How cold it gets in your area is one of the most important factors in determining which bamboos will grow well for you. Gardeners in South Florida have the greatest range of bamboo diversity to choose from, and the further north in the state you live, the fewer the choices. However, even those of us in the “cold country” of North Florida have some excellent types of clumping, noninvasive bamboos available to us that can handle a hard freeze, especially if some basic precautions are employed.
The most cold hardy of the bamboos offered by Florida Bamboo are the Bambusa multiplex varieties (Green multiplex, Silverstripe, Alphonse Karr, Golden Goddess and Chinese Goddess), which can take temperatures down to the lower teens with little to no damage. These should do well in most North Florida locations.
Next in hardiness is Royal, which is very nearly as cold tolerant as Bambusa multiplex, handling temperatures down to the mid-teens. Buddha’s Belly and Blue Bamboo are next, taking temperatures to about 18 degrees. The least cold hardy of the varieties I sell is Giant Timber (Bambusa oldhamii), which is good to about 20 degrees – it reliably handles winters for central and south Florida, but can get knocked back by the occasional colder winter in North Florida.
These temperature figures represent the approximate level below which a bamboo plant will have substantial damage to the above-ground portions. A bamboo plant won’t usually die if the temperature dips a few degrees below this level, but it is likely to get set back considerably in its growth, sending up much smaller shoots the season after having been frozen to the ground.
Around the state, there are many “cold pockets” and “warm pockets” that can be determined only by experience, but in general, the three factors that contribute to determining winter lows for your area are: (1) How far north you are; (2) How close you are to the ocean or other large bodies of water; and (3) How close you are to an urban area. The most freeze-prone areas of Florida, correspondingly, are inland, rural areas north of about the latitude of Gainesville. Within the Gainesville developed area, an urban “heat island” creates milder winter temperatures, and heading south from Gainesville, the winters become steadily warmer.
If you live in an exceptional cold pocket, you should pay attention to some precautions about cold for best results. The most important factor is that coverage of the sky by buildings or evergreen trees offers considerable protection to bamboos. The greater the percentage of sky that is covered, the greater the protection.
Of course, more sky coverage will reduce the sunlight reaching the plant, which is needed for growth, so it may be necessary to compromise, selecting a planting location that has sky coverage to the north, east and/or west, but is open to the south, or at least open directly overhead, so the plants get at least a few hours of sunlight. Summer is the season of maximum growth, and in the summer the sun passes almost directly overhead, so a patch of sky directly overhead can allow for good growth in a plant surrounded on all sides by trees or buildings.
Another important technique for growing a species on the edge of its cold hardiness is simply to plant in early spring, rather than later in the year. As a bamboo plant gets bigger, it gets more cold hardy, so planting in early spring gives the plant the maximum time to get larger before winter comes around again. For plants that are still fairly small when a hard freeze is predicted, wrapping the plant with burlap or blankets as high as you can reach can help minimize damage the first winter or two, when it is most vulnerable. Also, giving your bamboos the best growing conditions possible, with regular watering, keeping the soil thickly mulched, and fertilizing periodically will help speed growth and turn your plants into larger, more cold-resistant specimens faster.
One important note about all of this: We’re not talking about the plants being killed altogether here, so you shouldn’t worry about losing your plants. Bamboos exposed to more cold than they can handle will first suffer leaf and twig damage (the plants can easily leaf out again after a couple of months of warm weather), or if the cold is extremely severe, all the above-ground growth can be killed, but the underground rhizome system will still be alive and will send up new shoots in spring. A bamboo plant could freeze to the ground every winter and still come back every spring, putting up an annual display of green foliage every summer, but it would not reach the full size for the species or make as good of a visual screen. So don’t interpret this section as a warning of the danger of losing your plants; it’s really about allowing them to be able to properly strut their stuff.
Winters in Florida are very variable, and there is always the possibility that next winter will bring a once-in-fifty-years freeze for the record books. If this should happen, you will be very fortunate to have landscaped with bamboo, as opposed to palm trees, for instance. A palm tree exposed to more cold than it can handle is instantly transformed into some very expensive firewood, while bamboo will come back and can regain much of its former stature and beauty in just a couple of growing seasons.