Handouts
Winterizing Your Garden Kacey Cloues * kacey@gardenhood.net
The two biggest enemies of the garden during winter are:
Dramatic changes in temperature.
Freezing when dry/exposed.
How to mitigate these factors:
Mulch appropriately.
Water the soil thoroughly before a severe cold snap.
Avoid cutting back plants that require extra protection from crown rot.
Don’t over think it! (Or: Why frost cloths aren’t worth the investment.)
Now, on to the details . . .
Mulching & Top Dressing Why use mulch:
It regulates soil temperature. This is a biggie here in Atlanta where temperatures can swing wildly from below freezing to 70 in the course of a single day. Extreme temperature swings mid-winter are devastating to plants; mulch helps keep the soil temperature regular despite changes in air temperature creating a more stable environment for plants’ roots.
It retains moisture around the roots of plants. At least a little moisture in the soil is necessary even when plants are dormant in winter. Moist soil also provides a little extra insulation for plant roots in times of deep freezes. It’s much, MUCH better for plants to experience a deep freeze with wet soil than with dry soil.
Different types of mulch:
Pine straw: Good for slopes and for areas where a leaf blower may be used to clear leaves in the fall. Stays in place very well even in heavy rain. Can be slippery to walk on and shouldn’t be used for pathways.
Pine bark nuggets: Large, chunky, 2”-3” sized pieces of pine bark; they’re good in flat areas where there aren’t a lot of small plants or groundcovers whose delicate stems could be easily damaged by their bulk. Pine bark nuggets will easily float away in rain; do not use on slopes.
Pine bark mini-nuggets: Smaller pieces of pine nuggets, usually 1⁄2”-1 1⁄2”in size. Easy to use around small, delicate plants; good for using in container gardens. Stays in place better than the full-sized nuggets but will still wash down slopes in heavy rain. Easy to walk on; good for pathways.
Shredded pine mulch: Longer, finer pieces of pine bark. Shredded mulch stays in place pretty well on moderate slopes. Easy to walk on; good for pathways.
Cypress mulch: A moderately chunky mulch that is good for using around trees, shrubs, and less delicate perennials. Will wash away if used on slopes. Light tan color.
Wood chips: Wood chips vary in size depending on the type of wood and how they were shredded. A number of tree companies around town will deliver wood chips to your yard for free. Just know that you may get a mixed load of different types of wood, meaning that the mulch will not have a uniform texture or color.
Wheat straw/hay: Lightweight and stays in place well on slopes, but isn’t a great insulator against cold when wet. It is also usually laden with seeds which yield lots of wheat sprouts come spring. Best used in agricultural settings.
Crushed stone/slate: Pea gravel, crushed stone, and slate chips retain soil warmth in both the winter AND the summer, making them suitable for plants that thrive in hot, dry climates but less than ideal for most other garden plants. Very useful for pathways.
Leaves: Nature’s free mulch! Using fallen leaves as mulch is a very smart – and cost effective – move. Just keep an eye out for leaves that may have come from plants/trees that are diseased or pest-plagued. These leaves should be raked up and removed. If you have a mulching mower, chop up the leaves then spread them over your garden beds at will. If you don’t have a way to break up the larger, heavier leaves, you can still make use of them in areas where they won’t lay heavily on delicate stems and crush or rot plants.
A note on dyed mulches:
If at all possible avoid using dyed mulch. The dye can stain hardscaping; it can leach out into the soil; and, in most garden settings, it looks incredibly unnatural.
A note on synthetic mulches:
Don’t use them! Recycled rubber mulch and other types of synthetic mulch contain chemicals
that can harm the microorganisms in the soil, your plants, wildlife that feeds on your plants, and the larger animals that feed on the wildlife that lives in your garden.
A note on frost cloths:
Frost cloths are NOT a substitute for mulch. In fact, frost cloths are rarely necessary in the winter because plants are already dormant and don’t need to have their leaves protected. Frost cloths are most effective in mitigating the damaging effects of mid- or late spring frosts that occur after plants have broken dormancy and have tender leaves and buds exposed.
* In the event of snow or ice: special instructions! *
Do not prune plants that are covered in snow or ice. Don’t even touch them!
In most cases plants are better off being left alone when they’re covered in snow or ice. The
exception is conifers that may splay open under the weight of heavy snow or ice. In that case, remove the frozen precipitation as it falls (yes, this requires that you go out with a broom several times during the storm to keep the snow from accumulating).
Once snow or ice is frozen in place, do not attempt to remove it; you’ll cause much more damage to the plant.
To Prune or Not to Prune in Fall & Winter Do NOT prune in fall/winter:
Anything with hollow stems. Examples: salvia, horsetail, and ornamental grasses. Prune these in early spring as new growth emerges from the base.
Marginally hardy plants whose stems provide extra protection against cold damage. This includes plants such as Russian sage, butterfly bush, and euphorbia. Prune these in early spring as new growth emerges from the base.
Plants that bloom in winter or early spring. Examples: bridalwreath spiraea, forsythia, certain camellias, Hydrangea macrophylla (big-leaf mophead and lacecap varieties), Loropetalum, and azaleas. Pruning plants in this category in fall or winter will remove their flower buds for the upcoming spring.
Anything immediately following a deep freeze. Resist the urge to clean up frost- damaged foliage. It’s actually protecting the plant from further damage; leave it in place.
Okay to prune in fall/winter:
Evergreens that are not grown for their flowers. Examples: boxwood, holly, conifers, tea olive, Loropetalum (if you’re growing it as a foliage plant not for flowers), and Cotoneaster.
