Winterizing your Roses
Ask three different rosarians how to winterize, and you'll get six different
Some don't winterize at all. Others go all the way - pruning back the
roses to waist height, stripping off all the leaves, and burying the bottom of
the plant with hauled-in mulch. If you don't winterize at all, some years
you'll lose a lot of roses. If you go the whole nine yards, some years
you'll still lose a lot of roses. In mild winters those who don't
winterize win, while those who do can lose roses to rot under all that warm wet
mulch. In cold winters those who don't winterize can lose everything,
while those who do shouldn't lose more than top growth, but no guarantees either
Some (like me!) wait to see if it's going to get cold enough, and then end up
winterizing in the dark after work as temperatures plummet, generally in sleet
repeat-blooming roses are not hardy to extreme cold.
Garden roses are complex hybrids of numerous species from all
over the Northern Hemisphere, and the repeat-blooming genes
nearly all come from semi-tropical, evergreen species from
China. They can take frost, but not extreme cold. My
own experience is that most modern roses can take temperatures
down to about 15?F (that's - 9?C) before sustaining freeze
Species roses and
once-blooming roses should not need winterizing, unless you're
growing semi-tropical species in cold-winter areas. Some
modern repeat-blooming roses were hybridized specifically for
cold tolerance: Buck roses from Iowa, and Parkland and
Explorer roses from Canada. Most rugosa hybrids are pretty
cold tolerant too. All the European, once-blooming old
garden roses are cold hardy: the albas, damasks, gallicas,
Other classes of
roses are notorious for being tender here, like the Noisettes,
semi-tropical roses hybridized in coastal South Carolina.
Tea roses have a reputation for tenderness that is not entirely
warranted - it's lack of summer heat that gets them here, not
winter cold. Climbers and tree roses can suffer physical
damage from snow load or high winds if not sufficiently
supported, and the top of a tree rose is particularly vulnerable
to freezing, being so far off the ground.
Frost and snow do
not hurt roses. What hurts roses is extreme cold,
particularly when combined with a dry wind. Wet snow and
thick ice can cause breakage from its weight but snow is an
insulator, it does not cause freeze damage.
When to Winterize?
repeat-blooming roses do not go dormant, they will harden off
when exposed to cold temperatures. This process prevents
the water in the cells from freezing and bursting the cell walls
- the cause of winter damage. Winterizing too early
prevents hardening off, and the roses will suffer winter damage
despite the protection you gave them. If possible, wait
until the roses have experienced at least one good solid frost.
Some years that won't be possible, as we often get sustained
mild temperatures in the 40s F and then a sudden plummet to the
teens in just a couple of days. It's best to watch the
weather rather than insisting on a set schedule. Some
years the cold will come in October, but most years not til
December or January, and some years not at all.
I have noticed, reading rose society newsletters from
around the country, that in truly cold winter climates, people tend to
winterize much later than we do! For instance, the Greater
Milwaukee (WI) Rose Society recommends waiting until there have been 'a
few' hard frosts - this in their November newsletter! And the Utah
Rose Society recommends waiting until the ground is frozen, IF you're
going to winterize at all(!).
How to Winterize?
First, plant your
grafted roses with the graft union just below the soil surface.
Soil is the best insulator, and the graft union is the most
critical part of a grafted plant. If that graft union
dies, then all you'll have is the rootstock sprouting up next
spring. Own-root roses do not have to be planted deep.
In mild winters this will be the only winterizing truly
Second, pile some
kind of insulating material over and around the bottom of the
plant. If you like you can prune the top down a bit and
strip off the leaves first, this does make the job easier, but
is not necessary. Ground bark, compost, mushroom compost,
wood chips, leaves, and soil are all good materials. Don't
scrape up soil from around the roses though, as this just
exposes the roots to cold and dry. You'll probably hear a
lot about how certain leaves should never be used as they rot or
skew the pH - don't bother. Use whatever leaves you have
at hand, they're all good unless you've got walnut or
eucalyptus, and those trees are rare here. If you do use
leaves use a lot as they will decompose and settle over the
winter. I like to add a cover of Douglas-fir branchlets
over the cone of leaves to help hold them in place.
are from the southwest, but the coldest, most damaging weather
usually features northeast winds, so pay special attention to
that side of your roses when mulching. Make sure you have
good cover over, under, and between all the canes for 6-8" from
the soil surface. Gaps will let in the cold. You
want to keep the extreme cold from getting to the base of the plant.
