Last July I was out in the vegetable garden, when a neighbor gardener approached and asked, “What are you doing?” I responded, “Smashing Mexican bean beetle larvae.” My neighbor gave me a puzzled look, followed by a smirking smile, as if I was committing a gardening no-no. I just had to ask, “You’re not having a beetle problem on your green beans?” He smiled and said, “Of course not I plant marigolds with my beans, and they keep the bugs out of the bean patch.” WOW! Could this be the silver bullet in controlling this obnoxious pest?
Now that the gardening season is over and the cover crop is planted, I’ve got a chance to catch my breath from sowing, planting, mulching, weeding and harvesting. Did I mention weeding? Anyway, now that I have a little time to reflect back on the garden season as to what may or may have not worked well, I’ve been returning to that conversation with my neighbor about the wonders of the marigold. The seed catalogs are starting to show up in the mail, and the planning for next year’s garden is in the beginning stage, so before ordering a ton of marigold seeds, now would be a good time to do a little research on the magical repelling powers of the marigold plant. I’ve heard marigold stories for years, how marigolds will repel every garden pest known to mankind, including bugs, snails, rabbits, ground hogs, and deer! I’ve even heard that it has been used to target and kill selected weeds. This sunny annual has been employed as a companion plant for generations just to do that — repel pests from the garden. Do they really benefit the garden as a repelling machine or are they just pretty and their repelling powers just a gardening myth?
Marigolds belong to the aster family (Asteraceae), genus Tagetes. Their natural range extends from the southwestern United States into Argentina, with their greatest distribution being in south central Mexico. Approximately 50 species are known, but in general, the three most common are African marigolds (T. erecta), French marigolds (T. patula) and Signet marigolds (T. tenuifolia). However, regardless of their name, all marigolds are native to subtropical America and have been cultivated in Mexico for over 2,000 years.
Tagetes patula, commonly called French marigold, is a compact annual that typically grows 6-12” tall and features single, semi-double, double or crested flowers (1-2” diameter) in shades of yellow, orange, red and bicolor. Their pinnate leaves with toothed, lance-shaped leaflets are aromatic.
Tagetes erecta, commonly called African marigold, Aztec marigold, American marigold or big marigold, is native to Mexico and Central America. Big marigold may be the most descriptive of its names because plants are noted for their large flowerheads. They typically grow from 1-4’ tall and feature huge, mostly double-globular flowers (2-4” diameter) in various shades of yellow, orange, and white. Foliage and flowers are aromatic when brushed or crushed. Triploid F1 hybrids (T. erecta x T. patula) combine the large flowers of the African marigold with the more compact size of the French marigold into vigorous plants with 2-3” diameter flowers on stems reaching 10-18” tall. These triploids are largely unaffected by high heat and usually bloom all summer.
Tagetes tenuifolia. Signet marigolds are compact, mounding plants with smaller flowers and leaves than most other marigolds. Yellow, orange, golden, or bicolored flowers are held either well above the fine-textured, dark green foliage or tucked in with the foliage, depending on the cultivar. This plant doesn’t have that overwhelming marigold scent but has a light, citrusy smell.
For generations, many vegetable gardeners have planted marigolds in their vegetable patches to repel pests. However, there is a lack of scientific evidence to support the notion that marigolds actually repel pests. Research conducted at Rutgers University concluded that marigolds failed to repel cabbage, carrot and onion pests. In fact the USDA lists a total of 15 pests that attack marigolds; included on their list are aphids, Japanese beetles, snails, and spider mites, just to name a few. On the other hand, researchers at the University of Vermont have reported that marigolds have been effective in luring pests away from other ornamental plants.
Although science has yet to prove that marigolds actually repel pests from vegetable crops, there is scientific evidence that marigolds CAN be an important tool in controlling certain nematodes. Nematodes are tiny worms, usually microscopic in size. Nematodes that feed on plants — called plant-parasitic nematodes — have spear-like mouthparts used to puncture plant roots to obtain nutrients. As a result, plant-parasitic nematodes can seriously damage or even kill crops, turf, and ornamental plants.
Marigold roots release a toxic chemical (alpha-terthienyl), and the presence of this chemical inhibits the hatching of nematode eggs. Therefore, control of the nematode population is achieved by interrupting the nematode life cycle.
