By Robin Rivet.
Imagine a hot summer day...
This year, you don’t need too much imagination. As average summer temperatures continue to rise, respite under a shade tree can feel twenty degrees cooler than surrounding sunbaked surfaces. We seem to be losing touch with two vital assets of urban trees: One is reduction of urban heat islands, the other is local food. What if you could have great shade and eat it, too? Nut trees have that potential.
Take pecans. (No, you cannot take mine.) But consider that pecan trees love heat, grow rapidly to forty feet or much more, and adapt amazingly well to San Diego’s mild climate. Pecans need less winter chill than most nut varieties, and in just a few short years, your lounge chair can find a cool spot where sweet nuts seemingly drop out of thin air, and onto your lap. Available locally during bare root season, the ‘Mohawk’ cultivar is considered self-fruitful and has large, thin-shelled nuts of excellent quality that drop when ripe in mid-fall. Other varieties like ‘Mahan’, ‘Tejas’, and ‘Western Schley’ are also good candidates for home gardens. Some prefer cross-pollination, while others may need harvesting by shaking the branches—with a tarp below to reap the precious cargo.
Hybrid English walnuts are another fine nut tree choice. Even the hybrids traditionally sold for Southern California become tall enough in stature to lure you underneath during sweltering afternoons. ‘Placentia’ has the lowest chill for San Diego backyards, and although ‘Pedro’ needs a bit more, its taste is considered exceptional. They’re both small trees as walnuts go, but large enough to provide more than sufficient canopy.
If you’re lucky enough to have space for two large trees and you get about 400 to 500 winter chill hours, I would plant chestnuts. These are spectacularly beautiful specimen trees, with ‘Colossal’ being the standard cultivar for backyards. ‘Nevada’ works as a pollinator, or you might try a ‘Dunstan’. If you’ve never eaten chestnuts, you’re missing out on one of the most tasty, nutritious, and versatile of all nuts. Plus, they are low in fat and high in protein—a true gourmet’s delight. Above all, their majestic branch structure would add character to any home landscape.
Evergreen and subtopical, the macadamia is unique in San Diego’s nut world. A strikingly beautiful species, it thrives surprisingly well here. 'Beaumont' is the hybrid to seek out, then all you’ll really need is a special hard-shell nutcracker to extract the succulent nut.
Are you a native plant devotee? Maybe you can’t eat nuts? Do not feel left out. The native Southern California black walnut may be just your ticket. Although allelopathic, the native wildlife will not mind at all.
Instead of going nuts during our increasingly hot urban summers, help combat climate change and grow some nuts.
Member Robin Rivet is an ISA Certified Arborist, a San Diego Master Gardener and City of La Mesa Environmental/Sustainability Commissioner. She can be contacted at: firstname.lastname@example.org.