Introduction to Hardy Bamboos
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Promoting the Beauty and Utility of Bamboo

Earle Barnhart and his wife, Hilde Maingay, have a landscaping business called Great Work, Inc. in Massachusetts. Great Work specializes in what they call “ecological landscapes", where many of the plants are herbs and food plants, areas for wildlife have been preserved and the emphasis is on using natural processes to maintain the health of the garden. Bamboo plays a prominent part in their landscaping.

Earle is an ABS member who has known the joy of bamboo for a long time and wrote an article about it for Fine Gardening magazine in 1989. The article is particularly about growing temperate bamboo in New England, where many people may not expect to see bamboo flourish, but it does.

Earle’s article touches on many subjects that are of interest and use no matter where you live and the species you plant.

In the article there are references to bamboo species that are highlighted by your Web browser. These highlighted words are links to the ABS Species Source List entry for that plant.

This article first appeared in Fine Gardening magazine in 1989. It is reproduced here with the permission of Mr. Barnhart and of Fine Gardening.

If you are interested in particularly hardy species, have a look at the index of bamboo that members have reported surviving temperatures of -5°F and colder.

The beginning

It’s midwinter as I write this, and outside my window stands a grove of bamboo - tall, green, and swaying gently in the breeze. Ten years old, its straight, strong culms are 25 ft. high and the largest are 1 1/2 in. thick. From it, each spring I enjoy a feast of succulent bamboo shoots to eat, and each winter I cut strong poles for building gates and fences. Most American gardeners would not think it possible to grow bamboo here in New England, where the winter temperatures drop below 0°F and the ground freezes solid. But there the bamboo stands - elegant, serene and useful.

Bamboo is a rare plant in American gardens, particularly northern ones. There were not native bamboos in Europe or in early European landscapes, which is where American landscape design draws much of it inspiration from. And, as most of the bamboo species grown in the United States today originated in Asia, many gardeners assume that all bamboos need warm climates. (The two native North American bamboos, canebrake and the smaller switch cane, were eradicated by early farmers because they grew in the richest soils best suited for crops.) What’s more, many introduced species are rapid spreaders and have been stigmatized as invasive pests.

I became interested in bamboo when I moved to Cape Cod, Massachusetts, in 1972 to work with the New Alchemy Institute, a research and education group seeking safer and more energy-efficient ways to provide basic human needs. Of the world’s major crops and trees we surveyed, bamboo stood out as a superstar, used by more humans on the earth for more different purposed than any other plant.

To my amazement, I soon found impressive stands of bamboo growing on the Cape, cultivated by a few local gardeners. The plant was yellow-groove bamboo, Phyllostachys aureosulcata, a cold-hardy species from China imported by the USDA decades ago and since then wide distributed because of its hardiness and edible shoots. The elegance of these tall, fully mature groves inspired me to include bamboo in my garden.

In April 1977 I transplanted several culms of yellow-groove to my property. I placed one against the north side of a building, six in the open by a parking lot to become a windbreak and four on a steep north-facing slope that was bordered by another building 40 ft. away. The first winter taught me a lesson about the conditions yellow-groove needs in order to survive in this climate. Plants sheltered by either building from the full force of the wind tolerated our coldest temperature, -5°F, while plants in the open were freeze-dried and killed. I also learned that when frozen leaves and culms are exposed to direct sunlight, they can be damaged and killed by drying. If the leaves wither, but the roots aren’t killed, the plant will produce new leaves in the spring.

Since that first winter, I’ve planted and observed bamboo here on the Cape and in numerous landscaping jobs I’ve done around southern New England. I’ve used the bamboo planting on the steep slope as my major test plot, where I observe hardiness and growth and measure the yields of edible shoots and useful poles. Because of its multiple uses and hardiness, I’ve done most of the backyard research with yellow-groove bamboo.

In the spring of 1980, however, I began a hardiness test with 17 other bamboo species started from divisions I took at the USDA’s bamboo collection in Savannah, Georgia (now operated by the state of Georgia). Planted on the north and south sides of a barn at the New Alchemy Institute, the plants were subjected in the two following years to unusually cold winters. Some plants were killed completely, others were killed to the ground but re-sprouted in the spring, and some suffered only leaf damage. Five species - Phyllostachys angusta, P. bissetii, P. congesta, P. flexuosa and P. nuda - seemed as hardy as our local P. aureosulcata.

