• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
Harlequins Gardens

Harlequins Gardens

Boulder's specialist in well-adapted plants

We are closed for the season, and will reopen in March 2023!

Gift Memberships & Gift Certificates  – available online!
See our seasonal hours and address, below.

Read our latest e-newsletter!

 

FacebookPinterestInstagram
  • Home
  • About
    • About Us
    • Staff
    • Display Gardens
    • Why the Name “Harlequin’s” Gardens?
    • Sustainability
    • Policy on Pesticides Including Neonicotinoids
    • Careers
  • What We Offer
    • Products
    • Plants
    • Gift Certificates
    • Membership
  • Plants
    • Annuals
    • Bulbs
    • Fruits
    • Groundcovers
    • Herbs
    • Natives
    • Ornamental Grasses
    • Perennials
      • Plants for Pollinators List
    • Roses
    • Vegetables
      • Tomato Starts
      • Pepper Starts
      • Other Vegetable Starts
      • Fall Vegetable Starts
      • Garlic
    • Xeriscape
  • Resources
    • Mikl’s Articles
    • Handouts
    • Newsletters
    • Links
  • Garden Tours
    • Virtual Garden Tours
    • Submit Your Garden!
  • Events
  • Classes
  • Blog
  • Wholesale
    • Wholesale Mailing List Sign Up
    • Who Qualifies
    • Wholesale Availability
  • Contact
Home | Blog | Fungus Gnats

Fungus Gnats

Fungus Gnat. Credit CSU Extension Service

Houseplants, especially ones that we keep outdoors in the warm season and bring back inside when frosts threaten, are likely to harbor Fungus Gnats. These tiny black flying insects (about the size of a fruit fly) can be very annoying but are mostly harmless. Adults lay 75 to 200 eggs that hatch in a week in the top 1” of soil, and when the larvae hatch, they survive mostly on soil fungi, but also feed on tender root hairs.  This life cycle lasts about five weeks, although the adults only live about five days. One plant infested with fungus gnats will easily and rapidly spread the insects to nearby plants.

Fungus Gnat on sticky card. Credit CSU Extension Service

Fungus gnats are attracted to overly moist soil full of decaying plant matter. If the infestation is new, letting the top few inches of soil of affected plants dry out completely should desiccate the eggs and kill larvae. If the infestation is already established, you can catch the adult gnats by inserting yellow ‘sticky traps’ on short sticks or wires just above the soil level – bright yellow card stock with a very sticky coating. This will control the adult gnats but won’t affect the eggs and larvae.

Fungus gnat larva on potato slice. Credit CSU Extension Service

The CSU Extension Service recommends capturing larvae by placing a half-inch thick slice of potato on the soil surface. The potato and shiny white, worm-like larvae with a dark head can then be discarded.

Brandi Spade, an assistant editor of Fine Gardening magazine, offers the following safe two-step process, said to eliminate the entire problem.

“STEP 1: Make the Sand Trap
Gather the affected houseplants, remove the top 2” of potting mix to dispose of the eggs and hatched larvae. Discard the soil immediately, and replace this top layer with dry builder’s sand, which is free of organic matter and dries quickly, making an unappealing medium for fungus gnat eggs. Let the soil below dry out completely before the next watering. This should eliminate all fungus gnat larvae and prevent new eggs being laid.

STEP 2: Set up the Open Bar
The adult gnats are easy to lure and drown using any sweet liquid that smells of decay. A cheap bottle of alcohol-free wine works well for bait. Pour the liquid into a small saucer or bowl and place it near the previously infected plant(s). Let it sit overnight, and in the morning, there should be dead gnats floating on the surface. Discard and refill the saucers until the adult gnats no longer appear.”

sidebar

Blog Sidebar

Sign-up for E-Newsletters!

Sign-up for our weekly e-newsletters to receive empowering gardening tips, ecological insights, and to keep up on happenings at Harlequin’s Gardens — such as flash sales and “just in” plants. We never share customer’s addresses!

We do not ship plants!

Our plants are for sale ONLY at our Boulder location. We DO NOT ship plants. Come visit us!

Hours by Season

MARCH HOURS
Thursday-Sunday, 9AM-5PM

APRIL-OCTOBER HOURS
Tuesday-Sunday, 9AM-5PM

Mondays, CLOSED

Footer

Contact Us

303-939-9403 (Retail)
staff@nullharlequinsgardens.com

4795 North 26th St
Boulder, CO 80301

Sign-up for E-Newsletters!

Sign-up for our weekly e-newsletters to receive empowering gardening tips, ecological insights, and to keep up on happenings at Harlequin’s Gardens — such as flash sales and “just in” plants. We never share customer’s addresses!

Map

Our Hours

Seasonally, MARCH to OCTOBER.
MARCH HOURS:
Thursday-Sunday, 9AM-5PM

APRIL-OCTOBER HOURS:
Tuesday-Sunday, 9AM-5PM

Mondays, CLOSED

The plants we grow are organically grown. All the plants we sell are free of bee-killing neonicotinoid pesticides.