One drawback with using marigolds for nematode control is that the benefit is not realized until the following year. To be effective the marigolds must be planted before the vegetable crop — at least 2 months before — and must be planted at the same location where the vegetable crop is to be planted; otherwise, no benefits will be gained from the marigold root exudates. For example, California research showed that tomatoes grown after marigolds had significantly lower numbers of root galls due to root-knot nematodes (Meloidogyne incognito). In addition, the tomato yields were higher (root length, shoot weight, number and weight of fruits were all higher in plants grown after Tagetes). UniversityofCaliforniaRiverside.edu.
Care should be taken when purchasing marigolds for controlling nematodes. That’s because “not all marigold varieties control all types of nematodes.” Univ.ofFlaExt.edu/ng045. For example, the California research mentioned above revealed that particular varieties are more effective at controlling root-knot nematodes. In that experiment, the “Single Gold” variety of Tagetes patula outperformed other varieties. You’ll get the best results if you determine which types of nematodes are in your local soils, and you can do this by sending soil samples to a nematode assay laboratory. Univ.ofFlaExt.edu/ng045 (look at the chart in this article identifying marigold species and varieties by their resistance to and effectiveness against particular types of root-knot nematodes).
In addition to helping control nematodes, marigold flowers attract beneficial insects that not only pollinate, but also help control bad bugs. Beneficial insects attracted to marigolds include: hover flies, lady bugs and parasitic wasps.
To date there is very little scientific evidence that the aroma of the marigold plants actually repel pests, however it is a generally accepted scientific fact that marigolds help to control nematodes and attract beneficial insects that aid in controlling unwanted pests.
There is growing concern about pesticides’ non-target effects on humans and other organisms, and many pests have evolved resistance to some of the most commonly-used pesticides. Together, these factors have led to increasing interest in non-chemical, ecologically sound pest management. The marigold is not only pretty but offers the gardener another arrow for the quiver in the bug war. Who wouldn’t want to plant a beautiful plant that was edged out by the rose for our national flower. I know I will!
Thanks for stopping by The Garden Shed. We members of The Garden Shed Team wish you and your family a safe and happy holiday season.
“Effects of Selected Marigold Varieties on Root-knot Nematodes and Tomato and Melon Yields”, Department of Namatology, University of California, http://faculty.ucr.edu/~atploeg/PDF PAPERS/PLANT DISEASE/PLANTDISEASE.pdf
“Marigolds (Tagetes spp.) for Nematode Management,” University of Florida Institute of Food and Agricultural Sciences, Univ.ofFlaExt.edu/ng045.
“Murdering Thrips with Marigolds, Fungi & Mites,” University of Vermont Entomology Research Laboratory, https://www.uvm.edu/~entlab/Greenhouse IPM/Workshops/2015/AFEProjectDesc&SummaryDec2014.pdf
Nothing can be more annoying than finding ants crawling all over your beautiful African marigold flowers. While ants themselves don’t damage the plants directly they can attract other harmful pests like aphids or promote diseases. Getting rid of ants on marigolds requires diligence and consistency but it can be done through safe and effective methods.
In this comprehensive guide, we will explore various natural, chemical, and preventative solutions to eliminate ants on African marigolds. Follow these tips and with persistence, you can enjoy ant-free marigold plants all season long
Why Ants are Attracted to African Marigolds
Ants are attracted to the sweet nectar produced by flowers. African marigolds, with their abundant pollen and nectar, are highly appealing to foraging ants. Ants also feed on the honeydew secreted by aphids and other insects that can infest marigolds. By controlling ants, you disrupt the pest cycle in your garden.
Safe, Natural Ways to Control Ants on Marigolds
For mild ant invasions, natural remedies are ideal. They are safe for children, pets and the environment. Some effective options include:
-
Sprinkling diatomaceous earth around the base of plants. The sharp dust damages ants’ exoskeletons and kills them within 48 hours.
-
Spraying a vinegar-water solution directly on ants. The acetic acid disrupts their scent trail communication.
-
Setting out citrus peels around plants. Strong citrus scent repels ants.
-
Applying sticky barriers like petroleum jelly or tape around pot rims or stems to block access.
-
Introducing beneficial nematodes to the soil, which parasitize and kill ants.
When to Use Chemical Ant Treatments on Marigolds
For heavy infestations, it may be necessary to use chemical treatments:
-
Ant baits – borax or boric acid-laced baits that workers take back to the colony. Highly effective but can take 1-2 weeks.
