The drought busters – drought-resistant trees and shrubs

The drought busters – drought-resistant trees and shrubs – includes related articles

Dave Carty

It takes a tough tree or shrub to stand up to the West’s heat and scarce water. Here’s 10 that make the grade.

I have two words of advice for those who would drench the sere West in an attempt to grow water-loving trees and shrubs: forget it.

Not only is growing inappropriate plants a waste of water, it’s a practice whose moral implications can no longer be ignored. With city after western city listing lack of water as a near crisis-level problem, can this region really afford to saturate its blue-grass lawns and exotic trees with thousands upon thousands of gallons of this precious commodity? But since urbanization causes our cities to be hotter and drier than the surrounding countryside, doesn’t it make sense to plant trees, which can help cool this urban heat island?

What’s the answer? Drought-resistant trees and shrubs, which, botanically speaking, are nothing new, Many of the trees and shrubs indigenous to this region – the Dakotas south through western Kansas, then northwest through eastern Oregon and Washington – are quite drought-tolerant and hardy, and able to survive the region’s dry, cold winters. A few non-native trees are also common in this area, most established long ago and now as plentiful in some locales as the natives.

What qualities make a drought-resistant tree or shrub ideal for urban and rural use? Nurserymen interviewed in Colorado, Montana, South Dakota, Nevada, and Utah all had different ideas. Yet there were basic similarities: all lived in regions with less than 20 inches of rainfall a year (some with as little as 10), and dramatic temperature swings and dessicating winter winds were problems across the board. The trees and shrubs they picked had to be hardy and easily established, with at least a moderate growth rate. And they had to be relatively easy to care for as well as attractive, a quality that eliminated such otherwise drought-resistant plants as the scraggly buffaloberry shrub and the messy and bug-infested boxelder tree.

The 10 trees and shrubs outlined below are only a fraction of the drought-resistant species available, and all may not be ideal for your area. Add or subtract to the list as you wish. On the other hand, chances are most of them will work just fine, and with a minimum of care they’ll provide years of beauty in exchange for a few well-spaced sips of water.

None of the plants outlined here will survive everywhere; in actual desert environments even these won’t make it. But these trees and shrubs are already widely used in most other areas where low water consumption is important, provident sippers of our precious groundwater, offering beauty and shade for mere drops on the gallon.

Scotch Pine (Pinus sylvestris)

This is one of the few trees that almost everyone agrees on. Many pines and junipers are drought-tolerant, but scotch pine also boasts an impressive growth rate, ranging from a foot to 18 inches or more yearly, depending on location. It grows to an average height of 25-35 feet. Easy to establish, these trees are sold in most nurseries. Of the varieties available, one boasts a handsome bluish hue that is less likely to fade to yellowish-brown during the winter, a characteristic some people like and others don’t.

Scotch pines are widely used in windbreak plantings, particularly in the upper Rocky Mountain and Plains states. Once established they need little extra water except during prolonged dry spells. One caution: Scotch pines tend toward spindliness when grown without pruning (especially under very dry conditions). Because of that, they’re best planted in groups or clusters of several trees, rather than as lone, specimen trees.

Rocky Mountain Juniper (Juniperus scopulorum)

One of the toughest, easiest-to-grow trees available, the Rocky Mountain juniper – like scotch pine – sometimes turns brown in winter, but by late spring its color returns, ranging from flat olive to silvery blue. Because of their dense branches and symmetrical, pyramidal shapes, Rocky Mountain junipers work as well in yards as they do in rural windbreaks. They’ve long been a good choice for windbreaks because of their robust survival rate in the face of howling prairie winds.

They make excellent habitat for many species of game birds as well, particularly when deep snows bury other forms of cover. For those who prefer more natural landscapes around their homes, Rocky Mountain junipers work well as accents to set off groves of aspens or other deciduous trees; at an average height of about 20 feet, they won’t overwhelm the house or the landscape. In addition to their other attributes, they seem unpalatable to deer – one of the few plants these ungulate lawnmowers seem to avoid. About their only serious drawback is their slow growth, perhaps six to eight inches a year.

Green Ash (Fraxinus pennsylvanica lanceolata)

In much of the upper Midwest and western Plains states, stately green ash trees – some 60 feet in height – line the streets of cities and small towns. Those who planted these trees 50 to 75 years ago evidently knew what they were doing, and ranchers in surrounding areas took note. They soon discovered the green ash to be durable in windbreaks as well, often with very little supplemental watering.

Sharon Vaughn, a nurserywoman in Rapid City, South Dakota, is an enthusiastic green ash supporter. “They’re hardy, they don’t bud out quite as early as some of the other (deciduous) trees,” she says. According to Vaughn, green ash grows about a foot a year, which is average for the drought-resistant species outlined here.

