Hosta Cold Tolerance
Prized for their color and texture, hostas can be grown in USDA zones 4 through 9. In these zones, the hosta growing season ends when temperatures dip below 50 degrees F. (10 C.) at night. Hostas in winter go into a kind of stasis and this temperature dip is a signal to the plant to become dormant until temperatures warm in the spring. All hostas thrive when subjected to freezing or near freezing temperatures during their dormant phase. The number of days or weeks varies depending upon the cultivar, but chilling promotes earlier emergence and better all-around growth. At this juncture, it is time for some hosta winter preparation.
Winterizing Hostas
To begin winterizing hostas, if necessary, keep supplying them with an inch (2.5 cm.) or so of water per week throughout the fall. If you have been fertilizing the plants, stop feeding them in late summer or they will continue to produce leaves. These tender new leaves can make the entire plant, including the crown and roots, susceptible to frost damage. As nighttime temperatures drop, hosta foliage will begin to dry out and fall over. Wait until the leaves have fallen over before continuing with any hosta winter preparation. Why is this important? The leaves are needed post-bloom to produce food for the next year’s growth.
Further Hosta Winter Care
While there isn’t much that needs to be done for hostas in winter, the foliage should be trimmed back. Once the leaves have fallen naturally, it is safe to cut them. Use sterilized shears (sterilize with a half/half mix of rubbing alcohol and water) to prevent fungal infection or rot. Cut the leaves all the way to the ground. This will discourage slugs and rodents as well as diseases. Destroy the cut leaves to prevent any possibility of spreading potential diseases. Mulch the hostas with 3 to 4 inches (8-10 cm.) of pine needles to protect the roots from cold temperatures. This will even out the differential between cooling and heating each day, which can interrupt the necessary chilling period. For hostas that are potted, bury the pot to the rim in the soil and cover with mulch as above. For hostas in zone 6 and below, mulching is unnecessary, as temperatures stay well below freezing through the winter months.
