Companion Planting: Creating Harmonious Garden Ecosystems

Introduction: What is Companion Planting?

Companion planting is the practice of growing different plants in close proximity to benefit one or more of the plants involved. It's a form of polyculture – growing multiple crops in the same space – that mimics the diversity of natural ecosystems. Instead of neat rows of single crops (monoculture), companion planting creates a more complex and resilient garden environment.

This approach leverages the natural relationships between plants to enhance growth, deter pests, attract beneficial organisms, and improve overall garden health. It's a technique rooted in observation and traditional knowledge, practiced by farmers and gardeners worldwide for centuries, including many sophisticated systems developed across Africa.

This guide explores the principles behind companion planting and provides practical examples applicable to various African gardening contexts, helping you create a more productive, sustainable, and harmonious garden ecosystem.

Companion planting integrates different species for mutual benefit.

Benefits of Companion Planting

Thoughtful companion planting offers numerous advantages for the gardener and the garden ecosystem:

• Pest Deterrence: Some plants release scents or chemicals that repel specific pests, protecting nearby vulnerable crops.
• Attracting Beneficial Insects: Certain flowers and herbs attract predatory insects (like ladybugs and lacewings) that prey on pests, or pollinators (like bees and butterflies) that improve fruit set.
• Improved Plant Health and Vigor: Some companions can enhance the growth or flavor of their neighbors, possibly through nutrient sharing or soil conditioning.
• Weed Suppression: Low-growing companions can act as a living mulch, shading the soil and suppressing weed growth.
• Maximizing Space (Intercropping): Combining plants with different growth habits (e.g., tall and vining with low-growing) allows for more intensive use of garden space.
• Nutrient Provision: Legumes (beans, peas, cowpeas) fix nitrogen from the air into the soil, benefiting neighboring plants that require nitrogen.
• Providing Support: Tall, sturdy plants like maize or sunflowers can provide natural trellises for vining plants like beans or cucumbers.
• Creating Beneficial Microclimates: Taller plants can provide shade or wind protection for more sensitive companions.

How Companion Planting Works

The benefits of companion planting arise from various interactions between plants:

• Chemical Repellency/Attraction: Plants release volatile organic compounds (VOCs) from their leaves, flowers, or roots. Some VOCs repel pests (e.g., marigolds deterring nematodes), while others attract beneficial insects (e.g., dill attracting lacewings).
• Physical Effects: Growth habits influence interactions. Tall plants provide shade or support; dense groundcovers suppress weeds.
• Nutrient Cycling: Nitrogen fixation by legumes is a key example. Some plants may also make certain soil nutrients more available to others.
• Trap Cropping: Planting a highly attractive species to lure pests away from the main crop.
• Camouflage: Interplanting can make it harder for pests that specialize in one crop to locate their host plants.

Planning and Designing Companion Plantings

Effective companion planting requires more than just placing recommended pairs together. Consider the overall garden design and plant needs.

Planning involves integrating companions strategically within the garden layout.

Common Companion Planting Combinations

Here are some widely recognized companion planting relationships, including examples relevant to African agriculture:

The Three Sisters (Maize, Beans, Squash)

A classic example from indigenous American agriculture, also adaptable to African contexts using local varieties:

• Maize (or Sorghum): Provides a stalk for beans to climb.
• Beans (or Cowpeas): Climb the stalks and fix nitrogen, benefiting all three.
• Squash (or Pumpkins): Large leaves shade the ground, suppressing weeds and conserving moisture. Prickly vines may deter some pests.

Tomatoes

• Good Companions: Basil (repels tomato hornworms, improves flavor), Marigolds (deter nematodes, other pests), Carrots (loosens soil), Onions/Garlic (deter various pests).
• Bad Companions: Fennel (inhibits growth), Potatoes (share common pests/diseases), Cabbage family (inhibits growth).

Cabbage Family (Brassicas)

• Good Companions: Aromatic herbs like Dill, Sage, Rosemary, Thyme (repel cabbage moths), Nasturtiums (trap aphids), Onions/Garlic.
• Bad Companions: Tomatoes, Strawberries, Pole Beans.