There are more bamboos suitable for northern gardens than the ones I’ve tried. I’ve talked gardeners who grow bamboo in temperatures as low as -23° F. The chart lists some hardy bamboos that are commercially available. It’ s based on information from the American Bamboo Society, a nonprofit group of bamboo enthusiasts that works to expand the range of bamboos available in the United States, sponsors testing and publishes pertinent information.

How bamboo grows

Despite it’s treelike structure, bamboo is actually a giant grass. Like many grasses, it self-propagates by spreading underground, or “running.” The culms (the above ground stems) in a grove are all connected by a network of rhizomes (the underground stems), and the grove acts more like a single plant than many separate ones. Unlike other grasses, however, bamboo plants rarely produce seeds. If they do, it may be at intervals of 15 to 60 years or more, and the plants often die after seeding. Interestingly, all plantings of some species seed at the same time, no matter where on the earth they grow.

Most hardy bamboos are invasive. Their rhizomes can grow as much as 5 ft. in a year, and a healthy, uncontained grove may double its root area every year. Varieties that spread this vigorously are called running bamboos. A few hardy bamboos and most tropical species are much more restrained growers. The rhizomes of these noninvasive, “clumping” bamboos grow only several inches or so a year. (Two hardy clumping bamboos, Fargesia nitida and Fargesia murielae, which are grown extensively in Europe, are now available here. See the chart for sources.)

Bamboo makes three strategic bursts of growth each year. On the Cape, the first occurs in April and May. As sunlight, warmth and rain increase, new shoots appear throughout the grove, roughly two shoots for each existing culm. Within a month or two, they've grown into full-sized culms. In June and July, after the new shoots are in full leaf, the older culms gradually drop their leaves and simultaneously replace them with a new set. Finally, in late summer and full, the grove extends its rhizomes into new territory, and stores large quantities of nutrients in the root system in anticipation of spring. Bamboo maintains its evergreen canopy of leaves year round.

Overlaying the grove’s annual cycle is the life cycle of each single culm. A culm starts life as big around as it will ever be - a new shoot emerges at full diameter, which for some tropical bamboos may be 5 in. or more. During its short, intense growth spurt, a culm can add a foot or more a day in height. In the next four or five years, the culm’s outward appearance changes little. Inside, however, hard silica is being deposited in the fibers, which helps give bamboo its extraordinary strength. Where I live, a culm dies after four or five years, its gradual demise indicated by a change in color from green to tan or gray.

In the first few years, a new planting of running bamboo spreads slowly, but then growth picks up. In addition, each year’s new culms are larger in height and diameter than the previous year’s, those in the center of a grove emerging larger than those on the perimeter. My biggest planting, which now covers 528 sq. ft., started in 1977 as four small clumps of yellow-groove spaced 10 ft. apart in a line, each clump having two or three culms, 10 ft. tall and 3/4 in. in diameter. By the fifth year, the clumps had grown together, and the largest culms were 18 ft. high and 3/4 in. in diameter. Now, after ten years, the tallest culms are more than 25 ft. high and 1 1/2 in. in diameter.

Starting and caring for bamboo

Hardy bamboos are tough plants. They’ll tolerate almost any type of soil unless it’s waterlogged. Slopes don’t bother them. They like sun, but will grow in shade, though not as big. Bamboos are reported to prefer sandy loam soil and moist air. On the Cape, our humidity averages 75%, but our soil is pure sand under 4 in. of poor topsoil. The bamboos thrive here.

I’ve started almost all my bamboos by taking large divisions from existing groves, bushel-basket-size root balls with two or three culms each. Mail-order suppliers send much smaller plants, which take much longer to mature. My mail-order clumping bamboos arrived in pots with 1-gal. root balls and one culm each, a foot or so high and thick as a knitting needle. Two summers later, they each had five culms, chest high and pencil thick.

Whether you buy mail-order or divide an existing clump, the procedure for planting is the same. I’ll describe how to divide and transplant from an existing clump. Ideally, the larger the clump of bamboo transplanted, the faster the new grove will develop. In practice, however, I’ve found bushel-basket-size root balls the easiest to handle. To divide bamboo, take the clump from the edge of an existing grove in spring before shoots appear. I use a very sharp spade to cut straight down in a ring around the clump, being sure to cut through the two or more tough, woody rhizomes connecting it to the rest of the grove. Bamboo is shallow-rooting, so after cutting around the clump you can pry it up and out like a cork from a bottle.

