As the first snow begins to fall in the north, it is time to prepare your evergreens for winter, so they emerge in spring fresh and healthy, not dry and sad. It just takes a few simple steps, but the difference can be enormous.
5 Simple Steps to Help Evergreens Survive Winter
- Water them deeply and well – the first and most important step
- Mulch the root zone – it reduces soil freezing, and keeps the soil moist too
- Spray with anti-desiccant – these sprays create a water-proof barrier to evaporation
- Consider netting – it prevents breakage, reduces wind damage, and beats burlap hands-down
- Feed with potash – it toughens the leaves against the cold
What’s the Problem?
Even the toughest evergreens – especially in their early years – benefit from some attention in late fall. Most gardeners have experienced a spring when some of their evergreens came out of winter brown and crisp. They might have re-grown, but they rarely recover completely, and if it is a hedge, the result can be devastating.
The clue to the problem lies in the name – ‘evergreen’ – because it’s the way these trees keep their leaves all winter that causes the problem. It’s not that the leaves aren’t hardy enough to survive the cold. No, the problem is water. When the soil freezes it becomes much harder for these trees to draw up the water they need to keep their leaves moist. The low humidity and cold winds of winter cause water to be lost from the leaves, even though these plants have tough, waxy coatings on those leaves. If the lost water cannot be replaced, the leaves slowly dry out, and die. They may not change color until spring, looking green as winter ends, but the damage has been done.
Water your evergreens
The first and most important solution is watering – late, just before the ground freezes. No matter how wet fall has been, beneath the foliage, and especially where trees around your home are protected by the eaves, the soil can be dry. The more water in the soil, the less likely it is that all of it will freeze. If there is some free water left, your trees can much more easily replace what they lose from their leaves. Winter burn, as that dead foliage is called, will be prevented. This is especially important when trees are young, because the roots will not have spread far, or very deep, so they are dependent on a small volume of soil for their water needs.
So leave a hose running slowly for a few hours near the base of each tree, or if you have a hedge put down a ‘leaky pipe’ hose and soak the whole length. Slow soaking is much better than using a sprinkler, or hand watering, because the water goes deep, and the soil will be completely wetted, not just moist on the top.
Mulch the root-zone
Once the soil is wet, let’s keep it that way. A couple of inches of mulch – perhaps shredded bark, or even chopped leaves from your trees – will reduce evaporation and keep the soil damp. Put it down within a few days of that soaking, keeping it off the foliage, and a few inches from the trunk. Cover a wide area, so that all the root zone is protected. There is a less obvious value to this too. By insulating the soil surface you trap the existing warmth in the soil, and reduce both the time it stays frozen, and how deep it goes. In a mild winter you may prevent freezing altogether, which is an ideal outcome. That mulch can be left in place to conserve moisture next year too, and just topped-up each fall. If you use something rich, like compost, it will also feed your trees, and improve the properties of the soil over time.
Spray with anti-desiccant
It is amazing how few gardeners use a product that professionals in cold areas use extensively. Anti-desiccant sprays create a thin, invisible plastic film over the foliage, which reduces water-loss dramatically. They are widely used by landscapers after planting all sorts of trees, as well as for winter protection. Pick some up at your garden center, and spray while the temperatures are above freezing, but as close as you can to that first hard freeze or snow fall. Once dry – which takes just a few hours – they resist rain, but they can in time wash off. If you have a lot of winter rain, and there is a warmer period at some point in the winter, then spray again if you can. If you are not familiar with anti-desiccants, give them a try. You will be amazed at the protection these products give, on both conifers and broad-leaf evergreens like Rhododendrons, Holly, and Cherry Laurel.
In cold areas there is a long tradition of wrapping evergreens in burlap for the winter, but there is a much better alternative available, in the shape of netting. Black or dark -green, with ½ inch squares, it is invisible from a few yards away. It doesn’t destroy the look of your yard, but it keeps the branches together, and stops them breaking under the weight of snow or ice. Surprisingly, it also reduces desiccation injury, because by holding the branches more tightly together it slows down the passage of the wind through the branches – a double benefit. In spring there is no rush to remove it, while burlap can cause fatal heating-up and premature sprouting, both of which are damaging. Just try and remove the netting before new growth begins, otherwise it can become tangled, and harder to remove safely.
Feed with potash
Potash, the element potassium, is known to improve winter survival, and bring evergreens through the winter in good shape. Starting as early as October, feeding your evergreens with a fertilizer high in potash (the last number in the fertilizer formula), but low in nitrogen (the first number in the formula), will help the foliage hold moisture, and thicken the walls of the cells against cold damage. You should be able to find these fertilizers labelled for hedges and evergreens in fall, and they do a great job of giving an extra level of protection.
You may not need to do all these things, depending on your plants, and where you live. But they are all great ways of protecting your evergreens from the ravages of winter – a little care goes a long way.