It’s the simplest kind of gardening: Plant some seeds and watch the flowers grow. And now that the soil has warmed up, there are plenty of bright annuals you can sow right outside in the garden.
You likely won’t see blooms until midsummer, though. That’s why many gardeners give annual flower seeds a head start of several weeks indoors under lights in spring: so they will bloom earlier once they are transplanted outdoors. In our relatively short growing season, even six weeks may seem too long to wait for flowers.
On the other hand, you can’t beat the simplicity of direct-sowing, or the price, either — a couple of dollars for a packet of seeds.
“It’s very easy to grow from seed and it’s very economical,” says Diane Blazek, executive director of the National Garden Bureau, a seed industry trade group that has a wide range of advice on its website.
You also are likely to find a much wider variety of plants available as seeds than as plants in the garden center.
Blazek offers these tips for sowing annuals in the garden:
Prepare the soil. Few seeds will sprout in dense, heavy clay. Dig in compost or other organic matter to lighten it. Rake the soil surface smooth and moisten it. You can sow annual seeds in pots, too: Use a good-quality, well-drained potting mix.
Read the seed packet. It will tell you how far apart to plant the seeds and how deep. Some seeds need to be well covered in soil to germinate, while others need to be more exposed to the sunlight. Some gardeners sow seed thickly and plan to thin the seedlings later. Do this only if you are sure you won’t forget to thin them, Blazek warns; if plants grow up crowded, none will thrive. (Even if you set seed judiciously, keep an eye on the seedlings; you may still need to thin some.)
Keep the seeds watered. Seeds need to be steadily moist until they germinate. Sprinkle often, using a very gentle spray to avoid disturbing the seeds or the soil. Once the plants sprout, water less often.
Be patient. Most annuals will sprout in five to 10 days, but this is dependent on the weather conditions.
Fertilize as needed. Once the seedlings appear, apply a liquid organic or synthetic fertilizer at one-half the rate specified on the label every other time you water. Annuals need a steady supply of nutrients to keep flowering, but too much fertilizer can damage the plants.
Here are some annual flowers that will brighten the midsummer garden if you sow the seeds outdoors in May in a sunny spot. A number of them have edible blooms.
Sunflower (Helianthus annuus). The big, happy yellow faces of sunflowers can make anybody smile. The garden varieties are descended from North American native plants. Some varieties grow 8 feet tall or more and have flowers a foot across; others top out at 3 or 4 feet. The seeds are edible, if you can beat the birds to them. Sunflowers need full sun and plenty of space. For kids, it’s a fun project to grow a “sunflower house” — a circle of seeds that will grow into a hideaway of tall sunflowers. (Don’t forget to leave a gap for a door.)
Bachelor’s button (Centaurea cyanus). This jaunty blue flower, also known as cornflower, nods on long stems about 30 inches high and has a casual charm. It combines well with bushy perennials such as calamint or prairie flowers such as coneflowers. This European native needs full sun and well-drained soil; it does best in cooler weather and likely will run out of blooms in July. “Blue Boy” is a popular double variety with fluffy flowers. The flowers are edible.
Marigold (Tagetes). Bold and bright in shades of orange and yellow, marigolds are among the most popular of garden flowers. Several species native to the Americas have long since been spread around the world, which is why the tall Tagetes erecta is often called “African marigold” and the smaller, bushier Tagetes patula is called “French marigold.” The flowers are edible, with a citrusy flavor, and some varieties have a lovely scent. They range in height from 6 inches to 3 feet. Marigolds are traditional companions for tomatoes, attracting pollinating insects to the vegetable garden. They need full sun and well-drained soil.
Nasturtium (Tropaeolum). These showy rambling plants have attractive rounded leaves as well as flowers in colors from creamy white through yellow and pink to orange. Most species are trailing vines, which can climb a trellis or swoop from a hanging basket. Many modern varieties hold their flowers above the foliage for a better show. And the flowers are edible, with a peppery kick. They do best in full sun but can handle a little shade.
Spider flower (Cleome hassleriana). The name is perfect, if you can imagine huge pink, white or purple spiders. Or else think of fragrant fireworks above your garden bed. Native to South America, cleome will grow to be 3 to 6 feet tall, although there are shorter hybrid varieties. It prefers full sun and soil on the dry side, making it a good candidate for less-watered areas, but it can handle some shade. Cleome can reseed to an annoying degree, so remove the seed pods while they are still green.
Four-o’clocks (Mirabilis jalapa). Every evening is a carnival with this colorful character, also called “marvel of Peru.” The trumpet-shaped flowers, with pink, yellow and white on the same plant and sometimes the same bloom, open in the evening, with an orange-blossom fragrance, and bloom into the night. A white variety (Mirabilis jalapa “Alba”) is hard to find but lovely in a night garden. Four o’clocks, which grow 2 to 3 feet tall, prefer full sun but tolerate some shade and a wide range of soils. They can self-seed, so be prepared to pull up errant sprouts.
Zinnia (Zinnia). Cheerful blooms come in shades of red, pink, yellow, orange, purple, lavender, green and white. Common zinnia (Zinnia elegans) prefers a rich, evenly moist soil in full sun; creeping zinnia (Zinnia angustifolia) can handle drier soil and its color lasts better in the heat of summer. There are varieties of zinnia from 6 inches to more than 3 feet tall. To avoid leaf fungus diseases such as powdery mildew, don’t overcrowd the plants. Native to Mexico and the southwestern U.S., zinnias have edible flowers.
Cosmos (Cosmos bipinnatus). The crinkled petals and bright yellow centers of cosmos flowers stand 2 to 3 feet high on slender stems with ferny foliage. The blooms are rosy red, pink or white, or a mixture. The simple five-petaled ones have a certain elegance, but there also are fluffy double varieties. Cosmos, a Mexican native, needs full sun. It does best in soil that is well-drained but evenly moist. The blooming may slow down in the hottest part of summer.
Moss rose (Portulaca grandiflora). Vivid ruffled blooms appear above a mat of foliage on a low-growing, spreading plant that can handle hot, fairly dry sites. The slender leaves are fleshy and succulent and the flowers may be pink, red, orange, yellow or white. Moss rose needs full sun; on cloudy or rainy days, the flowers won’t even open.
Morning glory (Ipomea purpurea). Climbing up a mailbox, a downspout, a porch or a trellis, morning glory is a summer classic. It will take some time to get started, but by late summer the vine may reach 6 to 8 feet, and its weight can collapse a lightweight support. This Mexican native reseeds heavily, so be prepared to weed out lots of sprouts; if left in flower beds, morning glories will twine around other plants and drag them down. Before you sow the seeds, nick each one slightly with a sharp knife to help them sprout faster.
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