-
Insecticidal soaps – potassium salts that penetrate the insect exoskeleton. Low toxicity to humans.
-
Insecticide sprays – Fast-acting but indiscriminate. Use as a last resort and avoid spraying flowers.
Always follow label directions carefully when using chemical ant treatments. Try to target ants directly rather than spraying entire plants. Spot treatments are best whenever possible.
Preventing Future Ant Invasions
Ant prevention is key to keep your African marigolds pest-free. Here are some tips:
-
Remove foliage touching marigold plants to reduce access points.
-
Prune back nearby trees/shrubs to eliminate protective cover for ants.
-
Seal any cracks or crevices in garden walls, sidewalks and structures.
-
Clean up fallen fruit/debris and fix leaky pipes or faucets.
-
Apply a 2-4 inch mulch layer around plants to create a barrier.
-
Use ant stakes or treatments around the garden perimeter.
What Not to Do When Removing Ants from Marigolds
Some common ant control mistakes to avoid:
-
Do not spray entire marigold plants with insecticide. This can damage flowers and kill beneficial insects.
-
Avoid using harsh chemicals like gasoline or bleach that can permeate the soil.
-
Do not dump boiling water on ants. This can burn and stress plant roots.
-
Do not ignore ants crawling on potted marigolds brought indoors. Treat promptly before they spread.
-
Do not let ant invasions persist. The longer they stay, the harder they are to eliminate.
When to Seek Professional Help with Ants on Marigolds
If you have attempted various control methods without success, or have a widespread infestation, do not hesitate to call an exterminator. Professionals have the experience, commercial-grade products and equipment to effectively eliminate ant colonies. They can also identify exactly where the ants are nesting.
Getting rid of ants on marigolds requires patience and vigilant monitoring, but it is very possible with consistent effort. Combine preventative landscape maintenance, natural remedies and targeted chemical treatments as needed to protect your flowers. With a diligent pest management routine, your African marigolds will thrive ant-free all season long.
Piedmont Master Gardeners • Sharing knowledge, Empowering communities PMG News
- By Cleve Campbell
- /
- December 2017 – Vol. 3 No. 12
- /
Last July I was out in the vegetable garden, when a neighbor gardener approached and asked, “What are you doing?” I responded, “Smashing Mexican bean beetle larvae.” My neighbor gave me a puzzled look, followed by a smirking smile, as if I was committing a gardening no-no. I just had to ask, “You’re not having a beetle problem on your green beans?” He smiled and said, “Of course not I plant marigolds with my beans, and they keep the bugs out of the bean patch.” WOW! Could this be the silver bullet in controlling this obnoxious pest?
Now that the gardening season is over and the cover crop is planted, I’ve got a chance to catch my breath from sowing, planting, mulching, weeding and harvesting. Did I mention weeding? Anyway, now that I have a little time to reflect back on the garden season as to what may or may have not worked well, I’ve been returning to that conversation with my neighbor about the wonders of the marigold. The seed catalogs are starting to show up in the mail, and the planning for next year’s garden is in the beginning stage, so before ordering a ton of marigold seeds, now would be a good time to do a little research on the magical repelling powers of the marigold plant. I’ve heard marigold stories for years, how marigolds will repel every garden pest known to mankind, including bugs, snails, rabbits, ground hogs, and deer! I’ve even heard that it has been used to target and kill selected weeds. This sunny annual has been employed as a companion plant for generations just to do that — repel pests from the garden. Do they really benefit the garden as a repelling machine or are they just pretty and their repelling powers just a gardening myth?
The Plant
Marigolds belong to the aster family (Asteraceae), genus Tagetes. Their natural range extends from the southwestern United States into Argentina, with their greatest distribution being in south central Mexico. Approximately 50 species are known, but in general, the three most common are African marigolds (T. erecta), French marigolds (T. patula) and Signet marigolds (T. tenuifolia). However, regardless of their name, all marigolds are native to subtropical America and have been cultivated in Mexico for over 2,000 years.
Tagetes patula, commonly called French marigold, is a compact annual that typically grows 6-12” tall and features single, semi-double, double or crested flowers (1-2” diameter) in shades of yellow, orange, red and bicolor. Their pinnate leaves with toothed, lance-shaped leaflets are aromatic.
