QMy heliopsis has little red bugs all over the stems. What are these, and should I treat the plants?
AThe little red insects on your heliopsis (Heliopsis helianthoides) are aphids. There are several different species of aphids, but all of them are very small, soft-bodied insects that suck sap from plants and can distort growth and spread plant diseases. The most common aphids are green, but they also can be black, brown, pale yellow or red.
An easy, nontoxic way to remove most of the aphids from your heliopsis is to blast the stems with water from a garden hose. Most of the aphids that are knocked to the ground will not make it back onto the plant. Try this water-blasting for three or four days in a row, then monitor the plants and blast them again if the aphids return. They can reproduce at an astronomical rate, so you'll probably have to check the plants once or twice a week for the summer.
Another option is to spray the plants with insecticidal soap, available at garden centers and through gardening supply catalogs. This low-toxicity pesticide kills the aphids by drying them out, but it is only effective when applied directly to the insect.There is no residual effect, so you may have to spray several times. The use of chemicals such as malathion or acephate (Orthene) will control aphids longer, but also will kill insects beneficial to your garden.
QTo get the nice orange fruits on bittersweet vine, do I need to grow three plants or just two?
AIt's not how many plants you have, but the sex of the plants that determine whether you get fruit on bittersweet (Celastrus scandens). This native vine is usually dioecious, which means that male and female flowers are born on separate plants. To get fruit on the female plants, you also must have a male plant nearby to provide the pollen. Ideally you would want to grow several female plants for the showy fruit, plus one male plant tucked in with them.
Unfortunately, few nurseries sell bittersweet identified by sex. This means you may have to purchase several plants in hopes of getting at least one male and female plant. Bittersweet is fairly easy to propagate by rooting stem tip cuttings taken during the summer. If you have a known female plant, you can produce more by propagation.
AWhere can I buy liquid organic fertilizer?Many garden centers and gardening catalogs sell organic liquid fertilizers. Many catalogs carry fertilizers based on fish products, either fish emulsion or digested fish product, some with kelp or other ingredients. Most of these have fairly low amounts of nitrogen, phosphorus and potassium, the three major nutrients in fertilizers, with rates ranging from 2-2-2 to 12-6-6. There is little danger of fertilizer burn when nutrient amounts are low, but you also might have to fertilize more often. The Territorial Seed Co. catalog carries several of these products (P.O. Box 157, Cottage Grove, OR 97424-0061; phone 1-541-942-9547; Web site: http://www.territorial-seed.com ).
-- Nancy Rose is a research horticulturist at the Minnesota Landscape Arboretum. She spends her spare time gardening, inside or outside, depending on the weather. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.