and roses.
VEGGIE SEASON EXTENSION
We’ve been so lucky to have such a long season to grow our fall crops without protection. But cold will come, and if you’re not prepared to cover your plants with our heavier-weight row cover fabric, ‘Ensulate’ come and get yours now! Here’s some more info about row-cover fabrics.
GARDEN CLEAN-UP
The most important thing to clean up in the garden is diseased foliage and wood. Be sure to remove and destroy plants that you know or suspect were diseased, and any of their fallen leaves so you don’t spread the disease to next year’s plants.
Apart from that, “Leave the Leaves”! The leaves on the ground will provide food and shelter for the beneficial insects. It’s worth it because those predatory insects will be laying their eggs and providing your garden with new generations of the most effective (and free!) insect control you can get. And among those leaves will be larvae and worms that will provide important protein for birds through the lean and cold months. Please leave stems, too! Especially hollow stems in which beneficial insects take winter shelter and/or deposit their eggs. If you are going to remove stalks, please examine them carefully for insect eggs, cocoons and egg cases before cutting.
MULCH
Mulching with the appropriate material is the easiest way to preserve moisture in the soil and preserve valuable soil microbes. If it doesn’t repel microorganisms, organic mulch will also protect and slowly feed the soil microorganisms. We have found that the best organic (composed of plant material) mulches for landscapes are fine wood chips and Soil Pep (partially-composted pine bark). Both are fine-textured, clean, attractive and stay in place. We do not recommend typical mulches made from cedar or redwood, or other bark. Think about it – what is the purpose of bark? It protects a tree trunk and branches from decay. What is decay? It’s the slow decomposition of organic material being acted upon by microbes – bacteria and fungi. So it makes sense that tree bark is made to repel microbes. And what are the most decay-resistant woods for building fences, decks, etc? Cedar and redwood. That’s not what you want covering your soil. Common wood chip mulch is fairly coarse, doesn’t look great, and doesn’t stay in place very well. Both our Fine Wood Chip mulch and Soil Pep knit together in a way that keeps them from blowing and sliding. Apply mulch 2” thick around perennials and up to 4” thick under shrubs and trees (mulching thickly under shrubs greatly reduces weed growth). There are dryland plants that should not have organic mulch touching their stems or crowns, so keep a small circle around the base of plants clear of mulch.
Xeric (dryland) plants will benefit from inorganic mulches – ‘squeegee’ or other small-sized gravel products like pea gravel. 2” is a good thickness for perennial beds, cactus, and succulents. You can use up to 4” under xeric shrubs and trees. Gravel doesn’t hold moisture, so it can be in direct contact with the base of the stems without promoting decay. Again, a 4” thickness is the ‘magic number’ to suppress weeds.
Lastly, mulches help keep soil from being displaced by rain or watering apparatus.
LEARNING
Books: As you prepare your garden for winter, you will probably start making plans for changes and additions for the 2025 season. Thinking of adding some stunning, hardy native cacti to your garden? Learn all about it from a Colorado expert, Leo Chance, in his book Hardy Cacti & Succulents for Cold Climates. And we have dozens of other books covering Permaculture, 4-Season Gardening, Container Gardening, Native Plants, Growing Fruit Trees, Crevice Gardening, and much more, perfect for helping you make fall and winter garden dreams come true!
Classes: Keep watching our e-newsletters and website for listings of our upcoming Classes! We’re planning to offer our cutting-edge, practical and informative classes earlier than ever, starting in the winter!