The Soil Addition That Can Prepare Hostas For A Cold Winter

While hostas might be notoriously hardy perennials, even they could use a nice warm layer of mulch before winter settles in. A layer of mulch protects roots against potential freeze damage. Providing that vital insulation is an essential task for healthy hostas before winter chills hit the garden.

Why mulch hostas? It's true that most hosta varieties survive cold weather down to USDA Plant Hardiness Zone 3? This even includes the upper most parts of Minnesota, which regularly dips into negative temps. It turns out some hosta varieties are hardier than others, and all varieties can be affected by wide swings in temperature. If you have a whiplashing weather pattern of hard freeze followed by a warm thaw, the ground often heaves — or pushes roots above ground, exposing them to freezing temps or dry air. This can ultimately hurt or even kill a hosta.

These outdoor plants that require little sun typically need minimal care, but a nice layer of organic mulch can help them stay healthy in the winter. Options for organic mulch that work best include shredded bark, straw, or compost. Hostas don't mind slightly acidic soil, so even pine needles or pine bark can be used for insulation. Layer mulch between 2 inches and 4 inches — or even a little thicker, depending on how cold your winter gets. In warmer zones, some decide to leave foliage or fallen leaves on the ground around hostas and call it adequate cover.

Hostas are more or less cold hardy, depending on the cultivar. Certain varieties like 'Frances William' or 'Blue Mouse Ears' will tolerate winter conditions better. The pale and regal 'White Feather' hosta even manages to survive down to zone 2. 'Guacamole' or 'Sum and Substance' hostas prefer warmer climates, such as zones 6 through 9. 'Ming Treasure' also only tolerates zones higher than 4. These cultivars definitely need mulch if you live in a place where freezing temperatures are to be expected. 

Whichever hosta variety you have, mulching helps — not just with regulating temperatures, but also with retraining moisture and adding nutrients to the soil. Just don't pile on too much mulch around the plant's crown. Keep at least an inch's worth of air circulation there to avoid rot. For serious cold snaps, cover the crown with burlap. 

It's best to mulch in November after the leaves have died, usually after the first frost but before the ground becomes hard. This fall task can help keep hostas healthy. When spring temperatures rise above freezing and you start to see signs of new growth, remove some of the mulch to give this hardy perennial room to sprout.