Gardener’s Notebook

by Joshua Burman Thayer

Did you know you can grow productive avocado trees here in the San Francisco Bay Area? We are close to the northern edge of where avocados will thrive, but with some planning and care, you can achieve long-lasting avocado success.

Years ago, I had a great opportunity to learn about avocado trees while designing two properties in Santa Barbara County. One sat in the hilly uplands of Montecito, California. This is natural habitat for avocados; they do not like to have water sitting around their roots, and the slope prevented that from happening. But down the hill at the coast, I had a design in the community of Goleta, where the marshy mudflats area was not at all a natural avocado habitat. To create a healthy environment for them there, I used soil mounds to help lift the trees’ root crowns out of the swampy ground.

I mention all of this because here in the Bay Area, you can have much more success by mounding your trees. Here’s how:

Make a 3- to 4-foot-wide mound that is 18 inches tall. Combine local soil, planting mix, and volcanic pumice to create a rich, yet aerated, soil mix. Plant more than one cultivar to invigorate pollination (For the East Bay, I recommend Haas and Bacon.) It’s best to get 15-gallon trees for the mounds.

Expect 4–6 years before you’ll get a heavy harvest, and you’ll also want to think long when you are placing your avocado trees, since they can grow 30 to 40 feet tall and 12 to 20 feet wide. Look for a spot on your north or east property line. This way you won’t lose valuable light flooding from the south or west onto the rest of your garden.

It’s also a good idea to create a wind break for your avocado trees, since they do not like strong winds. Wind break trees to consider include the Pacific wax myrtle (Myrica californica) and the purple hops bush (Dodonaea viscosa ‘Purpurea’).

One way to protect your avocado trees during summer is to foliar feed them with kelp meal once a week at dusk. This will deliver nitrogen and beneficial microbes directly where it can be used. Fill a 750ml spray bottle with water and add 2 teaspoons dry kelp powder. Shake it up and spray it on the leaves.

Summer heat notice: Make sure you are watering your garden twice a week in June. At this time of year, the soil is rapidly drying out, and with the lowering water table, our plants can get stressed.

Read more of our stories on growing and enjoying avocados:
The East Bay Avocado and Avocado Adventure at Chetwyn Farm

Artist Mary H. Brown is a figurative oil painter and ceramicist. Find her work on Instagram @maryhbro.

This Gardeners Notebook is one of Joshua Burman Thayer’s monthly columns for this newsletter. He also contributes longer articles for Edible East Bay’s print magazine, all archived. Search “gardener’s notebook.”
Check out his design site: nativesungardens.com