Short answer
It depends on the type. Running bamboo can spread several feet a year and, in extreme cases, much more. Clumping bamboo widens slowly, typically a few inches a year. Both types grow tall quickly once established, but height is not the same as spread. If you want a similar upright look with almost no spread, consider non-invasive clumping ornamental grasses.
Running bamboo
Running bamboo spreads by rhizomes, which are underground stems that grow sideways and send up canes along the way. Nursery figures give a feel for the range:
- Larger running types (such as many Phyllostachys) spread about 3 to 5 feet a year on average once established, with some cases over 10 feet in a season.
- Smaller running types (such as Sasa) often spread around 1 to 2 feet a year, although some can reach 5 to 8 feet in a season.
- Rhizomes can travel a long way. One university extension notes they can extend more than 100 feet from the parent plant over time, and rhizomes may surface far from the original plant.
These are typical figures from growers and extension sources, not guarantees. Conditions on your site make a big difference.
Clumping bamboo
Clumping bamboo has short rhizomes that turn upward to form new canes right beside the old ones. The clump expands outward gradually, often by a few inches a year. Over many years a clump can become large, so check mature width, but it does not send out long runners the way running types do. Growth direction and size are predictable, which is why clumpers are often recommended for boundaries. See running vs clumping bamboo.
What affects speed
Faster spread
- Loose, loamy, well-mulched soil. Rhizomes tend to grow toward moist, loose, organically rich ground.
- Regular water and warm, long growing seasons.
- Full sun for sun-loving species.
- Mature, well-established plants.
Slower spread
- Dense clay, compacted soil and gravel. Rhizomes tend to avoid compacted ground.
- Competition from other plants and from dense roots or weeds.
- Cold or dry climates.
- Shade, for many large runners, although some small ones prefer it.
- Very wet or saturated ground for most species.
The first years
A new planting usually takes two to three years to settle in before it spreads in earnest, because the plant is still acclimatising. After that it can accelerate. This is why bamboo that seemed well-behaved for the first few years sometimes starts escaping later. Do not wait until it is a problem to plan containment.
How to keep spread in check
- Choose a clumping type if you want low-maintenance. See planting a bamboo privacy screen.
- Install a rhizome barrier before planting a running type. See how to install a bamboo rhizome barrier.
- Edge or root-prune yearly, or twice a year, cutting any rhizomes at the edge of the planting.
- Grow in a large pot, with the pot raised off soil so rhizomes cannot escape through drainage holes. See growing bamboo in pots and containers.
- Know how deep to look. Rhizomes are usually shallow. See how deep bamboo roots grow.
- If it has already escaped, see how to control and remove bamboo.