Is There A Hardy Bamboo In Your Landscape Future?
By Merle M. Moore
Previous Director of Horticulture & Grounds Maintenance
Denver Zoological Gardens
Copyright Denver Zoo/Merle M. Moore
In 1991 I began an experimental planting of 24 so-called "hardy" bamboo varieties at the zoo in preparation for landscaping what is now our "Primate Panorama" exhibit. A total of 34 plants were grown with 12 of those coming from "Our Bamboo Nursery" in Tennessee (all field-grown clumps of 4 or more culms), and the other 22 coming from Bamboo Sourcery Nursery in California (in either 1-gal. or 5-gal. containers). Ten of the varieties tested compared the establishment of the field grown bamboo with the identical species in either a 1-gal. container or 5-gal. container. Out of that trial emerged seven varieties of bamboo that have proven, so far, to be reliably hardy at the zoo (USDA Hardiness Zone 5). Six of them are Chinese species and one is considered a southern U.S. native. The seven varieties are:
Arundinaria gigantea, southern (U.S.) cane bamboo, from Virginia to Florida and Louisiana. The least attractive and graceful of the bamboos we are growing but a good "browse" plant for our primates and red panda. While it holds is leaves fairly well into the winter the overall effect is somewhat "ragged" until the new growth matures in June. Our plants average 6-7 feet high with culm diameter as large as 3/4 inch.
Phyllostachys aureosulcata, golden groove bamboo, from east China in the regions of Jiangsu and Zhejiang. Named for the distinct yellow coloration of the inter-nodal furrows, this bamboo has proven to be very hardy, maintaining good green leaf color well into winter. The species appears to be somewhat more susceptible to wind desiccation than some of the others we are growing. Therefore, in considering planting locations for this species I recommend a site that protects the plants as much as possible from winter wind. Our plants average 10-12 feet high with culm diameter as large as 3/4 inch.
Phyllostachys Bissetti, David Bissett's bamboo, from Sichuan, China. Rated equal in hardiness to golden groove bamboo, this species also has a similar overall habit and general appearance. The leaves are dark, shiny green as are the culms that lack the golden coloration of the former species. They have been evergreen all but one winter since planted in the original trials. Where commonly grown David Bissett's bamboo is often recommended for use as a hedge, an isolated clump, or in a jardinère. Clum size is about ½ inch in diameter and 10-12 feet high.
Phyllostachys glauca, from the Jiangxi region of China. Although not rated as cold hardy as either P. aureosulcata or P. Bissetti, this species has proven to be the most impressive of all the bamboo varieties we are currently growing. With clums approaching 16-18 feet high and 1 inch or more in diameter, it appears to be the species most adaptable to our soil pH and climate. The young clums are almost completely covered with a kind of white powder which gives them a very nice grey-green color. The sweet, young shoots are considered quite delectable by Asian food gourmets. They have been consistently evergreen in our plantings at the zoo.
Phyllostachys heteroclada (aka P. purpurata 'Straight Stem'), from south China. Similar in hardiness to P. glauca, this species has green culms with very dense foliage giving a very pleasing overall effect. A particular attribute is while the species is not very particular to soil type, it has the ability to thrive in wet soils that most other bamboos would not tolerate. Where commonly grown it is recommended for use as a hedge, windbreak, on a bank or as an isolated clump. Our plants are averaging 12-15 in height with culm diameter as large as ½ in. They have been evergreen each winter except one since the original trial planting.
Phyllostachys nuda, from the Zhejiang region of China. With culms reaching 10 feet or more in height and up to 1/2 inch in diameter, this has proven to be a very hardy species for us, remaining evergreen through most winters since 1991. The dark green culms have nodes that are noticeably underlined with a white powder when sheaths fall. It is known in China for its choice edible new shoots.
Phyllostachys rubromarginata, red-margined bamboo, from Zhejiang and Guangxe in So. and SE China, its common name is derived from the small red margins of discoloration on all the new edible shoots. The species is noted in China for its tolerance to cold, dry winds where it is used as a screening bamboo. It has been a healthy and strong grower attaining height more rapidly than most of the other bamboo we grow. Our plants average 12-15 feet in height with culm diameter as large as 1/2 inch.
I do not consider the bamboo varieties we grow to be xeriscape plants. They require moderate amounts of water during the growing season and in winter during dry spells.
At the zoo we winter-water all bamboo whenever temperatures rise above 55 degrees and especially during prolonged dry spells. I recommend mulching the root systems of bamboo with a minimum of 12 inches (perhaps double that the first two winters) of lose organic mulch once the ground is frozen to encourage plants to stay dormant as late in the Spring as possible. The water content of newly emerging bamboo shoots is very high and even a mild frost will quickly kill them. Each time this occurs food reserves in the root system are depleted, and several such episodes of freezing in quick succession will kill the plant. Slowly lowering the depth of the mulch, a few inches at a time, to about 6 inches can begin in early April and new growth should be evident by the end of May, early June.
Bamboo should be planted on north or east exposures, NOT south or west. Preventing pre-mature emergence of the new shoots in Spring is very important to their survival hence, the importance of proper site selection and mulching. We fertilize bamboo with an organic Turf Food in mid-April and mid-June, applying 1 handful of fertilizer/sq. yd. of feeding area. Water the fertilizer in well after each application.
So, am I advocating the promotion of hardy bamboo for every garden in Colorado? Am I suggesting hardy bamboos are "the hedge plant of choice" in future landscapes? Certainly not! I am merely suggesting that with proper placement, soil preparation, adequate supplemental moisture during the growing season and in winter dry spells, plus generous application of organic mulches, one may successfully grow certain hardy bamboo varieties in Colorado landscape applications. I suspect there are additional varieties of bamboo to be tested for Colorado growing conditions and we may be trying some of them in the future.
