As the days shorten and the stress of the sun lessens, we’re in a prime window for planting perennial evergreen species that can provide your household with edible abundance. That window stays open from early October until the third or fourth day of our first big storm, when the soil will start to be too saturated for planting. Put these items in the ground now, and then you can “turn them loose,” sit back, and enjoy harvests year after year.
Subtropical perennials that do well in the East Bay include olives, pomegranates, citrus (lemon, lime, kumquat, Satsuma mandarins), currants, loquat, avocado, and lots more.
Dig an Oversized Hole for Planting
Most of the East Bay has clay-rich soils that need conditioning. While sheet mulching can help break up and enhance clay over time, digging oversized holes for planting will help right away.
Generally, holes should be dug to three times the width and two-to-three times the depth of the pot the plant comes in. Thus, a one-gallon plant needs a hole dug to the size of a five-gallon pot. (If you live in one of the few places, like Alameda, blessed with sandy loam, this caveat may not apply.)
Root Crown Height Placement
The most important part of a young plant is the interface between earth and sky, which is known as the root crown. It’s the place where the roots branch out at the base of the plant’s trunk. For Mediterranean species, this root crown must be planted slightly higher than the flatlands around it. This can be achieved simply by mounding the root crown’s planting height two-to-three inches higher than the surrounding ground level. You’ll want to create a dome mound to ensure that the new root ball is covered. (See chart above.)
Take your new plant gently out of its pot and use a stick or ruler to measure from the bottom to top of the root crown. Use the same stick or ruler to measure the hole depth. You’ll want it one inch shallower for wet species like avocado or three inches shallower for a Mediterranean species like olive. If the hole is too deep, build a volcano (mini-mound) in the bottom of the hole and tamp down with your fingers. Then sit the root ball on top of this mound. Re-measure to check that the plant sits the proper height above the surrounding soil level for your particular plant.
Open Up the Roots
Opening up the roots stimulates growth. Use a hori hori (see below) or a butter knife to gently stab into the root ball, but do not remove an excessive amount of the root ball’s soil, since that helps the roots adjust in the hole. Use a stick or ruler to recheck root crown height one last time.
Banded Soil Layers
Now that the plant is placed, begin to fill your hole with an appropriate soil mix (see above), adding it in layers like a stack of doughnuts. The top layer should be a cap of native soil, since native soil is able to withstand the impact of a rainstorm without compressing or eroding. Bagged soil mixes will run away with the first rains if not capped over with either native soil or wood chips. This cap should be the last couple inches you put into the hole. Sort this soil by removing large chunks and pieces bigger than the size of ball bearings.
Now that your new plant is in the ground, you should protect it by mulching it three or four inches deep with wood chips or straw. This will conserve moisture, reduce weeds, and provide a slow release of nutrients to the roots. When putting down this layer, make sure to remove any mulch that’s landed directly over the root crown, which needs to be free to breathe fresh air. When the root crown is buried, it runs the risk of rotting.
Natural Mulch Alternative
If you don’t wish to purchase wood chips, you can take advantage of the autumn bounty and collect fallen leaves. I’m sure someone on your block with a deciduous tree canopy will be thrilled for you to “harvest” a few trash bags’ worth. Note: Avoid eucalyptus and sycamore, as they are known to spread disease.
Tools and Recommendations
You’ll need a metal rake and a shovel, or course, but here are some additional tools worth investing in:
Hori Hori: A Japanese digging tool available at Hida Tool on San Pablo Avenue in Berkeley.
Mattock: This super pick is the best thing for working through our East Bay clay.
Steel digging bar: For larger trees, this amazing tool can often be the only way to penetrate hard clay and rocky soils.
If you need a new shovel, I like the all-steel model made by Fiskars.
Want to Learn More?
Watch for Joshua’s Bare Branch Planting guide in a later installment.
Check out Joshua’s articles in back issues of Edible East Bay, especially this one on creating layers in your food garden.
Joshua Burman Thayer is a San Francisco Bay Area ecological and permaculture landscape design-er and consultant specializing in dry-land landscape design. He can be reached at 510.332.2809, nativesungardens.com