Planting for Seasons and Garden Zones

When is the Best Time to Plant Tomatoes and Other Crops?

Planting for Seasons and Garden Zones

Knowing when to plant your garden involves a combination of researching garden zones and knowing the individual crops.

If you’re new to gardening, you may not know when to plant vegetable seeds. And I don’t blame you; it’s confusing and there’s a lot of misinformation. For instance, an old saying in my area advises: “Don’t plant until the snow is off Peavine.” This refers to a nearby mountain peak that’s too low for skiing but high enough that it still experiences winter when we’re wearing short sleeves. But there are flaws in blanket advice such as this. In 2012, the snow melted off Peavine in January. Considering our average final frost date is May 15th, any gardener who put tomatoes in the ground during January 2012 probably wept bitter tears when the plants froze.

Determining when to plant comes down to three factors: planting zones, type of vegetable and your available frost protection methods.

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Here’s what to do first: Look up your garden zone. This will state the average date of your last seasonal frost. Determine your zone and pad the numbers a little. What does that mean? If the map says you’re within zone 7, consider yourself in zone 6 just to be safe. Factors such as elevation, microclimates, or proximity to large, open spaces or bodies of water can affect whether your garden will freeze or stay safe. A garden near a wide road can freeze when the one across the street, protected by a cinderblock fence, may not.

Now what do you do? Look on your seed packets to determine when you can plant. Don’t worry about the lingo. I’ll explain that.

When Soil Can be Worked

The coldest of the cold crops don’t care whether the air freezes. They only want dirt that isn’t frozen or waterlogged. The soil must crumble with a gentle touch and fall off the scoop of a shovel instead of clinging in a big mass of mud.

In my area, that’s two months before my final frost date. I plant my hardiest crops around St. Patrick’s Day. For other areas, this may be a month before it stops freezing.

And there’s really no exact time for this. But planting before the soil can be worked can result in seeds which rot and never sprout. No need to rush it. Be safe and let it warm up a little if you’re not sure.

The crops that need to be planted “when the soil can be worked” include radishes, lettuce, peas, Asian greens like bok choy, onions, broccoli, kohlrabi and spinach. They will grow in temperatures as low as 40 degrees and can withstand a frosty night.

An easy way to remember: Research your garden zones. Deduct at least a month. Then walk outside and test your soil. If it crumbles and doesn’t stick in a muddy mass, plant the appropriate seeds.

Photo by Shelley DeDauw

As Soon as Soil is Warmed

Semi-hardy vegetables will withstand frost but won’t be happy about it. They prefer temperatures over 50 degrees to grow well and may be harmed in a hard frost (below 28 degrees.) These semi-hardy crops also sprout easier if the soil is between 65 and 85 degrees.

Though these crops can be planted as soon as the soil can be worked, you may be wasting your time. Instead, plan these halfway between the hardy crops and the frost-sensitive ones. For me, that’s April 15th. They come up readily if I wait that extra month

These crops include carrots and parsnips, Swiss chard, cauliflower, beets, and potatoes. Keep in mind that potato tops will still be damaged in a frost, but the tuber will survive as long as the ground doesn’t freeze.

An easy way to remember: Identify your garden zones and final frost. Deduct two weeks but no longer than a month. Plant when it looks like it’ll be nice for a while.

After the Last Frost

Do not let that corporate garden department fool you. They sell tomatoes in the early spring because people plant them, watch them die, and return for more plants. Again and again. I once heard a lady lament, “I’ve planted my tomatoes five times and they keep freezing!” This was mid-April. I mentioned that my last frost date is mid-May, right?

Unfortunately, some vegetables will die a horrible demise if you plant them too early. They’re worth the wait. Do not…do not…plant before the final frost date according to your garden zones. Certain crops, such as eggplant and basil, don’t even like temperatures below 40 degrees.

Warm-weather crops include tomatoes, peppers, eggplant, basil, corn, beans, squash/pumpkins, cucumbers, melons and celery. Growing seedlings indoors can give you a huge head start.