Carrots

• Good Companions: Onions/Leeks (repel carrot rust fly), Rosemary, Sage, Lettuce, Radishes.
• Bad Companions: Dill (attracts spider mites), Fennel.

Peppers

• Good Companions: Basil, Onions, Carrots, Marigolds.
• Bad Companions: Fennel, Apricot trees.

Cowpeas

• Good Companions: Maize/Sorghum, Carrots, Cucumbers, Potatoes. Fixes nitrogen.
• Bad Companions: Onions, Garlic, Fennel.

Trap Cropping Strategies

Trap cropping involves planting a sacrificial crop nearby that is more attractive to a specific pest than your main crop. Pests congregate on the trap crop, which can then be removed or managed.

• Nasturtiums for Aphids: Aphids are often drawn to nasturtiums, potentially sparing nearby beans or brassicas.
• Blue Hubbard Squash for Squash Bugs/Vine Borers: Planting a perimeter of Blue Hubbard squash can attract these pests away from less resistant varieties.
• Collards for Diamondback Moths: Planting collards around cabbage can attract the moths, allowing for targeted management on the collards.

Trap crops require careful management. Pests must be dealt with on the trap crop before they multiply and move to the main crop.

Attracting Beneficial Insects

Planting flowers and herbs that provide nectar and pollen sources is crucial for attracting beneficial insects that help control pests naturally.

• Predators: Ladybugs, lacewings, hoverflies, praying mantises, predatory wasps. They feed on aphids, caterpillars, mites, and other pests.
• Parasitoids: Tiny wasps or flies that lay their eggs in or on pest insects, eventually killing them.
• Pollinators: Bees, butterflies, moths, and some flies are essential for fruit and seed production in many crops.

Plants to Attract Beneficials

Include a variety of these plants throughout your garden:

• Umbellifers (Carrot Family): Dill, Fennel, Cilantro (Coriander), Parsley, Queen Anne's Lace. Their small, clustered flowers are accessible to many beneficials.
• Asteraceae (Daisy Family): Sunflowers, Marigolds, Zinnias, Cosmos, Yarrow, Chamomile.
• Lamiaceae (Mint Family): Basil, Mint, Thyme, Sage, Rosemary, Lavender, Oregano. (Plant mints in containers to control spreading).
• Others: Alyssum, Buckwheat, Borage, Nasturtiums.

Planting flowers provides food and habitat for beneficial insects.

Traditional African Polyculture Systems

Many traditional African farming systems are inherently based on polyculture and companion planting principles, developed over generations to suit local conditions.

• Agroforestry Systems: Integrating trees (often nitrogen-fixing or fruit-bearing) with annual crops and sometimes livestock. Trees provide shade, improve soil fertility, and offer diverse products.
• Homestead Gardens (Shamba): Highly diverse gardens near homes, often mixing vegetables, fruits, herbs, medicinal plants, and staple crops in complex arrangements.
• Specific Intercropping Patterns: Examples include maize/sorghum intercropped with cowpeas or groundnuts; cassava intercropped with legumes; coffee or cocoa grown under shade trees.

Learning about and adapting these traditional systems can offer valuable insights for sustainable gardening in the region.

Common Mistakes to Avoid

• Ignoring Plant Needs: Don't pair plants with vastly different light, water, or soil requirements.
• Overcrowding: Give all plants enough space to grow and access resources.
• Planting Antagonists Together: Be aware of known negative interactions (allelopathy), like fennel inhibiting tomato growth.
• Expecting Miracles: Companion planting is one tool in an integrated pest management strategy, not a magic bullet. Combine it with healthy soil, crop rotation, and sanitation.
• Not Enough Diversity: Relying on only one or two companion types is less effective than integrating a wide variety of beneficial plants.

Further Resources

• Dilulu Fact Sheet: Natural Pest Management
• Books: "Carrots Love Tomatoes" by Louise Riotte, "Great Garden Companions" by Sally Jean Cunningham.
• Local agricultural resources and experienced gardeners in your community.