Bamboo Considerations

Selecting the right species

 

Obviously, the first consideration in choosing bamboo is what its going to look like.  Is it going to be tall or short?  Will it have black canes, yellow canes or green canes?  Will the canes be striped?  But, there are environmental concerns as well.  There are hundreds of temperate bamboos that grow in a wide variety of conditions.  Here are some considerations to take into account when choosing the right bamboo for the job:

 

Sun:  Under American Bamboo Society nomenclature, every species of bamboo is assigned a number from one to five to indicate its preference for sun or shade.  A five means that it likes full sun, while a one indicates extreme shade.  A bamboo that prefers full sun will grow in partial shade, but will not reach its full size.  Its important to take into account what part of the day the bamboo will be in the sun.  Afternoon sun is harsher, so a bamboo that prefers shade will be better off with morning sun.

 

Height and diameter:  The numbers assigned in this category are the maximums a bamboo will reach in ideal conditions, in the climate of origin.  All aspects of climate will affect a bamboo's size, including high/low temperatures, sun/shade exposure, humidity/aridity, water supplied and length of growing season.  Generally if a bamboo is grown in a hot and humid climate with a long growing season and kept within its cold tolerance with plenty of water and the correct amount of light it will reach its maximum.

 

Temperature:  Bamboo is normally not assigned a zone.  Instead, it gets a number representing the lowest temperature it can tolerate for two or three nights at a time.  Some species will suffer leaf burn, drop leaves, or even die to the ground at minimum temperatures, but the well-mulched rhizome will shoot again in spring.   It is always important to remember that microclimates proximity to large bodies of water, shelter from harsh winds, south facing sites can significantly ameliorate the larger climate.

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Running or clumping:  One of the major differences in bamboo is whether they are runners or clumpers.  Clumpers will get tall faster, but spread more slowly.  If spreading is a concern they might be a better choice.  Runners spread with underground rhizomes, but there are a variety of ways to control them if so desired (see containment below).  There is a small group of open clumpers, mostly Yushania and some Chusqueas, that exhibit characteristics of both root types.

 

 

Selecting a site

 

The three considerations to make when selecting a site are amount of space, type of soil and amount of light.

 

Space:  Don't let a perceived lack of space keep you from growing bamboo.  Pots, planters and barriers can be used.  As a general rule, bamboo likes an area that's at least as long and wide as the maximum height of the plant, but this doesn't mean bamboo won't grow in a smaller area.  It just won't grow as large.  So, when selecting bamboo for a smaller area, find a species that is supposed to grow taller than your desired height.

 

Soil:  Bamboo likes well-drained, fertile soil that is rich in organic material and has a near neutral to slightly acidic pH.  For the most part, this describes what we have in the Northwest.  However, if necessary, soil amendments can be made.

 

Light:  Like other plants, bamboo needs the proper amount of light to do well.  Most species in the Phyllostachys and Bambusa genera prefer full sun exposure, but new plantings of all bamboo can benefit from some form of temporary shading until they become established.  Species of Pseudosasa and Sasa genera typically originated as understory plants in forests and prefer partial shade.  They will not generally do well planted in direct sun.

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Site preparation

 

Bamboo likes well-drained, fertile soil that is rich in organic material with a pH between 5.5 and 6.5.  Sandy soil can be improved with the addition of organic materials such as compost, peat, manures, nitrolized sawdust, or bark chips.  Clay soils can be improved with the addition of sand and organic materials.  Most bamboos will suffer root damage if submerged in water for several weeks.  Drainage can be improved by mounding the soil (mounding also helps to increase soil temperature) or ditching around the planting.  The planting hole should be as deep as the root ball and twice as wide.

 

 

Planting

 

In the maritime Pacific Northwest bamboo can be planted year round.  In the summer, of course, water will be a factor.  It is very important to keep it moist.  Other considerations are staking tall plants and mulching.

 

When to plant:  In cold winter climates, the best time to plant is usually as soon as the ground can be worked in the spring.  This gives the plant time to establish itself before the next cold season.  In a hot, summer climate, where the ground does not freeze, the best time to plant may be fall so that the plant has time to establish itself before the dry summer.  Even so, sufficient watering will be necessary.

 

Mulching:  Mulching bamboo is very important as it protects rhizomes from the cold and extends the growing season by keeping them warm.  Also, it helps to retain moisture in the soil and retards competitive weeds while the bamboo is getting started.  Almost any organic material is a good mulch.  Grass is one of the best as it is high in nitrogen and silica.  Home made or commercial compost works very well too.  Manure works well as long as it is aged.  Limited amounts of hot fertilizer like chicken manure are okay if used with care.

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Staking:  Staking is especially important when planting tall bamboos.  Since bamboo has a very shallow root structure, it is very easily uprooted when first planted.  In addition to keeping new bamboo from being uprooted, staking keeps newly formed roots from being damaged while the bamboo is establishing itself.  The best method for staking is to place one to three substantial stakes around the root ball and secure them to the cane using non-abrasive rope or nylon stockings attached about halfway up a culm.

