How and When to Start Seeds Outdoors

Outdoor seed sowing is a rewarding experience. You plant seeds, watch them sprout, and grow more amazed each day as they morph into giant plants. Know when and how to sow outdoors and you’ll have plants growing in every nook and cranny of your garden.

Written by Madison Moulton Last updated: December 17, 2024 | 8 min read

A shot of several different tools and equipment for start seeds outdoors

Contents

Seed starting is like magic. You put tiny, hard seeds into the dirt, and they sprout into plants with beautiful flowers and delicious fruits. Most gardeners start seeds indoors and transplant mature specimens outdoors when ready. However, outdoor seed sowing is best for species with sensitive roots, cold-loving crops, and plants that dislike change.

When you sow your plants outdoors, they must adapt to your local climate to survive. There are some techniques we’ll use to create optimal growing conditions that boost germination rates. Despite these techniques, you must have a level of trust in your seeds. You must believe they’ll sprout!

And sprout they will. You’ll see seedlings a few days or weeks after planting. Some seeds require weeks or even months to germinate. Have patience, start some backup plants indoors, and watch as nature does the work for you.

Precious Pollinators Seed Shaker

Make outdoor sowing easier with a convenient seed shaker mix! Each shaker covers 800 square feet for hassle-free direct sowing. The ‘Precious Pollinators’ mix contains beloved pollinator favorites like:

Purple coneflower
Giant zinnia
Coreopsis
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When to Start Seeds Outdoors

Using your first and last average frost dates is best to determine when to start seeds. To determine your approximate last frost dates for planting, input your zip code into this calculator from the National Gardening Association. This information will allow you to adapt your gardening strategy to your climate, helping you take advantage of every opportunity during the growing season.

Follow Nature’s Lead

The seed head of an umbel-shaped flower stands out against a gray sky. — Many plants naturally drop their seeds in the fall.

Some species are easier than others when it comes to outdoor sowing. Native plants already have adaptations to your local climate—they’ll sprout readily with little help or maintenance. Simply plant them when they naturally fall to the ground in your region. For many plants, this means direct sowing in fall, allowing the seeds to have a natural period of cold stratification before sprouting in spring.

Heirloom plants sometimes naturalize in gardens and perform similarly to native plants. They grow seedlings with the same qualities, and they sometimes propagate themselves in your garden with self-sown seeds. Plants like forget-me-nots, lettuce, and sorrel reseed readily and need little help from us gardeners. Let them spread into bare patches of soil, or dig them up and transplant them to new sites.

Spring or Fall?

A close-up shot of a person wearing a yellow sweater, red pants and yellow boots, in the process of digging a hole to plant flower bulbs in a well lit area outside — Some plants, like popular tulip and daffodil bulbs, perform better when planted in fall.

Certain crops appreciate starting in the fall, others like the spring, and some function well in either season! When to sow seeds outdoors depends on when you want to harvest or when you’d prefer flowers to appear.

Heat-loving species prefer to start in winter, spring, or early summer. They thrive under summer sunlight and grow their best when days are warm. Cold-loving and frost-tolerant species work well in spring or fall. Plants like broccoli, cauliflower, and true spinach need cool weather with consistent moisture; they’ll thrive during the colder months but suffer if you grow them in summer.

First, decide when you’d like to harvest your vegetables, fruits, or flowers. Then, determine when to start seeds outdoors. Growers with mild winter climates can grow cold-loving species throughout fall, winter, and early spring. You can consider yourself a mild climate gardener if you live in USDA hardiness zone 9 or above.

Consider Days to Maturity

A close-up shot of growing seedlings of a plant, from the soil ground in a well lit area outside. — Consider the “days to maturity” of crops to determine ideal planting times.

Alongside frost dates, “days to maturity” is another rating that helps you decide when to start seeds outdoors. Some crops reach maturity quickly, like radishes. They’re ready to harvest around 30 days after you plant them! Others, like peppers or watermelon, require many months to become adults.

Look to the packet your seeds come in to see their days to maturity rating. Then, you can adjust your seed starting dates to give your plants the time they need to grow into adults. If you live in cold climates with winter frost, you’ll want your summer crops to grow into adults well before the first frost dates.

