Native Plants

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Sunday - August 03, 2008

From: Arroyo Grande, CA
Region: California
Topic: Invasive Plants, Non-Natives, Pruning, Shrubs
Title: Pruning of Grape Kool Aid Plant in California
Answered by: Barbara Medford

QUESTION:

I have a Grape Kool Aid plant and was told it would grow to 6 or 7 feet tall, but it is well over that and I need to know if I can prune it and if so how?

ANSWER:

Is this a test? Is somebody out there trying to trick Mr. Smarty Plants into making a mistake? Well, it's not hard, but maybe we dodged the bullet this time. Turns out there are two plants referred to as Grape Kool Aid Plant, one native to Texas and New Mexico and one to Africa.

Our first thought was that you were referring to Sophora secundiflora (Texas mountain-laurel. The flowers of this tree (see pictures below) are said to smell like grape Kool-Aid. Personally, we never stick our nose into flowers pollinated by bees, but that's what we're told. At the Lady Bird Johnson Wildflower Center we are devoted to plants native to North America, and planted in the area to which they are native, because they are accustomed to the conditions and will require less water, fertilizer and maintenance. The Texas mountain laurel is basically a desert tree, a legume with very poisonous seeds but absolutely beautiful in the blooming season of February and March. A member of the Fabaceae (pea) family, it is native to the Texas Hill Country and is often found growing among granite rocks. We did find indications that it is being grown in California, but found no information on pruning it. Ordinarily, pruning for shape and to remove damaged limbs would be about the limit. Dispose of prunings carefully, as all parts of the plant are poisonous. We always recommend pruning during the dormant season, mid-winter in California.

On the other hand, we suspect that you may have Psoralea pinnata in your garden. This is a native of Africa, also a member of the Fabaceae family, which blooms in Spring and again in late Summer. It grows 8 to 10 feet tall and 10 feet wide. The flowers also are purple and smell grapey, so maybe it's the color, who knows? Again, we found no information on pruning, but would still recommend pruning for shape. It is a short-lived tree but is prolific in seedlings and suckers. It is, in fact, classified as an invasive in Australia, so that might be a risk in California which is such a good place to grow, invasives love it. Again, prune in mid-winter.

Probably the only way you can be sure which plant you are dealing with is the leaves. On this page of images of Psoralea pinnata, you can see that the foliage is needlelike, although we understand it is soft and non-allergenic. In contrast, as you can see from the pictures below, the foliage on the Texas mountain laurel has shiny, leathery compound leaves made of 7-9 leaflets that are rounded at the ends.