Spring Gardening: Is It Safe To Plant Outdoors Yet?

Is it safe to plant yet? That’s the number one question in spring for cold climate gardeners as the days grow warmer and we’re eager to get outside and grow something. Use these tips to know what to plant when as winter fades away and gardening season gets underway.

For a list of tasks to take care of in spring, see The Spring Garden Checklist here.

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It’s Spring! Is It Safe To Plant Now?

I admit I’m completely biased but I think those of us who live in cold climates with four distinct seasons find the greatest joy in the changing of the seasons. It’s all so beautiful, dramatic, and unpredictable.

The combination of a long winter and the urge to get outside in the garden is the perfect recipe for spring fever. The days are getting warmer and longer and we’re impatient to do something—anything!—with the garden.

But, while it’s officially astronomical spring, the weather has plenty of surprises yet to come. We may get frost or snow one day and jacket-free temperatures the next. And back and forth it goes.

Meanwhile, as gardeners raring to go, we just want to know:

Is it safe to plant yet?

And if so, what can I plant or sow?

And the good news is, there are options—you just have to know a few basics first.

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Contents

• Know Your Garden Basics
• What to Plant When
  • 12 Weeks Before Last Frost
  • 8 Weeks Before Last Frost
  • 6 Weeks Before Last Frost
  • Average Last Frost
  • 3 Weeks After Last Frost
• Resources

Know Your Garden Basics

First, these are helpful things to know about your garden:

• Your average last frost date in spring and first frost date in fall.
• How many frost-free days you have from spring to fall.
• Your plant hardiness zone.
• Your growing conditions (soil, sun, water).
• The cold-tolerance of whatever you want to plant.

For average frost dates and hardiness zone, you only need look up this information once and it will help you not only with spring gardening decisions but throughout your life as a gardener.

You can tell by the word ‘average’ that the actual first and last frost days will vary each year.

In any given year, your last frost date in spring may be a few days or weeks before or after the average.

But, by knowing the average, we have a date on the calendar to help make planting decisions, separating the plants that can tolerate some frost and cold from those that cannot, while allowing a buffer period in between.

Your plant hardiness zone is important for plant selections in general. It’s related to the lowest average winter temperatures in your area to ensure you don’t choose perennials or trees that can’t cope with those lows.

Don’t Be Fooled By Other Gardeners Or The Weather

For spring planting, there are two things that may fool you: other gardeners and the weather.

A gardener in your same state or province may tell you to plant peas in April but, besides the fact that not all pea seeds have the same cold tolerances, our growing conditions, hardiness zones, weather, and climate do not abide by geographical boundaries.

There can be surprising differences between gardens just miles apart—let alone hundreds of miles. Best to understand your own garden and make decisions based on its facts.

Weather—what we can we say?—spring is a crazy mixture of winter and summer all rolled into one.

Regardless of some warm weather—in any month leading up to your last frost—there’s one thing we know for sure—it isn’t going to last.

You’re always at risk of frost until a couple weeks after your average last frost.

This means we need to be careful with anything we plant or sow up to that time, sticking to plants and seeds that are cold-tolerant and keep protective covers at the ready for seedlings or other tender plants.

What To Plant When

Knowing what to plant when depends on a combination of factors:

• Your average last frost date
• The weather
• Soil temperatures and workability
• The cold-tolerance of what you want to grow.

12 Weeks Before Last Frost

Even if crocuses or tulips pop up early during a warm spell, don’t be fooled!

Late winter is prime time for pruning trees, shrubs, and vines, but it’s not yet time for planting.

What you can do is start slow-growing seeds indoors. This may include some (super slow-growing) tomatoes, onions, leeks, broccoli, and flowers like milkweed and columbine, although prime time for indoor sowing starts a few weeks later.

It’s also a time when you can do the special outdoor seed sowing method known as winter sowing. See How To Winter Sow Seeds & Recommended Sowing Schedule for details.

But otherwise, hold tight.

