Time To Winterize Dahlias – AG Matters

It may not be full blow winter yet, but it's time to winterize dahlias before it's too late. The Master Gardeners at Cornell Cooperative Extension have dug up the Dahlia Garden bed and you should too.  They are offer some tips on the proper way to dig them up and store them for the winter.

The tubers of dahlias are tender and will rot if left in the soil over winter. After the first killer frost, the leaves will blacken and stems begin dying back. After removing any support structures (ties, stakes, trellises) be sure to label different varieties before making any cuttings. Next, cut stems 4-6 inches above the ground, then wait 3-7 additional days for a dry day to start digging. This will allow tubers to further develop "eyes" or new growth points. If the stem stalk is open at the top, you may decide to cover stalks with aluminum foil to prevent water entry and potential rot.
Carefully dig tubers without damaging them -- typically garden forks are preferred but a spade or shovel also work. Insert your fork straight downwards about 9 inches from the base of the stalk, then gently pry back on your fork & loosen the soil. After you encircle the entire base, get underneath the tuber clump and lift carefully. You may have to cut feeder roots if it is stuck, but be certain not to pierce tubers as this will damage them & invite disease. Lift the clump out and remove large soil chunks by hand and lightly shake it off. Be gentle as many tubers have small necks that can be torn or broken, and invert the stem to drain any water collected within. Rinse your tubers: use a garden hose on a light shower setting. Be forewarned; excess moisture may encourage rot. Some growers opt to dip them in 10% Clorox solution, to destroy harmful insects & microorganisms.
Find a dry, airy location above freezing for a minimum of 3-5 days, or maximum 2 weeks, to hang your tubers upside-down; this will remove excess stem moisture and promote additional tuber development. One vital step in overwintering Dahlias is ensuring the outermost skin slowly dries, to a toughness that when written upon it with a felt pen, doesn't rub off. An ideal winter temperature is around a constant 40-50 degrees, such as in a garage, screened porch or cellar basement. For more information on storing dahlias for the winter months call the Horticulture Hot Line, Wednesdays & Fridays from 9 a.m. to noon at 315-736-3394.

SOURCE: Cornell Cooperative Extension