Pacific Northwest

October, 2009
Regional Report

Favorite or New Plant

Lemon Verbena
Lemon verbena (Aloysia triphylla) isn't what I consider an attractive plant, but it makes up for its natural unruliness by producing a pungent, clean, sharp, lemony fragrance that I love. On a sunny day the fragrance permeates the entire garden, and touching the leaves releases even more fragrance.

The plant will grow to 6 feet or more and has narrow 3-inch leaves arranged in whorls of three or four along each branch. If it is pinched and pruned, it can be trained against a wall where heat from the sun will intensify its fragrance.

While it appreciates a light and well-drained soil, poor soil produces stronger plants able to survive cold winters. Sow seeds in the spring or take softwood cuttings in late spring to propagate. I harvest the leaves and dry them to add to potpourri or dessert recipes. This way I can enjoy the sunny lemon fragrance all year long.

Clever Gardening Technique

Fall Webworms
The insect pest commonly known as fall webworm is beginning to make its annual appearance. People often confuse fall webworms with another pest, the tent caterpillar, which is active only in the spring season. Fall webworm is only considered a nuisance while tent caterpillars can cause serious problems.

Fall webworm caterpillars (larvae) produce a web of fine silk over the terminal branches of more than 100 deciduous tree species. Some favorite trees are elm, ash, alder, willow, poplar, walnut, sweet gum, and fruit trees. The caterpillars feed only within their silk nest. Nests become quite unsightly over time as they expand and the branch tips within them become defoliated. Webworm feeding causes no health danger to the tree, but it lowers the overall beauty of the tree because their nests are ugly.

The caterpillars occur in two forms: black heads with yellowish white bodies, and red heads with brown bodies. Both forms have black spots on their backs. Adult moths are about 3/4 inch long, with wings of all white or white with black spots.

There are 86 different predators and parasites of fall webworms and, given the opportunity, these beneficial insects generally keep pest populations under control. A biological control is also available (Bacillus thuringiensis var. kurstaki), but it is best applied in August when caterpillars are small. I like to give the beneficial insects time to do their work, but I've also pruned out some unsightly fall webworm nests. If you opt to use Bt, be sure to read and follow all label directions.

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