In fact, starting tomatoes, peppers, and eggplant indoors is crucial if you don’t live in a semi-tropical and frost-free climate. The “days to maturity” on a pack of tomatoes and other nightshades indicates the days after the plant has been transplanted into warm, frost-free soil. This is normally six to eight weeks after the seed sprouts.

The other crops don’t do as well transplanted. Starting them indoors can be detrimental if they become rootbound by final frost. Squash and pumpkins can suffer so much from transplant shock that a seed sown directly into the ground can mature faster than a shocked plant. Corn and beans also do better if sown directly. If you wish to start squash or pumpkin seeds indoors, use a large container, at least six inches wide, for only one or two seeds. Start no more than a month before your garden zone’s final frost because these plants grow fast. If they become even slightly rootbound before the last frost, carefully transplant into a larger container with more soil.

But when is the best time to plant tomatoes? Purchase or grow a seedling then wait until your average last frost date for your garden zone. Either plant then, and have frost protection ready, or wait a couple more weeks to be safe.

Photo by Shelley DeDauw

And Again in the Fall

Semi-hardy and hardy crops can be planted again when temperatures cool down, especially those that mature in fewer than sixty days. Though these vegetables can withstand frost, they prefer temperatures that are warm but not hot. Sow these when the weather winds down but make sure it’s not too hot or the soil will dry out and the seeds won’t sprout.

An easy way to remember: Research your garden zones and determine the average first frost of the season. For me, that’s September 30th, though lately it’s been in mid-October. Sow your cold-weather crops about a month before this first frost date. And keep the soil moist.

Watch the Weather, Pad the Numbers

Were you looking for an exact planting date? I hate to disappoint you, but it’s not that easy. If you live in Florida, tomatoes could be hanging heavy on the vine while Minnesota still has two feet of snow. Even when it’s close to your garden zone’s “date of last frost,” there can be discrepancies.

I could plant my tomatoes mid-May, but half the time it freezes after the 15th. Two years ago, we froze June 9th. Planting my tomatoes mid-May would be fine if I had frost protection for each plant…but I had 35 tomato plants, 30 peppers, and 15 eggplants. I do not have that many walls o’ water. So I transplant my frost-sensitive crops into larger containers, let them grow a couple more weeks, then take them outside. Don’t worry about the lost time; they’ll catch up.

Ask the gardeners nearest to your yard about frost patterns. They’ll advise whether you live in a “banana” belt or if the fog rolls in frigid when the rest of the valley stays cozy.

Most importantly: watch the weather. Find the most accurate weather app or site for your area and check it every day. And again, pad the numbers. If the app says temperatures will drop to 38, deduct at least five degrees. That’s 33. One degree above freezing. You’d better go cover those tomatoes!

Frost Protection Methods

Also called season extenders, certain tools allow you to plant outside sooner. These can be as complex as a greenhouse, as technical as seed starting mats and grow lights, or as simple as throwing a quilt over your raised beds when cold weather rolls in.

Season extenders only give you so much leeway. A heated greenhouse can allow cultivation during a blizzard but a quilt may protect by just five degrees. When you buy frost protection, pay attention to the rating. If it only protects against a light frost, don’t trust it if temperatures drop below 29. Doubling up frost protection can also help, such as growing tomatoes within walls o’ water to protect against light frost but throwing a quilt atop both wall and plant when the frost gets heavy.

Trusted Resources

So who do you trust? Jim Bob’s homesteading blog? Gardening forums? The problem with those is they don’t know your particular area. The very best resource is your local university extension office. They might not tell you what you want to hear—I didn’t want to hear that my soil is too alkaline to grow blueberries—but they will give you the most trusted and accurate advice for your area. They can also help you solve problems with pests and disease. If you don’t have a local university, search the broad extension database and find the resources closest to your area.

Do your homework first. Find your garden zone. Identify your average final frost date. Separate seeds into hardiest, semi-hardy, and those which will die in a frost. Then plant accordingly. Are you ready to start planting? Do you know your garden zone? Let us know when you’ll begin.

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