In cold winters, your rose canes will probably die back to the
level of the protection so heap it high.
Tree roses are
best protected with pipe insulating foam on the trunk, soil
piled at the base, and the top graft wrapped in bubble wrap or
some other nonabsorbent insulation. Make sure the whole
thing is securely staked, too. Some people put christmas
lights on their wrapped-up tree roses for decoration.
plain have to be cane-hardy here, and most are, with the
exception of the Noisettes and Hybrid Giganteas. You
should insulate the base of the plant just like any other rose,
and then make sure the canes are tied up securely. Then
hope for the best. Usually that's enough and you don't
lose much top growth.
Potted roses need
the root area protected as well as the top. Sink the pot
into the ground, the compost pile, or a plastic crate filled
with wood shavings or leaves. Many people like to move
potted roses into shelter for the winter but you have to have an
unheated, lighted shelter - unheated garage or shed with
windows, or an unheated hoophouse or greenhouse. Don't
bring them into the heated house, that's too warm and dry and
dark for them. They'll try to continue to grow but the
inside of your house is too dark and dry for healthy rose
growth. If you use extruded-foam insulated pots then you
don't have to worry about the roots, just leave them in place.
When to remove it all?
When the forsythia bloom. Be gentle so you don't break off
wearing her leaves and Doug-fir skirt for winter:
Drip systems (from the DripWorks website): the components most susceptible to winter damage
are timers, electric valves, filters, regulators and fittings.
Timers and filter-regulator assemblies should be brought in and
stored in a warm, dry place for the winter months. The parts of
the drip system left outside should be capped to prevent bugs or
dirt from getting in. A female hose plug can be handy for this
purpose. Be sure to remove the battery from any battery-operated
timer to prevent corrosion of the battery compartment. Fittings
(female hose beginnings, elbows, T's, etc.) can be left in place
on the system as long as they have been cleared of standing
water that can freeze and cause cracking.
The easiest way to clear your tubing and fittings of standing
water is by opening the end (or ends if you have multiple lines)
of the line and blowing compressed air through the system. If
you don't have a compressor readily available, gravity can be
your friend in draining the system. You can elevate a middle
portion of the tubing so that any water in the system drains to
the lowest point, where you have opened up the line. You may
need to work your way around your system to work the water out
the open ends. Another helpful part in draining your system is a
flush valve. A flush valve (or valves) can be installed at
the low point (or points) in your system. The flush valve works
by opening up when the water pressure in the line drops below
about 2.5 PSI.
Once your tubing and fittings have been cleared of standing
water, they are safe to leave outside through the winter. Make
sure you close the ends of the lines and use female hose plugs
at the line beginning where you have removed the
filter-regulator assembly. This will prevent insects from
crawling in and will ensure that the lines stay dry. If you
cover your garden beds with mulch or straw to prevent winter
heaving, be sure to mark where your tubing is to prevent
accidentally cutting though it with a spade or pitchfork come
Soaker hoses: I leave these in place, undrained; all I do
is remove the end caps to allow water to drain out on its own.
PVC systems: since PVC is a rigid material, these systems are
somewhat more susceptible to shattering than the flexible PE
plastic used for drip systems, or the recycled tire rubber used
in soaker hoses. Pipes should be installed at least 12"
below the surface for winter protection. Your PVC system
should also have its own shutoff valve which allows you to turn
off the water to the irrigation system without having to shut
off water to the house. Use it when winterizing.
Underground valves are generally installed in a valve box for
accessibility, which leaves them somewhat susceptible to
freezing. Once you've shut off the water to the system,
manually open all the control valves to allow them to drain,
then pack the valve box with bubble wrap or other nonabsorbent
insulation. Ditto for any pressure regulators or filters.
These are expensive and not easy to replace; you don't want them
shattering just because not all the water drained out.