Your Guide to Fall Gardening

Submitted By: Egan Davis, Principal Instructor (UBC Botanical Garden), with Matias Taylor, Marketing Assistant (UBC Botanical Garden)

Every year, fall rolls around with its brown-leaved, sweater-wearing familiarity, and, with it, gardening enthusiasts new and old prepare for a season of pruning, cleaning, and planting.

Common wisdom often tells you to cut flower stalks regularly, meticulously prune every tree, and freely use chicken manure as mulch. You’d be surprised, however, that following these methods can severely harm your plants and would have horticulture experts shaking their heads!

So what are the best fall gardening techniques to follow? We’ve got the scoop courtesy of Egan Davis, Principal Instructor at UBC Botanical Garden’s Horticulture Training Program: read on for how to truly make the most of your garden in the fall, improve its effect on the environment around it, and make it friendlier to the animal life that calls it home.

Instead of Cleaning Up, Put Your Feet Up

Conventional fall cleaning conflicts with ideal sustainable gardening practices and outcomes, mainly because it hampers natural nutrient cycling processes, which are necessary for healthy soil. Skipping your fall clean-up helps recycle nutrients, aids in adding carbon back into the soil, protects soil from the damaging effects of rain and sun, and contributes to creating habitats for insects, worms, micro-organisms, and birds. Having an exceptionally tidy garden with bare soil will also stimulate weed growth, damage the soil surface through erosion and drying, and encourage pests and disease through a less diverse garden ecosystem. Exposed soil can also result in plant stress because of lost nutrients and exposed roots.

Leaves: Pile ‘Em Up!

Fall leaves become an issue for most gardens as they pile up and retain moisture. It’s not always suitable to leave them alone—blow them around and move them under shrubs, to the back of the garden, to compost, or add them to rot in a leaf mould pile.

TIP: ‘Mulch’ – material such as bark or leaves – can be spread around a plant to enrich or insulate the soil. Fall leaves can be used as mulch, but be sure to mix different materials (like different kinds of leaves or leaves with chopped flower stalks or twigs) to maintain plenty of air in the mix.

Seeds & Flowers: Let ‘Em Grow!

Seed heads and flower stalks should not be cut until spring, or for as long as you can tolerate them. This is because seeds provide food for certain kinds of birds, and flower stalks can be a safe environment for ground birds like juncos and spotted towhees. The remaining plant debris is also useful to birds for nest-building. On the ground, this material reduces opportunities for weed growth, as well as providing raw material for mulch after decaying during the winter.

To Prune or Not to Prune?

If you’re in the south west of British Columbia, avoid pruning completely in the fall. The warm and wet fall season creates the perfect conditions for the transmission of plant diseases, and pruning cuts are wounds that provide opportunity for infection. Some plants are particularly susceptible, such as cherry trees and Japanese maples. For some plants like lavender, rosemary, and fuchsia, newly exposed branches from fall-pruning can be damaged by cold exposure over the winter. Hedges are an exception; clip these to your heart’s content.

Weeding Away

During the cool season, annual weeds (like snapweed and chickweed) are active in milder coastal climates like the Metro Vancouver region. Cover the soil around plants with mulch to supress them.

Nutrition & Fertilizers 101

Never use fertilizers in the fall, as they can stimulate soft growth that will burn in the cold, as well as contaminate ground water. Note that like synthetic fertilizers, high salt content of animal manures can leach over the winter with the rain (and also burn tender growth if applied fresh in the spring. Lime is recommended in the fall for lawns and plants that prefer less acidic soil. Check online to find out about your plants soil pH preference.

TIP: Dolomite lime requires a lot of water to dissolve and affect soil pH—rain from the fall to spring should be enough, but make sure to scratch the lime well into the soil.

A Great Season for Planting: Fall

Fall is a great time to plant (and transplant) trees, shrubs, bulbs, cover crops and herbaceous perennials. The soil is warm in September and October, and the rain in fall and winter settles out soil and air pockets created by planting. Plants get established before the next year, lessening a new planting’s dependence on spring and summer irrigation. Exceptions include plants that may not establish and harden off in time for the winter cold; these are likely to become stressed and die.

Every Crop at its Time

Vegetable gardens are a staple of home and community gardens. Who doesn’t cherish picking up newly grown, fresh tomatoes and strawberries?

Here are some tips to make the most of your patch of fruits & veggies:

Sow winter cover crops (such as winter rye) in the fall. Turn the crop into the soil in soil in spring
Mulch beds with composts or manures: they protect soil, suppress cool season weed growth, and contribute to carbon and nutrient cycling.
Leave crop residue from last year and allow material to decompose on site. This aids nutrient cycling, and improve soil structure.
When it comes to direct-sow planting, arugula, corn salad (mâche), scallions, radish, and lettuce and soy beans (under a crop cover) are great in September, and broad beans and radish (if warm, otherwise under a crop cover) in October. Garlic should be planted anytime between late September to early November.

Keep an Eye on Containers

Don’t forget to check containers for water through the fall and winter—many plants in containers die from lack of water in winter if they are kept under overhanging balconies, decks, and other coverings. Also, be prepared to move or protect plants if the temperature gets very cold, and huddle plants together in small containers for insulation.

TIP: Be sure that containers are not sitting in water: allow for drainage (3mm is enough) using 25mm tiles as spacers.

Grow Your Own Winter Wonderland

Garden stores across Metro Vancouver, including the Shop & Garden Centre at UBC Botanical Garden, usually have plants for winter interest from mid-fall onwards. Have fun with them as you create your own winter garden—what about a winter-themed container or hanging basket?