Friday, September 7, 2012
Interest in drought tolerant plants is increasing as the specter of less reliable, and less abundant rainfall settles in. But the term ‘drought tolerant’, while thrown around a lot, is rarely clear or terribly exact. It is meant to indicate plants that survive through drought conditions, look good despite great heat or extravagant watering. But just how well a given species performs, or how little water you can use to get it through is a voodoo art at best. Identifying the parameters of drought tolerance is an arduous business. Most of us don’t want to leave our plants to their own devices long enough to let them wilt, or nearly die, to find out just how low they can go. Yet that is what it takes to know for sure.
Instead we rely on experience, both our own and that of others, to provide clues for how often to water them to keep them fit, how long we can go between waterings, or whether they will survive our vacation plans.
It was this entirely unscientific approach to drought tolerance that pointed out the sturdiness, and yes drought tolerance, of two plants I never would have guessed to be so tough - pittorsporum (Pittorsporum tobira) and Japanese yew (Podocarpus sp.).
We inherited two pittosporum and one yew here at the South Texas house. Considering their size, they have been here a long time, possibly the life of the house which is just over 50 years. They form a loose row along the western side of house, sheltering bedroom and bathroom windows from the afternoon sun. During the year and half that the house was for sale they, like most of the yard, were not purposefully watered. To make matters even more dire for this trio, it was a record drought year with half of normal rainfall coupled with higher than average temperatures.
Once we moved in, we continued to neglect them leaving them to meet the weather on their own. From the first we planned to remove them. Why waste the water? we said, we will just leave them there until we find plants we prefer.
But plants hold surprises for me every day. Although there has more normal rainfall this calendar year, I still never water them. They just sit there all on their own. One day, I looked at them, fully leafed out, vigorous, and recalled their short history during our time here. It was then that I spent a moment of shame for thinking of them as unworthy of a garden on the dry side. These are highly adapted, drought tolerant plants right under my nose. It is just that I didn’t consider them that way.
In my mind, these two species fell into the category of water thirsty plants through what I call the theory of association. When I lived in Phoenix, the plant that defined this attitude was oleander (Nerium oleander). It grew everywhere but particularly in the old flood irrigated neighborhoods. Therefore, it was widely, and loudly reviled, as a terribly thirsty plant. But the truth is that it is one of most drought tolerant plants on the earth, right up there with creosote. It was identified with its neighborhood, not with its own performance. Its association with vast swaths of lawn created the illusion of a water-needy species.
Here I was falling into the same trap with these two Asian species. Sure I can read in California publications that they tolerate heat, maybe even drought, but I learned a long time ago that what my dear friends in California west of the Coachella Valley call heat is only a faint shadow of the real thing. Both have been in horticulture a long time, well over 100 years. Both come from Asia (although there are Podocarpus species in Africa) and have been hideously overused in medians, commercial plantings and countless home gardens.
I simply dismissed them as denizens of gardens that relied on lawns and other water-thirsty plants. I was wrong, on all counts about these two.
Opinions based on prejudice or half-truths are always flawed and these two species have provided me with a valuable lesson in not taking too much for granted where plants are concerned. So my new pledge is that the next time I come across a plant that doesn’t fit into my garden plan, is just too common for words, or appears not to have the level of drought tolerance I want, I will take the time to find out more. Then, even if I cannot love it and won’t have it in my garden, I will be casting it aside for a clear reason, not simple ignorance.
Waiting patiently for the saw, demanding nothing, taking very little, it seems a shame to consider getting rid of such great performers. But I just can’t love them. I cannot see how they fit into the vague but emerging plans we have for the back garden. So the day will come when plans are more settled and they have to go. I can’t say that I will miss them, but they have certainly impressed me with their stamina and vigor.
So if these two dense, evergreen shrubs fit the look and style of your garden, they will indeed need only the most minimal care and watering. They are clearly able to live on the rainfall regimen of South Texas, no matter where they come from or how long they have been associated with much more water intensive plantings.