Summer- or fall-blooming shrubs. This includes: peegee hydrangea (Hydrangea paniculata), oakleaf hydrangea (Hydrangea quercifolia), smooth hydrangea (Hydrangea arborescens), summer-blooming spiraea; roses, chastetree (Vitex), sweetshrub (Calycanthus), summersweet (Clethra), and beautyberry (Callicarpa).
Perennials that maintain active basal growth at the crown during the winter. This includes plants such as catmint (Calamintha nepeta), garden sage (Salvia nemerosa), ornamental oregano (Origanum rotundifolium), Shasta daisies and garden mums, goldenrod, and beardstongue (Penstemon).
Perennials that die back to the ground and don’t require the presence of woody stems to protect their crowns against rot through the winter. Examples: toadlilies, hosta, certain iris, candylily, blackberry lily, swamp hibiscus, canna, and hardy banana.
Diseased, dead, or damaged parts of plants.
Basic Rules of Thumb for Pruning:
Controlling plant size is low on the list of reasons for pruning, because pruning is not a substitute for proper plant selection. Most plants have perfectly lovely natural shapes that can be enhanced and somewhat controlled through proper pruning practices; very few adapt well to shearing. Most plants stay healthy and attractive longer if allowed to grow naturally, so reserve the hedge shears for formal hedges.
The process of removing stems at their point of origin is known as thinning, while shortening a
stem from the top is known as heading. Technically, shearing is just making a lot of heading cuts. Thinning cuts are preferable because they open the shrub up to sunlight and air circulation. Heading cuts result in a profusion of growth below the cut that creates a wall of growth on the outside of the shrub that blocks sun from the interior of the shrub and impedes air circulation. Even formally sheared hedges should be opened periodically to encourage new growth from inside the plants.
Shrubs with a suckering growth habit such as forsythia and lilac should have the oldest, biggest stems removed at ground level periodically. Rejuvenate badly overgrown specimens removing the biggest oldest stems at ground level. This can be done all at once if the shrub is healthy and vigorous, or it can be spread out over a three-year period if it is not by removing one-third of the overgrown stems each year. Keep the sturdiest, well-placed younger stems and remove those that are damaged, spindly or too close to one another. New suckers will sprout from the roots that will have to be similarly thinned later in summer. Hard pruning should always be done in early spring, before the shrub leafs out. It is less stressful for the plant, and you can clearly see the stems when they are leafless.
Top Dressing & Fertilizing
Top dressing:
Top dressing is the application of compost to the top of the soil around a plant’s rootball area.
Worm castings make an amazing top dressing that is suitable for nearly all plants (except succulents).
Top dress plants in fall to help add a tiny amount of essential nutrients to the soil without the jolt of a full-on fertilizer. Pull back mulch, sprinkle a thin layer of worm castings around the top of the rootball (don’t mound it up around the crown/trunk), then push the mulch back in place.
Top dressing with worm castings is also really helpful in late spring as it can boost moisture retention during the hot, dry summer without stressing roots with too much of a nutrient boost.
Fertilizing
The goal of fertilizing in the fall is to stimulate healthy root growth. Use only slow-release fertilizers that are specifically formulated to target root growth. Avoid fall applications of fertilizers that target foliar growth or flower production (unless you’re applying it to winter annuals).
As a general rule, in fall you should apply fertilizer at 1⁄4-1⁄2 the rate you would apply it in spring. You want to give the plants just enough to keep their roots happy and strong while the rest of the plant is dormant.
For evergreen trees, shrubs, and perennials: Holly Tone. For deciduous trees: Tree Tone or Garden Tone.
For deciduous shrubs and perennials: Garden Tone.
For annuals: Flower Tone.
If you miss your fall fertilizing window, don’t fret. You can still give your plants love with a top
dressing of worm castings and then fertilize in late winter (March) as plants are beginning to break dormancy and start their new growing cycles.
Protecting Plants in Containers
Plants in containers are more exposed – especially their roots – than plants in the ground. They are even more susceptible if they’re in hanging baskets or window boxes, or on a table, deck, or balcony where cold air will freeze them from beneath.
The best protection is to move them to an unheated garage, carport, or crawl space. (Resist the urge to bring them indoors; that will put them into shock.)
If those options aren’t viable, move pots next to the foundation and surround them with a thick layer of mulch or leaves. Pile the mulch around the base of the pots to protect the roots.
As with your in-ground plants, container plants benefit from a thorough watering before a deep freeze.
*Remember to allow pots to drain before the freeze so they don’t crack. If pots are in direct contact with concrete or another solid surface, slide pieces of ceramic tile beneath them to raise them at least 1⁄4 inch to allow water to drain and/or expand when freezing.
A note on frost cloths:
Frost cloths can help stave off damaging effects of moderate cold snaps on container plants. The frost cloth must cover the entire pot and be anchored securely at the base. Simply wrapping the foliage while leaving the pot – and roots – exposed will offer no protection at all.
Planting in Winter
Yes! You can plant in winter here in Atlanta!
But be smart about it:
Don’t plant when the ground is frozen.
You can plant when rootballs are frozen, but if it isn’t a matter of life or death, wait until the rootballs have thawed out.
Be gentler when planting in winter. Frozen roots and stems break easily. Use a light touch when ruffling the roots of cold plants and be careful not to break stems that may be extra-brittle from the cold.
Do water in any new plantings. This helps settle the soil around the rootball, squeezing out air pockets and snugging in the roots.
Do apply mulch to all new plantings.
Do NOT fertilize new plantings in winter. Ever.
Water winter plantings at least once a week if there’s no rain.
Remember to disconnect and empty your hoses and leave spigots dripping in advance of deep freezes.