Laidback Gardening: What to Do in May?

Here in Quebec, May signals the start of the outdoor gardening season: the mercury rises, the soil warms up, the plants wake up, the days get longer, and the Patriotes Day vacation, the Monday before May 25, is the high point for many. Beware, however: there is still a risk of frost in some regions until the beginning of May, and until the end of June in the colder regions. This is just an average: to be sure there’s no more frost, add 2 weeks to the average for your region.

What to do in May

• Sow plants that require indoor sowing;
• Start sowing cold-hardy plants outdoors;
• Transplant your seedlings into larger pots if necessary;
• When the weather permits, start acclimatizing your seedlings outdoors;
• Wait for temperatures to stay above 13°C (55°F) at night before transplanting your chilly plants outdoors;
• Cover your transplanted plants with a row cover or plastic sheeting if you want to add a few degrees to the temperature;
• Once the soil has dried out, remove piles of leaves, twigs and other garbage from your lawn;
• It’s a good time to plant or transplant perennials, shrubs and trees;
• Clean your birdhouses;
• Protect your more fragile houseplants from the increasingly intense direct sun;
• Take your dusty houseplants outside and clean them up;
• Wait until the mercury stays above 10°C (50°F) before tidying up your flower beds, or don’t do it at all!

Indoor Sowing for May

You thought the planting season was over? Think again! Many plants don’t particularly like to spend a lot of time indoors, but still benefit from the warmth of our home to germinate and begin their life. Others can be sown directly outdoors, but we can speed up our harvests by a few weeks and leave them indoors.

Here are some seedlings to sow indoors in early May.

Outdoor Sowing for May

Once the risk of frost has passed, some cold-hardy plants, such as beets, carrots, lettuces, onions, parsley, parsnips, radishes, etc., can be sown directly in the garden when the soil temperature reaches 7°C (45°F). For others, which are more sensitive to cold, wait until the soil temperature reaches 12°C (59°F). For warm-climate plants such as beans, cucumbers, squash and melons, wait until 21°C (70°F).

To learn more about temperature and sowing, see Larry Hodgson’s When Is It Safe To Plant Out Vegetables?

Transplanting Your Seedlings

Whether you sowed your seeds in small containers, shared containers or your seedlings grew faster than expected and are now cramped, it’s vital that their roots don’t run out of room to ensure their success. So you’ll have to transplant them into a larger container. Here’s how!

Acclimatation des semis

Plants accustomed to the stable conditions of our homes can suffer shock, damage or death if exposed too quickly to the changing environment and intense sunshine of the outdoors. They must therefore be gradually acclimatized to harsher conditions such as intense UV rays, wind, rain and temperature variations, thus strengthening their physical structure and their ability to tolerate these changes.

This process, known as acclimatization, takes place 7 to 10 days before the plants are due to be released, and begins with placing them in the shade and out of the wind when the temperature exceeds 15°C (59°F), bringing them inside if it drops below 10°C (50°F) at night, then gradually exposing them to half-shade and wind, and finally to direct sunlight, to prepare them for life outdoors, adapting their final placement according to their specific need for light.

Learn more about acclimatization.

Transplanting Seedlings Outdoors

Once again, the date for transplanting plants outdoors depends not only on your regional climate, but also on the variety of plant. The best way to do this is to consult the 14-day weather forecast for your location and make sure that the mercury doesn’t drop, even at night, below the minimum threshold for the type of crop you have.

Some cool-climate vegetables such as lettuces, onions, leeks and cabbages can be sown indoors and transplanted to the garden early, as soon as night-time temperatures stabilize above 7°C (45°F) without risk of frost. However, warm-climate vegetables, although they can withstand cool night-time temperatures, see their growth slowed down and harvesting delayed by these conditions; for example, a tomato plant exposed to nights that are too cold can suffer shock and fall behind in its growth. We recommend waiting for minimum night-time temperatures of 12°C (55?) for tomatoes, 18°C (64?) for cucumbers and peppers, and 21°C (70?) for eggplants, melons, okra and squash before planting, or covering plants on colder nights to avoid stunted growth.

Protect Plants When Temperatures Drop

Despite all our precautions, an unexpected freeze or drop in temperature can jeopardize our beautiful work. Always keep floating covers, plastic sheeting, tarpaulins or even blankets on hand to be ready when the mercury drops with only a few hours’ notice.

Row covers can also be used to raise the temperature by a few degrees, enabling earlier sowing or transplanting.

Cleaning Your Lawn

Raking a lawn in early spring is useful for removing dead leaves, fallen branches and other debris. However, it’s important to wait until the ground is no longer soggy after the snow has melted, to avoid compacting the soil by walking on it, which would be detrimental to the lawn’s growth. The lawn is ready to be raked when it starts to turn green, generally two weeks after the snow has disappeared. Raking too soon, especially on damp soil and a lawn that is still brown (an all-too-common practice among many gardeners) may actually cause more damage than benefit.

Use a plastic-toothed lawn broom to minimize damage to grasses.

Plant or Transplant Perennials, Shrubs and Trees

Although plants can be planted in spring, summer or autumn, doing so early in the season is beneficial for hardy plants such as perennials, shrubs, trees and conifers, which tolerate frost well and acclimatize better when the soil is cool. It’s important to wait until the soil is well drained to avoid damaging its structure, however. This cooler period means less watering is needed, spring flowering can be enjoyed and nursery crowds can be avoided.

Clean Your Birdhouses

To prevent the proliferation of parasites and diseases that can harm birds, we recommend annual cleaning of nesting boxes. At the end of the nesting season, usually in autumn or early winter, or before the birds return in spring, we recommend emptying the nesting boxes of all worn nesting materials, such as twigs, feathers and other accumulated debris. Use a dilute bleach solution or an ecological disinfectant to thoroughly clean the inside of the nesting box, followed by a good rinse to remove any chemical residue. Finally, allow the nesting box to air-dry before closing or replacing it.

Protect Your Houseplants From Direct Sunlight

The majority of houseplants suffer more from a lack of light than an excess of it, including so-called low-light plants, which thrive best in abundant light. Damage caused by excess light, often confused with that caused by overheating, occurs mainly near south- or west-facing windows or in a greenhouse, especially in late spring and summer, whereas in winter almost all houseplants tolerate full sun. Overheating behind glass can raise temperatures up to 60°C (140°F), affecting even heat-resistant plants. To alleviate the problems associated with excess light, we recommend moving plants away from windows, placing them in less exposed locations, using translucent curtains, planting outdoor trees to shade windows, or positioning sensitive plants behind those that are more tolerant of intense light.

Clean Indoor Plants Outdoors

Bringing houseplants outdoors during the summer can be beneficial, offering more light, natural rainfall and aeration that improve their health, although they should be cleaned before being brought inside in autumn to avoid introducing unwanted insects. For those who prefer not to take their plants outside, an occasional rain bath, or hose down, is advisable to clean the foliage, remove contaminants that clog the stomata, and reduce insect infestations. However, they should not be left in direct sunlight, to prevent burning of leaves unaccustomed to bright light. Also, wait for a day when the temperature is above 15°C (59°F).

Delay Spring Cleaning, or Don’t Do It at All!

Waiting for spring temperatures to stabilize above 10°C (50°F) before cleaning the flowerbeds helps protect beneficial insects such as pollinators, natural predators and decomposers, which may still be inactive or coming out of hibernation. Dead leaves and dried stems provide refuge for these insects, which are essential to the garden’s ecological balance.