By Julia Frisbie
posted April 22, 2021 — Earth Day!
Dahlias are ridiculously popular, and it’s easy to find information about how to grow them in a conventional way: plant, stake, and label them eighteen inches apart from each other in a straight row at the same time as tomatoes; set up automatic irrigation to water the soil rather than the leaves, but don’t start watering until they’ve emerged; pinch them once they have 3 or 4 sets of leaves. It’s good advice, but I’m not into monocultures. It seems too lonely.
So I’ve been experimenting with companions. Here are some good ones for dahlias:
- “Wrinkled crinkled” cress is tall and skinny, taking up almost no space, and I like to plant it between two rows of dahlias because it makes these delicate wand-like seed heads that look good next to fluffy dahlia blooms. This year I’ll experiment with other tall and skinny companions like dill.
- Nasturtiums sprawl over the ground and don’t compete too much with dahlias, making a lush carpet under them. In early summer they make our salads more interesting, and in late summer they seem to draw aphids away from the dahlias.
- Salad greens can function as a “quick crop” at the base of dahlia plants in early spring, ready for harvest around the same time as dahlias want a hard pinch. After the pinch, when the dahlias really start to bulk up, the greens are starting to think of bolting, so I cut them off at the soil level and feed them to the chickens.
- I like to grow bush beans at the base of each dahlia plant. Two reasons: 1) it saves space, and 2) beans have these little nodes on their roots where symbiotic bacteria live, and they fix the nitrogen in the air pockets of the soil into a form that’s available to the plant roots. Basically, having a living carpet of beans or clover is like a mild, constant fertilizer. It’s a pain to harvest beans under all the dahlia leaves, so I grow shelly beans rather than green beans that I’d have to pick several times a week. When they dry down in September, I cut the bean plants off at the soil line and leave their roots down there with the dahlia tubers while I hang their tops upside down in the garage until I’m ready to shell them. Many dry beans don’t mature reliably in our climate, but I’ve had good luck with “Rockwell” and “Ireland Creek Annie.”
- Ducks love slugs more than anything, and slugs are a dahlia’s number one enemy. You can’t leave the ducks with the dahlias 24/7, but supervised daily visits are beneficial to all involved. Plus, a basin of dirty duck water dumped on a dahlia’s leaves once a week seems to really float their boat. I do this first thing in the morning because that’s when the plants’ stomata are most able to absorb water and nutrients. Stomata are microscopic holes in plant tissue that open when photosynthesis starts each morning to let them take up carbon dioxide, and close at night and also when the weather gets hot to prevent too much moisture from being lost. So the morning– when the sun has just started shining, but it’s not too hot yet– is when you get the most bang for your buck in terms of foliar feeding.
The following are not great companions for dahlias in my experience:
- Chickens. They prefer worms and bugs to slugs, and in pursuit of their favorite prey they will scratch up all the mulch and uproot the tubers.
- Sunflowers. I thought maybe they’d provide support, but they just shaded the dahlias out.
- Tomatoes. They need similar things and don’t mind being side-by-side, but there’s no space savings to be had by planting them on top of each other because they compete.
- Root vegetables. Dahlia tuber clumps can get huge. You don’t want any other big-rooted thing down there taking up space.
Perhaps I’m anthropomorphizing dahlias. Maybe they’re not capable of loneliness. But have you read about mycorrhizal networks?! I think plants are communicating all the time, and we just don’t know how to participate in the conversation yet. I don’t want to live with only members of my own species for company… so why should they?
Julia Frisbie has been gardening in Coast Salish territory for six growing seasons, and is thankful to learn from plants, animals, and people who have been here much longer. She’s grateful to her mom, Anne Kayser, for cultivating her curiosity, and also to Robin Wall Kimmerer for writing the book Braiding Sweetgrass, which transformed her relationship with the more-than-human world. Follow Julia’s micro-farm on Facebook, Instagram, and/or TikTok.