Watch for Frost Dates

A close-up shot of growing seedlings of a plant, sprouting for a soil that is covered with a layer of mulch in a well lit area outside — Find your average frost dates before planting.

Average frost dates are the best indicators of when to sow seeds outdoors. The chart at the beginning of this article provides information on when to plant flowers, vegetables, and herbs. First, find your average frost dates, then look at the chart to see how long before or after the frost dates you should start seedlings.

Cool weather-loving species start best a month or two before the last average frosty days. Warm weather-loving plants start best outdoors one to four weeks after the last frost date. For fall plantings, sow frost-tolerant flowers and crops three to four months before the first frost date in autumn.

Gardeners with garden beds in greenhouses or cold frames can cheat a bit! You’ll want to adjust your starting dates one to three weeks earlier. The protective structures warm the air inside to be hotter than the air outside. This creates the ideal conditions for seed starting in late winter or early spring while not much else is growing.

How to Start Seeds Outdoors

Now that we know when to plant seeds outside, let’s learn how to do it! We’ll use materials you might have lying about your yard and some tools that most growers should have in their arsenal. Follow these simple steps from start to finish so you’ll have dozens of seedlings throughout your garden!

Step 1: Gather Materials

An overhead shot of several tools, equipment, bulbs and plants placed on soil ground in a well lit area outside. — Sowing outside requires less material and maintenance.

Before you begin, you’ll want to gather your tools and materials in one place. This makes for easy sowing without interruptions. Here are the things you’ll need to begin:

Potting soil, compost, or leaf mold
Rake
Hand trowel
Seeds of your choice
Hose nozzle or watering can

Outdoor sowing requires less materials and maintenance than indoor sowing. It’s not necessarily easier, although it is nice that you can conserve your supplies when planting outdoors. You’ll need a site with bare soil, like a raised or in-ground bed, container, or border.

A rake allows you to make the soil’s surface even, while a hand trowel makes for easy digging. After planting, you’ll water the site with a hose or watering can. Gardeners in areas like the Pacific Northwest often get away with letting natural rainfall water their seedlings.

Step 2: Prepare the Site

A shot of a wheelbarrow with several debris from flowers and other plants, placed alongside a garden bed, in a well lit area outside. — Clear the site of any debris like overgrown weeds.

Some sites may have dozens of overgrown weeds, while others have nutrient-poor soil with a weak structure. Prepare the site first so that the seeds germinate successfully. Start by removing any weeds, spent annuals, and debris.

Soils low in nutrients benefit from amendments like compost, leaf mold, or packaged organic mixes from the store. Place a layer one to three inches thick on top of the soil and rake it in evenly. The amendments decompose over time, boosting the dirt’s nutrient levels and structural integrity. They house growing seedlings with loose particles that are good for root growth.

If using containers or raised beds, first ensure they’re full of dirt that’s nutrient-rich. Old soil in containers compacts over time, creating less-than-ideal conditions for root growth. Fix it by adding drainage materials like perlite and vermiculite, and add more organic matter like compost or leaf mold to boost nutrient levels.

Step 3: Condition the Seeds

A palm facing up holds a few nasturtium seeds with thick outer coatings. — Seeds with a thick outer coating, like nasturtiums, may benefit from scarification.

Seeds often require conditioning before you plant them. Large seeds with hard coatings benefit from scarification, while cold hardy seeds often need cold stratification. Treat them before planting, or use the seasons to meet their needs.

Scarification is a process where you file away or prick a piece of a seed’s hard outer coating so it germinates quicker. Peas, beans, and nasturtiums form thick outer seed coverings to improve survivability. Use a nail file to sand away a piece of the coating.

Cold stratification is a different process where seeds need a certain amount of cold days to germinate. Native plants and cold-loving species often require this treatment. Sow the seeds so they receive this cold period outdoors or cheat with your refrigerator. Put the seeds in a bag with sawdust and a little moisture, then keep the bag in the fridge for as long as the cold stratification period requires.

Step 4: Plant Seeds

A shot of a person wearing light blue plaid shirt, blue jeans and blue-green boots, in the process of inspecting and sowing germs in soil outside — Once all the prep work is done, sowing will become an easy process.

