Gardener’s Notebook by Joshua Burman Thayer | Illustration by Charmaine Koehler-Lodge
Microclimates matter when it comes to what will grow well on your property, but did you know that you can manage the moisture diversity around your property by reshaping its topography? Even if you have a small or flat piece of land, you can create moisture microclimates by building mounds that direct the flow and retention of water.
The level of moisture your plants receive can make a big difference to their health, which is why you want to place your plantings strategically to support varying needs. Here in the East Bay, the clay soil that predominates can act like a terra-cotta pot, restricting root development or swamping roots and causing excess fungal growth during prolonged winter wetness. Mediterranean fruit trees—like fig, olive, pomegranate, and citrus—thrive here, but they prefer drier, aerated root zones, which is why they do well when raised up on mounds. Conversely, apples, cherries, and most berries like to have extra moisture directed toward their roots, so if you plant these in lower spots in your reshaped terrain, they will gladly drink up that extra water.
Mounds offer other key advantages beyond the intentional directing of water around your property. For instance, they can help create an appealing design. I like to think of them as backstops that add dynamic effects and give the impression of larger vistas.
Mounds also expand your property’s surface area, which means you have more places to plant. With that extra space, you can add seasonal vegetables and a diverse array of flowers and herbs that will attract pollinators to your garden. Aromatic plants like mint, rosemary, thyme, and oregano can dissuade rodents.
Mounds can be made from leftover branches, leaf duff, and excess soil that you have on-site, so rather than removing these materials to a dump where they may emit CO2 into the atmosphere, you are moving carbon into the ground where it becomes valuable to your plants.
How To Build Mounds
Flag each mound site. A rule of thumb is that you will need at least 3 feet by 3 feet of usable space.
If you are planting large fruit trees, your mounds should be 2 feet tall and 3–5 feet wide with 5–8 feet of distance between each tree.
If you are planting a sub-canopy of vines like grapes or semi-dwarf trees like citrus, your mounds should be 1–2 feet tall and 3 feet wide with 3–5 feet between these plantings.
As you dig, keep the excess soil nearby to use in your mounds.
To enhance fertility, you’ll need several bags of planting mix, to which you can add up to 10 percent compost you might have on-site.
Collect branches and twigs from around your property and pile them up to form the base of each mound.
Cover the branches and twigs with planting mix (plus compost).
Add excess garden soil over top and shape the mounds in gently sloping ovals. These shapes will maintain integrity as the soil settles.
Plant your new fig, olive, pomegranate, and citrus trees in the centers of the mounds and your apple, stone fruit, and berry plants in the low spots between mounds. You can also add flowers, herbs, and vegetables at appropriate times in the planting seasons.
Finally, cover your mounds in 3–4 inches of wood chip mulch, hay, or fallen leaves.
Joshua Burman Thayer is a permaculture designer and educator. A regular contributor to Edible East Bay and Mother Earth News, he also offers valuable gardening advice monthly in Edible East Bay’s e-newsletter, East Bay Appetizer. Learn more about Joshua’s work at nativesungardens.com and follow him on Twitter @nativesungarden.