How to find out the best time to start your vegetable seeds?

When to start vegetable seeds

Before starting your vegetable seeds, you’ll need to make sure that it’s the right time to start them. This depends on the type of vegetable and the climate of your location.

Starting too early could mean that they either take a long time to germinate or that they have to be kept long in smaller pots or seed starting trays until outdoor conditions become suitable. Starting too late could lead to insufficient time at the right temperature range for your vegetables to grow until they are mature enough for harvest.

If you are growing your vegetables directly from seed, you should make sure that the temperature of the soil is within the correct range before putting your seeds in the soil.

If you are going to start your seeds in seed starter trays or smaller pots and then transplant them into your garden, you can start them outdoors if the soil temperature is right or indoors if the soil isn’t warm enough as yet.

To estimate the best time to do so, you’ll need to know how old your seedlings would have to be ready for transplanting and the correct growing temperature for your seedlings. Then, you can work backward and find out when you should start your seeds so they will be old enough to transplant when it’s warm/cool enough outside and if it’ll still be warm/cool enough when they reach maturity.

Let’s work this out together using Tomato as an example.

This is the information that we’ll need:

  • Should tomato plants be transplanted or direct seeded? Tomato plants do best when they are transplanted. This also implies that tomato seeds can be started indoors.
  • What is the best soil temperature for tomato seeds to germinate? Tomato seeds will germinate at a minimum soil temperature of 10°C but germination is very slow at this temperature and can take over 40 days, on the other hand, tomato seeds won’t germinate at all if soil temperatures are above 35°C. The optimum soil temperature for tomato seeds to germinate is 25-30°C and germination will take only 6-8 days.
  • What is the optimum growing temperature for tomato plants? Tomato plants grow properly only when the temperature is over 16°C and under 32°C but grow best when the temperature is 25-30°C and are easily killed by frost.
  • How old should seedlings be to be transplanted? Tomato seedlings are ready for transplanting when they have grown their first true set of leaves or two sets of leaves and are 3- 4 inches tall, which usually takes 6-8 weeks from when you put the seeds in the soil or seed starting mixture.
  • How long do tomato plants take to reach maturity? Tomato plants take 100-120 days (about 3-4 months) to reach maturity from the time seeds are sown, but this depends on the variety and environmental factors.
  • What is the average air temperature or if possible, soil temperature in your area each month? Depending on where you live, you may be able to find this data on your local weather station website or you can ask a local gardening center. If you’re in the US, you can find soil temperatures for your location on this website.

Once you’ve gathered this information, we have to start working backward.

We found that it takes about 3-4 months for tomato plants to reach maturity and that they grow best at temperatures of 25-30°C, so you can start by finding out the latest date at which you can harvest your tomatoes.

For example, if your area has an average soil temperature of 25°C during the end of August/start of September before temperatures start to decline, you can go back 3-4 months to find out when you’ll need to start seeds. This would be during the month of May.

Next, you’ll have to see if the soil is warm enough for tomato seeds to germinate during the month of May. If the soil would be warm enough at 25-30°C, you can start your seeds outdoors in seed starter trays or pots. If it won’t be warm enough yet, you’ll have to start your seeds indoors, 6-8 weeks before it gets warm enough so that you’ll have seedlings old enough to be transplanted.

This information would give you a rough outline of when you should start your vegetable seeds, but you should also make your own observations of the actual weather in your area and how your vegetable seedlings are doing.

You can use this process to find out the best time to start all your vegetable seeds and whether you should start them indoors or outside. You can use the links given below to find similar information on other types of vegetables:

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How to find out the best time to start your vegetable seeds?

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