Hi again it's Jason from Fraser Valley Rose farm I'm sitting here amongst my miniature
roses and I'm going to say about them that most of them are Hardy to zones five and six
and when I say that I take it for granted that most of you will know exactly what I mean that
cold hardiness is baked into the way that we look at plants in North America certainly but
what does it mean and is it reliable and maybe even the better underlying question is is it
cold that kills your plants over the winter after all and my answer to that my argument for that in
this video is not as often as you might think but we can't go much further without at least
doing a brief recap of those climate zones that I just talked about one of the first and still the
most widely accepted at least in North America of these hardiness zones is the USDA zone maps
if you look on their site you can see this map and the way that you're intended to use it is to
find yourself on the map and what it will do is it will give you a hardiness zone or a sign to your
area hardiness zone so for instance instance if you're in zone six they expect that the coldest
temperatures that you will on average have in that zone is negative 10 degrees Fahrenheit and
there's obviously Celsius conversions to this and Canada more or less followed the lead of the USDA
so they have their own hardiness Maps based on these same zones now if you were in the zone 6
and you were expecting negative 10 Fahrenheit then other parties could go in and fill in the
blanks as to what plants are expected to survive in that area so the Botanical Gardens and The
Trial Gardens of big Horticulture would go and they would test the plants and then they would
assign the plant a matching zone so if you're in zone six and the plant is rated for zone six you
have a win also if the plant is rated for zone five or four or three it's rated to accept cold
that is deeper than your cooled and so you can choose from most of those plants so those of us
lucky enough to live in a good climb Zone Zone 8 zone 9 can choose from a wide range of plants
whereas if you're living in zone three you know that your selection is a little bit more narrow
sadly the hardiness zone won't tell you for sure that your plant Will Survive a season in fact the
number one reason why plants die over the winter in my experience has been their overall health and
vigor their condition going into the season if the cold didn't kill them then they would have
been killed by another environmental stressor they could have been killed by drought they could have
been killed by disease there's lots of ways that a plant can die in the landscape and this time it
just happened to be the cold so I will give you my experience over the last year is that last
year we had a deep cold after Christmas in our farm and all of my roses were rated to survive
those temperatures I mean they would have been fine to the slightly deeper temperature that we
had but three of them died now if you'd asked me ahead of time which three roses are in trouble in
your field those are exactly the three I would have named they were ones that were weak thin
poorly established in the ground struggling anyway and the winter just happened to be the
thing that tipped them over was it the Deep cold you know they were Hardy to those zones it could
have been just that they ran out of energy before the spring came up remember plants store energy in
their tissues once they drop all their leaves they can't photosynthesize anymore they have limited
stores of energies those plants that are strong and healthy and have been growing well have stored
enough energy to get through the winter those that are weak and struggling haven't so the first
thing you need to consider before you talk about winterization or hardiness zones is the condition
of your plants themselves are they growing well and of course you can react to this earlier in the
season by saying well if this plant isn't doing well it's in a pot maybe I'll leave it in a pot I
won't put it in the landscape to struggle over the winter maybe I'll leave it in the pot give it some
babying over the winter or bring it back to health next spring and season and I really won't leave
it to the stress of winter until I have it well established I'm going to rank winter wet as the
number two reason why plants die over the winter certainly here in The Damp Pacific Northwest it
by far outstrips the direct impact of deep cold is the fact that roots are sitting in moisture
over the winter and the plant just doesn't have enough access to oxygen to to fuel itself what you
will see oftentimes in the descriptions of plants and catalogs is doesn't like wet feet or requires
excellent drainage these are Clues to you that you better assess that before the winter season what's
funny about the plant hardiness zones is that some plants that are considered for instance dahlias
that say you have to dig and lift these out of the ground and the primary reasons why they have to
come out of the ground doesn't have to do with the cold itself in fact I've seen some videos recently
and maybe I'll see if I can put in a at least a link but maybe if I can get a clip as well of a
daily grower who actually overwinters her daily is in the ground just by covering them over with
a mulch and then getting a tarp over top of that to keep the wet out it's such an important thing
now imagine a situation where you've got a plant in a container or a rose in a container say and
you've stuck that up against the house thinking that's going to protect it from all that cold and
