If you grow tomatoes, and let’s be honest, who doesn’t, then you’ve probably been inundated with the message that you have to grow marigolds, too. After all, marigolds are the best companion plant for tomatoes, right? Right? Well, hold on to your beefsteaks; there might be a better buddy for your tomatoes after all.
Peer Pressure Companion Planting
How many of you out there companion plant simply because everyone else does it, and you’ve been told you should? (Raises hand.)
How many of you don’t bother with companion planting, but plant marigolds with their tomatoes because you’ve been told over and over again that tomatoes and marigolds go together? (Raises hand again.)
Companion planting is one of those things that confuses the heck out of a lot of gardeners, myself included. I can never remember which vegetables not to plant next to each other and which ones you are supposed to plant next to each other. When you add flowers and herbs into the mix, forget it. I give up.
And if you’re like me and you want peer-reviewed research to back up these buddy-buddy plant claims, then it gets even more confusing. For many of these companion plants, the research hasn’t been done. Much of what we’re basing these companion planting guides on is anecdotal evidence, which doesn’t mean it doesn’t work; it just means we’re only guessing that it does.
However, when it comes to tomatoes and marigolds, the research has been conducted, and there is indeed evidence to support the claim that these two plants complement each other.
Sort of.
As is often the case, the actual research has been conflated and twisted to make for good headlines.
Whiteflies
This particular study is often touted as evidence that marigolds help reduce whitefly populations around tomatoes.
Let me ask you, friend, have you ever had an issue with whiteflies around your tomatoes? Neither have I. That’s because, unless you grow your tomatoes crammed together in greenhouses, it’s unlikely this will ever be an issue.
A few other things of note about this study that are rarely mentioned in gardening articles:
- Only French marigolds were studied, not any other variety of marigolds.
- This study was set up for a commercial growing setting, meaning it was intended for commercial growers, not home gardeners. (Think large greenhouses.)
- It only works if you plant your marigolds and tomatoes together from the start.
- Most importantly, this study tracked from the seedling stage to a 48-day infestation period. Yes, you read that right, infestation. Apparently, this little parlor trick of planting marigolds and tomatoes together only slows the growth of whiteflies. It doesn’t prevent whiteflies.
I’ll be sure to keep that in mind if I ever decide to grow tomatoes commercially inside greenhouses. For now, though, I’ve never had an issue with whiteflies on my tomatoes with or without marigolds. Phew!
Root-Knot Nematodes
Okay, this study looks to be more promising. We often see this one pointed to as proof of marigold/tomato companion planting effectiveness against root-knot nematodes, a common pest of tomatoes.
The study used row intercropping to plant marigolds among Angelica (Angelica sinensis, also known as female ginseng or dong quai) and found that the combination was effective in reducing the occurrence of root-knot nematodes by as much as 23%.
In Angelica.
A root crop and member of the carrot family, not the nightshade family.
Not tomatoes.
That’s some pretty impressive extrapolation.
But it is at least proof that marigolds prevent root-knot nematodes.
Hang on! I’ve got one more popular ‘Marigolds and Tomatoes are BFF’ study. This one, and it’s quite interesting. Tomatoes were planted in a field after two different marigold varieties (Tagetes patula var. Single Gold and Tagetes hybrid var. Polynema) to study the effects on root-knot nematode infestation, root-galling and overall yield.
The study showed that the fields where tomatoes had been grown after marigolds had a 50% higher yield. The field with tomatoes grown after Single Gold marigolds had a significant decrease in root-knot nematode infestations and root galling.
Finally! Results! But only if you plant your tomatoes in the same spot you planted your marigolds next year. I wish they had followed up with another study to see if the results were similar when marigolds and tomatoes were planted together. Regardless, a 50% higher yield is nothing to sneeze at. I need to find some Single Gold marigold seeds.
So, are marigolds really good for tomatoes? Maybe? Possibly. Sort of. If you plant specific types? Don’t look at me, I have no idea after reading all of those studies.
Ahem, yeah, so about growing sweet alyssum instead of marigolds.
Why Sweet Alyssum is the Better Flower to Plant with Your Tomatoes
Before we jump into why sweet alyssum is the better bestie for your tomatoes, let’s pause for a moment and think about all of your tomato woes.
Yes, whiteflies are a problem for commercial growers, but rarely for us home gardeners.
And yes, tomatoes are susceptible to root-knot nematodes, but I’ll bet the majority of your tomato woes (and mine) happen above ground and show up with either six legs or wriggling across the leaves, munching as they go.
- Aphids
- Tomato Hornworms
- Cutworms
- Stinkbugs
- Thrips
- Flea Beetles
I could go on, but you get the idea. Every summer, my inbox is filled with subject lines from gardeners that read, “Help! Insert Bug Here is destroying my tomatoes!”
