5 Reasons To Plant Marigolds With Tomato Plants (Explained + Tips)

Growing tomatoes can be a fulfilling experience, but they can also be challenging to grow. These challenges include pests, diseases, soil-borne problems, and nutrient deficiencies.

However, planting marigolds with tomatoes can have several benefits, aiding in the healthy growth of tomatoes. These include benefits such as pollination, pest control, and soil improvement. Marigolds work best when planted as a border or barrier around tomato plants.

Read on to discover the reasons why you should plant marigolds with tomato plants plus tips for growing success.

Marigolds & Tomatoes: The Perfect Garden Pair (5 Reasons Why)

1. Pest Repellent

Marigolds are known for their strong fragrance, which helps to repel certain pests such as aphids, whiteflies, caterpillars, and nematodes that can damage tomato plants. 

This odor is produced by chemicals called thiophenes and terpenes, found in the roots and leaves of marigold plants. 

The odor may also mask the scent of the tomato plant, making it harder for pests to find the food source. 

Marigolds can help to repel pests such as rabbits, cats, deer, and the Tomato Hornworm (moth form).

2. Attract Beneficial Insects For Pollination & Pest Control

Marigolds are attractive to beneficial insects such as ladybugs, butterflies, parasitic wasps, bees, hoverflies, and lacewings. These insects help to control harmful pests and improve pollination. 

Several types of insects feed on other insects that invade gardens. These help control pest populations without the need for harmful pesticides. 

For example, ladybugs feed on aphids, scale insects, mites, and other soft-bodied pests, and lacewings feed on aphids, mealybugs, and thrips. 

Hoverflies feed on nectar and pollen, but their larvae feed on aphids and other soft-bodied insects. 

Parasitic wasps lay their eggs inside the bodies of the tomato hornworms, which then hatch and eat the hornworm from the inside, killing it.

When these beneficial insects visit the marigold flowers to collect nectar and pollen they transfer pollen between plants, aiding in the plant’s reproduction. 

By attracting these beneficial insects to your garden with marigolds, you can help control pest populations, reduce the need for harmful pesticides, and pollinate the tomato plants. 

3. Natural Insecticide

As mentioned, marigolds produce thiophenes, a natural insecticide, that can help to protect tomato plants. This chemical compound is found in the roots of the plant.

The production of thiophenes in marigolds is thought to be triggered by the presence of nematodes in the soil. The roots of marigolds then release thiophenes to protect themselves and consequently the nearby tomato plants as well.

The chemical compound is toxic to many insect pests. It disrupts their life cycle, making it difficult for them to reproduce and then cause damage to plants.

This natural insecticide is environmentally friendly and safe around tomato plants.

4. Slug & Snail Barrier

Slugs and snails have a particular liking for tomato plants and can cause significant damage by creating holes in the fruit.

To protect tomato plants from pesky slugs and snails, plant a row of marigolds around them. By planting marigolds, you create a barrier that slugs and snails will not cross. 

Marigold roots also produce a chemical compound called alpha-terthienyl, which is released into the soil. This can repel slugs and snails because it irritates their bodies and causes them to avoid the area, acting as a natural deterrent. 

The fern-like foliage of marigolds also makes it easy to spot and remove these pests in the early morning. 

5. Improve Soil

Marigold roots help to improve soil drainage and aeration. This also benefits tomato plants which need well-draining soil.

When marigolds die, they release nutrients such as nitrogen and potassium into the soil, which can benefit neighboring tomato plants. 

Also as mentioned above, marigolds produce alpha-terthienyl, which suppresses certain soil-borne pathogens such as Fusarium, Pythium, and Rhizoctonia. 

These pathogens can cause diseases such as damping-off, root rot, and wilt in many plants, including tomatoes.

Tips For Growing Marigolds Successfully With Tomato Plants

Types Of Marigolds

Several varieties of marigolds are effective for planting alongside tomatoes. 

The most commonly recommended species are Tagetes erecta (African marigold) and Tagetes patula (French marigold). 

These species are known to have strong scents and produce high amounts of thiophenes and alpha-terthienyl, which help to repel pests and improve soil health. 

Tagetes tenuifolia (Signet marigold), another popular variety, in particular, is attractive to beneficial insects.  

Consider planting all 3 varieties for the best results. 

Make sure to follow planting instructions for each variety to ensure they receive proper sunlight, nutrition, and deadheading (if necessary).

When To Plant Marigolds

Marigolds can be started from seed indoors 4 to 6 weeks before the last expected frost. 

Or, directly plant them in the garden after the danger of frost has passed and the soil has warmed up. In most areas, this is around late spring to early summer.

Marigold Needs

Marigolds and tomatoes have similar growing conditions and thrive well in the same environment. 

Both plants require full sun, well-draining soil, and regular watering. 

However, please note that marigolds prefer slightly drier soil than tomatoes. Therefore, plant marigolds slightly away from the base of tomato plants to avoid overwatering the tomato plants. 

Do the following as well to help your marigolds thrive:

• Planting Soil: Loosen the soil to a depth of 6 to 8 inches. Amend it with compost or other organic matter if necessary.
• Watering: Water deeply once or twice a week, depending on rainfall.
• Sparingly Fertilize: Marigolds don’t require much fertilizer. Too much fertilizer can lead to leggy plants with fewer blooms. 
  • If fertilizer is used, opt for a balanced one and only use it once or twice during the growing season.
• Use Insecticidal Soap: Marigolds are mostly pest-resistant, but they can attract spider mites. Use insecticidal soap or neem oil, if necessary.

Conclusion

Marigolds are a fantastic companion plant for tomato growers due to their pest-repelling qualities and ability to improve soil health.

They have organic compounds that repel caterpillars, nematodes, deer, and more while attracting beneficial insects such as parasitic wasps, hoverflies, lacewings, and ladybugs. 

Marigolds also act as a slug and snail barrier and improve soil drainage and aeration. 

African, French, and Signet marigolds are recommended for best results when planted with proper maintenance techniques.