Happy Friday! It's dahlia planting time around here, and I thought I'd share my tips for growing dahlias. When I give tubers to friends and neighbors I like to include a little one page document with my tips so that they have something to reference, especially if they are growing dahlias for the first time. I wanted to share that here with you all too! I am not an expert on growing dahlias, but this is my 7th year growing them, so I've learned a few things that work well for me.
- Keep dahlia tubers in a cool dark place until you're ready to plant.
- Tubers can be planted once your soil is at least 55 degrees F (ideally 60 F) and the danger of frost has passed (this is early/mid May for me!). Avoid planting before lots of rain in the forecast to prevent rotting.
- Dahlias like to grow in full sun (6+ hours) if possible with good drainage. I find dahlia varieties that produce smaller flowers (3" in diameter or less), can thrive with less than 6 hours of sun.
- Be careful when handling tubers, the necks are fragile. If you break off a sprout, don’t panic! It’s okay, it will sprout again from that spot.
- Plant tubers 4-6” deep, 12-14” apart in ground or 1 tuber per minimum 3-gallon container, Place in hole with any sprouts facing upwards, laying the tuber horizontally in the hole. Add a spoonful of fertilizer (I use Bulbtone by Espoma) in the hole. Cover with lightly moistened soil.
- Do not water tubers until you see a sprout with leaves cracking the surface of the dirt. Unless it gets super dry, then you can give them a little water.
- Place a stake for each plant at planting time so that the tuber isn’t accidentally pierced. Plants will need to be tied to this support as they get taller.
- Alternatively, you could place stakes every 6-8 ft and use a corralling method for support. Kristine Albrecht has a great video on this:
Staking Dahlia Plants: The Corral Method. Last year I used Hortonova Netting (by Tenax) for the first time, and it worked really well!
- Slugs love dahlia sprouts, they may need some protection or an application of ‘Sluggo’.
- Fertilize every few weeks if desired with a basic, balanced fertilizer. Switch to a fertilizer with less nitrogen when plants start to bloom to encourage more bloom production.
- After the plant is around 1’ tall, pinch off the center main stem, leaving at least two sets of leaves on the plant. This encourages branching and results in many more flowers!
- Plants will need consistent watering throughout the season.
- You should get flowers starting in August, and they will bloom until you get a hard frost!
- Dahlias are a “cut and come again flower”, typically the more you cut, the more flowers you’ll get! Cut stems above a set of leaves. Cutting deep into the plant will encourage longer stems.
- Cut flowers only last a few days inside. Even if you don’t want to bring flowers inside, your plants will benefit from regular deadheading.
- After frost or at least 120 days of growing, cut back plants to a few inches above the ground. Let tubers cure underground for 2-3 weeks.
- Carefully dig up tubers with a pitchfork to avoid damaging tubers. Gently remove dirt with a brush. Divide clumps now or in the following Spring when eyes start to sprout. In my personal experience, tubers store easier as whole clumps if you have the space. There are a lot of resources online to guide you through the dividing process, this visual explanation of tuber anatomy and dividing is excellent:
Dahlia Tuber and Splitting Guide from Summer Dreams Farm.
- Dust tubers with sulfur fungicide dust or cinnamon if desired to help prevent mold in storage.
- Store tubers in plastic tubs with pine shavings. Ideally tubers like to be stored at temps around 45-55 degrees F. They can stand colder temps as long as they don’t freeze (32 F). Warmer storage will be more prone to rotting. I keep the lids on, but not snapped shut to allow some airflow.
- Check tubers every few weeks for rotting or shriveling. Mist shavings with water if the tubers start to dry out. Remove and discard any rotting tubers or overly wet shavings.
- If you have time at the end of the season, go ahead and amend your dahlia patch after digging up tubers, but before raking the dirt back in place. It's a great way to use up leftover potting soil from the season. I usually try to mix in any leftover straw mulch, or mulched leaves. I also put a thick layer of leaf mulch on top of the patch to finish.
- In April/May of following year move tubers to warmer storage to encourage them to wake up in preparation for dividing and planting!
Happy Growing!
