Companion planting is the art of combining different plant species in a group so all the plants in the group benefit from each other. A group of mutually beneficial companion plants are known as a guild.
Companion planting brings a range of benefits to a food garden. It can improve soil fertility, attract beneficial creatures to the garden, help repel pests and diseases, improve the flavour, scent or colour of fruits, flowers and herbs, discourage or smother weeds, protect the soil, retain moisture in the garden, provide shelter, or provide shade or protective ground cover for tender plants.
Before you create a guild of companion plants in your food garden, think about what you want to achieve through companion planting.
These are some common types of guild:
- Guilds to build up and maintain soil fertility
This guild combines plants with complementary root systems and nutritional needs to restore and maintain soil fertility. Plants with deep tap roots are mingled with plants that have shallow or branching roots. The deep rooted plants draw nutrients from deep soil layers and recycle these into the top soil layers, where they become accessible to the shallow rooted plants. Deep roots create pathways through the soil and improve soil structure.
Shallow, branching root systems hold soil in place and prevent soil erosion. Comfrey and Globe Artichoke, for instance, are excellent soil mineralizers and soil breakers. Their deep roots break up compacted soil and their leaves add mineral rich organic layers to the soil surface. In his book ‘Permaculture’ Bill Mollison suggests cultivating deep rooted perennials such as comfrey and globe artichokes in fruit tree orchards, as the deep tap roots don’t interfere with the shallow tree feeding roots, and the leaves add nutrients to the soil around the trees. Add legumes, such as clover, to the mix to increase nitrogen levels.
- Guilds of plants with similar needs
This type of guild is designed around specific environmental conditions. Nearly every garden offers a range of different micro-environments. Various combinations of sun and shade, moisture, exposure, garden topography and soil conditions create a variety of niches and micro-climates. Exploit these slight variations in your garden to expand the diversity of food plants you can grow. Group plants that have similar needs for sunlight, shade, temperature, water and soil conditions. For instance, save on irrigation and effort by growing all your water thirsty plants in one area, and plant less water dependent plants in another area.
- Guilds to protect and shelter other plants
These are designed to create shelter and protection belts in a new garden, and to develop plant friendly micro-climates in harsh conditions. Plants that provide shelter to more tender varieties are sometimes called ‘nurse’ or ‘mother’ plants.
Dense hedges, windbreaks and shrubberies placed in strategic places provide protection and shelter for more sensitive food plants against heat stress, sunburn, cold, and wind. Densely growing companion plants can create ‘barriers’ that prevent grass encroachment and unwanted weed growth. If fast growing, short lived varieties are planted amongst slower growing plants, the faster growing plants will provide ground protection for the slower growing plants. In food gardens tall growing plants such as maize, sweet-corn and sunflowers, for instance, can shelter plants that prefer cooler conditions, such as lettuce.
- Guilds to attract beneficial garden creatures
Predatory, pollinating and soil building insects and other small creatures are a vital part of healthy food gardens. This sort of guild is designed to attract and shelter beneficial garden creatures by providing suitable food and habitat. To create a guild for useful garden creatures, first find out as much as you can about the habits of the creatures you wish to entice into your garden. What food and habitat do they need, and what plant species may supply these?
- Guilds to repel garden pests
Some plants contain chemicals and enzymes that repel insect pests. Plants can actively ‘switch on’ these natural pest defenses when attacked by pests. Combining plants that repel insect pests with plants that attract beneficial garden creatures is known as a ‘push-pull’ pest control strategy, and is an effective way to reduce problem insect pests in the garden.
When planting a guilds for food gardens, you can combine flowering plants with vegetable companions to attract beneficial insects. Mix plants up randomly, plant the companions in alternative rows, or plant in blocks adjacent to each other.
Companion plants for food gardens
This table lists combinations for companion plants in a food garden. Don’t be afraid to experiment and find which combinations work best for your garden. Each row in the table shows plants that make suitable companions for each other.
By Valerie Payn
Valerie is the author of the e-book, An Ecological Gardeners Handbook (available from Amazon and other e-book sites). Val also blogs regularly about sustainable landscape design and ecological gardening.