Protect Unplanted Trees And Shrubs From Frost

Don't let your potted trees and shrubs succumb to frost damage. 'Heel in' extra nursery stock to shield the delicate roots all winter long.

by Susan Brackney

If you’ve ever ordered young trees or shrubs in the mail, you’re likely already familiar with bare-root nursery stock. Typically shipped according to your climate zone, these items usually arrive in spring or sometimes early fall. Obviously, the sooner you plant each of these future giants in their final locations, the better off they’ll be. The same goes for woody specimens that have been planted in pots.

For my part, ever since I became an avid sapling collector, the numbers of potted trees I’ve kept around have increased. I don’t have room to plant most of these on my own property. Instead, I’ll nurture them until I can find someone who is willing to take them on. While I wait, I’ve had to find ways to keep all of these trees cozy, even in prolonged, freezing temperatures.

What’s more, when my local nursery offers an end-of-year clearance sale, I invariably bring home extra witch hazels, spicebushes and serviceberries I just can’t resist. These bargain plants’ root systems are slightly better protected than those of their bare-root counterparts, but they still need adequate shelter—especially during the chilliest months of the year, when frost poses a very real threat.

Temporary Digs

If you live in a cold climate like I do, winter is already underway. But what if you’ve run short on time to properly install your saplings or new shrubbery? Or what if you haven’t decided exactly where you want everything to go? You may be able to buy yourself some extra time—and stave off serious frost damage—if you heel in all of that unplanted nursery stock.

Heeling in simply means planting in a temporary trench, usually for a short period of time. The word “heel” is said to have come from Old English terms meaning to cover or conceal. But heeling in could also refer to the similar Old and Middle English words for tilting or leaning to one side.

Since they are actively growing, plants that are heeled in during spring and summer months must be watered and more carefully looked after than those that are heeled in during wintertime. Trees and other woody plants that are heeled in for winter spend these cold months in dormancy. They’ll remain in this hibernation-like state until the days begin to lengthen and temperatures become consistently warmer.

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Getting Started

Ideally, the spot you choose for winter sheltering should act as a windbreak for your woody plants. If you have a shed, garage or other outbuilding, consider digging near one of these. Your heeling-in location should also provide adequate drainage. Don’t have a suitable outbuilding to dig near? You can create an alternative windbreak with rows of straw bales.

As long as the ground hasn’t frozen solid, you should be able to dig a relatively deep, V-shaped trench. If the ground is a little hard, you may be able to soften it up by tightly covering the area you wish to dig with plastic. Leaving this in place over a few sunny days can help warm the soil enough for you to be able to work.

Planting Your Stock

For woody stock contained in pots, you’ll want to position these in the trench so each pot is mostly buried and the plants themselves protrude above the soil line at about a 45-degree angle. (Angling plants in this way further helps to protect them from harsh, winter winds.) Next, carefully pack soil in between each pot so they’ll stay in position.

The heeling in process
photo by Susan Brackney

Similarly, bare-root stock should also be placed in the trench at an angle. Cover roots completely with soil, but take care not to bury your plants’ delicate crown areas.

For extra insulation and to help guard your heeled-in plants against frost heaving, you can surround them with a few inches of bark mulch. (But, again, avoid covering crowns.) Finally, you might want to mark the area with colorful flags or stakes, so your tucked-in trees and shrubs will be easy to see and unearth when spring arrives.

Other Options

What can you do if digging outside turns out to be a no-go? If you do have an unheated garage or similar outbuilding, you can temporarily plant your nursery stock in a large tub or trough to protect against cold and frost. In this case, you’ll cover bare-root or potted woody plants as you would have in the outdoor trench. But since you won’t have soil at the ready, you’ll need to use bark mulch or a similar material instead.

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