Bamboo

Native to China – now around 75 species of Phyllostachys grow in temperate climates around the world.

All Phyllostachys have a spreading root system with rhizomes (underground stems) running outward from the parent plant.

Roots growing from rhizomes take in nutrients and culms (above-ground stems) rise up along the rhizome’s pathway. This enables bamboo to inhabit a large area. In Chinese forests this is a good thing, providing food for humans and wildlife, and timber as a renewable resource.

In city gardens this can easily cause plants to travel to areas they were not intended to go, causing problems for both plant owners and their neighbors.

For this reason we strongly recommend planting running bamboo in containers or with 60ml plastic bamboo liner.

Grasses and bamboos come in clump-forming types and running types.

Clumping types stay where you plant them and won’t ever hop your fence or stray across your yard. Running types are the ones that can get away from you.

The good news is that if a few precautions are taken when planting, bamboo and grasses that want to stray can be kept in place. Download our Bamboo at a Glance handout for a handy reference to clumping and running bamboo types.

Bamboo root barrier works well to contain running grasses as well as bamboo. Blue Lyme Grass Elymus, Japanese Blood Grass Imperata and Giant Reed Grass Arundo donax are candidates. The barrier is made of 60ml (very thick) plastic and is planted in a 3 feet deep trench and sealed with a stainless steel clamp.

A few inches of barrier are allowed to show above ground. Bamboo roots are most likely to attempt to escape by hopping over the top of the barrier, so if that happens, roots can easily be seen and cut back before they become a problem.

Step by Step instructions for installing Bamboo Root Barrier.

The Bamboo Garden recommends digging a trench around plantings and pruning roots as they attempt to move into the trench.

Step by step instructions for the trench approach.

Culms grow very fast to their full height in one growth period of about 5-8 weeks, emerging from the ground at their full width.

Most bamboo have plain green culms, but Phyllostachys is blessed with culms of several additional colors including yellow or black.

Some varieties grow in a zigzag pattern instead of straight up. Culms are usually hollow except at the nodes, the horizontal stripes on stems where leaf-forming stems emerge.

Phyllostachys are easily identified by a deep groove called a sulcus that stretches between nodes and is sometimes a different color than the culm.

Leaves stay on through winter and are replaced gradually through the growing season with old leaves falling and providing mulch at the base of the plant.

Growing conditions, the age and size of the grove and genetics decide the ultimate size of an individual culm. Air pollution, compacted soil and freezing temperatures during winter all work to keep Phyllostachys smaller in Portland than it would grow in its native habitat.

A grove will produce full-size culms after 10-15 years and usually the smaller culms are older. If you limit the size of the root system as we have recommended, it will also limit the plant’s ability to grow to its full potential.

There are at least 75 species of Phyllostachys and 200 or so cultivated varieties, so there is a great size range available.

Culms can be more slender than ½ inch or fatter than 12 inches in their native habitat and some species are listed to grow 70-100 feet tall. The largest we’ve seen in the Portland area is 35-40 feet tall with 6-7 inch culms – not to say that larger plants do not exist.

 If bamboos are planted in the ground, water them regularly during the period after planting to establish a strong root system, and back off once they are established, just giving a few deep drinks in summer.

Plants grown in containers will need regular water.

The most important time to apply fertilizer is in early spring when new shoots are forming. Use fertilizer that has a full range of nutrients including phosphorus and potassium with a relatively higher amount of nitrogen. Many lawn foods are suitable, as is manure.

Bamboos can develop leaf-burn when too much salt-based fertilizer is used, so stagger applications of salt-based fertilizer with other forms of food.

Plants grown in containers rely mostly on humans for nutrients, so providing fertilizing is important.

Phyllostachys prefers to grow in full sun, at least 6 hours a day. Hardiness varies with species – all are hardy in the Portland area.

Bamboo looks great growing in containers and using them is a good way to control spreading as well. The first step in container-planting bamboo is to choose a large pot that is wider at the top than the bottom–or one that has sides that are straight up & down. Any type of lip that narrows the opening will be very difficult to work with when roots require pruning. The pot should have drainage holes in the bottom as well.

The roots of this bamboo have grown under the sidewalk and sprouted on the other side. Once this happens it is very difficult to handle.

Removing the growth above ground will only work until new shoots come in spring. To dig out the roots, the sidewalk will have to be removed.

Spraying with herbicide to kill the roots becomes a viable option.

Aphids and mites are the most common problems encountered in the Northwest, with sooty mildew following if infestations are allowed to get a foothold.

Aphids and mites are sucking insects that can cause damage to leaves. Sooty mildew, a black mold, feeds on the secretions of sucking insects. Several insecticides are available to combat bug problems.