Finally, we get to plant seeds! Sowing becomes an easy process after all the preparation work. To start, dig trenches or furrows as deep as your seedlings need; look to their packets for proper digging depths. A general rule of thumb is to plant small seeds near the surface and larger ones further down.

Place the seeds with proper spacing in between each one, then cover them up with the soil or compost from nearby. Try not to press the dirt down too much, as it’s more difficult for sprouts to pop up through compacted soil.

Some species benefit from surface sowing, where you rake their tiny seeds into the surface of the soil. Start by raking an even portion of the dirt, then broadcast the seeds evenly throughout the site. Carrots, chamomile, and lettuce appreciate surface sowings.

Step 5: Maintain Consistent Moisture

A close-up shot of growing sprouts of plants on top of moist soil in a well lit area outside — Near-constant moisture levels are needed for successful sprouting.

Seedlings need near-constant moisture levels to succeed. They’re sensitive when small—their tiny root systems are prone to drying out. Water them consistently so they grow well from the moment they sprout. If your garden is wet from natural rainfall, avoid watering your seedlings until the dirt dries on top.

You want your sensitive seedlings to have moist, not soggy, soil. You’ll know it’s perfectly moist when it feels like a wrung-out sponge. If rain is frequent while you’re sowing, place a row cover or umbrella above the baby plants so they avoid soggy conditions.

Summer seed starting is difficult outdoors as warm temperatures and ample sunlight encourage dry dirt. Use a sprinkler on a timer to ensure they stay moist or use a drip irrigation system to avoid the hassle of daily watering with a hose.

Step 6: Thin Overcrowded Seedlings

gardener thins lettuce seedlings. — Thin seedlings to provide enough room for the strongest to grow.

Crops like beets have multiple seeds in a fruit-like structure. When you plant a single “seed” you’re planting three or four! You’ll see multiple seedlings pop up in the same location. Simply thin the extra seedlings and let one plant thrive in the open space. Remove the weakest, shortest seedlings, and let the strongest and tallest ones remain.

Beets, lettuce, and other leafy greens grow edible sprouts! Use them like microgreens in salads, on charcuterie boards, or inside sandwiches. Some flowers, like sunflowers, form deliciously nutty microgreens while young and tender.

Step 7: Support Leaning Plants

A close-up shot of a person wearing blue jeans and orange garden gloves, in the process of ting a growing plant to a green plastic stake in a well lit area outside. — Plants will need support while they grow tall.

Peas, beans, and other twining spreaders like squash need support while they grow tall! Give them something to lean on while they’re young and they’ll morph into hardy, strong, and tough adults. What type of cage or trellis to use depends on the plants you’re growing.

Squash, cucumbers, melons, and climbing beans need strong supports made of metal, PVC, or wood. They have fruits that weigh heavy on the vines, and strong supports ensure they ripen fully before falling to the ground. Cow panels are an easy material to use for this purpose, as they’re already strong and you can stick them in raised or in-ground beds.

Thin twining species like flowering peas, bush beans, and trailing nasturtiums don’t need much support. Let them attach themselves to a bamboo stake, or tie them up on other woody plants nearby. Crops like tomatoes, bell peppers, and eggplants appreciate tomato cages for support. The structures make harvesting simple by allowing easy access to every part of the plant.

Step 8: Successive Sowings

A close-up and focused shot of a person wearing a black sweatshirt, holding a packet of germs and in the process of sowing on a dug hole in a raised bed in a well lit area outside — Successive sowings can ensure a near-constant supply of crops.

While your seedlings grow it’s time to start thinking about planting more! Quick growers like radishes are ready for harvesting a month after they germinate, meaning you’ll quickly run out of fresh veggies from your garden. Make successive sowings to have a near-constant supply of leafy greens, tender roots, and delicious fruits.

Most growers sow seeds every two weeks to grow the food or flowers they need. This is best for annual herbs, flowers, and quick-growing vegetables. Some other good plants to succession sow are cilantro, spinach, and bok choy.

Repeat this process for each sowing. It works for fall, spring, and midsummer plantings. Combine outdoor sowing with indoor growing and you’ll have more fruits, veggies, and flowers than you can process!