You may have read or heard that combining certain plants in one bed can prevent insect and nematode problems. This is called companion planting and generally, research doesn't support it! However, in some instances there can be benefits.
A good example is the marigold, frequently recommended as a companion plant for vegetables. Marigolds can suppress a plant-parasitic nematode known as the root-knot nematode—microscopic worms that live in the soil. However, it does so only under certain conditions. As is often the case, the use of marigolds for nematode control has been applied too broadly.
As far as stopping insect damage, research has shown that there are no real benefits. In fact, marigolds have their own pest problems. Spider mites are particularly attracted to marigolds, and they are a leading pest for tomatoes and other vegetables. Populations of spider mites can build up on marigolds and then move on to vegetable plants.
But, planting marigolds near vegetables for nematode control does contain some kernels of truth. These microscopic worms attack the roots of many vegetables, reducing yield and quality of your crop. And so, by mid-summer, many vegetable gardens show the adverse effects of the pests. But how and when you plant the marigolds is the key as to whether they will provide the results you desire.
Planting them simply as companion plants next to crops that are susceptible to root-knot nematodes doesn't seem to work. The root-knot nematode can still develop on susceptible plants. Instead, it's best to plant marigolds as a cover crop in the rows or areas where you want to reduce the nematode problem. You plant the marigolds in the exact spot where you will be growing your vegetables. Grow them there for at least two months, then dig them into the soil and plant your vegetables. This will solve your nematode problem provided you planted the correct marigold-- the French Dwarf Marigolds (Tagetes patula). The marigolds attract the nematode and as they invade the marigold root, the number of nematodes is reduced because they die—it is the wrong feeding site for the nematode. So, when you plant your vegetables right after the marigolds, you have less damage because the population has been greatly reduced.
This will work in climates with longer growing seasons but will not work in much of the northern hemisphere as it is very difficult to dedicate two months to marigolds in a shorter growing season. And there is one last word of caution-- do not expect the marigolds to be effective for more than one crop or one season's reduction of the nematode. This pest quickly rebuilds its populations, right back up to damaging levels.
• Marigolds are wonderful when used to add color to your garden all summer and are effective as a trap crop for Japanese beetles that congregate on the flowers. Simply shake the collected pests into a can of kerosene where they will expire.
• The blooms are edible, with the dried and crumbled petals pinch-hitting for saffron. They are colorful and tasty in rice, soups or stews or sprinkled on salads. They are nutritious as they contain carotene that provides vitamin A.
• Mix 5 tablespoons of petals into a bowl. Cover them with 1 cup of heated sunflower oil (about 120 degrees), allowing them to soak for about 4 hours before straining the petals and storing what is now a Marigold Balm in a jar. This gives you a soothing rub for tired, aching feet.
• If you have a short growing season, forget the use of marigolds to control nematodes. Just enjoy their beauty from May through October. Save their seeds and plant again next year.
Marigolds as well as other annuals, perennials, vegetables and herbs will be available at the Annual Plant Sale that Garden Club RFD has each May at the Little Red School House on the corner of Middletown Lincroft and Dwight Roads. It helps support our historic site and our work in the community. Join us on May 12, from 12 noon to 6pm and/or May 13, from 9am to 3pm. Your spring flowers will have faded and you should be ready for more plants to dot your landscape with color and beauty. One featured plant will be the Hydrangea—including one that climbs. Another is the “Phenomenal” lavender—the toughest lavender there is, able to tolerate heat and humidity, deer proof and—it survives the winter. With flowers perfect for fresh and dried arrangements, the fragrant 24” plants are beautiful in the cottage garden, on a border or around the patio. There will also be a variety of hostas to choose from, some for the shady areas of your property and others that are sun tolerant. Additionally, there will be plants grown in our members’ gardens.
And new this year will be a Help Desk where your questions can be answered by Master Gardeners and where information sheets from Rutgers Gardens can be obtained that will answer other questions. Contact Linda Paula at firstname.lastname@example.org or 732-681-9189 for more information.
If interested in finding out more about our club that recently celebrated its 75th anniversary, call Nancy Canade at (973)-452-4846 for further information. The wonderful world of plants and flowers awaits you.
Garden Club R.F.D. is a member of the Garden Club of New Jersey, the Central Atlantic Region of State Garden Clubs, Inc. and the National Garden Club, Inc. We welcome all inquiries and are open to accepting new members.