Foreigner Plants Invade Local Woods- Natives Up In Arms, Demand Quotas - by Tom Spencer / Soul of the Garden
Yesterday, I took a walk with a friend of mine to his “secret place,” an isolated patch of Hill Country wilderness located on the property of his employer. He took me there to collect some honeycomb limestone that he had found. He knew that I like using “holey” limestone as an accent in my garden and we were hoping that we’d find some cool looking pieces. As we walked, I was impressed by his knowledge of the area- he recounted stories of seeing deer and other wildlife along the trails including a face-to-face encounter with a fox- apparently neither party wanted to blink and the stand off lasted for several magical minutes. Eventually, we found the cache of stones and it was a good one. I collected a few especially holey stones and we set off back to the car.
As we hiked down the trail, I kept spotting familiar shapes amid the twisted juniper and oak thickets. As it turns out, we were not the only invaders in this otherwise pristine space- nearly everywhere I turned I saw nandina shrubs and Japanese ligustrum, chinaberry trees and yarrow- all species of plants not native to the area, but “escaped” from cultivation.We may have been the only humans to walk down these paths in years, but the footprints of man were growing everywhere.
Since October is the ideal month of the year to plant most species of trees and shrubs, I thought it might be worth a few minutes of your time to meditate on the use and abuse of non-native plants. Over the course of the past twenty years, I have advocated for the use of native plants, but I have tried to steer clear of natives-only dogma. To me, just the term Texas-native has always been problematic; a plant is may be native to the swamps of East Texas, but that does not make it better suited to the slopes of the Hill Country than a well-adapted specimen from Mexico or China. And, besides, there is no evidence that some of my favorite native Texas plants, like lacey oaks or bigtooth maples, ever grew in this part of Central Texas. So, can I even recommend them as native?
The term native has become as political as the boundary lines we draw on maps. The problem is that plants don’t care which side of the border they are growing on. Still, one of the primary causes of native plant extinction in the United States is loss of habitat to non-native invaders, so when I saw those otherwise unremarkable plants growing in my friend’s remarkable little wilderness retreat, alarms starting going off.
There are too many excellent plants that from exotic locales for us to ban them all from our gardens. The best of these are plants that will not escape from cultivation (read cannot reproduce) and have proven them selves to be Texas tough. However, that being said, there are some plants that are highly irresponsible for us to use. I usually try to write positive things about plants I love, but what follows is a list of plants that we should avoid, especially if we live in areas close to preserves or natural habitat.
The various forms of japanese ligustrum, or privet, are noxious weeds with little redeeming value to our home landscapes. These large shrubs attract garden pests, like white fly and scale, by the droves and escape cultivation courtesy of the birds that gorge on their berry like fruits or drupes. Ligustrums look absolutely horrible in the typical Central Texas summer, but they manage to hang on even during the worst of droughts. My advice is to never use these and to remove existing specimens where possible. If removal is not an option, at least take the precaution of pruning off the fruit clusters before they ripen. This plant has become ubiquitous in nearly all settings surrounding Austin, even in the roughest canyons where it out competes many slower growing natives.
Golden bamboo (Phyllostachys aurea) is a notorious invader. This plant should never be planted unless it is within a strictly confined area, like the enclosed courtyard of a home. Golden bamboo is a lovely, tough plant, but if left to its own devices it will not only escape cultivation- it will over run civilization. If you have bamboo running amok on your property my advice is to cut it to the ground, immediately, then suppress any secondary growth. (Supress being a euphemism for spraying it with liquid death.) My backyard used to be a sea of bamboo; I eradicated it by using the technique described above. We keep it at bay by using a heavy-duty plastic bamboo root barrier that runs along the perimeter of my yard to a depth of three feet.
Nandina is a much trickier issue. This tough shrub comes in a multitude of different forms and is an attractive determined survivor, a plant that deserves our admiration for enduring just about any garden indignity that Texas throws its way. The only problem is that the bright red berries attract birds that tend to be somewhat indiscriminate about where they “deposit” them. As a result, nandinas are popping up in nearly every patch of wilderness in Central Texas. What to do? My advice is to stop planting nandina in all areas except in the urban core. This may not eliminate the problem completely, pardon the pun, but it will at least prevent direct deposit into wilderness areas.
Central Texas attracted many of us to it because of its unique identity and beautiful setting. It would be a shame if we gardeners bury what sets us apart in a sea of escapees.
Return to Soul of the Garden Library