Do You Dig Dahlias?

By Dawn Pettinelli, UConn Home & Garden Education Center

Dahlias in a bed at Enders island
Dahlias at Enders Island. Photo by dmp2024

A couple of weeks ago, I was fortunate to visit the spectacular dahlia gardens on Enders Island in Mystic. For those unfamiliar with this retreat, an 11-acre seaside estate was donated to the Society Edmund by Mrs. Alys E. Enders in 1954. This Roman Catholic religious community offers ministry, retreats and respite to many. The grounds are open to all for contemplation or just unbound appreciation of nature and horticultural beauty.

Gardeners will delight in the gorgeous, well laid out garden rooms but especially be entranced by the vast array of dahlias. The gardens at Enders Island are filled with over 300 varieties of prize-winning dahlias in all colors (except blue), shapes and sizes imaginable. A Dahlia Preservation Trust was established to preserve the dahlia collection that is rated as one of the largest in New England.

Any of us growing dahlias while appreciating their cheery, attractive blossoms lasting long into the fall, do realize they are not winter hardy, even with milder winters attributed to climate change.  Dahlias are native to Central America. In fact, they are Mexico’s national flower. Those wishing to save the tuberous roots for replanting next year, must dig them up and store them over the winter.

Ideally, gardeners should wait until a frost blackens the foliage. Then, if possible, wait a week so any carbohydrates left in the above ground tissue can make their way to the roots to enable good sprouting next spring when the tuberous roots are replanted. This has been a particularly confusing fall to both plants and gardeners. Frosts have hit some areas but often not severe enough to affect all plants and dahlias in more protected sites are still blooming their heads off, a trait most appreciated by pollinators such as bees.

On the other hand, it is November. Time to reign in gardening activities and begin preparations for the holidays. What’s a gardener to do?

Since my plants were losing bottom leaves to disease and looking a little ragged, I just decided it was time to dig them and move the tuberous roots into the cellar. Before digging any dahlias, be sure to note their names. If tags were not written out when planting, make them out now if color and flower type are important.

Cut back stems to 2 or 3 inches and carefully dig the tubers starting at least 8 inches away from crowns so tubers do not get sliced or speared. Use a spade or pitchfork but dig in carefully. This year the soil is so dry that it was not necessary to leave the tuberous roots in the sun for a few hours so the soil clinging to them could dry and be shaken off. Every one I dug up was dry enough so that practically no soil clung to the roots. Each was placed in a separate container with repurposed labels.

Dahlia tubers with a white tag
Dahlia tubers tagged for storage. Photo by dmp2024

Perusing through online sources, many suggest washing tubers off with a hose and letting them dry before storing. I have let them dry out in wet falls and shaken dried soil from them before storing but have never hosed them off. Maybe follow the approach that makes most sense to you. If any remaining soil is washed off, the tuberous roots should most likely be stored in lightly moistened peat moss or other slightly damp organic material, so they will not desiccate over the winter. For me, leaving a bit of soil around the roots that are stored in pots in the cellar over winter helps to keep tubers from shriveling with only a sparse sprinkle of water once or twice a month.

When happy, dahlias will multiply but it is probably best to leave the whole clump together and separate it before planting next spring when multiple buds or eyes can be seen. Keep the tuberous roots at 45 to 55 degrees F and check every 2 to 3 weeks for signs of decay or desiccation.

For an early start, the tuberous roots can be set into beds usually by late April unless unseasonably cold weather is predicted. If you have questions about overwintering dahlias or for other gardening questions, contact the UCONN Home & Garden Education Center, toll-free, at (877) 486-6271, visit their web site at www.homegarden.cahnr.uconn.edu or contact your local Cooperative Extension Center.