Starting Seeds Outdoors (in Spring and Early Summer)

Starting your seeds outdoors when the weather warms up has many benefits. Many seeds benefit from direct sunlight as this allows the plants to grow stronger with vigorous root systems. Here’s a complete guide on how to start your seeds outdoors.

In colder climates, many people must start seedlings early indoors (under lights or in a greenhouse / cold frame). Yet, while some plants benefit from an early jump-start of a few weeks or months indoors, a surprising number of flowers and vegetables grow better if sown outdoors a bit later in the season.

Regardless of where you garden is and what you are growing, outdoor sowing has plenty of benefits. Direct sunshine provides the ideal light quality, especially in late spring and early summer. The full spectrum light combined with light wind and breeze naturally aids growth, resulting in stronger, robust seedlings with thick stems and vigorous root systems.

Many of your plants will be much happier if they are started outdoors. The following information will give you step-by-step guidance on how to start your seeds outside successfully.

Do Your Research

Begin by assessing what each seed requires for good germination. Every type of seed has slightly different requirements in regards to temperature, moisture, and light. As with baking, gardening is sometimes more of a science than a craft. It’s wise to research the specific requirements each type of seed needs in regards to temperature, moisture, and light before you begin seeding.

Be sure to consider climate and location as well. A gardener in Los Angeles must contend with a different set of growing conditions than a gardener living in London.

Timing Is Everything

It’s best to organize one’s seeds by planting time rather than alphabetically. Many flowers and vegetables prefer to be sown much later than the earliest date suggested on a seed packet. Nearly all flower and vegetable seeds germinate faster and grow better when they are sown later in spring or early summer.

They also thrive when seeded outside versus indoors. Flowers like marigolds, cosmos, asters, zinnias, and even rudbeckia, while offered for sale in early spring (often already in bloom) at stores, will truly grow much taller and have a far more extended bloom period if sown outdoors. If there is any doubt, note that this is how many flower farmers grow them – in successive plantings all summer long.

Make a Seedbed

An outdoor seedbed is often ideal for starting many seeds that are pre-started indoors. The seedbed can be a simple area set aside from other plants and competition where the soil is bare and where one can easily access it to water and weed. Some people used a portion of a raised bed in their vegetable garden as their seedbed. The seedbed can also be within an outdoor cold frame with heating cables if located in a colder climate.

Prepare the Soil

Most seeds prefer a loose, friable soil that is neither too wet nor too dry. Prepare the soil by turning it over with a tiller or fork to loosen it and remove any large rocks or roots with a rake. Compost added to the soil will add moisture retention and nutrients. Extra fertility is rarely needed, but a water source nearby will help during dry spells. Few seedlings can tolerate dry periods due to their small size. A sprinkler or a nearby hose will be helpful.

Very small seed can be mixed with sand to help distribute it evenly.

Sow Seeds Thinly

Few seeds grow well if sown too thickly. Since you will be transplanting seedlings to different locations, leave some distance between seeds. A tiny seed can be especially challenging to sow thinly, but a good trick is to mix a packet of dust-like seed in some dry sand before sowing, which will help distribute the seeds more broadly. A kitchen sieve can be helpful for this task.

Note the Specific Light Requirements for Each Seed

Some seed requires exposure to daylight to germinate, while others require complete darkness. Daylength (Photoperiod) too can affect growth and bloom time. For example, marigolds and zinnias will bloom quicker if planted in mid-summer rather than in early spring. Use the description on the back of the seed packet as a starter guide and research online to see if there is more information available. The larger seed companies often offer commercial grow-sheets as free, downloadable pdfs that offer in-depth cultural details for most of the larger crops they sell.

Monitor and Maintain the Seedbed

Keep outdoor seedbeds watered during dry spells and free from weeds. The goal is to reduce any stress that can interfere with the growth of young plants. Thin any seedlings that are growing too close to each other. A good guide is to leave at least one inch (25.4 mm) between seedlings. This distance will provide enough room to dig out plants without damaging nearby seedling roots. If one sowed seed thinly, this should not be an issue.

Zinnia seeds sown outdoors in a tray after the weather is warm will grow many times faster than any started early indoors.

Starting Seeds in Outdoor Modules

Sowing seeds outdoors in cells, plug trays, or modules is a convenient alternative to sowing directly into the ground. This method is different from preparing seed trays for germinating indoors under lights or in a germination chamber. Plants often respond far better to conditions outdoors. They germinate and grow stronger with the benefit of bright, natural sunlight. Furthermore, the natural temperature differentiation between night and day and some light wind will ensure that the stems will grow sturdier and thicker than if they were grown indoors.

Ideal Containers and Soil

While nearly any container will suffice for starting seeds (from recycled yogurt cups and take-out containers to professional plastic pots, modules, and plug trays), be sure that the containers are at least 2 inches deep and have drainage holes. Be sure not to use garden soil as it will become too compact in the containers. A sterile professional potting mix is ideal as it will be both well-draining and have some moisture retentive material in it (usually coir or organic compost).

Warm weather annuals that dislike root disturbance such as flowering tobacco are best transplanted to their final flower beds just as the young plants have produced their second or third pair of leaves.

Moving the Seedlings

Lastly, don’t allow seedlings to grow too large before transplanting them to their final location. A good rule of thumb is to lift and divide seedlings once they have produced their second or third pair of true leaves (never count the first leaf or first pair of leaves). Lift the young plants carefully with a fork or spade and relocate to their final growing spot in another bed or container.