Dahlias Are A Bad Match In The Garden For Three Vegetables From The Same Family

Dahlias Are A Bad Match In The Garden For Three Vegetables From The Same Family

“When placed in a vase with other flowers, dahlias can be a beautiful addition, as their striking colors complement almost any arrangement. However, if you plant them in your vegetable garden, they may not get along with their neighbors. Three of the worst companions for dahlias are broccoli, cauliflower, and cabbage, all of which belong to the brassica family.

The first issue that arises when planting these plants together is that they all require acidic soil, between 6 and 7 on the pH scale. This means they will be competing for nutrients and may struggle to thrive. You can try to mitigate this issue by giving them proper spacing, but then comes the next hurdle: pests. Dahlias are prone to insect problems, with aphids being particularly fond of the flower. Unfortunately, these pesky bugs also like to nibble on broccoli, cauliflower, and cabbage. Planting them together creates an aphid-friendly feast.

Additionally, these plants share diseases with each other. Powdery mildew and a fungus that causes wilting are common ailments that affect both brassicas and dahlias. When grown in close proximity, they can easily pass these diseases to one another.”

Favorable flower matches for brassicas

Farmer harvesting broccoli crown

Caterina Trimarchi/Shutterstock

While dahlia may be out of consideration, growing flowers next to members of the brassica family isn’t an unattainable dream. There are actually a number of blooms that can bring beauty and benefit to your vegetable row, with nasturtium serving as one of the top options. This flower usually grows shorter than our three brassica vegetables, and that extra ground cover lowers the soil temperature and helps with water retention during the hot summer months.

Nasturtium also serves as a great pest deterrent, as does yarrow. This flowering plant attracts a number of beneficial insects, including those that attack brassica-loving pests. Cabbage moths can be particularly harmful, not only to its namesake plant but to broccoli and cauliflower, too. Those moths, however, have an enemy in certain wasp species. Coincidentally, it’s the same wasps that are attracted to the alluring scent of yarrow. Plant the flower near your crop, and you’ll be gifted with a natural defense.

Stick with herbs, not vegetables, for dahlias

Two people harvesting yellow dahlias

Maryviolet/Getty Images

While broccoli, cauliflower, and cabbage are particularly unmatched against the dahlia plant, it’s best to avoid vegetables altogether when planting near the bloom. The risk of pests and disease is just too high to justify any visual benefit that can be gained from the pairing. Instead, try growing herbs next to the flower.

There are a number of herbs that make for a good companion to dahlias, namely because of their ability to repel troublesome insects and attract beneficial ones. That list includes rosemary, thyme, coriander, mint, anise, and cilantro. Lavender can provide that same benefit while adding a beautiful pop of color, too.

If you want to match your vegetable garden to the dahlia area of your yard, nasturtium will do the trick. The plant is versatile in its pest defenses, keeping annoyances away from broccoli, cauliflower, and cabbage, while serving as a trap crop for dahlias. Aphids, specifically, will go for the nasturtium, leaving the delicate dahlia alone.

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Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.