Tagetes erecta, commonly called African marigold, Aztec marigold, American marigold or big marigold, is native to Mexico and Central America. Big marigold may be the most descriptive of its names because plants are noted for their large flowerheads. They typically grow from 1-4’ tall and feature huge, mostly double-globular flowers (2-4” diameter) in various shades of yellow, orange, and white. Foliage and flowers are aromatic when brushed or crushed. Triploid F1 hybrids (T. erecta x T. patula) combine the large flowers of the African marigold with the more compact size of the French marigold into vigorous plants with 2-3” diameter flowers on stems reaching 10-18” tall. These triploids are largely unaffected by high heat and usually bloom all summer.
Tagetes tenuifolia. Signet marigolds are compact, mounding plants with smaller flowers and leaves than most other marigolds. Yellow, orange, golden, or bicolored flowers are held either well above the fine-textured, dark green foliage or tucked in with the foliage, depending on the cultivar. This plant doesn’t have that overwhelming marigold scent but has a light, citrusy smell.
Fact or Fiction
For generations, many vegetable gardeners have planted marigolds in their vegetable patches to repel pests. However, there is a lack of scientific evidence to support the notion that marigolds actually repel pests. Research conducted at Rutgers University concluded that marigolds failed to repel cabbage, carrot and onion pests. In fact the USDA lists a total of 15 pests that attack marigolds; included on their list are aphids, Japanese beetles, snails, and spider mites, just to name a few. On the other hand, researchers at the University of Vermont have reported that marigolds have been effective in luring pests away from other ornamental plants.
Although science has yet to prove that marigolds actually repel pests from vegetable crops, there is scientific evidence that marigolds CAN be an important tool in controlling certain nematodes. Nematodes are tiny worms, usually microscopic in size. Nematodes that feed on plants — called plant-parasitic nematodes — have spear-like mouthparts used to puncture plant roots to obtain nutrients. As a result, plant-parasitic nematodes can seriously damage or even kill crops, turf, and ornamental plants.
How marigolds help fight nematodes
Marigold roots release a toxic chemical (alpha-terthienyl), and the presence of this chemical inhibits the hatching of nematode eggs. Therefore, control of the nematode population is achieved by interrupting the nematode life cycle.
One drawback with using marigolds for nematode control is that the benefit is not realized until the following year. To be effective the marigolds must be planted before the vegetable crop — at least 2 months before — and must be planted at the same location where the vegetable crop is to be planted; otherwise, no benefits will be gained from the marigold root exudates. For example, California research showed that tomatoes grown after marigolds had significantly lower numbers of root galls due to root-knot nematodes (Meloidogyne incognito). In addition, the tomato yields were higher (root length, shoot weight, number and weight of fruits were all higher in plants grown after Tagetes). UniversityofCaliforniaRiverside.edu.
Varieties Matter
Care should be taken when purchasing marigolds for controlling nematodes. That’s because “not all marigold varieties control all types of nematodes.” Univ.ofFlaExt.edu/ng045. For example, the California research mentioned above revealed that particular varieties are more effective at controlling root-knot nematodes. In that experiment, the “Single Gold” variety of Tagetes patula outperformed other varieties. You’ll get the best results if you determine which types of nematodes are in your local soils, and you can do this by sending soil samples to a nematode assay laboratory. Univ.ofFlaExt.edu/ng045 (look at the chart in this article identifying marigold species and varieties by their resistance to and effectiveness against particular types of root-knot nematodes).
Attracting Beneficial Insects
In addition to helping control nematodes, marigold flowers attract beneficial insects that not only pollinate, but also help control bad bugs. Beneficial insects attracted to marigolds include: hover flies, lady bugs and parasitic wasps.
Conclusion
To date there is very little scientific evidence that the aroma of the marigold plants actually repel pests, however it is a generally accepted scientific fact that marigolds help to control nematodes and attract beneficial insects that aid in controlling unwanted pests.
There is growing concern about pesticides’ non-target effects on humans and other organisms, and many pests have evolved resistance to some of the most commonly-used pesticides. Together, these factors have led to increasing interest in non-chemical, ecologically sound pest management. The marigold is not only pretty but offers the gardener another arrow for the quiver in the bug war. Who wouldn’t want to plant a beautiful plant that was edged out by the rose for our national flower. I know I will!
Thanks for stopping by The Garden Shed. We members of The Garden Shed Team wish you and your family a safe and happy holiday season.
