July 2001 Q & A
by Michelle Le Strange, UC Master Gardener Advisor

Q. My butterfly bush and honeysuckle vine are growing too well! How and when can I prune them?

A. The most commonly grown butterfly bush is Buddleia davidii, which blooms on current season's growth. Therefore the best time to prune it back is in early spring before it has begun to grow again. Annual pruning is recommended for this shrub, otherwise it will become woody and leggy and have fewer flowers.

If by chance you have a butterfly bush that flowers on the previous season's growth, like the fountain buddleia (B. alternifolia), you should prune it back by about one-third after it has finished flowering in midsummer.

If your honeysuckle vine produces paired purple-flushed, white flowers on the current season's growth, it is Lonicera japonica, which should be pruned back when the plant is still dormant in winter or early spring. It can be cut back a little or a lot, depending upon how much it needs to be contained.

If your vine produces many long, narrow whorls of scarlet and yellow tubular flowers, then most likely it is L. sempervirens. This honeysuckle should be pruned immediately after it has finished flowering. Cut back as much as you'd like, but make sure to cut right above a nonflowering shoot.
If the vine is hopelessly overgrown and tangled, you need to take more drastic measures, cutting the stems off to within 6-10 inches of the ground. Let the foliage die and dry out and it will be much easier to remove. If you do this now to a vine that flowers on the previous year's growth, you will have to wait one year until it flowers again.

Q. How can we design a long, narrow back yard so it doesn't seem like a bowling alley?

A. Stay away from straight paths and flowerbeds. Build curving, meandering pathways down the center of the space, and break up the space with garden beds that curve out into the yard at uneven intervals.

Use shrubs and small trees to break up the area, planting them not straight across from each other but along diagonal lines, so that the eye goes from left to right and not up and down.

You could construct two or more garden "rooms" by partitioning one area for a patio garden and another for a children's play garden or vegetable garden. Raised beds, living hedges, or a vine covered trellis fence could separate the sections.

Q. Some of my homegrown sweet corn has an ugly bluish growth on the ears. What is it?

A. What you describe is called common smut of sweet corn, which is caused by a fungus, Ustilago maydis. Those large bluish growths are galls and they can form on any part of the plant. Galls start out shiny and greenish to white in color. Galls on leaves and tassels stay small and become hard and dry. Galls on ears and stems expand and fill with masses of powdery spores. Eventually these galls rupture and the spores are spread through the garden by wind, rain, or irrigation water.

Believe it or not corn smut is edible and is considered a delicacy in several countries. In Central and South America there has long been a tradition of eating corn smut (huitlacoche). Farmers there receive a premium price for their infected corn. In Mexico canned huitlacoche is available in grocery stores. However huitlacoche is just now becoming a gourmet item in the United States, with trendy restaurants in California and New York offering it. Because of the increasing demand, farmers in Florida and Pennsylvania, in cooperation with the USDA, have actually begun cultivating it.

Development of smut is favored by dry conditions and temperatures between 78 and 93o. Incidence is usually higher in nitrogen-rich soils or after heavy applications of manure. Any kind of injury to the plant tissue increases the potential for smut infection.

Plant corn as early in the season as possible after the soil warms to around 55o in the spring because common smut becomes more prevalent in later harvests. All corn varieties are susceptible to some degree. Leaving your garden free of corn for as long as possible will help reduce the number of spores overwintering in the soil. To prevent the spores from getting into the soil, remove and destroy them as soon as you notice them.

July 19, 2001