Chapter 76 Bamboo (multiple species)

76.1 Bamboos

Bamboo bonsai in Baihuatan Park, Chengdu, China. As impressive as this specimen is, the large culms will not live more than 5-10 years. Link to original image.

76.2 Soil: Moist Deciduous Mix

Ratio: 3 parts bark, 1 part grit

Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)

pH: ~6.5 (slightly below neutral)

Moisture: bamboos prefer even moisture, but tolerate dryness once established. Potted specimens tend to be more lush in soil with a high level of organic matter.

76.3 Light

Bamboos do best in half-day sun to full sun.

76.4 Cultivation Notes

76.4.1 Potting

Repot shortly after growth resumes in the spring. Watch out for congested roots, which are susceptible to root rot.

76.4.2 Pruning

Bamboos cannot be pruned in the same way as woody trees. The culms emerge from the ground at their final diameter. Culms should be allowed to reach 2 feet or more before cutting back. Cut back to a node with a well-developed side branch or bud. Trim stubs back close to the solid wall of a joint so that water does collect in the open end.

Repotting a densely packed clump takes some time and patience. Canes send runners in all directions, then the roots that emerge form a tightly tangled mass. Wetting the root ball thoroughly makes the roots more pliable.

After repotting I cut the main culms back to the lowest side branch so the roots have as little top growth as possible to support. The existing culms may not survive though. Often they will a dusty green, gray, or yellow-brown. I cut these off flush with the soil line, but keep watering the pot. Most of the time new culms appear from the growing points within 2-4 weeks.

Bamboo does not respond well to leaf pruning. Remove individual leave blades that are too large at the joint where they emerge.

76.4.3 Feeding

Bamboos are large grasses that need more nutrients than trees. Feed with a lawn fertilizer or with soluble fertilizer at full strength.

76.4.4 Pests & Problems

Bamboos are relatively pest-free.

Chemical Warnings

Avoid any chemicals that are listed as hazardous to lawn grasses.

76.4.5 Winter Storage

The culms are evergreen, though will drop leaves in autumn. Temperate species are cold tolerant in our area, so can be stored outdoors packed in leaves or mulch. Culms may die back in very cold winters, but the root mass will resprout in spring. Tropical species do better if brought into an unheated garage that stays above freezing.

76.5 Propagation Notes

Do not worry if the stock plant you buy has matted roots; bamboos actually establish faster from congested rootstock. Once you move a bamboo to a training pot though, keep the roots pruned to avoid overcrowding, as it encourages root rot in small containers.

Like trees, the best way to get bamboo rhizomes to form large culms is to let the rhizomes spend time in open ground. Amend black garden soil with lots of organic matter, and situate the rhizomes so they will get ample water.

76.6 Artistic & Styling Notes

Bamboos are best suited to clump styles and forest style.

76.7 Additional Information

76.7.1 Natural History

76.7.2 Cultivation Notes

Bamboo is not often used by Asian stylists. They may construct a large group planting on a slab to imitate a natural grove. More often, bamboo is an accent plant, or a foundation plant in gardens. However, Western stylists are experimenting with non-traditional uses and varieties.

One big advantage of bamboo is that it regularly sends up new culms (the segmented, trunk-like stems) from the basal root mass. If you make a styling mistake, cut off the culm flush with the ground, wait for a new one to emerge, and try again.

Bamboos can be divided into running and clumping subtypes. Running bamboos all have scientific names that begin with one of these genera: Arundinaria, Phyllostachys, Pleioblastus, Pseudosasa, Sasa, or Semiarundinaria. Running bamboos grow almost exactly like Bermuda grass. They have thick underground rhizomes that grow long distances, and send up multiple culms along their entire length. Most running bamboos are native to temperate regions of Asia. The invasive bamboos found throughout the US are members of this group.

Within the running bamboos are two subgroups. Dwarf and ground bamboos are so named for their overall height. They rapidly colonize hillsides and other bare areas, preventing erosion. Examples include Kuma bamboo grass (Sasa veitchii) which reaches a maximum height of just 2 feet and has culms 1/4-inch in diameter. Pygmy bamboo (S. pygmaeus) is smaller still, reaching 1 foot high with 1/8-inch diameter culms. The leaves on both species are too large for bonsai, but newly emerging leaves after a well-timed pruning could provide a delicate accent plant.

