As record cold sweeps much of the country, and white-out storms engulf highways, towns and of course our gardens too, there will be many people, when warmer weather returns, looking at collapsed hedges, broken branches, and seeing years of growth destroyed in a matter of hours. Hedges are vital components of many garden landscapes, bringing privacy, reduced noise, extra warmth and creating a calm neutral garden backdrop. When damaged all that is destroyed, and there is no such thing as ‘instant hedge’ to replace it with. Could the damage have been prevented? Can I repair it now? Do I need to plant a new hedge? These are the questions that will be going through everyone’s head as they survey the situation in their garden.

Has the cold killed my hedge?

Consider this – current record-breaking low temperatures are bringing lows from much colder zones than your own ‘normal’ one. If the difference is slight, you will probably only see browning and scorching of foliage. If it is significant, then you could easily see a lot of dead plants, including hedging evergreens, when spring arrives. Since this deep freeze has lasted several days, the low temperatures have had time to ‘bite’ into your plants. While smaller plants below the snow will probably be fine, shrubs, trees and hedges could easily be damaged. If you know what plants your hedge is made off, here are the minimums usually recommended for some of the most common ones, in the Fahrenheit system normally used in America. If your neighborhood experienced temperatures more than 10 degrees below these, then there is a very good chance you will need to replace your hedge come spring – sorry.

  • Emerald Green Arborvitae – minus 50 degrees
  • Thuja Green Giant – minus 20 degrees
  • Leyland Cypress – minus 20 degrees
  • Italian Cypress – 0 degrees

If you are replacing a hedge, the question becomes, ‘should I use a hardier plant this time around?’ In the past we would have said, ‘no’, because in most areas a low temperature significantly outside your zone only happens about every 40 years – otherwise you would be in a lower zone, right? But with an increase in extreme weather, probably due to man-made global warming, these events could become more common, as the climate shifts to a new normal. So if you are already at the bottom of the hardiness range for a plant, moving to something a zone or two hardier could be a good idea.

What now? Can I cut it back and re-grow it?

This is a common question when hedges are broken, and if only we could say, “yes”. That of course depends on what plant has been used to make it. Hedges of broad-leaf evergreens, like holly, can be cut back as much as you need, and they will quickly re-sprout, so no problem at all. But most people prefer the smooth surface and easy trimming of conifers – the needle evergreens, especially Arborvitae, Cypress, and of course Thuja Green Giant. These plants cannot re-sprout from older, bare branches – which is why it is best to trim regularly, starting right after planting, and trim little and often. There are just a few evergreens of this type, with yew trees being the most well-known and widely used for hedges, that will re-sprout from older branches. They can be cut right back to a few limbs, and they will quickly regenerate. For the rest the answer is, “No”.

This means that when you are cleaning up your damaged hedge, cut branches back to a side-branch with foliage on it – otherwise you will be looking at that bare stump for a very long time. Even if the result is a very ‘gappy’ hedge, with care, fertilizer and regular trimming, a lot of it may fill in again. Give it a couple of years, and then re-assess.

Can I fill in gaps with young plants?

This is a possible solution when only part of a hedge is damaged, but it can fail, mainly because it is hard for new plants to become established in soil full of the roots of the older plants. There are three things you can do to improve your chances. First, use the biggest plants you can handle. These will have a large root-ball and be able to cope better with the surrounding trees. Secondly, prepare as big a planting hole as possible, removing old roots, and making a good-sized gap for the new plant. You can also put a root barrier on both sides – not all around – to slow the invasion of that nice fresh soil by the older plants in your hedge. Landscape fabric, or barriers for bamboo, are usually available at local garden centers. Finally, be sure to water and fertilize the new plants regularly and thoroughly, for the first two growing seasons, to give them a chance to compete.

Remember when planting to put the stem of the new plant in line with the existing ones, and not, as some people do, with it in front, level with the existing hedge front. If you do that, the new plants will not be able to develop properly, as they will be over-trimmed on one side.

Should I just replant?

In the end, this is often the best advice. Fixing damaged hedges is difficult, unless the damage is minor, and removing the old one and replanting can be easier. It will also liberate a large area of your garden, as old, over-grown hedges – the type most likely to collapse in a snow-storm – are often very wide and steal lots of your garden. Of course, a new hedge will take time to grow, but if you choose fast growing trees like Thuja Green Giant, then the time will soon pass, as with growth-rates of 3 to 5 feet when young – really, this has been demonstrated in trials – you will be looking at a great hedge in just a few years. Remember this time to keep it well-trimmed, and narrow, especially at the top, as wide tops and overgrown hedges are the ones that usually fail.