One of my favorite things about gardening is the opportunity to start over. After a winter of reflection, spring is a fresh beginning. We get to take what was learned from the previous year(s) – the good and the bad – and apply our lived experience to the next generation of crops.
Continuously learning, tweaking, and experimenting, particularly so when in pursuit of the perfect tomato.
Because there’s more than one way to grow a tomato.
With so many tips and tricks to try, it’s an annual choose-your-own-adventure. Will you plant your tomatoes deeply or sideways, or perhaps upside down this year? Will you be sticking anything at all in those planting holes? Should you support the tomato’s lumbering limbs with stakes or obelisks or maybe espalier is worth a shot? Have you heard about the Florida weave?
Then, once the tomatoes are in the ground, there’s a whole new range of potential problems for the tomato grower to tackle. After you’ve learned how to deal with tomato pests and blights, avoided blossom end rot and fruit splitting, figured out how and when to prune them, and kept them warm in the cold – after allllll that, what if your tomatoes are…kind of ugly?
Well, no one said growing perfect tomatoes would be easy!
The gardening lore around tomatoes is rich and varied; much of it is steeped in oral tradition. Growing marigolds with your tomatoes is one piece of advice that has endured for so long that we can’t quite pinpoint where or when it all began. Generation after generation of tomato gardeners have observed that wonderful things happen when these two plants are paired up.
Why Plant Marigolds & Tomatoes Together?
Is there a companion plant that enjoys as much esteem as marigold (Tagetes)? I think not. As a friend to all in the vegetable garden, marigolds are as universally loved for their long-blooming flowers as it is for the wide array of “ecosystem services” they provide.
Marigolds can serve as a companion to most any crop, but there is a special kinship between these plants and tomatoes.
Pollinators Love Marigold
The bright colors, pungent fragrance, and superabundance of nectar make marigolds irresistible to any insect flying overhead.
The fiery colors are first to grab their attention, coming in a palette of vibrant autumn hues. Some might find the spicy-musky scent of marigolds unpleasant, but the pollinators would disagree. And because marigolds bloom continuously, from around June to frost, the flowers are a generous source of nectar and pollen for our insect friends all the way to winter.
Having bees and butterflies visiting your garden is always a good thing. The more pollinating insects you can entice, the better the fruit set on your tomatoes will be – along with every other flowering crop growing in your rows and fields.
Marigolds Attract Predatory Insects
Although bees and butterflies get most of the glory as the garden’s mainstay pollinators, other nectar-sipping bugs will similarly be drawn to marigold flowers. These good guy insects provide round-the-clock pest control for several of tomato’s worst pests.
Hoverflies and lacewings are excellent little pollinators, happy to feed on marigold nectar. Although the adults are gentle and harmless, their offspring are some of the garden’s fiercest predators. Roaming over the foliage of plants, each one will eat hundreds of soft-bodied pests. Aphids, mites, scale, leafhoppers, whiteflies, small caterpillars, and thrips are no match for these hungry larvae.
Both adult and larval-stage ladybugs have a healthy appetite for small insects. When the adults aren’t munching on aphids and thrips, they are spotted drinking nectar from marigolds and other flowers.
And wasps, love them or hate them, are some of the greatest tomato defenders. Fueling themselves with flower nectar, wasps feed their young with a steady diet of hornworms, armyworms, cabbageworms, grubs, weevils, leaf miners, and more.
Marigolds are Useful Trap Crops
Numerous pests happen to love these flowers as well. According to the USDA, pests drawn to marigold include aphids, earwigs, armyworms, cabbage loopers, leaf miners, spider mites, thrips, whiteflies, as well as snails and slugs.
This is not a bad thing.
Marigolds are incredible as trap crops – luring in insects and invertebrates with an alternate food source to divert them away from your main crop. When a pest finds marigolds more delicious than your tomatoes, the flowers take all the heat. But you need to plant them away from your tomatoes to benefit.
Although the science of companion planting is slowly catching up to what gardeners have insisted for decades, studies have confirmed that marigolds are preferred by whiteflies and tomato fruit borer over the tomatoes themselves.
Trap cropping with marigolds also helps foster a balanced food web within your garden. By hosting aphids and other plant-eating insects, you’re also encouraging ladybugs, lacewings, and hoverflies to reproduce.
In return for your tolerance, you will be getting the very best in all-natural, broad-spectrum, biological pest control out there.
Tomatoes and Marigolds Have a Non-Compete Clause
These two get on well in the same bed because their root systems – for the most part – occupy different layers of the soil.
Tomato roots grow deeper into the ground. They have a long primary root that extends vertically to a depth of around 2 to 3 feet. From this root, many secondary roots branch out laterally.
Meanwhile, marigolds have fibrous roots. Instead of a single long root, numerous roots develop from the stem and fan out horizontally, closer to the soil surface.
Because marigold’s roots are shallower and tomatoes are deeper, these plants aren’t directly competing with each other for resources like water and nutrients.
Marigolds Beautify the Tomato Garden
Since about 1950, there has been an unnecessary divide between food and ornamental plants in the garden. Fruits and veggies here, flowers over there – and never the twain shall meet.
Yet, in the eons before that, polyculture was how we farmed and gardened—not in single-crop monocultures, but by growing two or more types of plants together in the same place at the same time.
It seems silly to keep flowers out of the vegetable garden when they supply so many helpful services. And let’s not overlook the value of beauty as a function of your edible landscape.
