A native of India, neem is an extraordinarily hardy tree that thrives in ecosystems ranging from the Sahara Desert to the wet salty environment of the Florida Keys. The only pests known to harm it are directly related to overwatering: slugs (which are mollusks not insects) and several strains of root rot.
In truly tropical climates, neem quickly becomes a valuable shade tree, growing up to eight feet per year under optimum conditions. Neem trees handle heavy weather exceptionally well, with trees in Key West covered in new growth after four hurricanes in 2005 including a storm surge from Wilma that left them standing in salt water for more than 24 hours.
Further north, neem trees will handle temperatures to about 30 degrees without damage and come back from the ground after temperatures as low as 24. After our last really cold winter with five nights below 26, they didn’t show signs of life until late June. By the end of the summer, however, they’d grown an easy eight feet tall.
In frost-free or nearly frost-free growing zones, we recommend planting neem in the ground rather than a pot. However it should be planted soon after the last expected freeze date for your location. That allows the neem tree to develop a large root system before cold weather threatens again. A heavy layer of mulch provides nutrients through the growing season and creates its own warm micro-climate as it breaks down. Along with regular fertilizer, we use Medina Soil Activator to ensure high levels of beneficial microbes, and supplement with kelp to protect the plant from stress.
If you would rather grow neem in a pot, you can bring it inside on the occasional night when temperatures are expected to drop below freezing. Another option is to cover the neem tree by turning the pot on its side and throwing a blanket over it on the ground. (Speaking from experience, it’s much easier than trying to protect a 10-foot-high tree and temperatures stay warmer closer to the ground.) You also may coppice the tree about Thanksgiving, then cover it with a large clean trashcan when freezing weather is expected.
Like many tropical plants, neem trees are day-length sensitive and stop growing in the winter unless supplemental light is provided, particularly if they are indoors. If you expect to harvest neem year-round, make sure your tree receives as much natural light as possible during the day, then several hours of artificial light at night during the short days of winter. It doesn’t need to be much, a nearby living room light is fine.