The second subgroup of running bamboos are moderately sized. Culms in managed groves range in average height from 10-25 feet, and from 3/4 to 3 inches in diameter. This group also has the most variety of colors. Colorful types include the black bamboo (Phyllostachys nigra), in which 2-year and older culms turn purplish black. This species is particularly happy in shade, and is very dramatic. On the other end of the color scale, yellow-grove bamboo (P. aureosulcata) has green culms with yellow zig-zap stripes.

Clumping bamboos form tidy mounds that spread very slowly from a central mass. This is identical to the way tall fescues grow. New culms only grow at the ends of rhizomes, making them easier to contain. Most of the clumping bamboos are in one of two genera: Bambusa and Fargesia. Most of the clumping bamboos originate from tropical or subtropical regions, so tend to be less hardy overall. However, many cultivars are available that can tolerate North Carolina winters and summers quite well.

Hedge bamboo (Bambusa multiplex and cultivars) is a subtropical species that is more cold-tolerant than most bamboos, so it can be left out later to kill overwintering insect pests. However, hedge bamboo adapts well to life in pots, and can live indoors for part of the year. There are dwarf forms that top out at 3 feet high (B.m. ‘Tiny Fern’) and large forms that reach 20 feet (B.m. ‘Alphonse,’ ‘Golden Goddess’). Both cultivars respond to small containers by reducing the height and diameter of the culms, as well as smaller leaf size. Hedge bamboo does not like wet feet, so it forgives under-watering well.

Another hardy clumping species that has been introduced to the US recently is sunset glow bamboo (Fargesia rufa). Its green culms have orange-red papery sheaths at each node that add a touch of color. It is evergreen in Zone 7, and the stems reach up to 8 feet tall.

The last category of Asian bamboos are the timber bamboos which include both clumping and running types. A grove of mature timber bamboo is said to be one of the wonders of the natural world. Giant timber bamboo (Bambusa oldhamii) is a clumping species that can grow 25 feet tall, with 4-inch diameter culms. Henon or blue bamboo (Phyllostachys nigra ‘Henon’) is a running bamboo with 3 to 4-inch diameter culms that reach 50 feet or taller. The emperor of the grove though has to be Japanese timber bamboo (Phyllostachys bambusoides) which reaches 35 feet high with 6-inch diameter culms! Sadly, entire groves of timber bamboo tend to die out suddenly, usually soon after flowering. Since they are connected by rhizomes, the death hormones spread to the entire stand. However, groves live for 60 years or more before flowering, so there still is ample time to enjoy them before that happens.

I’ve written a separate guide to the North American native species of Arundinaria.

76.7.2.1 Field Growing Bamboo, and Keeping Bamboo in Check

Clumping bamboos are simple to contain, because they spread very slowly, and only around the edges of a colony. To remove them, just dig out the clump. To keep rhizomes of running bamboos in check, insert a 3-foot wide strip of aluminum flashing into the ground to form a metal barrier around the roots. Leave 4-6 inches exposed above the ground. The rhizomes will turn back at the boundary, and sprout inside the ring.

If a clump of running bamboo escapes, push a shovel into the ground to split the runner from the main group. Cut off all of the culms, then regularly check back for new sprouts. Keep cutting off the new sprouts before they reach a foot or more high; this starves the isolated runner, and it eventually dies. To speed up the process. paint the freshly cut ends of any culms with undiluted Round-Up or other herbicide containing glyphosate.

76.7.2.2 Sources

If you are interested in trying your hand at growing your own bamboo for bonsai, the fastest way to start is to follow the nearest creek. Invariably you will come across a patch of naturalized bamboo. Dig up a length of rhizome with roots and 3 or more buds, and cut off the culms just above a node. Transplant it to a pot or tray in black topsoil, then plant it out (if desired) once new growth appears. For more exotic species, several online specialty nurseries carry bamboo. New England Bamboo Company (www.newengbamboo.com) carries the largest variety of species and cultivars that I have found. In addition to plants, NEBC offers advice and extensive descriptions. Other vendors may carry unique cultivars that they have isolated and expanded locally.