Hey Bugs! Can I Clean My Garden Now?

Waiting for spring temperatures to stay above 10°C (50°F) before tidying up your flowerbeds is a common practice for preserving beneficial insects. This strategy aims to protect pollinators, pest predators and decomposing insects that may still be in diapause or idling. Dead leaves and dried stems provide a refuge for insects that contribute to a garden’s ecological balance. However, it’s important to recognize that this simple approach may sometimes require nuance, as insects’ response to spring warming can vary according to their species and local conditions.

Here are a few examples of beneficial insects found in North American gardens, along with their role and reaction to milder temperatures.

Pollinating Bees

Pollinating bees, whether native or domestic, usually wake up in spring when temperatures are between 10 and 15°C (50-60?), and they particularly appreciate sunny days. Some species of solitary bees become active as soon as temperatures reach around 5°C (41?), but generally this will be around 8-10°C (50?). They become more energetic as temperatures rise, intensifying their search for nectar and pollen. Bees play a crucial role in the garden as they pollinate flowering plants, helping to produce fruit, vegetables and seeds.

Ladybugs

During winter, ladybugs enter diapause, a state of dormancy that reduces their metabolism to save energy in times of cold and food shortage. They often gather in large numbers in sheltered places such as under tree bark, in rock crevices, or inside buildings, to stay warm and protected.

Although some ladybugs can start waking up at lower temperatures, most need warmer temperatures, around 10-12°C (50°F) before they become more active. They are highly valued in agriculture and gardening for their role in natural pest control, eating large numbers of aphids and mealybugs as well as other small insects harmful to plants.

Green Lacewings

Like ladybugs, lacewings, spend the winter in diapause. They also seek out protective shelters, such as under tree bark, in leaf piles or building cracks, to protect themselves from the cold and predators. They are common on houseplants.

Lacewings join the spring hustle and bustle when temperatures rise above 10°C (50°F), becoming more active as the temperature rises. Their contribution to the garden is invaluable as important predators of aphids, mealybugs and other pests. Their larvae are particularly effective in biological pest control. Lacewing larvae are particularly voracious and are often used in agriculture and horticulture for biological pest control. They are known for their appetite for a wide range of insect pests, and can consume large quantities of aphids as they develop.

Parasitoid Wasps

During winter, parasitoid wasps also enter diapause, but some species lay their eggs in hosts in late summer or autumn, and the larvae only emerge in spring, perpetuating their life cycle.

Parasitoid wasps are active as soon as temperatures rise above 10°C, actively seeking out hosts to lay their eggs. Their beneficial role in the garden lies in their ability to parasitize the eggs or larvae of other insect pests.

Predatory Spiders

Spiders employ several strategies to survive the cold. Many go into diapause, but other species produce a natural antifreeze to avoid the effects of freezing. Others lay their eggs in autumn, spending the winter sheltered in cocoons, ready to hatch in spring. This period of low activity is essential, as food is scarce and spiders depend on their accumulated energy reserves. These adaptations enable them to survive the winter and quickly resume their activities with the arrival of spring.

Spiders become active again when the weather warms up, often around 10-15°C (50-64°F), but their activity and efficiency generally increase as the temperature continues to rise. They often require 15-20°C (59-86°F) to be fully active. Spiders, like many other arthropods, are cold-blooded, which means that their level of activity is strongly influenced by ambient temperature.

Hoverflies

Many hoverflies, which are cold-blooded predatory flies, lay their eggs in late summer or autumn, and the eggs or larvae spend the winter in diapause, ready to hatch or resume growth the following spring when conditions become favorable again.

Hoverflies are most active at temperatures above 10°C (50°F), their activity being highly dependent on sun exposure and accumulated heat. Although they can remain somewhat active at relatively low temperatures, they are particularly effective in warmer conditions, where they actively hunt aphids. Hoverfly larvae play a crucial role in managing aphid populations, as they consume these pests voraciously, reducing the need for pesticides and contributing to the health of agricultural and natural ecosystems.

Earthworms

Earthworms adapt their behavior to survive cold temperatures by migrating to deeper layers of the soil where it doesn’t freeze, thus avoiding frost damage. They also enter a state of torpor, significantly reducing their metabolism to lower their need for food and oxygen. In addition, they reduce their activity, feed less and may cluster together to conserve heat and maintain the humidity they need to breathe.

They start to become active in spring when soil temperatures are generally between 5 and 10°C (41 and 50°F), and their activity intensifies as temperatures rise. They play a crucial role in improving soil structure by digging tunnels that promote aeration and water circulation, while contributing significantly to the decomposition of organic matter. This activity transforms organic waste into humus, enriching the soil and releasing essential nutrients that support plant growth.

Pollinating Butterflies

Butterflies use a variety of strategies to survive the winter, depending on their species. Some, like the Monarch, migrate to warmer climates, while others enter diapause. Those that don’t migrate or diapause seek protective shelters such as cracks in rocks or tree trunks to shield themselves from the elements and predators, reducing their activity until spring returns.

They are particularly effective on sunny days, being active when temperatures exceed 10°C (50°F), however, the ideal temperature for most butterflies to fly and feed effectively is often a little higher, usually around 20°C (68°F). They are important for pollinating flowering plants, helping to produce fruit and vegetables, and their larvae feed birds.

Moths

In winter, moths often go into diapause to reduce their metabolism, seek shelter from the cold and predators, and some may produce antifreeze substances, allowing their eggs or larvae to survive until spring to continue their life cycle.

Finally, moths, which are active when temperatures warm above 10°C (50°F), are often most active at night or dawn. However, many species require higher temperatures, often around 15-20°C (59-86°F), for significant activity. Their beneficial role lies in their contribution to the pollination of nocturnal flowering plants, as well as in their role as an important food source for various nocturnal animals, including nocturnal birds such as owls and bats.

Why 10°C (50°F)?

The temperature of 10°C (50°F) is a physiological trigger for many insects, stimulating their metabolism, mobility and reproductive activity. Insects’ internal biochemical processes intensify at this temperature, providing the energy needed for daily activities such as searching for food and mating partners. Some insects will quietly emerge from their torpor before this threshold, but will be less active. In addition, warming to 10°C (50°F) often triggers larval development. This temperature also signals the awakening of their prey, such as aphids.

It’s important to note that some insects can also be influenced by other factors, such as the availability of daylight or weather conditions specific to their habitat.

When Will It Be Warm Enough?

In North America, the maintenance of night-time temperatures above 10°C (50°F) in spring varies according to latitude, altitude and local climate. Milder nights make it possible to reach this threshold in the southern United States and parts of the West Coast in early spring, sometimes as early as March. Further north in the U.S. and in parts of Canada, this occurs later, usually in late April or May, but can extend into June, particularly in mountainous areas.

Insects don’t wake up all at once; they become progressively more active as temperatures rise. This starts a few degrees above zero and intensifies as the temperature rises, with a peak in activity when temperatures are between 20 and 30°C (68 and 86°F).

So it is just a number! It’s not very precise, but it’s still a good average and easy to remember! In any case, be patient with beneficial insects. Wait before doing any spring cleaning, and keep it to a minimum. The insects will repay you a hundredfold.