Like all grasses, bamboo goes through a flowering and seeding cycle. Most grasses do this each year. Temperate running bamboo does this, on average, about every 80 years or so. Some bamboos haven't flowered since they've been keeping scientific records, for over 200 years.
Bamboo flowering is something scientists still don't fully understand we usually can't predict when it will happen. There are some thing we do know, though. Even those a single grove, a single culm, or even a single branch can go into flower at any time, the most common method of flowering for most species is called a gregarious flowering, where an entire species, or at least a single clone, will flower all around the world at about the same time.
Since in the United States we don't have a lot of clonal diversity of many of our species, this essentially means that an entire species will go into flower at around the same time, generally in a time frame of about five years. There is some evidence to suggest that gregarious flowering isn't contained only to a single clone but often multiple clones within a species.
When a temperate running bamboo flowers, it concentrates most of its energy on creating flowers and seeds and therefore produces little vegetative growth. It is common for smaller groves or potted plants to die completely before the cycle is complete. Larger established and healthy groves will usually recover, but it can sometimes take a decade or more.
The seeds produced by flowering usually have low viability with low germination rates and are sometimes completely sterile.
Since we have so many species at our nursery, we always have several that are in flower. We remove them from their normal rows and put them all together, hoping for some possible cross-pollination, but we have never made the time to try to collect and germinate seeds so I am unsure if this even works.
What should you do if your bamboo if flowering? It depends. If it's a larger grove that is established, it is recommended that you fertilize and water so that it has as many nutrients as possible to make a full recovery. If it is in a container, I can say the best possible scenario is that it will barely survive after 3~5 years of flowering and will look almost-dead most of that time. I recommend replacing it.
Since we never know when bamboo if is flowering, it is not something we can guarantee or warranty against. When customers are making large orders of bamboo I usually recommend getting at least two species to guard against flowering. The chances of two unrelated species flowering at the same time is indeed very small.
Yellow leaves on bamboo
Does your bamboo have yellow leaves? Is this a concern? It depends. Below I'll list several different conditions where yellow leaves happen and what to do about it if anything. Remember, bamboo is a tough plant, but it is possible to kill, and 99% of the time people accidentally kill their bamboo, it is due to either over-watering or under-watering or a combination of those things. Everyone wants to know how often they should water, but there is no set answer for this. It depends on the weather, the soil, the type of bamboo, and the time of the year. The only sure-fire way to know if your bamboo is getting the proper amount of water is to check the soil at the root ball several inches down if possible. It should be moist but not soggy. Remember: bamboo typically likes a moderate amount of water: not too much and not too little. So my advice whenever someone has a concern about their plant is to check the root ball. It would be best if you did this regularly until you feel you have an idea of what the bamboo needs and/or until the plant is established. Most plantings in the ground can take care of themselves after 6~24 months, depending on the size of the plants you started with. For bamboo in containers, you'll always need to make sure they have water since a container cannot store water like the ground.
Less than 20% yellow leaves at any time of year: normal
When a bamboo leaf turns yellow, it means that it is dying, and for most types of bamboo will soon fall off the plant. Like all evergreens, bamboo will lose leaves throughout the year, and thus you'll always have at least a few yellow leaves. Bamboo leaves typically last about a year. Look for an even distribution of the yellow leaves throughout the whole plant.
Up to 50% of yellow leaves in spring and fall: normal for some types
Some bamboo types will drop more leaves than usual two times per year: once in the spring when the weather turns from cold to warm, and once in the fall when it does the opposite. These are essentially stress responses from the plant due to the change of conditions. If you notice bamboo having more yellow leaves during this time of the year, check the soil at the root ball to make sure there is enough moisture but not too much.
Localized yellow leaves or lots of yellow leaves: could be not normal
If you have many yellow leaves in one place or all over, this isn't normal. This could be due to several reasons:
1 - Overwatering. This is the most dangerous condition and needs to be remedied immediately. If you check the ground around the root ball and determine it is in fact too wet, the water needs to be reduced as quickly as possible. If it is too wet due to either automatic or manual irrigation, stop all irrigation until the situation returns to normal conditions and then adjust watering times and durations to fix the problem. If there is mulch, then that can be removed to help it dry out quicker. If the bamboo has too much water due to excessive rain, see if you can drain the excess with a ditch and redirect future excessive water with diversion techniques: usually either a berm or trench. If the bamboo has been recently planted, you may need to dig it up and re-plant it higher.
