For dahlias to thrive, they need to be planted in a sunny location with well-draining soil and given ample moisture. The amount of time that dahlia bulbs need to remain in the ground will depend on the variety, but most will thrive when planted at least 6–8 weeks before the last frost.
When planting, make sure to bury the bulbs approximately 5–8 inches deep and 6–8 inches apart, making sure to plant with the pointed end facing up. Planting the bulbs deeper will help to protect them from the cold temperatures and give them a better chance of survival.
Once planted, dahlia bulbs will need to be watered regularly. The soil should be kept moist, but not soggy. Adding a layer of compost or mulch will help to keep the soil moisture consistent.
To ensure that the bulbs are getting the nutrients they need, you should fertilize them every two weeks. In the late summer and early fall, you can stop fertilizing and allow the plants to rest.
In warmer climates, dahlia bulbs can stay in the ground for years. However, in areas that experience cold winters, the bulbs should be lifted in late fall. To lift the bulbs, wait until the foliage has died back and then carefully dig up the bulbs, being careful not to damage them. Once the bulbs have been dug up, shake off any excess soil and let them dry out in a warm, dark, and dry place.
Once the bulbs have dried, they should be stored in a cool, dry place until it is time to replant them in the spring. By following these steps, you can ensure that your dahlia bulbs will survive and thrive year after year.