In the Garden: Cashews, Mangos, Pistachios and Poison Ivy?!

Rhus glabra in its fall colors (Photo: Ellen Honeycutt)

These four plants actually have something in common. They’re all members of the Cashew Family, the Anacardiaceae. Some members of this family are a lot more people-friendly than others, however.

Among the tropical Anarcardiaceae, the familiar cashew (Anarcardium occidentale) is native to northeastern Brazil and widely cultivated in warmer regions. The cashew nut may readily be eaten by most of us, although 5 percent of the population is allergic. The cashew shell is more problematic, containing a potent skin irritant related to urushiol, the nasty substance found in poison ivy and poison sumac. Roasting destroys the anacardic acid in cashew shells, but according to Wikipedia this must be done outdoors. (I presume you might want to stand pretty far upwind from the smoke! And this is not the same thing as roasting raw cashew nuts at home. Here the shells have already been removed.) Mangos are another tropical member of the cashew family; Mangifer indica is the species most commonly cultivated in warmer regions.

As for species from temperate regions, I had once championed the Chinese Pistache (Pistacia chinensis, a cousin to the edible pistachio) as a good landscape tree. Now I am having my doubts. A small, drought-tolerant tree with brilliant fall color, it is reportedly becoming invasive further south and west. Plus, I have seen trees that appeared to be less than healthy, perhaps owing to clay soils and too much water. Probably better to avoid this plant.

I hope everyone who spends any time outside is familiar with the ubiquitous Poison Ivy (Toxicodendron radicans, formerly Rhus radicans). “Leaves of three, quickly flee!” etc. Much less well-known but actually more deadly is Poison Sumac (T .vernix or Rhus vernix). A large shrub or small tree, fortunately for us it is generally uncommon in Virginia except in swamps.

Despite some bad players, several members of the Cashew family can work in your garden. The sumacs (Rhus), large shrubs or small trees, can provide outstanding fall color, attractive fruits, and bold form in the right situations.

Several of the sumacs are native to our area, so you might already have one on your property. The Smooth Sumac (Rhus glabra) and the Winged or Shining Sumac (R. copallina) are common across most of Virginia. Both have large, compound leaves with many elongate leaflets; in the fall, the medium-to dark green foliage will turn crimson red on the former shrub, and to yellow, orange-red or purple on the latter. Greenish-yellow flowers appear in early summer on Smooth Sumac, late summer on Winged. Fruits that follow in the fall are showy crimson-to-scarlet clusters measuring 4” to 8”. Neither of these sumacs are small in any sense of the word, with heights between 10 and 20 feet and with an equal spread. In fact, their suckering nature means rapid spread may be their greatest virtue—if you want to cover a lot of ground—or their greatest vice.

Given their running nature, planting these sumacs around any other plant is not advisable. If you have a “wild” area on a large property, plant them where they have “plenty of room to romp,” as some of the plant catalogs phrase it. On a smaller property, you might be able to contain them with a driveway or some other concrete barrier. Otherwise, plant your sumac in the middle of your lawn and mow around it to remove the suckers. Also, consider the texture of sumacs in any design scheme. Fairly coarse even when in leaf, in winter the stout bare stems can look gaunt. Or perhaps “architectural” if you want to put a more positive spin on it. Putting one in front of a wall would highlight the form; just make sure it’s not the wall of your house, or the suckering shoots might pop up in your living room.

Another species among the large sumacs offers an alternative to rampant spreading, at least in one variety. More common in the mountains and up north, Staghorn Sumac (R. typhina) gets quite large as the straight species, easily growing to 15’ to 25’ in the landscape. Its hat-rack growth habit and velvety hairs on the younger stems resemble a deer’s antlers. Like other sumacs, female plants will have bright crimson fruit clusters in the fall, along with brilliant foliage. ‘Dissecta’ and ‘Laciniata’ are two cultivars—or perhaps just one plant with two different names— featuring finely dissected fern-like foliage. These varieties both still run and grow to large proportions, however. A reasonable option for smaller spaces is the variety Tiger Eyes (officially known as ‘Bailtiger’), reportedly only reaching 5’ to 10’ at maturity and not suckering as much as the larger varieties. Tiger Eyes is arguably the showiest of the sumacs, with bronze-yellow new spring growth, maturing to yellow-green in summer and closing out to orange-red in the fall.

One more sumac is much tidier in size, growing only to 2’ to 6’ in height and suckering to a width of about 10 feet. A cautionary note: Fragrant Sumac (Rhus aromatica) has a scary resemblance to poison ivy; if you had both plants on your property, someone could make a serious mistake. The major difference: poison ivy’s central leaflet in the cluster of three has a noticeable stem; fragrant sumac’s central leaflet joins the other two directly. Also, fragrant sumac does not climb. If you’re adventurous, the straight species, as well as the cultivar ‘Grow-Low’, are available from Lazy S’S Farm Nursery by mail order..

All these sumacs are not fussy about growing conditions, as long as they’re not water-logged. Full sun, dry, rocky soils or Virginia clay are just fine, which means they would be perfect for reclaiming a nasty bare slope or a road cut.


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