It’s all too easy to get excited about the forthcoming season and plant out Dahlia tubers too soon. Unfortunately they fare very poorly in cold, damp soil and are liable to rot. If you’re looking to get a jump on things and see those knockout flowers as soon as possible, start some tubers in containers. Here’s a straight-forward how to:
Round up your supplies. You’ll need: Potting soil, trowel or scoop, Dahlia tubers, empty pots, and a watering can. Scissors and gardening gloves are also helpful.
Tubers come in a wide range of sizes and shapes. Some look like fingerling potatoes, others resemble string beans. Some are in bunches, others can be a single tuber. Choose your pot size accordingly.
Trim off any shriveled, moldy, or dry growth.
Fill the bottom of a pot with a few inches of potting soil. Holding the tuber by its stem, settle it into the soil.
Fill in with potting soil until the tuber is entirely covered except for the tip of the stem end. (If you’re unsure which end is the stem, lay the tuber in the soil sideways and cover it with 2-3” of soil. Mother Nature will sort it out.)
Water the tuber lightly, using just enough to moisten the soil around it and eliminate any air pockets. Do not water again until the soil is very dry (i.e. pulling away from the sides of the pot) or you begin to see growth. (Over-watering may cause rot.)
Insert the planting tag so you can identify your Dahlia variety.
Set the pot in a sunny window or under a grow light where temperatures are ideally 60 degrees F or warmer. (Do not place plants on a radiator or other heat source.) As temperatures warm outdoors to 60 degrees F or higher, take your potted Dahlias outside and introduce them to sunshine and breeze. Gradually increase their exposure to the elements as planting time approaches. (This is called “hardening off” your plants.) Some tubers will begin sprouting growth within a few weeks, others may take longer to shake off their dormancy.
When the soil temperature reaches 60 degrees F, transplant your already-growing Dahlias into the garden. The plants will begin producing flowers earlier than if you had planted still-dormant tubers into the ground.
