Self-sowers may be annuals, biennials, or short-lived perennials. The trait they share is an eagerness to procreate in the garden without coddling or hassle on the part of the gardener. Their seeds germinate readily from one season to the next. I always sow them directly into garden soil, whether I’m introducing a new plant or replenishing an old favorite. From there, Mother Nature takes over, and the seeds sprout and grow when garden conditions are right for them.

Annuals, and some of the perennials, bloom the first year. The biennials grow foliage the first year and bloom the next spring. So, in the relatively short time frame of two years, these plants fill beds with attractive foliage and beautiful flowers. I’ve come to rely on them as workhorses of the garden; self-sowers are at the heart of my garden’s design.

Unity through repetition

Self-sowers provide strength in numbers—many seeds germinate and quickly develop into masses of bloom. Their repetitive appearance in beds unifies the garden and ties color schemes together. For example, big-flowered evening primroses (Oenothera glazioviana) undulate through my beds in waves, providing cohesiveness with their buttery-yellow flowers and strong, upright form. Likewise, billowing masses of tiny snow daisies (Tanacetum niveum) punctuate the beds at regular intervals, their cool-white flowers and sage-green foliage a wonderful contrast to larger, color-saturated blooms.

Some self-sowers have terrific foliage. One of my favorites, red orache (Atriplex hortensis var. rubra), has tiny seedlings emerging in early spring in a deep purple color. As the vigorous plants grow, the foliage color softens to reddish purple. Then by midsummer, at a height of 5 feet, this wonderful plant adds a vertical accent. Its insignificant flowers mature into beautiful seed stalks by autumn. I like to leave some for winter interest; the birds like them, too.

With self-sowers, seedlings spring up where you least expect them. Not only do they fill gaps in borders, they also provide fantastic plant combinations. One self-sower that blooms early in my garden, bronze-leaved corydalis (Corydalis ophiocarpa), appeared last spring amid dusky, dark-purple ‘Queen of Night’ tulips. Its soft, maroon-tinged, yellow flowers contrasted wonderfully with the tulips. A patch of bronze fennel (Foeniculum vulgare ‘Purpureum’) also grew nearby; its purple-hued foliage provided a rich backdrop for the velvety tulip blooms.

Other self-sowers give exclamation points to the garden. In its second year, biennial clary sage (Salvia sclarea var. turkestanica) sends up stately spikes with lovely pinkish-white flowers. Similarly, spiny plume thistle (Cirsium spinosissimum) emerges from a tight, variegated rosette into bold stalks topped with spiny, purple blossoms. Both add drama and excitement to beds.

Sow seeds directly in the garden

I acquire the seeds of self-sowers from a variety of sources. I order some from gardening catalogs or from organizations like The Hardy Plant Society. I’ve also been lucky to have generous gardening friends who give me seeds. One of the great things about these plants is they usually produce more seed than one gardener could possibly want. If you time your visit well to a garden of self-sowers, its owner may gladly send you off with small packets of seed to grow in your own garden.

I like to spread seeds quite early in the year—late February to early March in my Pennsylvania (USDA Hardiness Zone 6) garden. I simply sprinkle the seeds in the area where I want to establish plants. This early sowing ensures a chilling period for seeds requiring a cool spell for germination. It’s a good idea to stick a label in the soil to mark the spot, especially if the plant is new to you and your garden. After a while, you’ll recognize the seedlings of your self-sowers as quickly as you recognize the seedlings of common weeds in your yard.

Once the seeds are sprinkled, I stand back and let Mother Nature take over. The seeds find their way into little niches in the earth, and rain washes them into contact with the soil. Although there are some plants I have to fuss over, these self-sowers are not among them. A completely relaxed approach has always worked for me with self-sowers.

Don’t worry about seedlings appearing too early. The seeds will germinate when conditions are right for their growth. Young self-sowers are a hardy lot, and freezing temperatures won’t harm them. Those seeds requiring warmer conditions to germinate will lie on the ground until the soil and air are suitable for them. Plants that germinate early get a jump on the season, growing and thriving in the cool weather and ample moisture of early spring. As the weeks slide into the spring season, temperatures moderate and the sun intensifies, and you’ll notice the profound growth rate of these robust, young plants.

Three weeks later, it’s time for the second thinning. This may be even more painful than the first thinning because now you must pull out perfectly well-grown plants. My goal is to allow each self-sower the space to develop into a full-grown specimen. With this thinning I may remove seedlings I missed the first time around, or decide one plant or another needs additional space to reach its full potential. In the end, it’s better to help one plant thrive than leave three or four to struggle and compete for limited resources.

A good organic mulch helps self-sowers thrive

It’s common practice to apply mulch to beds in early spring as perennials are emerging. But in a garden filled with self-sowers, you’ll need to modify your mulching methods. Spreading mulch in early spring is likely to smother tiny, emerging seedlings. So, I wait until after my second thinning to put down mulch. This is also about the time I add frost-tender annuals to the garden.

Any organic mulch such as shredded leaves, compost, or finely ground bark will work. Your goal is not only to protect the garden from weeds and summer dry spells, but also to ensure a friable, porous soil surface upon which seeds will fall at the end of the season. That’s why it’s important to mulch with an organic material that will decompose over the course of the season. Never use heavy bark chips or black plastic in a garden of self-sowers.

I spread the mulch to a depth of 1 to 2 inches, erring on the thin side rather than spreading it too thick. It takes a bit more finesse to deliver mulch around all your seedlings, and a little more time as well. Rather than pouring mulch around plants by the bagful, or tossing it on beds by the shovelful, you’ll need to spread your mulch around self-sowers by the handful. It’s a slower process, but well worth the effort.

Remember that, once they’re established, what self-sowers do best is return on their own each year. They are likely to spring up in new places from season to season, with the help of birds, the wind, and the rain. This only adds to their charm, as plant combinations happen unintentionally rather than by our own plotting. Every time I pass through my crowded walkway, I marvel at the lavish growth and the bounty of blooms, all from a handful of seed.