Q. My mature yard has many beautiful trees, but the shade makes it difficult for other plants. What can I grow?
A. Many plants do well in shade, even where grass won t grow. The trade-off may be that blooms might not be as profuse as those grown in the sun. Since most shade plants bloom in spring, you will have to make plans for blooms all summer. Foliage plants such as hostas are beautiful in shade. Also snow-on-the-mountain and sweet woodruff have nice foliage and flowers in shade, but can be invasive. They are best in a large space where you won t mind them spreading out. Ground cover plants like ajuga, periwinkle, evergreen kinnikinick and creeping Oregon grape holly do well in shade and have some blooms.
Other upright perennials that do well in medium shade include bleeding heart, edelweiss, astilbe, foxglove, ladies mantle, pasque flower, primroses, columbine, several types of campanulas, Rocky Mountain penstemon, plumbago, dianthus, coral bells, lupine, candytuft and daylilies.
Annuals that can take some shade include impatiens, four-o-clock, snapdragons, alyssum and pansy.
Q. I have a swarm of tiny flying insects in my home that seem to come from my houseplants. What are they?
A. They are probably fungus gnats, a common but controllable problem. They do not bite and present no health threat, but are annoying. Over-watering is usually the cause of these pests – they love excess moisture. Use potting soils that allow good drainage and reduce your watering schedule so the plant dries out completely between waterings. Keep the soil surface clear of dead leaves and debris so the gnats don t have a place to hide.
Other options include catching the pests in purchased yellow sticky traps, or make your own with a piece of yellow paper with automotive oil on it. Another option is to fill a small container with 1/8 inch of red wine and place this near the plant to attract the gnats. You can spray the soil with an insecticide containing resmethrin, which controls the adult insects. Try attracting the larvae by placing half-inch thick slices of potato on the soil surface, and then discarding the potato slices a few days later.
If all else fails, repot the plant in new soil, shaking off as much of the old soil as you can without injuring the roots.
Q. What is the difference between pre-emergent herbicides and post-emergent herbicides for controlling weeds?
A. A dense and healthy grass is the best way to reduce weeds, but a totally weed-free lawn is rarely attainable. Pre-emergent means the weed seeds have not yet germinated. To be most effective, a pre-emergent herbicide must be applied before seed germination, usually late March and early April along the Front Range. Warm, moist springs cause earlier germination and cool, dry springs delay germination.
Pre-emergent herbicide application will not control the weed once it begins to form leaves and should not be used when planting grass seed because it also will be affected. Post-emergent herbicides are used after seed germination as the plants mature. These herbicides are most effective against young seedling weeds. Once the herbicide is applied according to directions, use good cultural practices (proper fertilization, mowing and irrigation) to encourage rapid fill-in of the grass. Herbicides are only one tool in a total weed-control program.
Marcee Perelman is a Colorado State University Cooperative Extension master gardener in Jefferson County. For more information, visit planttalk.org or AnswerLink.info.
