Extend your garden season and increase your harvest by learning what vegetable plants can be started early out in the garden before the risk of frost has passed.

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What to Plant Before the Last Frost Date in Spring

One of the most common mistakes I see new gardeners make is starting all their seeds at the same time.  I’ll be honest, I made this same mistake when I was first learning too!

After a long cold winter, it can be very tempting to get some garden seeds started indoors.  Who doesn’t want to escape from the cold weather and get a jump start on warmer weather?

Although there are a lot of seeds that can (and should) be started early, there are others that shouldn’t.

Plants that can handle light frosts and colder temperatures (or even prefer cold temperatures) can often be started indoors, as early as January in some cases!

Other warm season crops (like tomatoes and squash) will outgrow their indoor setup relatively quickly and shouldn’t be planted until later in the spring when the danger of frost is gone and the warmer weather is here to stay.  Let’s dig into this further!

What plants can be started indoors early and planted outside before the last frost date?

Typically plants that can be planted in the garden before the frost-free date are considered cold hardy plants.  Think of plants like onions, peas, swiss chard, radishes, and beets.

While some of these plants can be started even earlier indoors, others do best direct seeded in the garden.

When starting these plants from seed, look at the seed packets for the number of weeks before your last frost date to sow seeds. You can find your last estimated frost date by googling your zip code followed by “last frost date.”

Remember last frost dates are just estimates based on the average frost dates from years of weather data.  This means there isn’t a guarantee you won’t have another frost after that date.  If you put plants out that can’t handle a cold snap, be sure to watch the weather forecast closely (especially the nighttime temps) and be prepared to cover them with row covers, frost cloth, a sheet, cardboard boxes, or anything you have on hand.

Hardening off seedlings

When seedlings are started indoors their growing conditions are very different than when they are moved outside.  It’s important to ease the tender plants into this transition outdoors by hardening them off.

Do this by putting the young plants outside in a shaded or protected area for 30-60 minutes a day and work your way up until they can tolerate the outdoor elements.

If you buy your seedlings from garden centers this process will likely already have been done, but it’s always a good idea to ask.

Let’s take a closer look at plants that can grow before the last spring frost date.

Cool Season Vegetables

Onions

Onions are the first garden seed I start every year.  Did you know you can start onions from seed?  I think this is an unknown fact because onions take longer to grow from seed so if they aren’t started early enough they won’t have enough time to fully mature.  However, if onions are started early enough they will grow better from seed than the dry onion sets commonly sold at stores.  This is because onions are biennials and sets are technically in their second year of life.  This means their biological time clock tells them to go to seed instead of sending their energy to form a large bulb.  By growing onions from seed you allow them to complete their natural first-year growth cycle which will result in large juicy onion bulbs come the end of the season.

Onions can be started from seed very early.  I start mine in early January but as long as they are started before the end of February they should have enough time to grow properly.  Onion seeds don’t need a lot to grow and should be planted very densely to save space.  Once they get a couple of inches tall trim off the tops so they don’t topple over.

Onion starts can be planted out into the garden about 6-8 weeks before the last estimated frost or when the ground is workable.  Be sure to harden off seedlings by gradually introducing them to the outdoors before planting.

Peas

Peas are one of my favorite spring plants to grow.  It has become my St. Patrick’s Day tradition to plant early snap peas in my garden.  As long as the ground is workable and the weather is favorable, I direct sow pea seeds on St. Patrick’s Day, or mid-March, which is 8-10 weeks before our average last frost date.  This means I plant the seeds straight into my garden instead of starting them indoors first.

I like to sow my pea seeds very heavy with the seeds almost touching each other in a long trench.  I’ve found this makes up for any lack of germination or damage caused by hungry animals.

Some people say to soak pea seeds before planting.  While this works, I’ve found it much easier to just give them a very heavy watering after planting.

Peas are pretty easy and will just need some trellising to grow up.  I like to use twine strung up on sticks or t posts.  They will be one of your earliest crops but won’t tolerate consistent warmer temperatures as well.  This will allow you to replace them with another crop for a double harvest in one space.

Radish

Radish seeds are another cool weather crop that can be directly seeded into the garden as soon as the soil is workable in very early spring.  I have planted them as early as St. Patrick’s day along with my snap peas with success.  Whenever direct sowing seeds into my garden I tend to over seed to account for lower germination rates.  I would rather thin out extra seedlings than have a lot of large gaps in my plantings.

Most radish varieties mature in 20-30 days; however, they tend to take a bit longer when planted out very early.  You can succession sow radishes for a continued harvest throughout the season.  To accomplish successive plantings, simply plant more seeds every 2-3 weeks in open spaces throughout your garden and you will have an endless supply of radishes!

Don’t think you like radishes?  I didn’t think I liked them either but when I learned how fast they grew I had to give them another try.  Turns out roasted radishes are delicious and so easy to make!  If you don’t think you like them I would encourage you to give roasted radishes a try.  Radishes are also a great cover crop and promote healthy soil so worst-case scenario you can always work them back into the garden.