wind and yet from the side of your roof is coming down a stream of water that's filling that up with
water and keeping it in mushy soil or soggy soil all the way through the winter season it's not
going to be a surprise to you when you come back and decide find that that's dead in the spring
certainly the other thing you can do is have an assessment around your landscape during the summer
or fall when you see that there are drainage problems and I try to address those or move
those plants before you go into the winter because aside from say you know Willows and dogwoods and
a few of those sort of Boggy type shrubs there isn't a lot that likes to have wet feed over
the course of the winter the third reason why allegedly cold hardy plants might die over the
course of a winter has a bit to do with wind or rather the effects of wind which is desiccation
I invite you to think for a second about why it is that an unheated Greenhouse like this offers
any protection at all certainly it reaches all of the same cool temperatures as the outdoor there's
no extra heat in here what it is doing is it's cutting down certainly you know it's got that
roof on there so it's cutting down on the moisture so I have more control over the moisture so that
addresses the last thing I talked about but it also cuts down on the wind and wind that is cold
air that is cold doesn't hold a lot of moisture what it does is as it pushes past the leaves and
through the leaves and stems of your plants is it actually sucks the moisture out of them that's why
sometimes you will see this scene where you've had say snow cover across your shrubs let's say
your rose is here and the Winter Winds have come and gone and you come to the spring and you look
and at almost a uniform level across a whole bunch of roses you see black stems above where the snow
line was that's the effect of having a wind come through and suck the moisture out of those stems
certainly in a climate like mine where we don't have reliable snow cover there are certain plants
that are more vulnerable to this think about plants that go fully dormant of course they don't
have the foliage to suck that moisture out of but think of something like a lavender or a rosemary
and how many of those have maybe you lost in a climate like this because they tend to hold on
to those needles or leaves over the winter and then of course when it gets that cold cold wind
come through it just sucks the moisture of that plant and kills them to the ground so if you can
provide for certainly for more sensitive plants if you can provide some shelter from wind it's great
if you have a greenhouse like this that's great out in the landscape you can do a lot by putting
some burlap around and maybe some dry leaves that's a method I showed in my on my video on
how to protect roses over the winter the fourth and final cause here I'm going to talk about is
plants in containers which may not actually be a cause in itself but just an exacerbation of
everything I've talked about up to this point plants and containers have limited capabilities
of dealing with the cold they don't have the moderating effects of the ground to moderate
the temperature they are especially vulnerable to that cut of the wind and also a freezing solid in
that pot so the desiccation can really destroy a plant in a container very very quickly when you're
talking about those hardiness zones so even though a plant may be considered you know cold hardy to
your Zone that if you put it into a container I think you should at least add a zone or two onto
that if you intend to overwinter it outside but even better if you can wait until it goes dormant
and then tuck it into an unheated location but is sheltered from the from the wind and from the rain
you have a better shot of bringing that through the winter and one of my favorite locations is
just my downstairs garage which really doesn't get heated but generally stays above freezing anyway
and if I can wait until my roses or other plants are completely dormant before I put them in there
I strip off the leaves I put them inside they make it through just fine at least through the hardest
patches of winter all you have to do is check on them every now and again just to see that they
haven't dried out so completely that the soil is shrinking away from the sides of the pot or the
pots have become light but that's my favorite way of overwintering things in containers I'm turning
now to the topic of those hardiness zone maps and their usefulness and of course they are a great
starting point to find out if your plant at least on paper Will Survive the cold the temperatures of
your Zone just so long as you keep in mind that it isn't always the cold that kills your plants
and so the onus isn't off of you to make sure that those other things are taken care of shelter from
wind keeping your plants out of the winter wet or making sure the drainage is okay making sure your
plants are healthy going into the winter those are all on you there has been a move in recent
years to try to factor in some other things into those climate zones I think the initial 11 zones
from the USDA climate map have gone up to about 26 now and the sunset guide I think has 45 different
climate zones that they talk about so what they've come up with is a an increasingly confusing and
high resolution way of saying maybe your plants will make it through the winter I hope that
answered some of your questions about what kills your plants over the winter if you have any other
questions or comments please drop those down below the video I'll see what I can do to help