In addition to the slew of essential garden supports they provide, marigolds will give you a long season of pretty flowers. Next to a mostly green backdrop of tomato foliage, marigolds bring bold pops of color – in ruby, apricot, amber, gold, cream, and any combination thereof.
Can Marigolds Suppress Root-Knot Nematodes?
Nematodes are microscopic worms that live in the soil. Not all nematodes are harmful; some species are beneficial. Parasitic types, like the root-knot nematode, can do a lot of damage, and tomatoes are among their favorite hosts.
Feeding on plant roots and causing root tissues to swell and gall, a severe infestation of root-knot nematodes manifests as wilting, stunted growth, and the untimely death of the plant. Once a plant’s root system is afflicted with them, treatment options are limited.
Marigolds are often recommended as an organic solution for root-knot nematodes. Below the soil, marigold roots exude one of the most toxic naturally-occurring compounds known to date – the nematicidal, insecticidal, antiviral chemical called alpha-terthienyl.
Marigolds can suppress 14 genera of parasitic nematodes, but there’s a catch.
It’s only effective as a cover crop planted at least two months before your tomatoes go in. Planting marigolds and tomatoes at the same time, or after you’ve spotted the nematode problem, doesn’t appear to work.
For gardeners with a long growing season, planting your intended tomato beds densely with marigold is absolutely doable. The parasitic nematodes in the soil cannot reproduce on marigold roots, which helps suppress their overall populations. Marigolds won’t fully eradicate them though, and you’ll need to cover crop with marigold in every planting bed, every season.
For gardeners in northern regions, the growing season is far too short to grow marigolds ahead of the tomatoes. For us, the best way to suppress root-knot nematodes is by adding plenty of organic matter to the soil. This creates a healthy soil habitat for predatory microbes and fungi to aid in keeping parasitic nematode populations down.
What are the Best Marigold Varieties for Tomatoes?
There are more than 50 recognized species within the Tagetes genus, and of these, only three annual marigolds are widely cultivated in home gardens. The good news is, any of these species of marigold will grow happily alongside your tomatoes:
French Marigold (Tagetes patula)
The most popular type of marigold, French marigold, is a mid-sized plant that grows 6 to 12 inches tall. It has a compact but bushy habit with fern-like foliage as strongly aromatic as the flowers. With around 60 cultivars to choose from, French marigold flowers come in single, semi-double, double, and crested forms up to 2 inches wide, in reds, oranges, and yellows.
You can pair up French marigold with any type of tomato, but due to their smaller stature, they grow well alongside the limited sprawl of determinate tomatoes.
African Marigold (Tagetes erecta)
African marigold grows tall and upright, reaching 3 to 4 feet high. Although there are hundreds of varieties of African marigolds, many have large double flowers, up to 5 inches wide, resembling pompons. The blooms come in warm tones of yellow, orange, and creamy white.
As the tallest of the marigolds, African marigolds are a good match for the ceaseless growth of indeterminate tomato varieties.
Signet Marigold (Tagetes tenuifolia)
The smallest of the marigolds, Signet marigold grows in mounds that usually reach 6 inches or less. The simple daisy-like blooms are about an inch across and arise densely from a thick mat of lacy foliage. Each flower produces a single row of petals arrayed around a cluster of pistils at the center. Signet marigolds come in 20 to 30 cultivars, with several choices in red, orange, yellow, and bicolor flowers.
If you can’t stand the musk of typical marigolds, Signet marigolds emit a rather pleasing lemony scent.
Before choosing a marigold variety or mix to grow – take a good look at the flowers.
Tagetes have been extensively bred and hybridized through the years, and some cultivars bear little resemblance to the original flowers. Heavily hybridized marigolds, bred for beauty and not function, may come in a form less appealing to bees and other beneficial insects. The insect community might skip right past them due to the flowers having an undesirable color, shape, scent, or size.
If the main reason you want to grow marigolds is to avail yourself of its ecosystem services, you’ll want to think like a pollinator. Skip the varieties with huge puffy flowers and look for marigolds that have single or semi-double blooms with an open and fully accessible floral disk.
How to Plant Marigolds and Tomatoes in the Same Bed
Marigolds can be started from seed indoors 6 to 8 weeks before the last frost date or sown directly in the garden once the soil has warmed to 65°F (18°C). Most plant nurseries carry marigold starts in six-packs in spring.
Before sowing or transplanting marigolds into the garden, plant up your tomatoes first. Now’s a good time to add stakes or whichever tomato support system you plan to use.
After the tomatoes are all set up, plant marigolds 18 to 24 inches away from the tomatoes to give both plants some room to fill in. Marigolds can be planted along the edges of the bed or in between rows of tomato plants.
Smaller French and Signet marigolds can be planted close together, about 6 inches apart. As they mature, they form a protective hedge around the tomatoes.
Larger African marigolds need 10 to 12 inches between plants. Varieties with large flowerheads may need staking to stay upright.
As the marigold flowers come into bloom, your tomato patch will soon be buzzing with life. When the marigold blooms fade, deadhead the flowers and sprinkle the seedheads around the garden for a second flowering in fall.
Get the famous Rural Sprout newsletter delivered to your inbox.
Including Sunday musings from our editor, Tracey, as well as “What’s Up Wednesday” our roundup of what’s in season and new article updates and alerts.