Ideal Soil Temperature for Your Plants

Compost & Soil
Soil Temperature For Plants

Seed planting is fun and rewarding. Not to mention it can be a great educational experience for the whole family. Many beginner gardeners are scared of staring their plants from seed, but the good news is that the process doesn't have to be complicated. There are many plants you can start from seeds easily, which will provide you with not just a valuable experience but with a beautiful garden.

When starting your plants from seed, keep in mind that one of the most important things for a success is that the seed is of a good quality. This will provide you with stronger and healthier plants. Other important things needed for growing healthy plants are rich, fertile soil and favorable environment ideal for making your plants thrive.

Favorable Conditions

When it comes to these three parameters, two are under your control: seed quality and soil quality. While not everyone starts with a great soil, and while it's not always possible to choose the best seeds (especially if you are a beginner gardener), with a bit of effort and practice, you can give the best soil to your plants and learn how to choose the best seeds.

The third requirement - climate conditions, however, is not always easy to achieve. A lot will depend on your climate zone and the micro-climate of your garden. Luckily, it's still possible to achieve good results, even if the conditions are not the best. All you need is to understand your garden, climate and conditions present in it, and to try to make the best environment for your plants.

One of the most important things you need to ensure, regardless of your climate conditions, is a good soil temperature. Soil temperature is crucial for making seeds sprout and this is why you should pay a close attention to it. Regardless of your climate conditions and micro-climate of your garden, chances are that you will be able to grow plants as long as you make them sprout. To make this happen, you need to provide your plants with the best soil temperature.

Ideal Soil Temperature

So, what's the ideal soil temperature you want to achieve? There is no one, universal answer to this question. Each plant has its own ideal temperature. Some plants don't require soil to be too warm to sprout, so you can plant them earlier in the season. Others require very warm soil, so you can't plant their seeds until it's hot enough to do so.

All gardeners are eager to start planting, but you have to be patient. Sowing seeds too early, before the soil temperature is adequate, won't do any good to your plants.

When it comes to starting seeds and soil temperatures, it's important to understand when and where you can start your seeds. Some seeds can be sown outdoors, directly in the garden, when the temperature is consistent and the soil is warm enough. Other plants have to be started indoors first and later transplanted to your garden.

One warning: soil temperature and the outside temperature you see on your thermometer don't have to be the same. Soil holds the temperature depending on various factors. In most cases, dark soil is the healthiest and it can hold both heat and water very efficiently. However, to tell the exact temperature of your soil, it's best to use a soil thermometer. These thermometers are inexpensive and will help you a lot when it comes to determining if the soil is ready and warm enough for your plants.

Seeds You Can Start Outdoors

You can start these plants outdoors, when the soil temperature is warm enough.

Chard is an interesting plant when it comes to soil temperature. Its seed actually prefers cooler temperatures to germinate. It means you can sow the seeds while it's still cold outside. As soon as you can work the soil, start your Chard seeds to provide the best results.

These seeds require soil temperatures of at least 40 degrees F to germinate:

  • Radish
  • Spinach
  • Potatoes
  • Herbs
  • Cabbage
  • Parsley
  • Turnips
  • Beets
  • Endive

The following seeds require soil temperatures of at least 45 degrees F to germinate:

  • Peas
  • Mustard
  • Leek

The following vegetables require a bit warmer soil. Start these seeds when the soil temperatures reach 50 degrees F:

  • Lettuce
  • Carrots
  • Cauliflower
  • Onions
  • Corn

The following plants require 60 degrees F to germinate:

  • Cucumber
  • Beans
  • Kale
  • Pumpkin
  • Squash
  • Cantaloupe
  • Gourd

The following plants require soil temperatures of at least 65 degrees F. It's important to wait for warm weather to start them! Warm-lowing plants are:

  • Okra
  • Chicory
  • Popcorn

Finally, these plants really like it hot! Start their seeds when Soil temperatures are at least 70 degrees F:

  • Watermellon
  • Eggplant
  • Kohlrabi (fall crop)

Seeds You Should Start Indoors

Keep in mind that there are some vegetables that are best started indoors. For these vegetables, you should always start seeds indoors early in the season, and then transplant them to your garden. These seeds germinate the best when started indoors, and they also produce the best crops if started this way. This is because they need warm indoor temperatures and later have to be hardened-off before transplanting in the garden.

Here is a list of the most popular vegetables you have to start indoors:

  • Peppers. Both sweet and hot peppers are best started indoors. They require temperatures around 80 degrees F. Start the seeds about 8 weeks before you want to transplant peppers to the garden.
  • Tomatoes. They are best to be started indoors. The seeds require soil temperatures of about 70 to 90 degrees F. Transplant them to the garden when the outside temperatures are consistently above 50 degrees F.
  • Celery. It requires temperatures of about 75-85 degrees F, and it's best started indoors. Keep in mind that the seeds are very small and you will probably over-plant them. This is why you will have to thin them to the strongest plants later. Use a handheld seeder to make the seeding process easier.
  • Broccoli. Start the seeds about 6 weeks before you want to transplant it to your garden. The seeds germinate at temperatures of about 85 degrees F.
  • Kohlrabi. For a spring crop, start it indoors. For a fall crop, you can sow the seeds outdoors, as long as the temperature is are at least 70 degrees F.

Photo credit: UGA CAES/Extension

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