With winter settling in around us we are turning up the heat and bringing out the duvets. Gardeners are casting an anxious eye on those border-line shrubs they planted in the now-distant spring and wondering if they will be back again in the next one. I gardened professionally for 30 years in zone 3, so this was always a big issue in my gardens, and I had plenty of winters to experiment and test ideas. Let’s look at some basic principles and practical methods to push the boundaries of what you can grow if you are gardening in zones 3 and 4 – everyone loves to push the boundaries and grow as big a range of shrubs as possible.
New Wood or Old?
If you want to grow flowering shrubs at the edges of their hardiness, winter damage is inevitable, even if we devise ways to keep it to a minimum. So, what plants will give you the best chance of success? You might already know one of the basic rules of pruning – the division of shrubs into those that flower on branches already formed the year before, and those that flower on new growth. Most spring flowering shrubs are in the first group, and shrubs that flower in winter and fall are in the second. When looking enviously at a beautiful plant, and wondering if you can grow it, see which group it belongs in. It is almost impossible to be successful with spring-flowering shrubs, because winter injury will kill the shoots you need for blooming. Stick to those shrubs that flower on new growth – most roses, some hydrangeas, butterfly bush (Buddleja), and Hardy Hibiscus are all plants that fall into that group. Even if they are killed back, as long as the base remains alive you will see blooms – although on a smaller shrub that you’ll see in gardens further south.
For some general thoughts on what plants survive winter best, check the blog, Will My Plants Die Over the Winter?
Protect Late and Expose Early
Hardiness in plants is a funny thing. Mostly it depends on dormancy – the ‘off-switch’ that puts them to sleep for the winter. Dormant plants can take a lot more cold, because once that switch is turned on, and a bud wakes up and begins to grow, it can usually not take even a few degrees of frost – a long way from the minus 20 it had no problem with all winter. So getting your plants deeply asleep, and getting them to sleep in as late as possible is key. It is one of the ironies of cold-climate gardening that the warm, sun-lit spots in the garden are not necessarily the best place for tender plants – they wake up too soon and are then damaged by spring frosts.
Don’t be in a hurry in fall to get winter protection in place. As long as snow isn’t forecast it isn’t going to get too cold yet, and the cold of early winter will get everything fully dormant, and so more resistant. Equally, when next spring rolls around, the last thing we want is for plants to start shooting too soon – and if they are tucked under blankets and protected, that is exactly what will happen. Remove winter protection as soon as you can, once the deep-freeze is gone and enough snow has thawed that you can get at the plants.
Protect from Diseases
The big killer of protected plants in winter is not always the cold – fungal diseases and rots often do much more damage than low temperatures. The best protections from them are cleanliness and dryness. There are two keys to doing that: remove all old leaves and use dry materials.
I learned the hard way that the stem of a climbing rose, for example, would be nothing but dead buds if you left on the old leaves, but full of healthy ones if you didn’t. The natural decomposers of that dead leaf easily spread from it into living buds – if they have no leaves to live on, the bud is safe. It can take a few minutes, but removing every last dead leaf, before putting protection in place, can make all the difference between success and failure.
When choosing material to mound up around the base of these plants, dry peat-moss is your friend, while wet leaves are not – it is amazing how water-resistant peat moss is, especially if pressed down tightly, and often it will still be dry inside when spring comes – and dryness is always your friend.
Simple, Neat, and the Best – Protect Your Plants for Winter
Here is how to protect the base of any deciduous shrub from winter cold – so that you have some living woody parts available to put out strong growth in spring. This method is the guaranteed best for roses, and it works well for other shrubs too.
- Find or make some rectangles of flexible but strong plastic or mesh, 12 inches tall and 3 feet long. That will give you a circle 12 inches across – you can always join two together with twist-ties if you need a bigger circle. If it isn’t mesh or perforated already, make lots of holes in it, to let water out.
- Clean the area around the base of the plant and cut it back to about 2 feet from the ground. There should be no leaves, weeds, twigs or debris around it.
- Bend the plastic into a circle and join the ends together – a few holes punched though lets you use twist-tie for that – quick and easy – fitting it around the plant.
- Fill the circle with new, dry peat moss – the ‘dry’ is important. Press it down as you go, until you reach the top. It should be firm, with no gaps or air-pockets. Don’t use soil, leaves, mulch or compost. Peat has natural anti-fungal and anti-bacterial properties, and it stays dry – both important things.
- Remove in late winter, as soon as possible, exposing the stems to cold so that they stay dormant late.
Try this method and I guarantee you won’t go back to whatever else you have been using.
Evergreens bring a different set of challenges in cold areas, and lots of the things mentioned here don’t apply for them. We have an existing blog – Protect Your Evergreens for Winter – that will give you lots of specific solutions for helping your evergreens survive well.
More Useful Tips
For more information on winter protection, take a look at the blog, 8 Fall Cleanup Tips. Good luck with your winter protection and enjoy the results next summer!