Perhaps the nicest feature of these trees is their bright yellow fall color, which appears in late summer. In much of the West, the green ash heralds the beginning of autumn.

Ponderosa Pine (Pinus ponderosa scopulorum)

This is a large tree, sometimes reaching 80 feet or more in height. Once mature, the ponderosa pine’s dark-orange bark and spreading form make it an extremely handsome tree, suitable for just about any application except small yards or places where a full-grown tree could interfere with overhead power lines. It is drought-resistant, heat-tolerant, and capable of weathering severe winters.

Ponderosa pines love the sun, but they’ll also grow in shade. One problem is their susceptability to bark beetles, which have killed off thousands of acres in Colorado. Still, Gary Ludwig, a veteran nurseryman in the high-altitude, near-desert town of Buena Vista, Colorado, gives the tree his hearty endorsement. Of the plants listed here in this piece, only the ponderosa pine and Rocky Mountain juniper were spartan enough to earn his full recommendation.

Russian Olive (Efaeagnus angustifolia)

With its silvery foliage and two-inch spiny thorns, the Russian olive is a striking and formidable tree, used for years in western windbreaks and more recently as a decorative species in urban yards. Mature trees will grow 20 to 25 feet in height, and occasionally develop the picturesque form of Bonsai miniatures. They’ll grow in alkaline soil and just about anywhere else, and hold their leaves into late fall, providing a handsome splash of silver well past the time when other deciduous trees have lost their color. Their hard brown berries are relished by birds, and deer usually (but not always) leave them alone.

But Russian olives are not native to the U.S., and were not embraced by everyone I interviewed. Colorado’s Ludwig, for instance, considers them an invasive weed that is displacing native species across much of the Southwest. The Russian olive is a problem in some areas of the country but in others has long been considered a well-liked, attractive tree. As long as it’s not allowed to spread, it can fill a variety of drought-resistant niches.

American Plum (Prunus americana)

On mature American plum trees, the bark splits and peels, adding a rough attractiveness to a tree that already has plenty of attributes. Most American plums are small, but each spring they produce clusters of fragrant white flowers followed by a fruit used to make jams and jellies. Birds and deer love them too, so a protective fence may be necessary.

American plums are one of the smaller trees listed here, generally growing no more than 15 or 20 feet in height. Once established, they’re tough and durable, and although they need some water for good fruit production, they’ll get by on very little.

Nanking Cherry (Prunus tomentosa)

Nanking cherry bushes are exceptionally dense and will grow six or eight feet tall. In the spring they’re covered with light pink flowers, and in the fall their branches droop with small, red cherries. The cherries are on the sour side, but birds relish them. Although Nanking cherries have been used for windbreaks and hedges, they’re most attractive as accent plants that enhance groupings of other trees and shrubs.

Common Lilac (Syringa vulgaris)

There are dozens of species of this popular shrub, and colors range from white to wine-red. But the common lilac’s lovely light-purple hue is the best known.

If there is anything that sets off the lilac from other drought-resistant shrubs, it is its intoxicating aroma. In spring, when the sheer number of blossoms turns these shrubs to soft purple clouds, their delicious scent is distinct 50 yards downwind. This moderately fast-growing shrub produces a thick hedge of nearly impenetrable stems 10 to 12 feet high.

Caragana (Caragana arborescense)

The caragana, called the Siberian pea shrub, is extremely hardy and seems to thrive in dry locations. Perhaps the caragana’s most notable characteristic is its pea-like pods that dry and then crack open during hot weather. Splitting pods make an audible pop, and sitting beside a caragana hedge in August or September is akin to sitting before a giant bowl of Rice Krispies. The plants grow quite rapidly, particularly if they’re given adequate water when young. They average about 10-15 feet in height. Unfortunately, some caragana bushes defoliate during extremely hot weather. This won’t kill the plant, however, and they’ll leaf out again the following spring.

Western Chokecherry (Prunus virginiana demissa)

An extremely tough, fruit-bearing shrub that, when properly pruned, will develop into a handsome, multi-stemmed small tree. As trees they can grow to 25 feet in height, but as shrubs they usually peak out at 15. Because they sucker heavily once established, they make good, thick hedges.

Although the tiny black fruit is much too tart to eat raw, it makes an excellent jelly and pancake syrup. But you’ll have to pick the berries quickly once they ripen, since they’re a favorite of robins and other fruit-eating birds.

RELATED ARTICLE: Bare-Root or Container-Grown?

