Let delightful dahlias diversify your garden

UC Master GardenerJuly 10, 2013 

Dahlias are relatively easy to grow in SLO County and come in a wide variety of colors, sizes and flower forms.

Q: I would like to grow dahlias. Where do I begin? — Becky, Morro Bay

A: Dahlias are showy flowers that encompass a wide variety of flower form, size and color. These tuberous perennials range in size from bedding plants to the stately tree dahlia, Dahlia imperialis, which stretches to a height of 12 to 15 feet.

Flowers are incredibly varied, from a petite 2-inch diameter to “dinner plate” dahlias with a 12-inch diameter. Nearly every color except blue is represented, and flower forms include single, double, pompon, cactus and fimbriated, among others.

Plenty of sun and moist, well-drained soil will suit your dahlias. They are most often planted as tubers in the spring but can be grown from rooted cuttings as well. Taller varieties should be staked for support as the stems of dahlias are hollow. These stakes should be placed five to six inches from the tuber at the time of planting. If you didn’t plant dahlias in the spring, they may be available now in nurseries as container plants.

The most common pests are snails and slugs. Handpick them in the evenings and bait with a product containing iron phosphate that is nontoxic to pets and wildlife. Earwigs can also damage leaves and flowers. A shallow cat food or tuna can with some vegetable oil and soy sauce, bacon grease or tuna oil will attract and trap them. For more ideas on controlling earwigs see the UC pest note: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74102.html.

Dahlias are native to frost-free climes of Mexico, Central America and Colombia, and are hardy to USDA zone 8. In areas with colder winters, tubers can be lifted in fall after the foliage has withered. Store them in dry peat moss or wood shavings until spring when they can be planted. Named varieties can be labeled directly on the tuber with an indelible pen.

If you would like to see examples of dahlias in person, plan to attend the dahlia show July 17 at the California Mid-State Fair. This is a wonderful chance to see their extraordinary variety and learn about them from both judges and exhibitors.


Contact the University of California Cooperative Extension Master Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-7190 from 10 a.m. to noon on Wednesday in Arroyo Grande; and at 434-4105 from 9 a.m. to noon on Wednesday in Templeton. Visit the UCCE Master Gardeners website at http://ucanr.org/sites/mgslo or email mgsanluisobispo@ucdavis.edu  .

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