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By: Abram Bicksler
Published: 2013-09-15

This article is from ECHO Asia Note #18

We are pleased to offer three new types of seeds (Cosmos, African Marigold, and Zinnia) at the ECHO Asia Seed Bank, none of which have been offered to our member network before. You will notice that these are not our “typical” ECHO seeds, because they are all flowers! Although not edible, these beautiful flowers form the basis for Integrated Pest Management, increase biodiversity in garden plots and farm fields, and offer market potential.

Companion Plants

Since inception, we at ECHO Asia have striven to produce our seed crops in a sustainable, earth-friendly way. We believe that increased biodiversity and natural pest attractants and deterrents mimic ecology, reduce risk, and benefit our production principles. A group of plants known as companion plants help to achieve all three goals on our Seed Bank farm.

Simply put, companion planting is “the establishment of two or more plant species in close proximity so that some cultural benefit (pest control, higher yield, etc.) is derived. The concept embraces a number of strategies that increase the biodiversity of agroecosystems” (Kuepper and Dodson, 2001). In this case, the flowers are companion plants that benefit our seed crops.

Companion planting can be beneficial in many different ways. To summarize the benefits, companion planting may increase garden efficiency, reduce dependence on synthetic (or organic) pesticides, mimic the biodiversity of ecosystems, mimic the functioning of ecosystems, break pest and disease cycles, and bring aesthetic beauty to a field or garden (Kuepper and Dodson, 2001; McClure, 1994; Riotte, 2004). Knowledge about companion planting has been around for hundreds or thousands of years, but very little mainstream agricultural research has focused on the topic. One reason that research is lacking about companion planting is the difficulty of assessing and quantifying the complex ecological interactions that are taking place with increased biodiversity in agricultural settings. The recommendations below are intended to be a guide, but should be tried first in a low-risk environment before applying them more broadly, owing to the fact that agriculture is context specific.

In a companion planting situation, flowers may act primarily as a way to break pest and disease cycles by repelling harmful pests, confusing pests, and/or attracting beneficial insects (that eat harmful pests). Companion plants are able to repel harmful pests by releasing aromatic organic compounds from their cells. These aromatic metabolites may act as a deterrent because of their odor; they may also mask the scent of desirable plants, preventing the insect pest from locating them. The combination of the scent and color of flowers may also work to confuse a pest, thereby hindering the pest from feeding on the crop plant (Rodale 1995). Try planting pungent companion plants on the outside of garden beds or in and among crop plants. Marigold is an excellent pest deterrent.

The presence of flower plants may also create physical barriers to flying pest predation by altering the stature and structure of the agroecosystem and changing air currents within the garden. Taller flowering plants such as cosmos, planted in the bed of a shorter crop, act to confuse insect pests.

Some flowers are able to “lure” pests toward themselves. Such “trap crops” that are attractive to insect pests can be planted around the border of a garden or field, “pulling” insect pests out of the crop and toward the companion plant. Once insect pests have concentrated on these trap crops, control using an organic or synthetic pesticide is much easier. Nasturtiums are an example of a trap crop; they are a favorite of aphids (Rodale 1995).

Besides luring insect pests away from crop plants, other companion plants are desirable because they can lure beneficial insects and animals into the crop production areas. Beneficial creatures include pollinators, birds, frogs, predatory insects, and parasitic insects. Beneficials may be drawn to flowers not only due to the color and scent, but also because of the habitat that its foliage provides, and because of the general biodiversity increase that the new plant provides to the ecosystem. Members of the daisy family (cosmos, marigolds, sunflowers, coreopsis, and coneflowers) are particularly well suited to attracting beneficials (Riotte 2004).

Farmers will need to decide where to place flowers when using them as companion plants. Some may want to plant companion plants (evenly spaced) within the bed among the crop. Others may plant them around the outside of a garden bed, or around the outside of a field.

In an effort to bring the benefits of companion planting to our network members, the ECHO Asia Seed Bank has begun evaluating and distributing three new flowers:


New Seed Bank Additions 1

Cosmos sulphureus

Description: Cosmos is a slender, upright herbaceous plant native to meadows in North and South America, and a member of the Aster family. The flowers come in many different colors. Although the flowers look delicate and the plant has feathery foliage, the plant is robust and tolerant of many different growing conditions. It attracts bees and other beneficials.

Variety: Thung Khang Tong

Local Thai annual semi-hardy herb with bright orange or yellow flowers, that grows one to two meters tall.

Usage as a Companion Plant: Cosmos attracts beneficial insects and birds. The thick, feathery foliage creates an ideal habitat for beneficial insects, and the flowers are favored by different types of birds (Rodale 1995).

African Marigold/ดอกดาวเรือง

New Seed Bank Additions 2

Tagetes erecta

Variety: Heirloom

This heirloom variety, originally from the United States, grows to be 0.9 to 1.2 m (3 to 4 ft.) in height. It is a hardy annual that blooms prolifically, with large yellow, orange and gold double flowers on vigorous bushy plants. Marigold prefers the warm season, but will survive cool weather. It prefers full sun, tolerates drought, and should not be over-watered. The plant requires welldrained soil but is tolerant of both acid and alkaline soils.

Usage as a Companion Plant: African marigolds can be added anywhere in the garden and serve as a beneficial companion plant. The plants’ strong odor repels pests and masks the smell of many crops, making it harder for pests to find and damage their host crop. Marigold flowers attract butterflies and other beneficial insects. The roots exude a nematicidal toxin, which has been shown to prevent damage from nematodes when planted in rotation with nematodesusceptible crops; compelling evidence points toward the beneficial use of marigolds with tomatoes to reduce tomato nematode damage. However, marigolds may stunt and reduce the yields of beans and cabbages due to allelopathy (leaching of toxic compounds from roots and other plant parts) (Rodale 1995).


New Seed Bank Additions 3

Zinna elegans

Description: Zinnia is an upright, bushy flower with a yellow center and petals of varying colors. Zinnia plants are often grown for sale as cut flowers, owing to their attractive form and ability to last after cutting.

Zinnia is a warm-weather annual that grows best in hot, dry weather. It will flower more often with shortening days, and prefers full sun. The plant grows best in a well-drained loamy soil, rich in organic matter, with a pH of 5.5-7.5.

Variety: Thung Khang Tong

Local Thai variety with a mix of purple and white flowers.

Usage as a Companion Plant: Zinnias can be planted around and in garden beds to attract beneficial insects of all kinds, including wasps and hover flies. The flowers also attract butterflies, and birds will eat the seeds if they are allowed to set. Overall, zinnia is an outstanding companion plant for use with any crop.

Additional Resources:

Carter, Kelle. 2008. Companion Planting: So Happy Together! 

Flowerdew, Bob. 1993. Bob Flowerdew’s Complete Book of Companion Gardening. London: Kyle Cathie Limited.

Golden Harvest Organics. 2008. Companion Planting

Kuepper, George, and Mardi Dodson. 2001. ATTRA: Companion Planting: Basic Concepts and Resources

 McClure, Susan. 1994. Rodale’s Successful Organic Gardening: Companion Planting. Emmaus, PA: Rodale Press.

Riotte, Louise. 2004. Carrots Love Tomatoes and Roses Love Garlic: Secrets of Companion Planting for Successful Gardening. Storey Publishing, LLC.

Rodale, 1995. Companion Planting Made Easy. Emmaus, Pennsylvania: Rodale Press. 

Sullivan, Preston. 2003. ATTRA: Intercropping Principles and Production Practices