Determining planting dates

Every growing zone is defined by the length of the growing season. This is determined by the latest frost date in the spring and the first frost date in the fall. While some cool season vegetables can withstand minor frosts, for most gardeners, the garden starts when the soil temperature hits 5C and there are no more night time frosts. The gardening season ends when a heavy, killing frost hits.

Before we can determine planting dates for our area, we must first find out our frost free dates. Growing zones are not straight lines; geography, weather patterns and altitude all help to determine them. You may find your area is in a pocket with a slightly longer growing season than areas around you. 

In order to determine your frost free dates, visit your the government website for your area and search for frost free dates. For those in Saskatchewan, you can use this graphic to find your frost free dates.

Once you have determined your frost free dates, count the number of days between them and you have the average growing season for your garden.

For example, if you live in Saskatoon, your last/first frost dates are May 21 and Sept 15. This means Saskatoon has an average growing season of 115 days. Remember this is average so frosts can still occur before/after these dates! 

A vegetable that needs 120 days to hit maturity is not going to ripen in a 94 day season so it is important to determine our growing season length so we are planting the correct varieties to mature in our growing area.

Once you know your growing season length, you can now look in seed catalogues to determine what varieties you can grow for your area. In Saskatoon, look for vegetables that mature in 100-110 days to give yourself a bit of wiggle room. If your growing season is 94 days, then look for maturity dates that are 80-90 days long. 

Germination dates tell us how many days it takes from the time we put the seed in soil to when the seedling is starting to grow it's first true leaves.

Some vegetables and herbs can take 3 weeks for germination so this needs to be considered when determining planting dates. Carrots for example take longer to germinate than peas so if you are planning on freezing bags of mixed vegetables of peas, carrots and green beans, then germination plus maturity date needs to be considered so all three vegetables are ready to harvest at the same time.

Our garden vegetables can be divided into two categories based on their temperature preferences.

Cold season vegetables can handle cooler temperatures, some can even withstand some minor frost exposure. These plants, like lettuce, broccoli, cabbage, peas, and carrots can be seeded into the garden when the soil temperatures hit 5C. Germination may take a bit longer for some of these vegetables at low temperatures but they will start to germinate once the soil temperatures hit 5C.

Warm season vegetables are those that love the heat. Corn, tomatoes, and peppers are examples of warm season crops. These vegetables will not germinate at cool temperatures and seeds cannot be planted until the soil temperature reaches 15C. For most warm season vegetables, their maturity dates are too long for our short growing seasons. It is for this reason that warm season vegetables need to be started as transplants as it gives them a head start to reach maturity before the end of the growing season.

If the maturity date is 90 days and your first fall frost is August 30, count back 90 days to get June 1. This means that vegetable needs to be planted by June 1 to be harvested before the last average frost date.

If the vegetable is a warm season vegetable and needs 100 days to maturity with a last frost date on Aug 30 and it has 14 days germination, then 14 days must be added to the growing time so the seeds should be planted on May 1.

So what variety do you need for your garden? Ask yourself if the maturity dates fit within your growing season? Seed companies will include maturity date information on seed packages and in the plant descriptions in their catalogues. Read descriptions of varieties carefully to ensure the maturity dates fit into your growing season.

Once you have selected varieties that fit your growing season and growing needs, then it's time to sit down and figure out what dates you need to be planting your vegetables. Traditionally, planting a garden on the prairies happened on May long weekend but many seeds can be started before and some need to wait a bit longer to go into the garden until risk of frost has passed. Planting can occur throughout the entire month of May instead of all in one weekend. This will help to ensure all plants reach maturity. Succession planting can be used to help a gardener harvest multiple harvests through summer or time harvests to preserved mixed veggies. Low tunnels can also be used to extend seasons and add heat units to heat loving plants to ensure harvest occurs when you time it. No till gardening can also help with season extension and increasing yields.

Use a garden journal and a calendar to help you keep track of when you should be starting plants. Keep notes on how the variety performed in your garden; did maturity dates expected match when you harvested it and make adjustments in next season's garden.