do you protect the plants in the winter? I have overwintered containered
hostas with only mixed success. Method used was to lie pots at about a
45 degree angle with the ground (patio) and cover with hay or straw. What
is the best method? Do you or does anyone else put the pots in an unheated
We probably winter about 40,000 hostas outside in containers. We
also winter some varieties in unheated cold frames, but those are generally
the ones that come up very early in the spring, plantaginea and montana
types and such, and the protection is from late spring frosts and freezes,
not winter temps. Our cold frames stay a bit cooler in the spring
and the plants stay dormant a bit longer. While we always have losses
due to one thing or another, in the great scheme of things, our percentage
of losses is very close to zero - knock on wood.
z5 Indy (brrrrrrrrr) IN
We winter our pots under microfoam and white plastic. Microfoam
is similar to styrofoam, but it is flexible and it comes in 6'x300' rolls.
The purpose of the microfoam is to keep temperatures from fluctuating rapidly,
not to keep the plants warmer. Microfoam is probably not practical for
the homeowner because I don't think it is available in small pieces, but
you can use other things that will serve the same purpose. Plastic goes
on top to keep any water from getting into the plants while they are covered.
In our area, we cover sometime in December, depending on the weather, and
uncover around the end of February. When to uncover is always a question,
because the plants under the covers will break dormancy earlier, so we
want to wait as long as possible to uncover, but make sure we do it before
they come up. Sometimes we have to recover if we get a cold spell.
Bait for the mousies is also necessary under the covers.
The main problem for the plants over winter is water, not cold.
They should be moist, but not wet, when covered, and as long as they are
covered with plastic, they should not need any additional water until spring.
I suspect the biggest reasons for losses are the soil mix people tend to
use and the size of the containers. Drainage is all important.
If you look at the mix that most growers use for hostas, you will see that
it is usually made of bark or some other very chunky material, not soil
or peat. Unfortunately, because most people don't like to pay much
for potting soil, most retail mixes are not very good. If you use peat
or soil based mixes, which hold a lot of water, you have to be much more
careful to make sure the plants don't have too much water. I always
suggest using the smallest container possible. If you are going to
give the plant room to grow, do it in the spring, when the plant is in
active growth. If you put a plant in a pot that is larger than its
roots can occupy before dormancy, it is probably going to hold too much
water and crown rot is likely. For the same reason, we do not like
to divide or pot plants after August so the roots have a while to grow
into the pot before winter. Also, resist the temptation to water
the plants when you uncover. Until they start to grow leaves and
the weather warms up, water will do more harm than good. Water
only enough to keep them from drying out completely, if the pots are damp,
that's all they need until they start producing leaves.
Since the main cause of losses is crown rot, we are considering using
ZeroTol as a drench to see if it makes any difference. Since ZeroTol
is essentially very strong peroxide and is effective on both fungi and
bacteria, it might be worth while to experiment to see if a peroxide drench,
maybe 10 oz of peroxide in a gallon of water, would be helpful. Since
ZeroTol is also apparently effective on nematodes, I would think peroxide
drenching would be a good idea as long as we determine that it does no
damage. I doubt that it can do any harm, but I don't make any guarantees
and I suggest you try it on your undulatas before you drench your Dorothy