Kale

Kale is another cold season crop that can be planted in the garden early.  I would recommend starting this one inside or buying starts from a local greenhouse.  The plant starts can be planted out in the garden about 6 weeks before the last frost.  Be sure to harden them off before planting them out.

Kale is a very hardy plant once it’s established.  I’ve had kale plants survive our zone 5b winters without any protection!  For fall (and even possibly winter) harvests, kale can be planted again in mid-summer.

Spinach

Spinach is a great cold-loving plant to direct seed into the garden.  The best time to plant spinach seeds is 4-6 weeks before your last frost or once the soil can be worked.  Spinach will have the best flavor when harvested in cooler weather conditions.

Cabbage

Cabbage can easily be started inside about 12 weeks before your last frost date and planted in the garden 6-8 weeks later.  Be sure to harden off your tender seedlings before planting them in your garden.

Broccoli

Broccoli should be started indoors about 12 weeks before your last frost date.  The recommended planting date for broccoli out into the garden is about 4 weeks before the last frost date. However, be sure to check the weather forecast because broccoli isn’t as hardy as other cold-loving crops before it’s well established.

Lettuce

Most lettuce varieties are cold hardy and will have a sweeter taste when grown in cooler temperatures.  Once temperatures warm lettuce tends to bolt and go bitter.

Lettuce seeds can either be started indoors 8-10 weeks before the last frost date and planted outside about 6 weeks before the last frost date or direct sowed into the garden.  Lettuce is also known to grow very well in a cold frame in colder climates.

Carrots

Carrot seeds are another vegetable that can (and should) be direct sowed into the garden in early spring.  Carrots like consistently moist soil to germinate and spring is often an ideal time for this.  If you don’t receive consistent moisture after planting out your carrot seeds be sure to water them frequently.  You can also cover them with burlap, a piece of cardboard, or a piece of wood to help lock in moisture until they germinate.

Potatoes

Potatoes are a great crop to get started early in the garden.  To plant potatoes, purchase seed potatoes, which are potatoes that have been disease-tested and are free from growth inhibitors.  You can cut your seed potatoes into smaller pieces, leaving at least 1-2 eyes (or growth sprouts) per piece.  Leave them out to cure for a day or two before planting them in the garden.

Potatoes grow best when planted in deep trenches.  About 2-4 weeks before your last frost date, dig a long trench and plant the potato pieces about 8-12″ apart.  Cover with 2-3″ of soil.  As the potatoes grow through the soil “hill” them by continuing to add back the trenched-out soil around them leaving just the tops of the plant showing.  Continue this process every time the potatoes have grown 4-6″ until your soil is back to level.  You can continue to hill with straw.  Every time the potatoes are hilled it signals them to continue growing and produce more potatoes.  Be sure to stop hilling when you start to see flowers on your plants.

Cilantro

Cilantro is a cold-loving herb that can be direct sowed into the garden up to 4 weeks before the last frost date.  Cilantro will start to bolt and go to seed as soon as temperatures get hot so be sure to preserve your harvest to use later in the summer when it’s time to make salsa.

Dill

Dill is another herb that can be direct seeded into the garden 2-4 weeks before your last frost of spring depending on your weather forecast.  Be sure to succession sow your dill for a continued harvest throughout the season.

As you can see, several crops can be started and planted out in the garden very early.  Don’t make the mistake of starting all your garden plants at the same time.  Instead, focus on the early plants first and wait until the appropriate time to start other plants like peppers and tomatoes.  Squash plants tend to do better when their seeds are planted directly into the garden; however, if you want to give them a head start don’t start them indoors any more than 2 weeks before your last frost date to prevent them from getting root bound.  Squash does not like their roots messed with.

If you want to plant a garden but feel like it’s already too late, remember that there are a lot of plants that don’t like cooler temperatures and shouldn’t be planted out until the temperatures are consistently warmer.  For example, peppers do best when they are planted in the garden a couple weeks after the last frost date when soil temperatures are consistently warm.

There are also a lot of plants that can be planted later in the season and still give you a great harvest.  Certain tomato varieties can mature after only 50 days.  Zucchini is also a very fast producer and can actually do better when planted later in the season when the squash bug pressure isn’t as strong.

In my experience, it’s best to prepare a garden space even if it may not be ready in time to fully utilize it during the current growing season.  Instead, just plant shorter maturing crops in the current growing season.  Come the following year, your space will be all prepped and ready for you to take full advantage of.

Learning about cool season plants and planting a spring garden has helped to extend my garden season and make my gardening season a lot more manageable. I no longer wait for one date to plant all my seedlings. This allows me more time throughout the season and physical space to start more plants indoors.

I hope this information is helpful to you and your gardening journey as well.

P.S. In case you missed it, I shared how to make an easy DIY Arched Cattle Panel Trellis.  This is a quick project and a great way to increase your growing space this season!

Happy Gardening!

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