Anyone who has had even a little exposure to the ideas and techniques within permaculture is likely to have heard the phrase ‘guild planting’. Also known as companion planting, this is the system by which species of plants are grouped together in certain locations to provide mutual benefits to the group as a whole. They are akin to webs, with each strand of the web on its own weaker than when all the strands work together. Guilds can be instituted in time – with plants growing and maturing together – and over time – by planting successive crops in the one location. Effective guild planting also means that you avoid its inverse – plating species next to each other that may have a detrimental effect on one another.
Guilds are typically instituted around a central plant, most often a fruit tree. The plants located around the tree offer it benefits and receive others in return, including shade and protection from wind. Guilds also include animals, both wild and livestock, as they can help influence growing outcomes as well.
Guild planting is one of the most effective ways to use the available productive space in the garden. This is because by planting species next to others that can provide at least some of the inputs they require, you can locate them closer together. For instance, stacking is a common feature of guilds – the planting a taller growing species beside more low-lying plants, providing those latter plants with shade or support. Common stacking combinations include planting lettuce and cucumber in the shade of sunflowers, and allowing beans to use corn stalks as trellises.
The other means of maximizing space with guilds is to plants species next to one another that mature at different rates, meaning that those that develop more quickly afford the slower-growing specimens shade. This means you can harvest crops at different times, giving you produce across the growing season. You could also plant species next to one another whose crops grow at different levels, making harvesting easier.
Furthermore, often in guilds, plants that grow well together also taste good together, so you can harvest some of both species at the same time for use in the same dish. For instance, dill hosts a predatory wasp that keep down pest populations that attack apples, so it beneficial if planted nearby, while also tasting great with the cooked fruit.
Guild planting can also help you ensure that good levels of the nutrients all plants need are in the soil and available to the roots, especially nitrogen. The family of plants known as legumes, which includes peas and beans, has a symbiotic relationship with a certain bacteria in the soil that allows them to ‘fix’ nitrogen from the atmosphere on their roots. This nitrogen also helps plants nearby to grow strong and healthy. Beans planted with plants of the cabbage family (such as lettuce, cucumber and parsley) helps these spices, which do not have the nitrogen-fixing ability, helps them thrive. Acacias planted near to fruit trees are another example of a guild that boosts nitrogen uptake.
An example of a guild working through time to improve nitrogen levels in the soil, is if you are trying to revitalize a piece of poor quality soil, perhaps one that has been used in intensive agriculture. When damaged bare soil is left exposed, the first plants that will colonize it are weeds such as white clover and dandelion. The former can fix nitrogen, while the latter has deep roots that break up the soil and access nitrogen and other nutrients lying further down in the soil profile. Allowing the weeds to grow helps bring nitrogen levels up towards the surface. You can then slash and mulch the weeds so that the nutrients are retained in the soil for you first crop planting to access.
Guild planting can also provide other nutrients, in the shape of organic matter that serves as natural mulch. For instance, sweet potato acts as living mulch, crowding out weed species that then rot into the soil as it grows, while other plants, such as poplar, shed organic material that then serves as mulch as it lies on the ground.
Guilds are also beneficial in protecting species from potential pest problems. Certain species can be planted next to vulnerable specimens to confuse or repel pest insects, using scents or chemicals to confuse insects or strengthen other species against attack. For instance, mature basil plants release a chemical that repels insects that are attracted to tomatoes and apricot trees, so should be planted as part of a guild that includes those species, while marigolds have a scent that repels the White Fly that can attack food crops.
There are other methods by which guild planting can deter pests. A diverse canopy of foliage can confuse pests, such as planting pumpkins and squash alongside corn, while shapes can also confuse insects and attract them to species that are less susceptible to damage. For instance, if moths are a problem in terms of attacking you cabbage, planting collards nearby can help draw some of the moths away from the more vulnerable cabbages.
In terms of a guild’s inter-relationship with animals that keep pest populations under control, providing sufficient canopy cover for nesting birds will attract insectivorous species, while allowing livestock such as chickens to forage will help keep slug and snail populations down.
It is not only from pests that guild planting can offer protection; it can also serve to modify weather conditions to help sensitive plants species. The most obvious one is that taller plants, such as your central fruit tree, offer those underneath it shade. The tree also helps to disperse rainfall so that the moisture falls over a wider area and does not cause soil erosion. Hardy tress and grasses, such as cane grasses, can be planted to act as windbreaks, protecting other species from the potential damage strong winds can do, as well as limiting evaporation of moisture from the soil.