Natural Pest Control for Your Garden
Pest control can be tricky in an organic garden. You know you want the best quality food for your family but choosing not to use chemical pesticides means you may see more bugs in your vegetable garden. Opting for raised garden beds can help to reduce the number of hungry pests you have to cope with. But ultimately, you will need to have a plan for pest control or insect removal to keep your organic vegetables safe from all that munching.
Many organic gardeners look to companion plants that repel insects from the vegetable patch. Many of these are strong-smelling herbs and flowers such as chervil, rue, or marigolds. You may also have read that companion plants like nasturtiums both repel harmful insects and attract beneficial pollinators such as bees, butterflies, and even hummingbirds to the garden. Based on claims like this, many gardeners grow nasturtiums in their container gardens and use them as edging plants in their vegetable gardens.
What? The Bugs are Eating the Nasturtiums?
I recently wrote a Facebook post highlighting the use of nasturtiums as a companion plant. The post published on the 24 Carrot Diet page and I then shared it on my personal profile. Within minutes, I received two responses talking about bugs and nasturtiums.
The first comment came from a neighbour who is starting a home-based greenhouse business. He mentioned that last summer he found small black beetles (maybe flea beetles?) attacking his nasturtiums. These same bugs also had a particular affinity for plants in the brassica, or cabbage, family. He was glad he planted the nasturtiums in his flower beds and not with his vegetables!
Another friend from back East mentioned that slugs were devastating her vegetable garden. She wasn’t so sure nasturtiums were an effective mode of pest control. Why? Because there were plenty of nasturtiums in the border around her vegetable patch!
Why Don’t the Nasturtiums Repel Those Bugs?
Until that moment, I had never questioned any of the pest control claims involving nasturtiums. The pungent smell of the leaves and flowers is supposed to keep many insects away, just as the smell of a marigold would. And since I had never had trouble with any insects in my nasturtium plants, I always believed that to be true.
Well, it turns out that I only had half the facts about using nasturtiums for garden pest control . . .
Yes, some insects do find the smell of nasturtiums unpleasant. But it turns out that nasturtiums do have natural predators. According to Burpee, nasturtiums fall prey to aphids, cabbage looper, leafhoppers, leafminers, and slugs. If you noticed that a lot of these yard pests also like to feast on brassicas, you are right. And that’s because nasturtiums are related to brassicas.
Now that’s something I’ll bet you didn’t know!
Nasturtiums are Related to Brassicas
I didn’t make the connection between nasturtiums and the bugs my friends were talking about until I did a little bit of digging – online, not in the garden this time. It took me a moment since nasturtium is not in the same genus as cabbage and its various cultivars (broccoli, kale, collards, cauliflower, and kohlrabi among them.) It isn’t even in the same family as the cabbage, the Brassicaceae which include many other brassicas besides the cabbage cultivars: rutabagas, turnips, mustard and cress, and seed crops such as rapeseed and canola that are used to make oil.
But the nasturtium, Tropaeolum majus, is a member of a larger order of plants that includes the Brassicaceae. It’s called Brassicales and its almost twenty constituent families include other familiar plants such as capers, horseradish and papaya. They also include the family Tropaeolaceae, of which the genus Tropaeolum is the sole member.
And that would seem to make nasturtiums and cabbages something like distant cousins. It’s good to know something like this when you’re trying to use nasturtium as a companion plant! Of course, that naturally begged the question, are nasturtiums an effective form of organic pest control if you’re growing cabbage plants? Or could the flowers actually attract the very insects you’re trying to repel from your garden?
Will Nasturtiums Attract Insect Pests to Your Garden?
Well, that’s probably a question for a master gardener. As I said, I’ve never had problems with insects attacking my nasturtiums. So I have no personal experience to draw on in answering that specific question. What I can say is that it’s best to experiment a bit and see what happens in your own garden.
But we did have a related pest control issue this summer, with our tomato plants and some cosmos. My daughter decided to plant the flowers in the raised bed with our tomatoes. It was a really hot, dry summer in British Columbia this year. The tomato plants were getting a bit dry and, apparently, this attracted some whitefly and aphids to the garden. We found a few of these sap sucking insects on the tomato plants. But most of them went to the cosmos. In fact, we found ants farming the aphids all up the stem of several cosmos.
If anything, the cosmos lured the aphids away from our tomatoes and other vegetables. There were very few aphids on the tomatoes, as you can see from the photo below. When we realized this was happening, we chose to sacrifice the cosmos blooms in order to get rid of the large number of insects in the garden. We cut the cosmos off below the point where the insects were gathering, and we immediately removed it from the garden. So, the cosmos had become an accidental trap plant that protected our tomato crop this summer. Next year, we plant to try interplanting more cosmos with our tomatoes for this very reason.
Using Nasturtiums as a Trap Crop
If you’re overrun with insects that attack your brassica plants, try using nasturtiums as a trap crop. Try to time the planting so your nasturtium will be blooming right around the time that you normally see the yard pest that you want to target. For example, if aphids are an issue in your organic vegetable garden during May and June, this is when you need your nasturtiums to be their most attractive.
Plant the nasturtiums close to your brassicas so the aphids will go to them instead of your developing broccoli and Brussels sprouts. Then watch the nasturtium plants for signs of an aphid infestation. You want to cut back the affected growth and take it well away from your garden, removing the aphids with it. This pest control strategy relies on physically removing a large group of the pests from your garden. You may want to pair it with other strategies, such as using insecticidal soap spray on your brassicas. And not to worry, nasturtiums grow back after you prune them!
Experimenting with Nasturtiums for Pest Control
Gardening is not an exact science so you’ll have to play around a little with the timing, placement, and number of nasturtiums you plant. Depending on how many insects invade your garden, you may want to plant nasturtiums right next to your brassicas and other vulnerable crops. This is called interplanting. (If you want to harvest the nasturtium leaves or edible flowers, grow another plant or two elsewhere in your yard/. This will help keep it safe from those nasty bugs!)
As I said in my introduction, do it yourself pest control can take a little work. But that’s OK! Because starting a home vegetable garden is an investment in your family’s health. Growing organic vegetables is one of the best ways you can be sure you’re putting healthy food on the table every day. So don’t be discouraged if it takes you a while learn about the pests in your garden. Eventually, won’t remember what life was like before you could grow your own organic vegetables. You’ll have all kinds of strategies for yard pest control. And you’ll be able to enjoy those lovely nasturtiums alongside their brassica cousins!
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Original content © 2017 Kyla Matton Osborne, aka #RubyWriter
Last updated 08/09/2017
This article was published on my food blog, 24 Carrot Diet. If you are reading this content anywhere else, it has probably been stolen. Please report it to me so I can address any copyright infringements. Thank you!