2 - Nutrient deficiency - Sometimes, bamboo can be short on a nutrient or combination of nutrients that may make its leave yellow. If the leaves are yellow but not falling off, this is often the case and gradually happens. Iron is the most common deficiency and can be fixed with a product like Ironite, which is cheap and readily available at almost any garden supply, including Lowe's and the Home Depot.
3 - Sun bleaching - some bamboo leaves and culms and branches can get bleached out from green to yellow due to sun exposure. This is normal.
Taking care of clumping bamboo
We carry two categories of clumping bamboo:
1 - The most cold-hardy of the subtropical clumpers
2 - The most heat-tolerant of the temperate clumpers
Once you make sure you're planting the correct bamboo for your conditions, care of these plants is not that dissimilar to any other shrub. In order of importance what you want to manage:
1 - Watering
Bamboo typically likes a medium amount of water - not too dry and definitely not wet feet. After the bamboo is established (6 months - 1.5 years depending on what size plant you start with) it can typically take care of itself and doesn't need to be watered.
2 - Fertilizing
Fertilizing is optional but will help rapid growth just as any other plant
3 - Pruning
Clumping bamboo has rhizomes that do spread underground, but they spready slowly (typically an inch or two per year) and it behaves more like a traditional shrub. After a number of years, if the base starts to get too large, you can simply cut back the outside culms. Alternatively you can cut the outside shoots when it is shooting (summer/fall for subtropical and spring for temperate types).
Although bamboo plants can last almost indefinitely, the individual culms (stalks) on bamboo typically last about 10 years and then die. So after the plant has been in the ground a few years it is recommended that once per year in the fall you cut out any dead growth.
If you would like to shape your bamboo, you can do this easily as cut growth doesn't grow back. For example, if you want your bamboo to stay at 10' tall but it's growing 15' tall, you can simply top it off and it will never regrow. However, new shoots come up each year so the new shoots may grow past that 10', but you would then just top off the new growth each year. Similarly bamboo responds well to shaping/pruning for a manicured look, or looks great in its natural form.
For more questions about taking care of clumping bamboo, contact us!
The Worst Bamboos for Cold Sensitivity
Of the 100+ varieties we carry at Brightside Bamboo Nursery, these are the most cold-sensitive, listed in order.
1. Any of the Bambusas, such as Bambusa mutiplex and subspecies, Bambusa textilis 'RG Dwarf', etc). These are really zone 8 plants that we keep for our customers in places in North Carolina such as Wilmington, Fayetteville, Greenville, etc. They are rated to 12°F. However, they can be grown in Zone 7b if you give them extra TLC such as thick mulch and frost blankets if the temperature dips close to 12°F. Also, if you have a warm and sheltered micro-climate they can be OK in 7b.
2. Phyllostachys nigra (black bamboo). This is probably our most popular bamboo. The problem comes when it is exposed to cold winter winds, which can damage the leaves at around 10°F. It won't kill the plant, but it can show damage. Rated to 5°F
3. Sasa palmata and other broad-leafed bamboos tend to be more sensitive to conditions when the frost line goes deeper than normal and they have frozen roots but the sun in shining. They dry out. Rated to 5°F.
4. Japanese timber bamboo (Phyllostachys bambusoides) and subspecies such as Allgold and Castillon. Leaf damage in single digits combined with wind. Rated to 5°F.
5. Phyllostachys viridis and subspecies, including Houzeau and Robert Young. Leaf damage in single digits combined with wind. Rated to 5°F.
6. Pseudosasa japonica (arrow bamboo) and subspecies are vulnerable in the same conditions as Sasa palmata above. Rated to 5°F. For central North Carolina, it is unusual to have these conditions, but they did happen during the 2017/2018 winter.
7. Phyllostachys aurea (golden bamboo) and subspecies such as Koi. Leaf damage in single digits combined with wind. Rated to 5°F.
We no longer recommend using the praised bed technique for containing bamboo except in the most impossible areas. We believe that in-ground a pruning trench or rhizome barrier are best and that above ground containers (such as galvanized metal stock tanks) are best. The raised bed technique described below works, but the maintenance has been more extensive that we initially believed it would be, requiring addition of material each year and re-shaping the top of the bed due more-than-anticipated volume and shape reduction from composting and erosion. That being said, the method does work and may be a viable option if you very wet soil, very rocky soil, and/or beds too large to make containers a viable option.
Original 2017 Article:
Many times containment is a second thought for people who have bamboo planted. Sometimes that’s OK since a pruning trench or rhizome barrier can be installed a year or two after the bamboo planting with good results and minimal, if any, rhizomes escaping to unwanted areas. However, I recommend that anytime you’re installing a running bamboo, you should either install containment at the same time or have a plan in place.
