Growing Dahlias

How do I grow dahlias?

Dahlias are cold sensitive and should not be planted until soil has warmed to above 15 degrees and the danger of frost has passed. In the Fraser Valley, this tends to be around mid to late April. I like to have them planted by May long weekend at the latest. You can plant directly into the ground or into a large container (at least 5 gallon or 12” diameter, but 7 and 10 gallons are preferred). Good spacing is very important for dahlias. At the very least, each tuber requires a square foot of space to develop. I like to err on the side of more space. I have mine planted 12” apart in rows 24” apart which allows more airflow which helps with pests and environmental issues. Airflow is vital in the garden. I also like to leave some space for my plants to develop large tuber clumps that I can save for the following season. 

Dahlias prefer well drained soil that is rich in organic material. I like to amend my soil with compost a few weeks prior to planting and work it in well. If you only need a small amount, I’ve had excellent results from the sea soil brand compost from your local nursery. You do NOT need to soak your tuber or wake your tuber in any way. Plant the tuber 4-5 inches deep with the eye (sprout) pointing upwards toward the sky. You can add a little bonemeal (optional) at planting time which provides phosphorus, nitrogen and calcium naturally into the soil helping with root development and overall plant and soil health. I like to also add my support stake at planting time so I don’t risk damaging the tuber later on. Fill up your hole, pat it firmly down and add a label if you wish. 

Once planted, you do not need to water your dahlias until you see the sprouts appear above the ground. Unless you are in extremely warm or dry conditions, the rain is usually enough to prevent your tuber from drying out. Containers have a tendency to dry out sooner than tubers in the ground and require supplemental fertilization which is why I prefer in ground planting. 

Watch for your sprouts and any pesky snails or slugs who like the taste of them while they are young and vulnerable. I like to use copper tape to prevent an early attack. Snails and slugs prefer wet weather and tend to be out at night when you don't see them. I also like to cover my sensitive sprouts with chicken wire tunnels cause I have kids and pets and it prevents them from being stomped on. 

Once sprouted, you can water deeply at least once a week. I prefer early morning watering with soaker hoses or drip irrigation for my dahlias so I don’t cause damage to their flowers or foliage. Watering deeply encourages a stronger root system vs watering a little bit here and there. Once your plant is about 10-12”, I like to “pinch” out the center stem which tells the plant to develop more stems and thus more flowers. Dahlias can be fine without pinching, but stems will be thicker and less desirable for cutting and there will be less stems and flowers overall. 

By mid July, you should see the beginnings of some blooms. Some varieties of dahlias take longer to bloom, especially the largest flowering varieties in my experience. I always find them to be worth the wait…

I’ll update my website and social media with digging and storing instructions which can take place just before or shortly after the killing frost. Please don’t hesitate to reach out should you have any questions or feedback at all on my socials or gardeningandprettythings@gmail.com