Bougainvillea

Q: My bougainvillea was damaged during a cold snap. Some branches still have foliage, but others lost all of their leaves. I started to prune the leafless branches and discovered that they still are green inside. Should I continue to prune them, or will they regrow their foliage?

 
A: It is not unusual for bougainvilleas to lose leaves during cold weather, so having bare stems doesn’t necessarily mean dead limbs. You should wait to prune until all threat of frost in your area has passed, so that tender new growth is not damaged by cold nights, remarks University of Arizona Maricopa County Cooperative Extension Master Gardener Susan D. Noack. (In Maricopa County, the average last frost date is mid-March, but the date varies depending on factors such as elevation, your area’s microclimate and weather.) There is no need to be hasty with trimming at this time of year, as the plant may not be as damaged as you think. Wait until you see new leaf buds come out, and then only prune dead wood that is above the new growth.
 

Q: Does holy basil (Ocimum tenuiflorum) grow in the Phoenix area?

A: The Arizona Herb Association (AHA) has grown holy basil in its demonstration herb garden at the Maricopa County Cooperative Extension, says AHA member and Master Gardener Carolyn Hills. “Like any basil, it does best in rich, well-draining soil, full sun and plenty of water,” she explains. Sow basil seeds indoors in February to have transplants ready when temperatures start warming in spring, usually early March. It will grow beautifully until temperatures cool in November and December. However, basils must be protected from frost or brought indoors on frosty nights if they are in pots.

Basils can be grown as perennials in the low desert if they are protected from frost. ‘African Blue’ basil is usually the most cold-tolerant, although other types (including holy basil) often make it through our milder winters. To learn more about growing herbs in the low desert, visitors are welcome at AHA’s monthly meetings. Visit azherb.org for details.
 

Q: How far apart should citrus trees be planted to create a mini citrus orchard in my backyard?

A: Standard-size citrus trees can grow to more than 20 feet in diameter at maturity, states Maricopa County Cooperative Extension Master Gardener Olin Miller. His trees have been in the ground for 25 years and canopies average 20 feet. He suggests a minimum spacing of 15 feet, which allows for some overlap. Depending on available space, dwarf citrus trees may be a better option. Dwarf citrus trees on ‘Flying Dragon’ rootstock often are advertised as growing 6- to 10-foot canopies, but Miller cautions that they may reach diameters of 8 to 12 feet; so dwarf citrus should be spaced about 8 feet apart.