One containment technique that can only be installed at the time of planting (or before) is the raised bed. This works on the same principle as the pruning trench: rhizomes are naturally shallow and grow horizontally. If they reach a vertical drop, either straight down or very steep, they’ll come out of the side the soil, thus exposing themselves, before they dive back in. With a pruning trench, which is a 12” deep, ~5” wide trench around the bamboo, the vertical drop is achieved below ground level. But you can also get this same result by created a raised mounded bed above the soil line.
There are two important factors when using a rhizome-pruning method of controlling bamboo: proper installation, and proper maintenance. For a proper installation, we’re looking for at least 12” of vertical drop within 12” or less of horizontal span. IE, a 45-degree angle or steeper. You can get this by simply mounding up soil and packing it down on the side to achieve the angle.
I recommend using at least a 2” shallow trench as an extension of the sloping soil to mitigate any wash out the new soil may have during the first years of rains. You can also use a deeper trench and shorter bed, as long as you have at least 12” of combined drop.
The raised bed technique is useful in areas with a lot of existing roots, utility lines, or other obstacles to trenching. It also can give your initial bamboo planting some added height, effectively speeding up the fill-in time for something like a privacy screen.
During installation, the first (lowest) layers of soil to be brought in should be heavier with more clay in them. As you build the bed up, use lighter and richer soil, topping it with pure compost and then hardwood mulch. What you’re trying to do is make the conditions favorable to the rhizomes at the top, and not favorable on the bottom. I usually recommend a single- or double-shredded mulch on raised beds since they will control erosion better and last longer than a triple-shredded mulch.
Maintenance for a raised bed is the same as it is for a pruning trench: walk around the edge 2-3 times per summer, and 1-2 times per fall, and once in the winter and spring depending on the weather. If any rhizomes have shown themselves, simply clip them with a pair of hand pruners. If you wish you can then pull the rhizome out on the outside of the bed, but this is usually unnecessary since it likely isn’t mature enough to survive on its own.
During maintenance, you’ll likely need to rake out the shallow trench of any leaves or other debris that may have filled it. If you are noticing rhizomes near the bottom, you may want to deepen your trench by an inch or to be sure nothing tunnels below. Some rhizomes can go deeper than others, depending on the bamboo type, soil type, and how much water is available on the top.
Speaking of watering, the best practice it to keep it moist on top, but not necessarily let the water soak deep. This is the opposite of conventional wisdom for most plants. Remember, rhizomes tend to follow the water, sun, and organic matter. A soaker hose set to a very short duration (try 5 minutes to start) every day or every other day is a good option, depending on the time of year and how much direct sun it gets.
For small beds less than 12’ long, you may want to perform maintenance more often, at least at first, to make sure your bamboo is spreading into areas you want it.
Most temperate bamboo won't do well indoors, but below is a list of species that can grow and thrive in the right conditions. Make sure you have enough light, water precisely, and use something like Bayer Advanced Tree & Shrub to get rid of bugs. This is the only time I recommend the use of the chemicals with bamboo.
Overview: There are several types of bamboo that can be grown indoors, but none of them are among the easiest indoor plants to care for, as you might expect from some mainstays like rubber plants, corn plants, golden pothos, etc. However, with some TLC, diligence, and knowledge you can grow bamboo inside very well.
Humidity: Bamboo will prefer high humidity. The low humidity of most indoor environments greatly contributes to infestation of pests and/or disease. It is recommended to mist the plants daily and/or set up rock trays below the bamboo that will evaporate water.
Watering: Watering can be a tricky thing and usually is required to be precise. Too much water can damage roots and invite pests. Too little can damage or kill the plant. Watering should be done regularly, whenever the top of the soil is dry and before the plant shows signs of drying out. Excess water should be collected in a tray and removed if excessive (not evaporating in 2-3 days). This will take some trial and error as each plant and container is unique and will require different amounts. Most plants will need to be watered 1-3 times per week.
Pests/Disease: In an indoor environment it is likely that pests or disease may develop. Common pests such as aphids, fungus gnats, scale, mites, whitefly, etc. should be promptly identified and a suitable elimination strategy started. We've tried organic and natural methods but have found them ineffective. A product with imidacloprid such as Bayer Advanced Tree & Shrub is what we currently use. This is the only time I recommend using synthetic chemicals on bamboo.
