Gardener’s Notebook by Joshua Burman Thayer
While microclimates might not seem like something you can create on your own property, in fact you can. Even if you have a small or flat piece of land, you can diversify your local topography by reshaping it with mounds that direct the flow and retention of water.
Since the type of soil that a plant’s roots sit in can make a huge difference to the health of that plant, it helps to be able to place each planting strategically to support varying needs.
An important consideration for gardeners in our area just east of the San Francisco Bay is that much of our terrain has clay soil. This can act like a terra cotta pot, restricting root development and swamping roots in the prolonged winter wetness. That excess moisture can cause too much fungal growth.
Mediterranean fruit trees—like fig, olive, pomegranate, and citrus—do well here, but prefer drier, aerated root zones. For this reason, they do well when raised up on mounds. Conversely, apples, cherries, elderberry, and berries like to have extra moisture directed toward them, so if you plant these in the flats or low spots below your mounds, they will gladly drink that water up.
Another good reason to create mounds is that they can contribute to an appealing design. I like to think of them as backstops that add dynamic effects and give the impression of larger vistas.
Creating mounds on your property will immediately confer many advantages:
- They are good planting areas.
- They can create interest in a flat lot.
- They can help aerate a planting area.
- They can help steer rainwater intentionally through your garden.
- They can be made from leftover branches, leaf duff and excess soil that you retain on-site so you are moving carbon into the ground where it becomes valuable rather than removing it to a dump where it may emit into the atmosphere.
Here’s how to create effective plant-able mounds:
- Buy several bags of planting mix to add fertility. You will also want to use any compost you have created on-site.
- Collect branches and twigs from around your property. These will be used to build up your mounds.
- Flag the areas where you wish to build mounds. A rule of thumb is that you will need at least 3 feet by 3 feet of usable space.
- As you dig, keep the excess soil nearby to use in your mounds.
- Start by piling up branches and twigs to form the bases of each mound.
- Cover the branches and twigs with planting mix.
- Add excess garden soil over the planting mix and shape the mounds in gently sloping ovals. These shapes will maintain integrity as the soil settles.
- If you are planting large fruit trees, make mounds that are 2 feet tall and 3–5 feet wide with 5–8 feet distance between each large tree being planted.
- If you are planting vines like grapes or semi-dwarf trees like citrus as a sub-canopy, make mounds that are 1–2 feet tall and 3 feet wide with 3–5 feet between these plantings.
- Your new trees and shrubs should get planted in the centers of the mounds. If you are planting fruit trees, also consider adding mint, rosemary, oregano, and nopal cactus around the mounds. The winter blossoms will bolster diversity and provide nectar for bees, and you may also find you can dissuade rodents. You can also add flowers and vegetables (in season) around your mounds.
- Finally, cover your mounds in 3–4 inches of wood chip mulch, hay, or raked fall leaves.
Get expert help with your garden from Joshua Burman Thayer at 510.332.2809. Learn more about food forests and permaculture landscape design at nativesungardens.com and from Joshua Burman Thayer’s new book, Food Forests for First Timers.
Joshua Burman Thayer’s Gardener’s Notebook is filled with gardening advice for every season. Visit the whole collection of articles here.