If you’ve never grown a dahlia before, it’s high time you did! Most gardeners can’t grow just one, and there are countless strains to keep you busy. Find helpful prep and planting guides, staking tips, end-of-season bulb storage tips and more.
How to prepare your soil for planting dahlias
Some plants can handle all growing conditions, but Dahlias really need the right conditions to produce the outstanding buds they are known for. With a well-prepared soil bed, your dahlias will develop a beautiful growth very quickly. Follow these steps for success!
Dahlias prefer rich, well-drained soil. Loose, nutrient-rich soil nourishes the tubers and promotes strong root growth. The soil needs to be well-draining as dahlias like lots of water, but moist soil will cause the tubers to rot. Dahlias are great for sandy, loamy, or acidic soil.
If you’re starting out with clay soil, dry soil, or compacted soil, it’s important to make sure you prepare your planting area properly to see growth and blooms. If you have difficult soil or live in an area with heavy rainfall, consider growing dahlias in berms or raised beds for optimal conditions.
Before planting, enrich your soil with compost work in a good organic fertilizer. Look for a fertilizer that is low in nitrogen to encourage flowering and not too much leaf growth. Organic matter nourishes your dahlias and helps the soil retain the moisture the plants need.
Dig at least 10 inches to 1 foot deep (or create a raised bed 10 inches to 1 foot deep) to loosen the soil and give the tubers enough room to grow and improve soil drainage.
When to plant dahlias
In general, we send your dahlia bulbs at the right planting time! Tender bulbs of dahlia are generally planted outside at about the same time as you plant tomatoes.
If that isn’t before late May or early June where you live, you can plant dahlias indoors 4-6 weeks before your last frost date. In containers, lay tubers on their side, stems up, and cover with 2 inches of soil. Wait until you see new growth breaking through to water. Then they can be planted outside when it is warm enough.
How to plant dahlia bulbs
1. First prepare your floor as described above. Don’t skip this step! Preparation is the key to success.
2. Digging holes for planting.
The distance varies depending on the variety. Most dahlias are spaced at about one bulb per square foot. The largest varieties of Dinner Plate Dahlias do best with wider spacing, about 12 to 18 inches, to allow for foliage and flowers to grow. Compact varieties can be planted with multiple bulbs per square foot. Observe the distance recommendations on your packaging.
The holes should be relatively shallow and wide enough to allow the bulbs to be spread out like fingers. Tubers for large varieties like Dinner Plate should be around 6 inches deep, while smaller varieties can be around 4 inches deep.
3. Plant tubers.
Place the tubers so that the crown (where the tubers connect) is a few inches below the soil surface. If the bulbs have buds or “eyes”, place them on top – that’s where the stems will grow.
Carefully fill in soil around the tubers so that they are completely covered by a few inches of soil. There is usually some stem material at the top of the tubers, and if there is, the stem may be at or just below the surface of the soil.
For dahlias with large blooms, and generally those growing 3 feet or taller, we recommend plugging when planting. See staking tips below.
After planting, soak the tubers thoroughly to remove air pockets and encourage root growth. Dahlia tubers do not need much water until they sprout.
5. How long until they germinate?
Usually about 3 weeks – depending on the weather it can take longer. Dahlias sprout faster when the soil and surrounding climate are warmer, and they may be delayed or take longer when the soil and weather remain cool. When planted in spring and depending on your climate, they can be variable.