Timing Your Garden: When To Start Gardening In Southern Ontario

Timing Your Garden: When To Start Gardening In Southern Ontario

Mar 01, 2023

Starting your garden takes great care and insight into the plants’ conditions. Every seed has its frost-date-dependent planting timeline. So you should follow the calendar before you put seeds into the soil.

In Southern Ontario, the differences in climate throughout the year can affect plants’ production. Whether you want to start with spring flowering plants or a fresh vegetable garden, you need to start at the right time.

Your Calendar To Gardening In Southern Ontario

It is important to get the timing of your garden just right! Many people in Southern Ontario use the May 24 long weekend as the time for planting. This is because many years ago the last frost date (the date after which you can begin planting outside) was around that time. But frost dates have changed over the years. For instance, the last frost dates for Brampton and Mississauga is now around April 21 - 30. For Caledon, it's May 1 - 10 and for Toronto, it's Apr 11 - 20.

As there are only a few weeks left in winter, now is the perfect time to start planning your garden in Southern Ontario.

Created with Southern Ontario's growing season in mind, this guide will provide you with all the information needed to start gardening.

January and February

January and February are not considered planting months in Southern Ontario, so this would be the best time to stock up on your gardening tools and supplies. A few gardening must-haves that should be on your buying list are:

  • good quality seeds,
  • a quality growing lamp,
  • a heat mat,
  • seed starting mix, and
  • a seed starter kit.

Always purchase the seeds before the winter ends because the popular ones always get sold out. If you are planning to grow peppers this year, start in mid-February because they need 10 to 12 extra weeks for proper growth.


March is the ideal time to start your seeds. Again the last and first frost dates determine the length of your growing season. For plants that need more time to mature than the length of the growing season, you can start these seeds indoors. So March is usually the right amount of time to give your seeds a head start o the growing season. So if you are planting peppers or onions this year, this is the best time to start the seeds. It will give these plants enough time to mature.


April is a slightly warmer month. At this time, you should take extra care to thin seedlings in a shared growing vessel. Snip off or remove the weakest seedlings and leave a more favorable growing environment for the remaining ones — less crowded.


May is usually the time when we begin planting. If you want to plant seeds, you can direct seed your cold-tolerant or cool-weather plants outside. These are crops like beans, asparagus, or root vegetables. Other than that, you can begin hardening off your cold-sensitive starts.

Victoria Day

It is a tradition in Canada to wait for Victoria Day to start seeds and gardens. Victoria Day is considered the most popular gardening weekend in Ontario. As it lies at the end of May, the risk of frost has usually passed in Southern Ontario. Before Victoria Day, you can plant many summer bulbs or spring annuals. This is also the perfect time to transplant your warm-season seedlings into your garden.


June provides warm and favorable weather for your plants. This month, you can plant annuals like tomatoes, perennials, and many other vegetable plants. In June, you also need to watch out for any weeds. To keep the roots of the plants moist and cool apply a layer of mulch to new plants.

July and August

July and August are the warmest months in Southern Ontario. If you have any shady areas in your garden, you can plant there during these warm months. Otherwise, your plants may burn because of the extra heat and direct sunlight.

During this time, focus on watering plants enough and keeping the plants protected from weeds and direct sunlight. If you are worried about pests, you can consider integrating natural pest management to eliminate pests while maintaining a better ecosystem.


September is known for the best production of cool-season crops. During this time of the year, you can plant your cool-season plants in Southern Ontario, to harvest before winter. The common vegetables you can plant during September are coriander, beans, spinach, or cabbage.

At the end of September, you can start the fall bulbs and some ornamental garden beds.

October and November

October is a month of lovely weather and warm soil. It is the perfect time for planting trees and shrubs. Mid-October is also the perfect time to plant garlic and get your first harvest in the coming spring and summer.

If you want to add color to your garden for the winter months, start planting evergreens. In some areas, you may be able to continue planting cold-tolerant crops until November, when the cold is not so harsh on the delicate seedlings.

Remember that plants need sufficient watering even during cold weather.


At the end of the year, planting in Southern Ontario comes to an end. It is the time to enjoy the beautiful landscape of your garden and relax with colorful flowers and plants while waiting for the next planting season.

Take Away

Starting your garden in Southern Ontario is not as difficult. If you are planning a garden, following this calendar guideline will help you remember the best time to start your seeds and when you can begin planting outside.