Gardening tips for overwintering dahlias in the ground

While the standard practice for dahlias—plants originally from the Mexican highlands that are frost-sensitive—is to dig up tubers and store them in a frost-free cellar, gardeners in mild climates may be able to leave them in the soil.

Success in mild regions, such as those along the Rhine or in protected courtyards, requires loose, permeable soil to prevent tuber rot caused by moisture and waterlogging. To protect plants left in the ground, gardeners should wait until the first light frost has turned the foliage black. Recommended steps include cutting stems to approximately ten centimeters above the ground and applying a thick layer (15 to 20 centimeters) of organic mulch, such as straw, dry leaves, or bark mulch.

To secure the mulch against wind, materials like fir branches, breathable garden fleece, or jute sacks can be used. It is critical to maintain air circulation; using airtight plastic sheeting or rotting, wet leaves should be avoided, as condensation can lead to tuber rot.