Neem trees can be very happy growing outdoors in frost-free zones in California and Arizona, but growers need to take special precautions to help them get through the transition from the jungle environment in our Central Florida greenhouse to your dry climate.
Prized in the Sahara for their cooling shade, neem trees will become very large over time. They can grow from four to eight feet per year under optimum conditions, so you need to carefully consider where you plant them. Their roots tend to grow straight down so the destruction of concrete isn’t as much an issue as long-term aesthetics.
Before you put a neem tree in the ground, however, you must help it acclimate to your hot, dry growing conditions. It does love full sun, but for best results put it in a pot with good soil in a spot where it gets early morning sun or dappled shade when you first get it. Water it in very well, then don’t water again until the soil feels dry. It’s gone from the jungle humidity of our Florida greenhouse to your desert, and it takes a little getting used to.
If leaves start to wilt in dry climates, spritz them with water or very dilute fish emulsion. Don’t overwater – that’s the easiest way to kill a neem tree. To learn about “watchflowers,” visit our blog at https://neemtreefarms.com/blog/using-watchflowers-with-neem/279 (you can also Google watchflower and it will pop right up). You can also “guestimate” the amount of water in the pot by weighing it while the soil is wet and dry. Wet soil is much heavier and the difference is easy to gauge. If the soil is already wet, getting those roots wet again is the fastest, most effective way to kill it.
In clay, try to dig a pretty big hole and back fill it with better soil. Mulch it well too, which I’ve heard breaks down the clay— there isn’t much of that to experiment with in Florida! For best results, use a fertilizer made for citrus and follow the directions carefully.
If they prefer any particular soil pH, we haven’t discovered it. The books say they won’t handle salt, but they’re doing just fine in Key West where the soil is extremely acid and the salt water table is about five feet below the ground. They do like a good layer of mulch and organic fertilizer, particularly if you have an occasional freeze.
If you get regular freezes, you’ll end up with a giant neem bush. They freeze back to the ground at about 28, but I’ve seen them grow back from temperatures as low as 22. To get the tree shape back, pick one to three of the largest branches and keep pruning the side branches until it looks the way you want it to. Of course, if you’re harvesting the leaf, all of those branches provide much more easy-to-pick leaf than a real tree. (Check out Growing Neem in Central Florida and Southern Texas for hints on protecting it from cold weather.)