In most ecosystems that offer easy food for humans, the ground needs to be covered. Layers of leaves, organic matter from animals (poo, fur, carcasses, meal remains, etc.) , dropped branches and twigs, fallen flowers and fruit, and whatever else gravity holds close to the earth, compost to create soil and retain water and protect the soil from erosion and compaction. Areas that don’t have this compost layer are called deserts. If you want to grow an assortment of food for humans, you have to start building soil. Even in desert communities where there are some food plants growing, such as edible cactus, mesquite beans, etc., there is biodiversity on a more microscopic scale than in old growth forests. In deserts the soil needs to absorb what little rain there is and do it quickly before it evaporates, and plants have leaves adapted to have small leaf surfaces so as not to dry out, and there are few leaves to drop. Whereas in areas where there are large forests the weather is usually wetter, tall plants and thick underbrush provide multiple layers of protection both on the plants and when they fall to layer the earth.
A quick way to build soil in plant guilds is to design for plants that will cover the ground. This isn’t necessarily the same groundcover as you would use to cover embankments. For instance, iceplant can be used in a pinch, but it really isn’t the best choice in most plant guilds unless you are in a very dry climate, and your plant guild is mostly desert-type plants: date palm, etc. Annuals can be squash or other aggressive food-producing vines such as unstaked tomatoes. However you don’t need to consider just ground-hugging plants; think sprawling shrubs.
When guests tour through Finch Frolic Garden, they often desire the lush foresty-feel of it for their own properties, but have no idea how to make it happen. This is where what I call ‘placeholder plants’ come in. Sprawling, low-cost shrubs can quickly cover a lot of ground, protect the soil, attract insects, often be edible or medicinal, be habitat for many animals, often can be pruned heavily to harvest green mulch (chop-and-drop), often can be pruned for cuttings that can be rooted for new plants to use or to sell, and are usually very attractive. When its time to plant something more useful in that area, the groundcover plant can be harvested, used for mulch, buried, or divided up. During the years that plant has been growing it has been building soil beneath it, protecting the ground from compaction from the rain. There is leave mulch, droppings from lizards, frogs, birds, rabbits, rodents and other creatures fertilizing the soil. The roots of the plant have been breaking through the dirt, releasing nutrients and developing microbial populations. Some plants sprawl 15′ or more; some are very low-water-use. All of this from one inexpensive plant.
Depending upon your watering, there are many plants that fit the bill, and most of them are usable herbs. Scented geraniums (Pelargonium spp.), lavender, oregano, marjoram, culinary sage, prostrate rosemary, are several choices of many plants that will sprawl out from one central taproot. Here in Southern California, natives such as Cleveland sage, quail bush (which harvests salt from the soil), and ceanothus (California lilac, a nitrogen-fixer as well), are a few choices. Usually the less water use the plant needs, the slower the growth and the less often you can chop-and-drop it. With a little water, scented geraniums can cover 10 – 15 feet and you can use them for green mulch often, for rooted cuttings, for attracting insects, for medicine and flavoring, for cut greenery, for distillates if you make oils, etc.
Groundcover plants shouldn’t be invasive. If you are planting in a small guild, planting something spreading like mint is going to be troublesome. If you are planting in larger guilds, then having something spreading in some areas, such as mint, is fine. However mint and other invasives don’t sprawl, but produce greenery above rootstock, so they are actually occupying more space than those plants that have a central taproot and can protect soil under their stems and branches. Here at Finch Frolic Garden, we have mint growing freely by the ponds, and in several pathways. Its job is to crowd out weeds, build soil, and provide aromatherapy. I’d much rather step on mint than on Bermuda grass, and besides being a superb tea herb, the tiny flowers feed the very small bees, wasps and flies that go unsung in gardens in favor of our non-native honeybees (there are no native honeybees in North America).
Here’s a general planting tip: position plants with fragrant leaves and flowers near your pathways for brush-by fragrance. You should have a dose of aromatherapy simply by walking your garden path. Mints are energizing, lavenders calming, so maybe plan your herbs with the pathways you take in the morning and evening to correspond to what boost you need at that time.
Consider groundcover plants and shrubs that will give you good soil and often so much more.
Next up: Vining Plants.
You can find the entire 9-part Plant Guild series here: Plant Guilds: What are they and how do they work? The first in a series. , Plant Guild #2: Canopy , Plant Guild #3: Sub-Canopy , Plant Guild #4: Nitrogen-Fixers, Plant Guild #5: Mining Plants, Plant Guild #7: Vines, Plant Guild #8: Insectiaries, Plant Guild #9: The Whole Picture.