How to grow Dahlias

 

Of all the summer blooming bulbs, Dahlias are one of the easiest and most spectacular flowers you can grow in your garden. From mid-summer to first frost, they will flower almost continuously.

Dahlias are available in a wide variety of colors, shapes and sizes, including ball dahlias, decorative and dinner-plate dahlias and cactus dahlias. All told, there are fourteen distinct groups of dahlias.

Dahlias are planted from tubers, generally in late May through early June. This is the when the soil temperature is warm enough to safely plant your tubers.

A good rule of thumb is to plant dahlias at the same time you'd plant tomatoes, when the soil temperature has reached 60 degrees F. Dahlias love the sun, so pick a place in the garden that gets the most sun during the day.  Dahlias will grow in an area where there is some shade, but the plants will be taller, and you’ll typically get fewer flowers.

When you open the package, your dahlias came in, you’ll find one or two eyes on the tuber. Sometimes you’ll find the tuber has begun to sprout. That’s okay. It’s still good to plant. Dahlias do best in slightly acidic soils. Since our Colorado soils tend to be higher in pH or more alkaline, adding organic materials will help make the soil more acidic and improve the drainage. Plan to add 3" to 4" of organic Earth Essentials Sheep, Peat and Compost to the existing soil 8" to 10" deep.  Once you’ve prepared your soil, add a handful of Bone Meal or Dutch Bulb Food and work it in a little before you plant your tubers.  The package your dahlia tubers came in can provide valuable information about your dahlia, including height.

Large dinner plate dahlias can easily reach 4' in height. Flower stalks this tall need to be staked. It’s best to place the stake when you plant your tubers. Set the tuber in the hole with the “eyes” or stalk pointed up. Next, set the stake near an eye or the stalk. Cover the tuber with soil and water deeply. As the stalk grows, tie it loosely to the stake to give it support. To do their best, dahlias need to be fed and watered regularly. Dahlias don’t need a lot of Nitrogen, but they do need Phosphorous and Potash, so select a fertilizer with numbers like 5-10-5 or 7-8-5. Fertilize your dahlias about 30 days after you plant them and again in another 30 days. Water your dahlias deeply, twice a week.

During the season, dahlias will provide forage for pollinators. Dahlias will not survive our winters, so you can elect to dig them up in the fall and store them or simply treat them as annuals and plant new tubers every spring.