Short of early and late blight (which no companion plant is going to help), most of us end up with some sort of insect causing tomato problems, no matter how many marigolds we plant.
Wouldn’t it be nice if there were a companion plant that helped with the bugs we actually deal with? Ahem, I’m totally not giving marigolds the side eye.
Enter sweet alyssum.
Yes, that’s right, the humble little ground cover most of us tuck into our flower beds here and there.
Growing lobularia maritima, commonly known as sweet alyssum, is like installing the Bat Signal in your garden. These tiny, nectar-rich flowers send out a clarion call to all nearby beneficial insects. “Hello! We’ve got plenty of nectar here, not to mention an all-you-can-eat buffet of aphids.”
Specifically, sweet alyssum attracts ladybugs (see you later aphids), hoverflies (so long thrips and spider mites), lacewings (get lost caterpillars and mealybugs), parasitic wasps (buh-bye, hornworms!), and more.
If you want to boost pollination rates in your garden, you would be hard-pressed to beat sweet alyssum. It’s one of the longest blooming flowers we grow, with blossoms showing up in the spring and continuing long into the fall. This is important when it comes to attracting beneficial insects and pollinators because it means a steady food supply.
You know the old saying about cooking enough to feed an army? Well, when you plant sweet alyssum, you’re doing just that. These tiny little floral powerhouses can feed an army of beneficial insects the high-carb nectar they need to take care of all the pesky bugs that want to feed on your tomatoes all season long.
But by far the best thing sweet alyssum has going for it is that it’s low-maintenance.
For such a delicate-looking flower, it’s surprisingly drought-tolerant. Not to mention you don’t have to deadhead it as you do with marigolds. It continues to grow and spread throughout the growing season, attracting and feeding the beneficial insects that patrol your garden.
The nice thing about sweet alyssum is that it’s already common knowledge that it attracts specific types of insects and is high in nectar, so you don’t need expensive studies to look at what’s happening underground with nematodes or some gas a flower is releasing in a greenhouse to prove its effectiveness. Sweet alyssum is a proven beneficial bug magnet. You can see the evidence with your own eyes in your own garden.
My Experience with Sweet Alyssum
I love watching gardening YouTube videos. (Big surprise.) Earlier this year, I was watching a video that discussed a method of string-training tomatoes.
I can’t remember what the channel name was, heck, I don’t even remember what the string-training tip was, but at one point in the video, they pointed out the masses of fluffy white flowers growing at the base of all their tomatoes – sweet alyssum. They mentioned that they used it exclusively for aphid control and talked about how effective it was.
I was thunderstruck. Duh, Tracey!
How many times have I passed a mound of sweet alyssum in the summer and found it positively buzzing with insect life? And yet, I’d been poking marigolds in the ground for decades because Mother Earth News told me to. Yet, here was a plant growing in my flower bed that was covered in all the beneficial bugs I needed to be patrolling my tomatoes, and I never put two and two together.
By the time I found this trick, it was too late to buy sweet alyssum seedlings from greenhouses. Instead, I direct-sowed seeds all around the base of my tomatoes and peppers.
I was stunned by the results. I don’t think I’ll ever go back to just marigolds.
This is the first time I’ve ever grown tomatoes without them being covered in aphids. And I did find a couple tomato hornworms, but they had the tell-tale white egg sacks of parasitic wasps attached to them, so I knew they weren’t long for this world. Honestly, I had a harder time keeping on top of the septoria leaf spot this year than I did with any pests.
I knew the sweet alyssum was doing its job because I couldn’t walk around my garden without having a hoverfly land on me. They were everywhere! At some point, the ladybugs started showing up, too, as I pulled several out of my hair.
The sweet alyssum also acted as a living mulch.
It grows low to the ground and spreads quickly. My raised beds looked beautiful with these puffy white clouds growing along the base of my tomato and pepper plants and spilling over the sides. I don’t think I would skip mulching in the future, but having the sweet alyssum growing did help to crowd out the few weeds that made it past my mulch.
I think this tiny fairy flower has earned a permanent place in my garden. I’ll be starting sweet alyssum seedlings each winter around the same time I start my tomato seedlings. I can only imagine how much better it will be with a few plants tucked in along every one of my raised beds instead of just two.
Now, I have to come clean. I lured you here under false pretenses.
Sure, sweet alyssum is great for tomatoes. That was my hook to get you here because let’s face it, we’re all a little fanatical about our tomatoes. But the fact of the matter is that sweet alyssum is great for your entire vegetable garden. With the number of different beneficial insects it attracts, it only makes sense that your whole garden would benefit. From insects that eat other insects to native pollinators, it seems all the best bugs adore sweet alyssum, and that’s bad news for all the pests you don’t want hanging out in your garden.
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