Sources:
“Tagetes L., Marigold,” Plant Profile, USDA https://plants.usda.gov/core/profile?symbol=TAGET
“Tagetes erecta, ” Missouri Botanical Garden, http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277371
“Effects of Selected Marigold Varieties on Root-knot Nematodes and Tomato and Melon Yields”, Department of Namatology, University of California, http://faculty.ucr.edu/~atploeg/PDF PAPERS/PLANT DISEASE/PLANTDISEASE.pdf
“Marigolds (Tagetes spp.) for Nematode Management,” University of Florida Institute of Food and Agricultural Sciences, Univ.ofFlaExt.edu/ng045.
“Companion Planting and Insect Pest Control,” Rutgers University, http://pemaruccicenter.rutgers.edu/assets/PDF/publications/2013-InTech-Companion_planting_and_insect_pest_control.pdf
“Murdering Thrips with Marigolds, Fungi & Mites,” University of Vermont Entomology Research Laboratory, https://www.uvm.edu/~entlab/Greenhouse IPM/Workshops/2015/AFEProjectDesc&SummaryDec2014.pdf
“Root-knot Nematodes: Biocontrol with Marigolds,” North Carolina Cooperative Extension, https://carteret.ces.ncsu.edu/wp-content/uploads/2013/07/Root-Knot-Nematodes-Biocontrol.pdf?fwd=no
“The Repellent Marigold And Other Myths Of Companion Gardening,” The Chicago Triburne, http://articles.chicagotribune.com/1992-09-13/news/9203230490_1_companion-plantings-carrots-love-tomatoes-bedding-plants
“Dispelling Marigold Myths,” Alabama Cooperative Extension System, http://www.aces.edu/dept/extcomm/specialty/marigolds.html
“Parasitic Wasps: A Gardener’s Best Friend,” North Carolina Cooperative Extension, https://brunswick.ces.ncsu.edu/2014/04/parasitic-wasps-a-gardeners-best-friend/
“PROMOTING THE MARIGOLD AS NATIONAL FLORAL EMBLEM,” The Dirksen Congressional Center, http://www.dirksencenterprojects.org/promotingmarigold.pdf
“Controlling Insects on Flowers,” USDA, https://naldc.nal.usda.gov/download/CAT87210014/PDF
2003 Annual Report of Accomplishments and Results, The Connecticut Agricultural Experiment Station, https://portal.nifa.usda.gov/web/areera/Reports/2003/Ct/AES.NewHaven.CT.pdf
“Attracting Beneficial Insects, Penn State University,” https://extension.psu.edu/attracting-beneficial-insects
Winter, the dormant season, is when the bare bones of the landscape are revealed.
In the Ornamental Garden
The eastern redcedar — is it a “weed” or a valuable native tree?
In the Edible Garden
“What are you doing?”
December is a good time to reflect on your gardens successes and failures.
Happy holidays from The Garden Shed! You’ve completed all your Christmas shopping and done all your decorating, so now youre looking for a few gardening tasks. Right? Well, heres our list of December tasks and tips for the edible garden:…
Recipe of the Month
Wow your holiday guests with this tasty make-ahead appetizer!
Ants on your plants? It may indicate a bigger problem.
FAQ
How do I get rid of ants on my flowering plants?
What can I spray on flowers to kill ants?
Do ants like marigold plants?
How do I get rid of ants in my flower bed without killing plants?
How do you keep ants away from Marigold plants?
Create a vinegar spray by mixing equal parts of water and vinegar in a spray bottle. Spray the solution on the affected areas of your marigold plants to keep ants away. 4. Diatomaceous Earth Diatomaceous earth is a natural substance made from fossilized remains of diatoms – tiny aquatic organisms.
Do ants eat marigolds?
Ants can be a nuisance when they invade your garden, especially when they start making their way onto your precious marigold plants. Not only do they disrupt the beauty of your flowers, but they can also cause damage by farming aphids and other pests that feed on your plants.
How do you treat root rot on African marigolds?
Treatment: To prevent root rot, ensure that your African marigolds are planted in well-draining soil. Avoid overwatering and water at the base of the plants to keep the foliage dry. If root rot is detected, remove the affected plants and replant in fresh soil.
How to get rid of ants in potted plants?
You can solve the problem with natural and even non-violent solutions, without using chemicals and insecticides. Possibly the easiest and most convenient method to get rid of ants in potted plants is to use essential oils (thyme, yarrow, lavender or citrus), pour a few drops in a spray bottle full of water then spray the plant, soil and pot.