Short answer
For a species that is capable of reaching 20 feet, a small nursery plant commonly takes roughly four to six years to get there, and sometimes longer in cool climates or poor conditions. Many bamboos never reach 20 feet at all, so the species you choose matters as much as the time.
Individual shoots are a different story. In a mature stand, each new shoot can reach its full height in about two to three months. The slow part is the plant building up enough strength, over several years, to send up tall shoots.
Why bamboo seems so fast
Bamboo grows in bursts. In spring, new shoots emerge from the ground and rise rapidly. Nursery growers report that large timber bamboos in an established grove can grow around a foot a day, or more, at peak. That speed uses energy stored in the rhizome system, so it only happens when the plant is already large.
A newly planted bamboo has not built that system yet. Growers generally say that:
- A young plant’s first new shoots are often only a little taller than the canes it came with.
- If it was freshly dug or recently moved, the first year may be short and bushy.
- Each year the new canes tend to be taller and thicker than the year before, until the plant reaches its mature size.
One nursery example: a plant with four canes about 8 feet tall might send up three more that reach about 10 feet, then perhaps five to ten shoots the next spring that reach about 15 feet. After several more years the same plant could be 30 feet tall and sixty canes strong, if the species and climate allow it.
Typical timelines
Rates vary a great deal with species, climate and care, but nursery guidance gives a rough picture:
| Type | Typical height gain per year (rough) | Notes |
|---|---|---|
| Hardy clumping bamboo (e.g. Fargesia) | about 1 to 3 feet | Many mature at 10 to 15 feet, so may not reach 20 feet |
| Larger running bamboo (e.g. Phyllostachys) | about 3 to 5 feet | Can reach 20 feet or more in suitable climates |
| Tropical clumping bamboo | varies, often fast in warm, humid conditions | Needs a mild climate |
On that basis:
- Small plants (one-gallon size) of a suitable running type spaced a few feet apart can give an 18 to 30 foot screen in about four to five years, according to one nursery.
- Larger plants (five gallons or more) start taller and may fill in sooner.
- Small bamboos reach mature size in about three to four years, large bamboos in five to six.
These are averages. Treat them as a planning guide rather than a promise.
What speeds it up or slows it down
Faster
- Warm, long growing seasons.
- Consistent watering, especially in the first few years.
- Rich, loose, well-mulched soil.
- A larger, well-rooted starting plant.
- Regular feeding with a high-nitrogen fertiliser.
- Shelter from wind while young.
Slower
- Cool climates. Some nurseries suggest subtracting a few feet of expected height for each zone colder than the one their figures assume.
- Dry soil, heavy compacted clay, or competition from weeds and grass.
- Too much shade for a sun-loving species.
- Planting very late in the year, or in the wrong season.
- A newly moved plant. Growth can be slow in the first two to three years.
Which bamboos reach 20 ft at all?
Many garden bamboos do not. Cold-hardy clumping Fargesia typically top out around 10 to 15 feet. Larger Phyllostachys species and tropical clumpers such as some Bambusa can exceed 20 feet in the right climate. Growers also note that a plant in a pot is usually shorter, about half to three-quarters of its in-ground height. Check the mature height for your zone on the plant tag or the nursery listing, not just the species maximum.
Tips
- If you need height quickly, buy larger plants rather than small ones, or fill the gap with tall ornamental grasses, which often reach full size in a season or two.
- Water deeply and regularly, especially in the first year.
- Mulch and feed, as covered in growing bamboo in your yard.
- For a screen, planting a bamboo privacy screen has spacing advice that affects how soon it fills in.
- If you are choosing between types, running vs clumping bamboo compares them, and does bamboo spread quickly? covers sideways growth.