When transplanting, it is crucial to keep the plant from drying out. I give the roots a good soaking the day before digging. Immediately after digging, I wrap the roots and foliage in polyethylene. An added precaution is to cut off the upper two-thirds of the culm, leaving just a few branches. This greatly reduces water loss through transpiration, and the transplants almost always live. But the plant looks terrible for at least a season. For my landscaping jobs, where appearance counts, I leave the culms whole but cut off every other branch. Protect the clump from the sun so it doesn’t bake in the plastic. I try to transplant as soon as possible, but I’ve successfully kept clumps for several days by wrapping only the roots and keeping the clump in the shade and out of the wind. (The mail-order bamboo I’ve received was wrapped in plastic and had no dehydration problem.)

I make the transplanting hole a bit wider than the diameter of the root ball, but never deeper than the ball - the plant doesn’t grow down. I loosen the soil back 1 ft. around the perimeter of the hole and add compost, or sprinkle a handful each of bone meal, blood meal and cottonseed meal in the hole and around the edges. Until the roots become established, a clump of untrimmed culms can be blown over by a stiff wind, so you might want to stake it for a couple of months.

For a few days after transplanting, I dump a 5-gal. bucket of water on the clump, In the following days I watch the leaves. If they begin to curl, I give the plant another bucketful. Our normal precipitation, about 3 1/2 in. per month, is enough for plants once they're established. In more arid areas, you may want to mulch.

Established bamboo requires only minimal care. Like lawn grass, bamboo grows faster, larger and greener if fertilized. In early spring and midsummer, I sprinkle 1/8th in. of chicken manure and composted leaves on the soil among the culms. In theory, commercial lawn fertilizer would work, too, though it lacks important trace minerals. Even with no annual fertilizer, however, bamboo generally will still thrive; it simply will remain smaller.

Keeping bamboo from spreading

A solid barrier wall in the ground completely surrounding the grove is the simplest and surest way to contain running bamboos. It takes work to install, but far less than removing unwanted bamboo. In China, a deep ditch of water is sometimes used because bamboo won’t grow in saturated soil. Contrary to common opinion, mowing off new shoots that appear where they're not wanted will not necessarily stop bamboo from spreading. The people at the USDA in Savannah told me that despite constant mowing around each of their plantings, rhizomes would routinely spread under the grass and eventually push up new culms in unmowed areas 20 ft. to 30 ft. away.

I make barriers from rolls of thin fiberglass sheet, normally used to cover greenhouses. I use Kalwal, which is made and sold by Solar Components Corp. (88 Pine St., Manchester, NH 03105; 800-258-3072). It can be bought in a variety of widths and lengths, and sells for $1.19 per sq. ft. plus shipping.

In my sandy soil, where the nutrients are in the top 12 in., a barrier extending about 18 in. underground is sufficient, in other conditions, barriers at least 24 in. deep are recommended. I dig a trench around the area to be filled by the grove, put the fiberglass vertically in the trench and back fill. I overlap the ends by a food and back the fill to keep the joint tight. I cut the roll down the middle with tin snips to get 24 in-wide strips, and leave 4 in. to 6 in. of barrier above ground to prevent the rhizomes from spreading in the moist surface mulch and going over the top - in ten years, no rhizomes have escaped.

I know of only three methods to get rid of bamboo that’s growing where you’ d rather it didn’t. The most laborious method is to dig up and remove every piece of the root system. This is what I’ve done; it does work, and it leaves the soil ready for something else. I haven’t tried the other two methods, which can be used if you want to kill an entire grove. One is to starve the root system by cutting a grove to the ground and cutting any new shoots that later appear. The other is chemical herbicide. I’m doubtful about both these methods; in fact, a man I know on the Cape has tried repeatedly to kill a grove with herbicide and failed each time.

Bamboo for harvesting

Bamboo has been harvested for centuries, the new shoots for eating, the mature culms for building material. We use the shoots in Chinese and vegetarian dishes, and their flavor is remarkably superior to that of canned shoots. I use the mature culms in the garden for stakes, trellises, gates and ornamental bamboo fences. Through experience and reading, I’ve learned some essential rules of thumb essential to getting large, sustainable yields of both poles and shoots.

