Hot, dry summers can cause water stress due to drying out of the hosta crown and root structure - see Heat Dormancy
Cold, Dry winters can also cause water stress especially when the fall rains are few and ground moisture is low. In both cases, hosta plants, if they do survive, will be considerably smaller during the next growing season. Extra summer and winter watering can minimize these effects if done before symptoms occur. Leaves are formed in the hosta crown in the fall for next spring's emergence, so if they cannot prepare for winter, the size of the spring plant will be smaller. Even heavy spring moisture may not overcome this fall/winter water stress - only prepare the plant for later growth.
Freeze and Thaw
Hosta plants are sometimes prone to late frost damage in the spring once the leaves have emerged past the protective outer scales of the dormant bud. The more emerged or unfurled the leaves the more sensitive the leaves are to temperatures below 32° F. Some gardeners protect the earlier emerging varieties during threats of frost with a nighttime blanket of foam insulation, burlap, inverted pots and bushel baskets, or even some of the commercially available material. If hosta plants are hit with late frosts it is best to cut off and discard the damaged leaf tissue so it does not inhibit the new leaves emerging.
Hostas are also subject to freeze damage in the fall. Again, nighttime protection to prolong the growing season is possible. If you decide to allow your hostas to succumb to winter, don’t worry. They will come back. Most varieties are hardy to zone 3 on the USDA chart, and can tolerate temperatures at least down to –35 °F.
Dormancy - There are two main types of dormancy. Natural winter dormancy, and stress dormancy, sometimes called summer dormancy or heat dormancy. Winter dormancy is brought about by the shorter and cooler days of fall. The above ground portion of the plant ceases to grow and prepares tight buds for over-wintering. Hostas may also quit growing, or become summer dormant as a result of heat or too much water stress. Frequently this can be overcome by the cooler fall nights and more rain.
Hail can damage hostas by piercing the leaves. Holes will depend on the size of the hail. In severe cases it may be easier and more attractive to remove intensely damaged leaves to make way for the newer sets of leaves.
Why are the leaves of my H. 'Frances Williams' turning rust colored around the edges?
Many of the yellow edged cultivars descending from the H. sieboldiana family appear to have this "rusting" problem. It is actually a dehydration of the leaf cells during low humidity periods and effects primarily the gold leaf edge or center of this related group of hosta. Many have tried moving the plant to a shadier location and others have provided the plant with more moisture. Both methods have met with limited success, but none seem to totally eliminate the problem. However, it should be noted that H. ‘Frances Williams' remains one of the longest running, "most popular" hostas, this "flaw" notwithstanding.
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