It’s mid-March and everyone is asking, “Can I plant yet?” Here in northern Utah, most people will tell you to wait until Mother’s Day (approximately the last frost date), but if you wait until mid-May, you may be missing out on an entire harvest – not to mention an extra two months of gardening excitement. The truth is that when you can plant doesn’t have just one simple answer. It depends on several factors, and if you understand those factors, you can extend your growing season by at least a month or two.
How cold is it?
Most gardening advice tells you to look at your average last frost date and plan your garden around that, but if you’re planting crops that thrive in cooler temperatures and don’t mind a little frost, then why wait? It’s better to understand how cold is too cold.
There are quite a few plants that can easily tolerate a light frost, but may not live through a hard freeze. What’s the difference? A frost is anything from 32° F and below. A light freeze is temperatures between 29-32° F. Your cold-hardy crops will be just fine in this range. A hard freeze includes temperatures between 25-28°F. There are some crops that can handle this range alright, but you might start getting some damage on your plants and you might want to consider covering them up and using frost protection. Anything below 24° F is considered a killing freeze. If it stays below 24° F for two hours or more, almost all plants will either die or sustain a lot of damage.
Take a look at the 10-day forecast. What’s the lowest temperature you’re going to get? If you live in a place like Utah where the weather can change drastically in just a few days, that may not be a surefire way to tell, but if the lows seem to be staying above 28° F for the most part, you’re probably okay to plant some cold-hardy crops.
Is the soil workable?
A lot of seed packets will tell you to plant “when the soil is workable,” but what does that even mean? There are a few things to take into consideration when deciding if your soil is “workable.”
- Is it frozen? You should be able to dig into the soil without running into chunks of ice.
- Is it covered in snow and ice? If you have to dig through a few inches of snow and ice to get to the soil, it’s probably not workable.
- Is it wet? Workable soil should be damp but not muddy. If there’s too much water in the soil, your seeds and transplants may rot and die.
The other thing to look at is soil temperature. Soil temperature is NOT the same thing as air temperature. Soil temperature tends to stay more consistent than air temperature, and the right soil temperature is crucial for happy plants. Too hot and the plants will be stressed. Too cold and plants just won’t grow. For cool season plants, soil temperature should be around 50-70° F for best seed germination and plant growth. For some of the more cold-hardy plants, you can start planting when the soil temperature is 40° F, but you’ll get the best results when the soil is a bit warmer.
You can test your soil temperature with a soil thermometer, although some people just use a meat thermometer. If you have it already, you might as well use it. Make sure you test the temperature in different areas of your garden. In my garden, the beds on the south side of my house warm up much faster than the beds on the north side of my house. Even within the same bed, one side might be warmer than the other.
What do you want to plant?
If you only grow tomatoes, then no, you can’t plant yet. Tomatoes are a warm season crop and they won’t do well until the overnight lows are in the 50s. There are a lot of crops, however, that thrive in the cooler weather and actually will do a whole lot better if you plant them now. Some crops will even taste better if you grow them in the colder weather.
Planting these cooler season crops can not only extend your growing season, it can give you a whole extra harvest before you put in your warm season crops. For example, peas should be ready to harvest in about 50-70 days from planting. If you plant them out mid-March, you could be harvesting peas by mid-May, right around the time when most people are telling you to start your garden. You’ve already planted and harvested before a lot of people have even started!
| Crop | Ideal growing temp | How cold tolerant | Average Days to Maturity |
| Peas | 50-70° F | 28° F without damage, can survive down to 20° F | 50-70 days |
| Kale | 25-75° F | 25° F without damage, older plants can survive down to 10° F | 50-55 days |
| Spinach | 40-60° F | 15° F | 45-55 days |
| Broccoli | 40-70° F | 26° F | 50-90 days, depending on the variety |
| Cauliflower | 40-70° F | 28° F | 70-100 days |
| Pac Choi | 40-60° F | 20° F | 45-60 days |
| Cilantro | 50-80° F | 28° F without damage, but may survive down to 10° F | 40-60 days |
| Radishes | 40-70° F | 26° F | 25-45 days |
| Beets | 40-70° F | 28° F | 50-70 days |
| Carrots | 55-75° F | 28° F | 55-100 days, depending on variety |
| Lettuce (Romaine and Butterhead are more frost tolerant) | 45-65° F | 28° F, some varieties survive down to 20° F | 45-100 days, depending on variety |
How much do you want to baby your plants?
If you are eager to get started and willing to do whatever it takes to get an earlier harvest, there are things you can do to get your garden going earlier. To raise the temperature of the soil faster, you can spread black plastic over your garden beds to trap in the heat of the sun. You can put up low hoops and frost cloth to protect your young seedlings from freezing temperatures, or cover them with cloches or other protection. You can build cold frames to act as a little mini greenhouse to extend your growing season. If you have the time and energy for that, go for it! There are lots of things you can do to get more growing time out of your garden, but you don’t have to. Just by understanding what to look for and how plants like to grow, you can get so much more out of your garden with minimal work.
Want some help learning how to get the most out of your garden? Let us know! We can help plan out a garden that gives you a harvest for most of the year!
Leave a Reply