Poles - A bamboo planting, properly managed, can supply sturdy poles annually. The most recent culms will be biggest, but they’ll be the weakest, lacking the silica that stiffens old culms. The strongest poles come from three- to five-year-old culms. I usually cut a culm in winter, about a year before it would die naturally, when its surface become splotchy and mottled. Cut the culm with a pruning saw at or below ground level. (Eventually the stub will rot down to an internode on the rhizome, which will seal itself, preventing damage to the rhizome.

I’ve harvested 60 to 70 poles each year for five years, each new crop longer and stronger than the last. The first poles were only 4 ft. to 8 ft. long and useful only as stakes. My recently harvested poles range from 10 ft. to 20 ft. long and up to 1 1/2 in. in diameter, and are suitable for making gates and fences. I can convert my steady annual supply of 900 linear feet of sturdy poles into 12 ft. of solid bamboo fence or roughly 50 ft. of open lattice fence. I use imperfect poles for garden trellises.

Yellow-groove bamboo isn’t known for its durability as are some species. After four to five years of exposure to the elements, a yellow-groove pole will begin to crack lengthwise from seasonal expansion and contraction. If the poles are used vertically, in a fence for example, this cracking isn’t much of a problem. But in a horizontal member of a trellis, cracks lead to sagging and failure.

Bamboo shoots - Harvesting bamboo shoots is very much like cutting asparagus. The first bamboo shoots emerge from the ground in the spring, and all the shoots come up over period of several weeks. They are most tender and tasty when about 6 in. high, and because they grow so fast, one day can make big difference in palatability. Yellow-groove shoots are good eating; unfortunately, many other species are too bitter. Diameter seems to be unrelated to tenderness. The 1-in.-thick shoots I harvest in my oldest grove are practically a meal in themselves. Fresh shoots are traditionally stored in a bucket of cold water, changed daily. In water, they’ll last a few days; in a refrigerator, wrapped, they’ll last about a week; blanched and frozen, they’ll keep for a year.

You can harvest shoots from a new planting, but don’t take them all or the adult plant will eventually dwindle and die. When managing a grove for harvests of both shoots and poles, I take only a quarter of the shoots each year, and I leave the largest ones to grow into poles. I cut them with a knife an inch below ground level, selecting the shoots for cutting to leave about 6 in. between remaining shoots and standing culms.

Bamboo in the landscape

My wife, Hilde, and I design and install landscapes professionally, and in our designs we often include bamboo for outstanding landscape qualities - it’s perennial and evergreen, and it can be contained to grow into either a circular grove or a long, narrow screen. It lends authenticity to Japanese gardens, and is most beautiful when used in coordination with a water feature such as a reflecting pond. One of our plantings is on a sandy 45° slope above a pond, where it helps control erosion and sets off the pond nicely. We also use bamboo as an understory plant beneath larger trees, though in the shade the plants grow more slowly. Bamboo’s form and texture, its pleasant constant motion and faint rustling are qualities quite unlike those of any other landscaping plant. And the introduction of more varieties of hardy, clumping species will increase its usefulness in the landscape.

One practical caution, however, is that wet snowfall can bend and completely flatten the culms to the ground. Usually the damage to the culms is temporary, but if you plant bamboo near a path, resign yourself to shaking the snow off periodically.

You may want to cut the dead culms out of an ornamental planting. This won’t affect the grove’s health one way or the other. Untended, dead poles will fall over and rot away in three to four years. You can also thin living poles to create a more open appearance in a clump. I thin crowded culms in late summer by removing the smallest and/or the oldest ones.

The soul of bamboo

Many Chinese poets who have lived with bamboo intimately have attributed to it near-human qualities - in my reading of bamboo lore, I keep coming across references to sages whose greatest pleasure was to stand in the bamboo garden and listen to the sound of snow and wind in the bamboo. I know that my life has been changed in many subtle ways by learning about the habits and cultivation of bamboo.

Often now, on a snowy or breezy night, I find myself going out into the bamboo grove, and listening. Sure enough, you can hear it, every time. In light breezes, there is a soft rustling. And in snowfall, there is the gentlest of tinkling as ten thousand tiny ice crystals bounce down from leaf to leaf.

 


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