Monday, May 7, 2012

Frost Damage on Hostas

We started off with a very early spring this year in Wisconsin.  It's the earliest I can remember seeing the hostas start to stick their noses up out of the soil.  Well the 70-80 degree weather we saw in March gave way to an April with temperatures dipping below the freezing point.  So a lot of the hostas that started to emerge early are now showing signs of frost damage.  In my garden it always seems the fragrant hostas are hit the hardest, and this year is no different.  I think it's because they come from the plantaginea family, and their leaves seem to be thinner than some of the other hostas.  But any hosta is susceptible to frost, and the damage can appear differently depending on how hard of a frost the hosta was exposed to.  See picture below for some examples of frost damage in my garden.

Is there anything you can do to avoid frost damage?  Yes, you can cover your hostas when you know the temperatures are going to drop.  You can use a sheet, a box, plastic pots (with drain holes covered), newspaper, burlap, rose cones, styrofoam boxes, bushel baskets, or practically anything.  I have also heard watering the soil, not the leaves of the hosta, which will help bring the temperature of the soil up 5 degrees.  You could also water the hostas with a sprinkler until the threat of frost is gone, but that sounds like a lot of water wastage to me (and you know how I love my hostas).  With over 400 hostas in my yard, I simply cross my fingers and hope for the best.

What should I do with hostas that have frost damage?  Once the damage is done, you obviously cannot reverse it.  It's best to cut off the leaves with the most damage, but leave some of the lesser damaged leaves on the plant so it can still make food.   Watch the hosta to make sure all of the leaves do not start to die off, as it could be a sign of crown rot.  If this happens you will need to dig up the hosta and check to see if any part of the crown have turned to mush and remove that part of the crown with a knife.  The good news is that hostas will usually produce another flush of leaves, though smaller, sometime later in summer.
You can see the brown burn mark of frost on hosta 'Rainbow's End'

Leaf tears and irregular marks are signs of frost damage on hosta 'Elegans'

Translucent spot on hosta 'Montana Auremarginata' 

Badly curled leaves of hosta 'Fragrant Bouquet' as it starts to emerge.

Another shot of badly formed and crumpled leaves, this one is hosta 'Hot Green Chiles'

Burn mark on hosta 'Lakeside Surf Rider'

hosta 'White Feather' leaves take on a translucent look to them which is a result of frost damage and sunburn since it emerged before the trees had their leaves.

hosta 'Iron Gate Supreme' is showing frost damage as spots in the leaves, which could be cells that burst during cold weather.


1 comment:

hostagirlcanada said...

Thanks for the pictures as I have finally been able to identify the problem with a number of my hostas this spring.