 

 

Containment

 

There are two basic types of bamboo, known as clumpers and runners.  Runners often get a bad rap for being invasive, but by taking a few simple measures they can be contained fairly easily.  Bamboo has a very shallow root structure (only about a foot and a half), so the real concern is with spreading.

 

Rhizome barrier:  This is the best method for controlling running bamboos.  Rhizome barrier comes in a rolled plastic sheet that is thirty inches wide and forty mil thick.  It is made from high-density polyethylene, which will not crack or rust the way concrete or metal can.  Generally, it is planted around the perimeter of the bamboo at a slightly outward angle so that rhizomes will be deflected upward when they run into it.  About two or three inches should be left above ground so that the rhizomes will not hop over it.  If they do, they can be clipped off with pruners or a shovel.  When installing the barrier it is important not to leave loose soil or air pockets next to it or the bamboo may go deeper than intended.  In addition, soil amendments should be kept in the top foot and a half so as not to encourage the bamboo to go deeper than the barrier.

 

Trenching:  Another way to control bamboo is to dig a narrow trench eight to ten inches deep around its perimeter, and check for rhizomes a few times in the late summer and fall, cutting them when necessary.

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Pruning:  It's possible to simply cut underground rhizomes using the blade of a flat-edged shovel by moving around the bamboo's perimeter.  Planting in a one or two foot soil-elevated mound can make edge pruning easier and quite effective.  Bamboo grows very well in raised beds due to the increased soil temperatures they provide.

 

Raised bed:  Treated lumber can be used to create a two-foot deep planter box.  The bottom should be left open for better drainage.

 

 

Watering

 

Bamboo likes plenty of deep watering and good drainage.  Mulching is an excellent way to help retain moisture and return nutrients to the soil.

 

Newly planted bamboo:  With ground plantings, a soaking of eight to twelve inches when necessary is much better than shallow watering every day, but new plants may need water every day during dry spells.  It is best to wait until the soil is just slightly damp before watering.  It shouldn't be wet and it shouldn't be bone dry.  In full sun, dry, windy or hot conditions it is a good idea to spray the foliage with water once a day for a period of two to four weeks.  If the leaves are curling along their edges this means the bamboo is stressed and not getting enough water.  If the leaves are drooping downward, the bamboo might be getting too much water and/or not enough drainage.  Over watering can cause excess leaf drop.

 

Established bamboo:  Older plantings can withstand dry conditions rather well.  Some species are more drought tolerant than others.   After bamboo has been in the ground for a few months, a spray-emitter irrigation system can be used if desirable.  Drip systems don't provide enough coverage.  In general, a good soaking once a week is sufficient when rainfall is scarce. If the leaves are curling along their edges this means the bamboo is stressed and not getting enough water.  If the leaves are drooping downward, the bamboo might be getting too much water and/or not enough drainage. 

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Fertilization

 

Bamboo responds very well to fertilizers with approximately two times the nitrogen as phosphorous and potassium.  Time released chemical fertilizers work well, but composted horse manure is the fertilizer of choice in Asia.  It should be spread about four inches deep in early winter to allow time for nitrogen conversion and use the rest of the year.  It is important to use caution if using nitrogen-hot fertilizers like chicken manure.  A good organic fertilizer is one part manure and two parts compost applied in the fall when bamboo is storing energy for spring production.  Remember that a good mulch is an excellent way to return nutrients to the soil and keep weeds down.

 

 

Pests

 

While bamboo doesn't have many pests, the few that it does have can be unsightly, if not a serious problem.  There are some simple steps, however, that can be taken to avoid infestation or stop the problem before it occurs.

 

Gophers and Moles:  Normally not a problem, but if they happen to be around, they may think that tender, new underground rhizomes are a real delicacy.  Planting inside a ¼ inch metal gopher basket will protect young plants until the basket has rusted away.  Established bamboo should not be affected by underground nibbling.

 

Mites and Aphids:  Mites are so small that they are very difficult to see with the naked eye, but their effects are quite noticeable.  They leave small, bleached out spots on the tops of leaves and a tiny amount of webbing on their underside.  A healthy, well-watered plant usually resists mites on its own, but if they do become a problem there are a few simple steps that can be taken, depending on the severity of the infestation.  Aphids leave a sticky residue on the leaves that eventually turns to a sooty, black film.  Often found together, the treatment for aphids and mites is the same.  The simplest and most environmentally friendly is to keep bamboo thinned and use a pressure washer to blast the leaves.  If this isn't enough, an insecticidal soap can be made with Arm & Hammer laundry detergent (1 tablespoon per gallon of water in a sprayer) and applied once every two weeks.  Another method of treatment would be to use Niem oil, an organic insecticide that kills mites, aphids, mealy bugs, white flies and other insects.  Follow the directions closely.  When more drastic measures are called for, a variety of miticides can be employed.  These chemicals are designed to kill only spider mites and leaf minors, but they can be difficult to find in retail stores.  As a last resort, Malathion can be used.  It pretty much kills everything.  In a worst-case scenario, bamboo can be clear cut, the debris cleaned up (since bugs will hide in it), and new shoots will replace the old.