Bambusa multiplex 'Alphonse Karr'
Bambusa multiplex 'Silverstripe'
Hibanobambusa tanquilis 'Shiroshima'
Phyllostachys aurea 'Koi'
Pseudosasa japonica 'Tsutsumiana'
3/31/20 UPDATE: We no longer recommend a sand trench but instead a pruning trench, which is basically the same thing as listed below except it's only 12" deep and it remains open. We find it is much easier to service and as long as you have heavy clay soil as is found in most of the Piedmont, the trench is very good about holding its shape year after year. You will have to clean out the leaves and other debris about once per year, which is probably the hardest part of the process but for most people is not more than 1~2 hours per year. The benefit the the open air is that you can see everything that is going on and most of the rhizomes will air-prune themselves. IE, once they hit the air they stop growing. About a third of the rhizomes will come out then dive down into the soil and these should be cut both at the point of exit and entry. Pulling any rhizomes out of the ground is unnecessary as newly escaped rhizomes won't be established enough to survive on their own - they'll just rot in the ground.
OLD ARTICLE BELOW:
Many people choose to use a sand trench to manage their bamboo. It is simply a 14" deep trench filled about 12" with sand. To maintain, simply take a flat-bottom spade and sink it into the sand, cutting through and rhizomes that have passed through. Pull the spade up and move to the side, making sure to overlap about an inch and repeat, until you've gone down the entire line. We find 100' takes about 15 minutes. Below is the schedule:
Two times per year
-end of July
-end of October
Three times per year (recommend)
-end of June
-end of August
-end of November
Four times per year (if having warm winter)
-end of March
-end of June
-end of August
-end of November
How to Plant Bamboo
Burlap coffee bags, often obtained for free, are applied before mulching to help smother potential weeds.
1. The depth of your planting depends on your type of soil and location. Heavy clay soils and/or wet areas will require a shallower hold (IE, planting higher). Sandy/well-draining soils require deeper holes (IE, planting lower). Determine your type of soil and planting area and dig a hole to the appropriate depth. For reference, most of the bamboo we plant in the Piedmont is in heavy clay soil, so we plant about 2/3 into the ground, with about 1/3 sticking up. For sandy soil, or soil on top of a berm or similar situation, we recommend planting at the same depth as the root ball.
2. If the soil is heavy clay, break up the bottom and sides of the hole with a pick or similar tool.
Mix Azomite/Rock Dust, Rock Phosphate, Greensand, Bonemeal, and Lime at a ratio of 3:3:2:1:1
Sprinkle the number of heaping handfuls listed below at the bottom and sides of the digging hole for the appropriate size plant
3 gallon pot: 1 handful
5 gallon: 1.5 handfuls
7 gallon: 2 handfuls
10 gallon: 3 handfuls
15 gallon: 3 handfuls
25 gallon: 4 handfuls
4. If you think you may have any problems with moles or voles, add in Permatill (also sold as Volebloc) to the bottom and sides of the holes.
5. Take the bamboo out of the pot (or cut the pot off). If it looks root-bound you'll want to gently coax the rhizomes out of their tight circling. It helps to cut some of the feeder roots in order to free up the rhizomes.
6. Apply mycorrhizal fungi to the exposed roots.
7. Place the plant in the bottom of the hole adjusting the base so it has full contact with the soil (no air gaps), is tilted so the bamboo is as vertical as possible, and the top of the rootball is level with the soil level. If the area is prone to be wet, plant a little high, 1"-3" above soil level.
8. Backfill with 50/50 mix of native soil and compost. If the rootball is above ground level, add soil up to the level of the root ball.
9. Compact the backfill moderately with the heal of your foot.
10. Apply fertilizer (organic preferred) and Ironite if necessary.
11. If weeds may be a problem apply around the bamboo a sheet mulch out of newspapers, cardboard, or (preferably) burlap.
12. Mulch liberally in a circle around the bamboo, taking care not to pile the mulch against the base of the culms (in a doughnut shape).
13. Tie and stake tall bamboo if necessary to prevent from blowing over in high winds.
14. Water in well.
1. Read instructions above about the difference between clay, loam, and sandy soils to determine planting depth.
2. Dig a hole about 30% wider than the size as the pot
3. If heavy clay, break up the sides and bottom with a pick.
4. If there are circling rhizomes, separate the rhizomes so they'll be able to spread.
5. Set the bamboo flat on the bottom so that it is sitting upright at the right depth and without air gaps.
6. Back fill the sides with a mix of native soil and compost or topsoil.
7. Add soil mix so that it covers the portion of the root ball sticking above the surface (if any).
9. Water in well.
David is founder of Brightside Bamboo and dreams of world where bamboo is utilized in helping solve our biggest problems.