Volunteers are not always welcome in the garden. Sure, there’s plenty of work that needs to be done and any free help would be appreciated. But a certain kind of volunteer may be no better than a nuisance or a pest.
Volunteers are seedlings of ornamental or edible plants that appear as if
from nowhere and grow vigorously without human assistance. Tomatoes and Swiss chard are famous examples. They appear to come from nowhere until you remember your tomatoes and chard from last summer. Still, you can’t quite explain how they got to the precise garden spot where they are now growing.
Confounding, isn’t it, how you slave to get certain seeds to germinate and then, all by themselves, they come up like so many weeds? The lesson here, of course, is that seeds are usually planted too deep. Most of the time, if seeds are merely laid on the surface of a lightly cultivated soil and covered with a little compost, they will germinate just fine.
Some volunteers can be absolutely fatal to a landscape if allowed to reach their full potential. In the September 1995 issue of the Western Arborist, the horrifying tale of the Shamel ash (Fraxinus uhdei) is told.
Mr. Shamel was a tree lover who lived in the Riverside area 50 years ago. Once, while visiting northern Mexico, he noticed a remarkable ash tree of evergreen habit that he thought would grow well in his own Southern California. He took a number of cuttings from this medium-size tree and brought them back to Riverside for further propagation.
Mr. Shamel had no idea what trouble these few cuttings would ultimately bring. True, they developed into handsome trees, but instead of taking more cuttings, in turn, from them – which would have continued to develop into predictable, average sized trees – seeds were harvested and sown.
What came from the seeds were entirely different trees, “100-foot monsters that break curbs and sidewalks and disperse seeds over a vast area, resulting in ‘arboreal weed’ growth and creating a horticultural nightmare.”
It was not Mr. Shamel, by the way, who planted these seeds of destruction, but some enterprising folks who wanted to make a few dollars growing ash trees the easy way.
If you happen to have a fully grown Shamel ash in your yard or near your garden, you will have spent many, many hours by now uprooting its seedlings. Shamel ash seedlings germinate with astonishing ease in every kind of soil, and will even do so in the leaf litter that accumulates in the crotches of trees.
Other volunteer trees commonly encountered include the Chinese elm (Ulmus parvifolia), the edible fig (Ficus carica) and the Southern California black walnut (Juglans californica). Chinese elms are briefly deciduous 60-foot trees with small, dark green leaves and mottled bark.
The behavior of fig tree volunteers is entirely unpredictable. In the garden of Rose Bilski, a horticultural expert whom I have come to know, a volunteer fig tree has attained good size and produces fairly well, except that all the fruit falls off before it ripens. Then again, I have seen volunteer fig trees that ripen sweet fruit year after year. Fig tree seedlings are like children. You never know how they will turn out until they have actually grown up.
The Southern California black walnut is a tree or large shrub that grows to about 20 feet high and 20 feet wide. It is moved around Los Angeles by squirrels – and perhaps birds – that swallow and excrete its seeds. This walnut is much smaller than the English or Persian walnut (Juglans regia) that was once grown commercially in the San Fernando and San Gabriel Valleys. Nevertheless, the Southern California walnut is tasty enough once you manage to crack open its frustratingly hard shell.