When you live in Colorado, and especially if you live in the mountains, you quickly develop an attitude that all living things are to be protected.  The geography, the wild life, the plants, the entire ecosystem is beautiful - and fragile.  We learn to "Leave No Trace." Children are taught to not feed the wildlife.  We name the flowers, but we do not pick.

Then how could some beautiful blooming plants be on the Colorado National Park's "Hit List," with hundreds of volunteers banning together each spring to dig and dispose of "flowers" growing in our parks?  What makes a plant so "noxious" that it needs to be pulled before it goes to seed?

First, a noxious weed is a plant that is not native to our area.   It has been brought from some other area of the world where it may have been grown without problems.  In our Colorado landscape, however, an "imported" plant may have few, if any, natural predators (insect, wildlife, or disease) to keep it in balance.

Second, a noxious weed is a plant which is extremely invasive, taking over large areas in a relatively short period of time.  The problem in our parks is that once established, noxious weeds have a tremendous capacity to invade adjacent, undisturbed plant communities, competing with native plants and eliminating the needed food and shelter for our wildlife.

So what can you do to help in the fight against these weeds?    First, learn to identify the major noxious weeds (see list below for a start).  Colorado State University Cooperative Extension offices and county Natural Resource Departments are a great source of information on the weeds causing problems in your locale.

Second, be sure your own property is free of these weeds.  If you must disturb plant communities, restore the land with native plants.  Help others to identify and remove areas that have become infested in your community.

Third, take great care when visiting our parks to not transport weed seed into the area.  Seeds cling to backpacks, tents, even the soles of our shoes, so clean all equipment before your next excursion into our protected areas.

Below are four common and easily identifiable noxious weeds that cause serious problems in Colorado.

Canada thistle (Cirsium arvense L.)

• Perennial with deep, spreading roots
• Erect, up to 4 feet high
• Dark green leaves, oblong, and lance shaped
• Beautiful flowers that are bristly, clusters of light lavender to deep rose
• One plant can colonize an area 3 to 6 feet in one year
• Be persistent in efforts to cut off the plant at the root every three to four weeks throughout the summer - to eventually starve the extensive root system.

Dalmation toadflax (Linaria dalmatica (L.) Mill.)

• Perennial, probably an escaped ornamental, originally from the Mediterranean region
• Erect, up to 3 feet tall
• Pale green leaves that clasp the stem and are heart-shaped with a pointed tip
• Bright yellow "snapdragon-like" flowers that have an orange spot on the lower lip
• Be persistent in efforts to cut plant off at the root throughout the summer - to eventually starve the extensive root system

Leafy spurge (Euphorbia esula L.)

• European perennial reproducing from seed and extensive roots as deep as 30 feet
• Erect, 1 to 3 feet high
• Pale green leaves alternate on stem, smooth, narrow, about 1/4 inch wide and 1 to 4 inches long
• Small yellow-green flowers enclosed in heart-shaped bracts
• Cut off plant at roots avoiding contact with milky sap.  Be persistent over 4 to 5 years.

Diffuse Knapweed (Centaurea diffusa Lam.)

• Eurasia biennial reproducing from seed
• Produces a single main much-branched stem that is 1 1/2  to 2 feet tall
• Thin nap in young leave and mature leaves are smaller
• Pinkish purple to whitish flowers on tip of branch producing up to 25,000 seeds per year that remain viable up to 8 years
• Eliminate plant before flowering occurs.  Avoid contact with sap.

Q:  When and how can I harvest flowers for drying?

A: August is a good time to harvest your flowers. For everlasting bouquets, cut blooms and let them air dry.  Harvest them before they are fully opened, strip all leaves from the stems and bind bunches with a rubber band. Hang these upside down in a cool dark place with low humidity such as a garage or closet.

Q:  How will I know when it is time to dig my potatoes?

A: Potato plants mature and begin to die about 70 to 100 days after planting, depending upon the variety. As plants mature, they use less water. To promote skin set, leave tubers in the ground for 10 to 21 days following vine death. This decreases bruising during harvest and permits better storage. Harvest when the soil temperature is 50 to 65 degrees.
New potatoes are harvested earlier, when vines are still lush and green. Skins of these small tubers are fragile and the tubers quickly dry out if they are not used immediately or refrigerated.

Q:  I seem to be seeing a lot of wasps lately.  What is going on and what can I do to control them?

A:  August seems to be the time when wasps are at their busiest.  They seem to be in abundance everywhere that you look. If the nest is not causing a problem, the best solution is to wait until it is abandoned in the fall. The nest can be safely removed in the winter or left alone, will break up after a season. If needed, insecticides found at your local garden center or nursery can be effective in destroying a wasp colony. It is often desirable to include a "rapid knockdown type of insecticide ", often found in the various wasp and hornet sprays, to reduce problems with flying wasps. Insecticide applications are best made during the late evening or cool periods in early morning when the wasps do not readily fly.

If your cucumbers are flowering but no fruit are developing, have patience. The first flowers formed are typically male flowers that drop off. Female flowers, which produce the fruit, will soon follow. Low honeybee activity can also lead to insufficient pollination needed for fruit set. Next year, plant annuals in your garden to attract more insect pollinators.

To set traps for earwigs, roll up moistened newspapers and leave them out during the night. The insects are attracted to the dark, moist environment. In the morning, dispose of them or crush them. Around your home exterior, maintain a dry zone that is swept free of debris: no wood piles, newspaper piles, old rugs or even simple dirt and leaf litter.

Going into fall after our dry summer, don't forget to deep water your shrubs and trees to carry them through the winter! A long slow drink in the entire root zone- not just up against the trunk- is far healthier than random short sprinkles every day. Visit the following web site for more information on properly watering your trees and shrubs during a drought: www.watersaver.org

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  August 18, 2003