It’s hard to compare the two forms of plants sold in nurseries because there are advantages to each. Container-grown trees and shrubs can be, and often are, expensive. And the larger the container, the more expensive they get. Despite that, they’re the most popular way to buy plants, for two reasons: They’re relatively care-free. Depending on their condition, most container-grown plants don’t need to be pruned; simply slide them out of their containers and into a water-filled hole in the ground. Second, they suffer relatively little transplant shock and may put on growth immediately. Consequently, they’re more likely to survive than bare-root stock, in which mortalities can reach 50 percent.

On the other hand, despite the extra care that is initially involved, bare-root trees and shrubs are usually used where large swaths of plants are desired, as in windbreaks and hedgerows. They’re far cheaper than container stock, and although they often suffer transplant shock, which drastically slows their growth for a year or two, individual plants are relatively cheap to replace should they die. Bare-root stock must be planted in the spring, however, prior to bud-break.

A couple of tips will increase bare root survival. First, prune back the tips of the roots; this will eliminate the dried-out ends, allowing the plants to more readily absorb water. Second, trim back the tops as well, cutting the side branches and leader (the main stem) back to the next bud down the stem. Finally, remember that the roots must always remain moist. If you plan to plant the next day, soak the plants overnight. Some nurserymen suggest adding vitamin B-12 (which can be bought at nurseries in liquid form) to the water; others claim they’ll do fine without it.


RELATED ARTICLE: A Helping Hand for New Plants

A misconception among those unfamiliar with drought-resistant plants is that, once put in the ground, they’re able to fend for themselves. Not true.

Even super-hardy trees like Russian olives and Rocky Mountain junipers need supplemental watering for the first few years of their young lives. Although farmers and ranchers for years have used floor irrigation and sprinklers to establish windbreaks, some form of drip irrigation is much more efficient for homeowners. It slowly saturates the ground around the roots with very little loss from evaporation. My favorite is a product called T-Tape, manufactured by T-Systems International in San Diego, California. It’s cheap, it’s durable, and it works.

The experts I interviewed differed somewhat on the amount, but most recommended thoroughly soaking new trees and shrubs at least every couple weeks for the first summer, watering less frequently, but just as thoroughly, during succeeding years. A good fall soaking just before the first hard freeze helps the plants store moisture for the long, dry winter to come.

Weed control is often overlooked but necessary to the successful establishment of any tree or shrub. Grasses are particularly pernicious thieves of water and nutrients. Dan Mecklenburg, a Mecklenburg gardens in Bozeman, Montana, recommends fallowing the soil – tilling or turning it over to expose the bare earth to the sun – for an entire year prior to plating. “If you summer fallow the land – fallow it for a while year before you plant, and get the ground so that all the organic matter is decomposed and there’s no competition, you will not believe the growth you get,” he says. “It’s a whole different proposition than sticking a tree in the sod. You’ll see three times the growth in trees planted in summer fallow than in trees planted in your lawn.”

Fallowing isn’t always possible, of course, but other measures may help. One is a once- or twice-yearly application of some form of herbicide (Roundup is commonly used) around the base of the plant. Many of those uncomfortable with chemicals choose to apply a thick layer of mulch instead, which conserves moisture and, depending on the mulch used, returns nutrients to the soil as it decomposes.


RELATED ARTICLE: A Word About Xeriscaping

Water shortages are nothing new in the West. But in the 1980s and ’90s, a critical lack of water and a persistent long-term drought forced the city of Denver to adapt radical strategies for lowering water consumption on suburban and city lawns. The result was xeriscaping, a word derived from the Greek “xeros,” which means dry, and “scape.” which means landscape.

In the mid-’80s Colorado’s landscape industry and the Denver Water Department joined forces to lower water consumption and maintain the city’s attractive, green landscaping. Their xeriscaping project was meant to conserve water through creative landscaping, and included seven key suggestions for a water-efficient, drought-tolerant garden or landscape:

1. Group together plants with similar water needs.

2. Keep lawns small.

3. Use efficient irrigation systems, e.g., drip irrigation systems.

4. Amend soils to increase their water-holding capacity.

5. Apply mulches to retain moisture.

6. Use drought-tolerant and native plants.

7. Stress regular maintenance.

Xeriscape aficionados say the savings m water use can run as high as 80 percent.

The National Xeriscape Council, Inc. was created in 1986 with a goal of teaching the rest of the country how to apply principles outlined by the Denver Water Department. The council has since disbanded, but the term has become a permanent part of the landscapiug vernacular, and is often used to refer to any number of water-conserving methods used in drought-tolerant landscaping.


Dave Carty is a freelance writer in Bozeman, Montana.

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