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Pollinators and Your Winter Garden

Crop Rotation
Crop rotation decreases the incidence of disease and pest populations, and helps maintain soil nutrients. It is especially important to rotate plants of the Solanaceae (eggplants and tomatoes), Curcurbit (cucumbers and squash) and Brassica (cabbage and broccoli) families. For instance, planting nitrogen-hungry plants, like corn, where nitrogen-fixing legumes, like peas or beans, grew previously, is a good idea.

Dead plant material
Pollinators and other insects need sheltered places to overwinter. Slightly less tidy gardens, especially around hedge and shrub bases, provide much needed overwintering sites. Plants with pithy stems such as elderberry, raspberry, sumac and annual sunflowers provide great nesting sites for bees. In his booklet How to Make a Pollinator Garden, Clement Kent warns us that removing these stems in the fall is fatal for the bees that may be nesting in them. Other butterflies and bees overwinter under loose bark and dead leaves (especially bumblebee queens), so if you choose to tidy these up, be aware that you may be removing next season’s generation of pollinators.

Logs and piles of branches can be artfully arranged and provide habitat for beneficial insects. The Canadian Wildlife Federation suggests burying logs halfway and leaving tree stumps in your garden. Consider allowing a patch on your lawn to grow longer before the winter, to provide habitat for hibernating critters.

Crops such as lettuce, squash, cucumbers, melons, eggplants and herbs can be left in your garden beds after they have been killed by frosts. Nitrogen-fixing legumes like beans and peas cut off at soil level will continue to feed the soil as their nitrogen-bearing root nodules decompose, while also aerating the soil and creating beneficial habitat.

Adding plant material
Providing flowers that nourish pollinators continuously from early spring to late autumn is very helpful. Autumn is one of the best times to do this, since plants are tucked into warm soil, and get abundant rainfall and low evaporation. These ideal conditions promote root growth, even after the above-ground parts of the plants are dormant. Add a layer of mulch to moderate soil temperature, add nutrients and retain soil moisture. Check out the City of Guelph’s Healthy Landscapes program for a list of trees, shrubs and perennials that prefer to be planted in the fall. 

Seeds naturally fall to the ground from perennials, annuals, trees and shrubs in the autumn, and several native plant seeds need cold temperatures to successfully germinate the following spring. If you’ve been sowing these seeds in the spring with marginal results, try seeding in the fall instead. Remember not to pick up more than 10% of the seeds from any one plant if you are collecting from the wild, and know that it is illegal to collect from conservation areas or national and provincial parks.

Cover crops
Consider borrowing a trick from farmers and plant a cover crop to increase the organic matter and nutrient content of your soil, improve soil structure and stimulate soil organisms. Rye, clovers, oil radish, oats and barley can be planted in the fall. In the spring, incorporate the cover crop into your soil about two to three weeks before you plant. Check out the Canadian Organic Grower’s guide to cover crops for some useful guidelines.

Mulching
Think twice about giving away your raked leaves!

Farmer Kelly Wood believes that the most important thing you can do for your garden before winter sets in is mulch the soil. Kelly once heard a gardener say, “bare soil is like an open wound on the skin of the Earth, and mulch serves as a bandage to help it heal.”

Mulch helps create an environment that protects the soil, shelters microorganisms, fungi and bacteria and encourages the natural organisms to do their work. Mulching forms compost at ground level, which nourishes both the shallow feeder roots and the deeper root zones. Natural mulch options include straw, hay, autumn leaves, wood chips, rice hulls, spent grain from brewing, dryer lint, pine needles, tree bark, sawdust, bundles of sticks or twigs, and moss.

Autumn leaves make the best mulch. Spread them about two inches high on all your garden beds, and place branches over them to keep them from blowing away. Mulching the soil also helps mitigate the devastation that winter can bring. Snow is actually one of the best things for a winter garden since it insulates and cushions any hail or ice that follow. Mulch under the snow adds an extra layer of protection and insulation for the soil creatures deeper down.

Earthworms love to eat leaves in the spring, and their castings are rich in nitrates, phosphates, potash and calcium. When temperatures reach at least 20C, and hibernating ladybugs and bumblebee queens have left their winter refugia, mulch can be safely cleared away. The soil underneath should be composted and aerated.

The more we can leave things as nature intended, the better … and it frees up our time to pursue other interests!

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