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Many good caterpillars also occupy our gardens. Caterpillars are the larval stage of moths and butterflies. While some caterpillars are serious pests of crops, forests and ornamentals, many cause little, if any, damage. Moreover, a lot of caterpillars transform into the beautiful butterflies adorned with brilliant, iridescent colors that we enjoy so much whenever we are outdoors.
Most of the caterpillars that eventually become colorful moths or butterflies cause little damage. While they feed on the foliage of a variety of common garden and ornamental plants, most are solitary feeders and cause no harm whatsoever. Furthermore, some of these caterpillars are quite colorful in their own right. Encountering a specimen or two in your garden can be a special treat.
One of the most colorful groups of butterflies in our area is the swallowtail. Most have a wingspan of more than two inches with patterns in hues of yellow, white and iridescent blue or black. The larval stages of the swallowtails feed on a wide range of plants, many of which are commonly planted around homes. The larvae of the yellow two-tailed swallowtail feed on the leaves of green ash and chokecherry. Several years ago, I encountered a solitary caterpillar of an eastern tiger swallowtail feeding on the Japanese lilac in my front yard. This caterpillar was a robust specimen, the same shade of green as the leaves of the lilac on which it was feeding and bore a conspicuous yellow spot on its thorax that looked like a large eye. Caterpillars of the black swallowtail butterfly feed on the fine leaves of dill, fennel, carrots and parsley. Last summer, I was fortunate enough to find two of the colorful yellow, white and black caterpillars grazing in the parsnips I had planted.
Many garden plants can attract both “good “ caterpillars and butterflies. Planting small patches of fennel, parsley or dill is sure to attract black swallowtail larvae and some gardeners establish small beds of these plants especially to raise a few caterpillars. The bright orange blossoms of the butterfly bush, a species of milkweed, is a popular garden plant and will attract many butterflies. They can also provide forage for the caterpillars of the stately monarch butterfly. These handsome, orange and black butterflies migrate to forests in California and Mexico to spend the winter.
If you should happen to encounter one of these good caterpillars in your garden, do not disturb it. I made the mistake one year of trimming the foliage around a black swallowtail caterpillar so that I could get a closeup photo. Within the next hour, he disappeared. I undoubtedly made him more visible to a passing bird who enjoyed a gourmet dinner that day. Also, if you decide to grow plants especially to attract caterpillars, establish them far away from vegetable crops, especially cabbages, lettuce, broccoli or tomatoes. These plants will undoubtedly require one or two applications of a chemical insecticide or the bacterium Bacillus thuringiensis to protect them from those other, not so nice caterpillars. The good caterpillars are also susceptible to these treatments so protect them by keeping the plants that provide their food source separated from plants that harbor the not so nice caterpillars.
A: Leaf lettuce is generally a better choice for a home garden
because the leaves can be picked as needed, allowing the lettuce plants
to produce more leaves.
Q: The young shoots of my aspen trees are covered with round galls. What are they?
A: These are galls produced by the poplar twig gall fly.
It produces smooth knot like galls on aspen twigs, which continue to expand
for years after they are produced. Poplar twig gall fly is a native
insect that has become much more abundant since the early 1980s.
Q: Is there any way to control the poplar twig gall fly?
A: Unfortunately, there are no known effective chemical controls for this insect. The galls are unsightly but seem to cause little or no permanent injury and as trees grow to larger sizes, they seem to sustain less damage.
Gardening in Colorado is a challenge to newcomers and longtime residents alike. The low humidity, high winds, greatly fluctuating temperatures and heavy-clay soils can make growing trees, shrubs, flowers and vegetables difficult. The key is to select plants that will tolerate our soil and climatic conditions, improve the soil with organic matter and develop microclimates where plants will thrive. For help and information contact the Larimer County Office of Colorado State University Cooperative Extension, 498-6000.
Start seeds indoors for peppers, tomatoes and eggplants. Use a sterilized medium to avoid damping-off problems. Many flower seeds can also be started now. Try ageratum, dahlia, lobelia, snapdragon, and verbene. These seeds should be started about eight weeks before the average frost-free date of May 12 in Fort Collins.
Core aerate your lawn to relieve soil compaction and control thatch accumulation. Leave plugs on the soil surface. The closer together the holes and the deeper they are, the more effective the aeration. Overseed bluegrass lawns now to improve the quality of the turf.
For an earlier start in the garden, build a simple cold frame. Seed can be directly sown or plants can be transplanted into the cold frame before being planted in the garden. Facing south, with a tight fitting lid, the cold frame will absorb sun during the day and keep the plants warm at night. If the temperature gets above 50 degrees, prop the lid open to prevent the heat from building up and cooking the plants. Close the lid in late afternoon to trap enough heat to keep the plants from freezing at night. You can find commercially made cold frames with automatic openers at local garden centers or in mail-order garden supply catalogues.
Fact Sheets are available at the Larimer County Extension Office, 1525 Blue Spruce Drive, Fort Collins, Colorado, telephone (970) 498-6000, or contact us by e-mail at larimer@coop.ext.colostate.edu
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