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Snails and Slugs:  Not generally a problem, but if something is chewing on new culms, it may be the slimy-slitheries.  Use a slug and snail bait, preferably one that is safe for animals. 

 

Other pests:  Since bamboo is part of the grass family, herbivores such as goats and cattle can be a problem.  They should be fenced out.  Fortunately, deer seem to leave bamboo alone.  Squirrels, once they develop a taste for bamboo shoots, can be a formidable pest.

 

 

Bamboo in containers

 

Soil:  When growing bamboo in containers it is important to use a good potting soil mix that combines organic and inorganic elements.  Most commercial or nursery mixes are quite satisfactory.  The soil should provide good drainage but also be able to retain moisture.  Sand, volcanic cinders and perlite are excellent stable, inorganic components.  Cinders or perlite are preferred as they have a good ability to retain moisture.  Fir bark, compost and peat are good organic components- the larger the particles, the more drainage.  Loam or clay may also be added for micronutrients, but as a basic rule, texture takes precedence over nutrition, as nutrition can be easily supplemented.

 

Repotting:  Every third year or so, bamboo will outgrow its pot.  In order for it to keep looking its best it should be divided, or simply put into a larger pot.  Annual pruning of old and dead canes will also improve the appearance and health of the plant.

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Bamboo indoors

 

Successfully growing bamboo indoors can be quite difficult, and it is generally not recommended.  However, with a considerable amount of care and attention the results can be quite rewarding.  Since indoor environments are less than ideal, rotating plants outside in mild conditions is a good idea for long-term health.

 

Humidity:  Daily misting is recommended to compensate for the lower moisture levels found in most interiors.  Placing a humidifier or small fountain nearby can also help.

 

Light:  A south facing window is the best spot for most bamboos, although some of the shade-loving species, such as the Fargesia genus, will sometimes do better in an east-facing window.  Severe leaf drop may occur when a bamboo is first placed indoors.  If this occurs, new leaves that are more acclimated to indoor conditions will replace the old ones.  When indoors, bamboo will grow towards its light source, so it may be necessary to rotate the plant 45 degrees every week to maintain an even growth rate.

 

Soil:  A light potting mix of 1/3 dirt, 1/3 peat moss, and 1/3 perlite will provide excellent drainage and allow the soil to dry out more quickly after watering to prevent root rot.  Placing a pebble tray under the pot or gravel in the bottom of the pot with a saucer will allow excess water to collect without soaking the roots.  This water will also aid in maintaining the humidity as it evaporates.

 

Watering:  Close attention to watering is very important for bamboo kept indoors.  The roots should be kept moist, but not so much that they stay soggy for days.  The top 2-3 inches of soil should be allowed to dry out before watering again.  Below the 4-inch depth, soil should be slightly moist around the roots at all times.

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Air circulation:  Airflow around indoor bamboo can be very helpful.  Fresh, outdoor air from a window or door is the most beneficial.

 

Fertilizer:  A slow-release granule with trace minerals works best- preferably 14-14-14 with a 4-6 month release rate, depending on temperature.

 

Height:  Bamboo will not grow vigorously indoors and will only achieve a fraction of its maximum height and diameter, so buying a plant as close to the ultimate size as possible is recommended.

 

Pests:  When indoor bamboo gets too dry, pests can be a problem.  Mites, aphids and other insects thrive on stressed plants.  Since bamboo indoors is already a little stressed it is important to watch for pests.  Use safe treatments for indoor plants.  See the above section on pests for outdoor bamboo.

 

 

Grooming

 

Grooming bamboo is cosmetic as well as beneficial to the plant's health.  In general, bamboo should be pruned enough for light to radiate down through the top 2/3 of the plant.  This allows space for air circulation and for new shoots to come up.  It is best not to prune newly planted bamboo, as it will need its leaves to absorb energy for the following year's growth.  To keep bamboo looking its best, approximately 1/4 of the old culms can be removed each year once the plant is established.  Use a saw or clippers and cut just above the node as close to the ground as possible.  To remove branches in a bamboo grove so that they do not snag on clothing, use a saw or sharp knife to undercut on the outside where the branch joins the culm and give it a quick tug.  Dwarf bamboos with winter damage can be trimmed to within 3-4 inches of the ground in the spring, just before new shoots come up.  Another treatment of bamboo is hedging.  The idea behind this is that bamboo can be topped and kept at a desired height, thus serving as a screen.  Trimmed bamboo has advantages over other hedging materials because it can be cut to different lengths each year.  It is a versatile, low maintenance, hardy screening material.

 

 

 

 

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