By Merle M. Moore
Previous Director of Horticulture & Grounds Maintenance
Denver Zoological Gardens
Copyright Denver Zoo/Merle M. Moore
In 1991 I began an experimental planting of 24 so-called "hardy" bamboo varieties at the zoo in preparation for landscaping what is now our "Primate Panorama" exhibit. A total of 34 plants were grown with 12 of those coming from "Our Bamboo Nursery" in Tennessee (all field-grown clumps of 4 or more culms), and the other 22 coming from Bamboo Sourcery Nursery in California (in either 1-gal. or 5-gal. containers). Ten of the varieties tested compared the establishment of the field grown bamboo with the identical species in either a 1-gal. container or 5-gal. container. Out of that trial emerged seven varieties of bamboo that have proven, so far, to be reliably hardy at the zoo (USDA Hardiness Zone 5). Six of them are Chinese species and one is considered a southern U.S. native. The seven varieties are:
Arundinaria gigantea, southern (U.S.) cane bamboo, from Virginia to Florida and Louisiana. The least attractive and graceful of the bamboos we are growing but a good "browse" plant for our primates and red panda. While it holds is leaves fairly well into the winter the overall effect is somewhat "ragged" until the new growth matures in June. Our plants average 6-7 feet high with culm diameter as large as 3/4 inch.
Phyllostachys aureosulcata, golden groove bamboo, from east China in the regions of Jiangsu and Zhejiang. Named for the distinct yellow coloration of the inter-nodal furrows, this bamboo has proven to be very hardy, maintaining good green leaf color well into winter. The species appears to be somewhat more susceptible to wind desiccation than some of the others we are growing. Therefore, in considering planting locations for this species I recommend a site that protects the plants as much as possible from winter wind. Our plants average 10-12 feet high with culm diameter as large as 3/4 inch.
Phyllostachys Bissetti, David Bissett's bamboo, from Sichuan, China. Rated equal in hardiness to golden groove bamboo, this species also has a similar overall habit and general appearance. The leaves are dark, shiny green as are the culms that lack the golden coloration of the former species. They have been evergreen all but one winter since planted in the original trials. Where commonly grown David Bissett's bamboo is often recommended for use as a hedge, an isolated clump, or in a jardinère. Clum size is about ½ inch in diameter and 10-12 feet high.
Phyllostachys glauca, from the Jiangxi region of China. Although not rated as cold hardy as either P. aureosulcata or P. Bissetti, this species has proven to be the most impressive of all the bamboo varieties we are currently growing. With clums approaching 16-18 feet high and 1 inch or more in diameter, it appears to be the species most adaptable to our soil pH and climate. The young clums are almost completely covered with a kind of white powder which gives them a very nice grey-green color. The sweet, young shoots are considered quite delectable by Asian food gourmets. They have been consistently evergreen in our plantings at the zoo.
Phyllostachys heteroclada (aka P. purpurata 'Straight Stem'), from south China. Similar in hardiness to P. glauca, this species has green culms with very dense foliage giving a very pleasing overall effect. A particular attribute is while the species is not very particular to soil type, it has the ability to thrive in wet soils that most other bamboos would not tolerate. Where commonly grown it is recommended for use as a hedge, windbreak, on a bank or as an isolated clump. Our plants are averaging 12-15 in height with culm diameter as large as ½ in. They have been evergreen each winter except one since the original trial planting.
Phyllostachys nuda, from the Zhejiang region of China. With culms reaching 10 feet or more in height and up to 1/2 inch in diameter, this has proven to be a very hardy species for us, remaining evergreen through most winters since 1991. The dark green culms have nodes that are noticeably underlined with a white powder when sheaths fall. It is known in China for its choice edible new shoots.
Phyllostachys rubromarginata, red-margined bamboo, from Zhejiang and Guangxe in So. and SE China, its common name is derived from the small red margins of discoloration on all the new edible shoots. The species is noted in China for its tolerance to cold, dry winds where it is used as a screening bamboo. It has been a healthy and strong grower attaining height more rapidly than most of the other bamboo we grow. Our plants average 12-15 feet in height with culm diameter as large as 1/2 inch.
I do not consider the bamboo varieties we grow to be xeriscape plants. They require moderate amounts of water during the growing season and in winter during dry spells.
At the zoo we winter-water all bamboo whenever temperatures rise above 55 degrees and especially during prolonged dry spells. I recommend mulching the root systems of bamboo with a minimum of 12 inches (perhaps double that the first two winters) of lose organic mulch once the ground is frozen to encourage plants to stay dormant as late in the Spring as possible. The water content of newly emerging bamboo shoots is very high and even a mild frost will quickly kill them. Each time this occurs food reserves in the root system are depleted, and several such episodes of freezing in quick succession will kill the plant. Slowly lowering the depth of the mulch, a few inches at a time, to about 6 inches can begin in early April and new growth should be evident by the end of May, early June.
Bamboo should be planted on north or east exposures, NOT south or west. Preventing pre-mature emergence of the new shoots in Spring is very important to their survival hence, the importance of proper site selection and mulching. We fertilize bamboo with an organic Turf Food in mid-April and mid-June, applying 1 handful of fertilizer/sq. yd. of feeding area. Water the fertilizer in well after each application.
So, am I advocating the promotion of hardy bamboo for every garden in Colorado? Am I suggesting hardy bamboos are "the hedge plant of choice" in future landscapes? Certainly not! I am merely suggesting that with proper placement, soil preparation, adequate supplemental moisture during the growing season and in winter dry spells, plus generous application of organic mulches, one may successfully grow certain hardy bamboo varieties in Colorado landscape applications. I suspect there are additional varieties of bamboo to be tested for Colorado growing conditions and we may be trying some of them in the future.
