So you splurged and treated yourself to a eucalyptus tree, an oleander, a mimosa tree, a lemon tree or an olive tree? Here is how to protect these plants over the cold season.
Cold-vulnerable plants are usually trees and shrubs, as well as certain flower bed plants. When purchasing your plant, check the label to see what temperatures it should be able to withstand. Some plants, where when winters aren’t too cold, will simply love to wear a few extra “clothes”, while others will have to be uprooted and moved to the cold greenhouse.
“Winter is prepared in fall” is what famed garden masters Brigitte Laouge-Déjean and Denis Pépin advise. They’ve authored a book in French that hasn’t yet been translated to English. Even before the first frost spells hit, in October for example, start getting your equipment ready: this is what you’ll need to protect all parts of the plants: roots, trunk and leaves. Frost won’t win!
For hanging plants or plants in containers, wrap the pot in a large cover and/or bubble wrap. Thick horticultural fleece also does the trick, that’s what it’s designed for. Another option: bury the pot!
For both hanging/potted plants and those planted in the ground, build up a layer of mulch around the base: you have a variety of insulating mulch materials to choose from, like straw, peat, flax straw, leathery plane tree leaves, evergreen oak or silverberry, and even ferns or conifers branches.
“Proscribe from this list any materials that retain water […]. Adequate materials are those that are and will stay dry.”
This is the setup both experts recommend: “Place a few stones or fist-size rocks around the base to provide for ventilation; on top of that, spread the material you’ve chosen, trying to trap air pockets inside, so don’t press it down. Make the layer about 2 inches (5 cm) thick. It’s important to not press it down. To hold this all in place, add a square of horticultural fleece in a simple or double layer, weigh it down with 4 large stones.”
And they add: “It’s also quite easy to protect small shrubs with an old plastic bag, piece of burlap, or a UV-treated polypropylene winterizing fleece. Even carton/cardboard from a delivery box can be filled with wood chips. Gather the branches of the shrub to tie them into a ball, and wrap the entire plant from stump to tip with straw, hay or leaves. Bring the sac down to engulf the plant, or wrap the plant with the roll of winterizing fleece cut to size.”
The right protection depends on what you are shielding — a pot, a set of roots, a whole shrub or a bare young trunk — and on how tender the plant is. This table gathers the methods described below so you can pick before you buy any materials.
| What it protects | Method | Materials | When |
|---|---|---|---|
| Hanging plants and containers | Wrap the pot, or simply bury it | Large cover, bubble wrap, thick horticultural fleece | Late autumn, just before the ground freezes |
| Roots and base, potted or in the ground | Stones for ventilation, then a 2 in (5 cm) mulch layer, never pressed down, held by fleece | Straw, peat, flax straw, plane tree leaves, ferns or conifer branches | Late autumn, before the ground freezes |
| Small shrubs, the whole plant | Gather the branches into a ball and wrap from stump to tip | Old plastic bag, burlap, UV-treated polypropylene fleece, cardboard filled with wood chips | Late autumn |
| Tender exotics: bougainvillea, banana, oleander, kumquat, abutilon | Move under cover to a cold greenhouse, windowed shed or cellar | Cool but frost-free, well-lit and well-ventilated space, very little water | Mid-autumn; back out once above 40°F (5°C) |
| Trunks of very young trees | Lather the trunk or tie material around it to stop bark splitting | Clay, or straw tied on | Before frost and freeze/thaw spells |
Whichever method you choose, open the packages on a mild winter day to air them out, and remove them in early spring.
Some plants like bougainvillea, banana trees, oleander, kumquat or abutilon would tolerate neither a cold winter outdoors, nor a hot stuffy winter inside the heated indoors of a house.
Here’s the solution to this conundrum: bring them to a cold greenhouse, a garden shed with windows, windowed cellar, or an “orangerie” if you even want to use the poetic word for this, around mid-October. What’s important is that it must be cool but never freezing, well-lit and well-ventilated. Just as for outdoor plants, limit your watering to as little as you dare to ensure the roots stay intact and don’t rot.
As soon as temperatures rise above 40°F (5°C), take them out for a spin but keep an eye on the weather, and bring them back in if freezing might occur.
“Snow tends to protect certain plants like perennials. What is fatal is alternating days of freezing and thawing, as well as windy settings”, adds Brigitte Lapouge.
However:
“don’t protect your plants too early in fall, or snails and slugs will wiggle into your protective cocoon […]. What’s best: cover it all just before the ground freezes. During winter, make the best of a nice, warmer day to open the packages up and renew air circulation, to eliminate moisture most of all. And then, in spring, remove your protective casings as soon as possible to let the ground warm up.”
Lastly, another tip is to lather the trunks of very young trees with clay or tie straw to protect them from splitting open during frost or during brutal freeze/thaw cycles.
Claire Lelong-Lehoang