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8 Weeks Before Last Frost

Somewhere around 1-2 months before last frost, the ground begins to thaw and the soil gradually becomes “workable”. Workable means you can get a shovel in and dig something up, which opens up some gardening opportunities.

But not so fast.

Regardless of any thaws, you have to assume there will be more frosts or freezes to come—despite the current weather—so stick with cold-tolerant plants and seeds that tolerate cold conditions. And keep some frost covers handy just in case.

Plants

The basic rule is for this stage is—if the ground is workable—you can transplant hardy plants that have already been residing outside throughout the winter.

You’re really just moving the plant from one location to another and, because the plants are dormant (not actively growing), they will be none the wiser.

• Perennials that have been residing outdoors all winter
• Trees or shrubs that have been residing outdoors all winter

Do not transplant potted plants that have been sitting in a heated greenhouse or indoors—even if they’re hardy for your zone. They must be thoroughly hardened off (prepared for outdoor growing conditions) before planting.

Seeds

This first group of seeds to sow outdoors in spring will say direct sow 6 to 8 weeks before average last frost on the seed packet.

Options include cold-tolerant varieties of:

• Carrots, onions, peas, parsnip, radish, spinach, turnip and more

Not all varieties of carrots or peas (or other cold-tolerant vegetables) are equally hardy: check your seed packet to confirm.

This is the seed sowing plan I follow for direct sowing vegetables and some flowers in spring before last frost.

6 Weeks Before Last Frost

Days are getting longer and that soil is getting warmer! On warm days you may even see bees or other insects flitting about.

Check the temperature of your soil in several locations throughout your garden beds over several days. You can use any basic kitchen thermometer. When it’s consistently around 50°F (10°C), more seed sowing opportunities open up—this is the preferred minimum temperature for numerous species.

Plants

During this phase you can continue to transplant existing perennials and other hardy year-round plants. Some will be budding and starting to grow at this stage. If a plant is an early bloomer or fruit producer, you may want to hold off transplanting until the flower/fruit cycle is done for the season (the move may disrupt it).

Digital thermometer with probe | Amazon

Seeds

There are a lot of seeds that sow nicely when soil temperatures are consistently around 50°F (10°C), which may happen during this period before last frost.

Again, always check your seed packets for specific, recommended sowing conditions.

And have cloches and frost covers handy, especially for night time when temperatures dip.

4 Weeks Before Last Frost

• Arugula, Brussels sprouts, cabbage, kohlrabi, leeks, lettuce, mustard, Swiss chard

2 Weeks Before Last Frost

• Beets, beans, pumpkin, watermelon

Average Last Frost Date

Yay! It’s average last frost which means we’re almost free and clear!

Although there is still a chance of frosts for the next few weeks.

This means, you can ease into sowing and planting more tender plants that have some frost or cold tolerance but it’s a bit soon for the true warmth loving ones unless you can keep them protected.

This may include:

• Pansies, primroses, violas, ranunculus, snapdragons, pericallis (Asteraceae family), diascia

You can also continue direct sowing vegetable seeds suited to this period.

Plant with caution and have your frost covers handy in case of cold snaps.

Start hardening off your indoor seedlings.

3 Weeks After Last Frost Date

We made it! Depending on where you live, it may be astronomical summer or close to it.

Now is the time to plant warmth loving plants including:

• Tomatoes, peppers, potatoes, zinnias and more

These are plants that have little or no tolerance for frosts or freezes.

If you are transplanting starter plants, be sure to harden them off first to avoid setbacks.

If you are sowing directly, the ideal soil temperature is 70°F (21°C).

You can also continue direct sowing more vegetables:

• Leaf lettuces, onions, peas, pumpkin, radish, squash, sunflowers, Swiss chard, turnips, zucchini

At this point we want to be careful the cool crops don’t bolt and that we have enough frost-free days available to allow any fruiting crops to mature and ripen.

There are lots more seed sowing suggestions here.

Resources

Ebooks

• Annuals & Perennials: What’s The Difference? What’s Best?
• How to Plan a Garden (Tips & Tools to Guide Your Way)

~Melissa the Empress of Dirt ♛