If a garden is to function as a pollinator preserve, there should be different plants coming into bloom throughout the season. In most temperate climates, there is a natural bloom gap in late spring, after the trees, bulbs and bushes have finished but before summer flowers come on the scene. Cold-hardy flowers to the rescue! When started from seed in early autumn, cold-hardy annuals and biennials including wallflowers, dianthus, larkspur, and forget-me-not will sail through winter with minimal protection, and burst into bloom in late spring, when they are most needed.
With the exception of larkspur, which requires direct seeding, these and other cold-hardy flowers can be sown in a nursery bed that can be equipped with a cover for extra winter protection. In early spring, when the little seedlings show new growth, lift them from below, taking care to keep the root ball intact, and move them to where you want bright color in late spring.
Dianthus are sometimes called pinks because the edges of the petals appear to have been trimmed with pinking shears. Fragrant strains developed by backyard breeders over a century ago are well worth seeking out, for example potently perfumed ‘Fringed Rainbow Loveliness’ and other vintage varieties offered by Select Seeds. For best results with these small plants, keep them in the pots sunk up to their rims in a nursery bed through winter, and move them to the vicinity of lavender when they show strong growth in spring. Or, bring them into bloom in containers stationed at nose level.
A much bigger, more robust dianthus, sweet William (Dianthus barbatus) is great fun to grow, and will reseed itself when given the chance. Sweet William’s stiff stems make it a great cut flower, and colors include bright red, whites, pinks, purples and bicolors.
Once a mainstay in English cottage gardens, wallflowers (long classified as Cheiranthus, now Erysimum) are traditional partners for tulips, or you can plant them with blue forget-me-nots. Fragrant and floriferous, wallflowers ask only for neutral to alkaline soil in full sun to part shade. The popular English wallflower (E. cheiri) is native to Greece, and it is not as cold tolerant as Siberian wallflower (often identified as E. allioni), which is actually an inter-species hybrid created in 1846. Yellow and orange are the strongest bloom colors in all wallflowers, as you might expect from a distant cabbage cousin. One precaution: Erysimums are poisonous if eaten in large quantities, so site them accordingly. When grown in hospitable sites, wallflowers are enthusiastic reseeders.
You hardly ever see larkspur (Consolida ajacis) seedlings offered for sale, because the plants grow best when they are never moved. Instead, plant larkspur where you want it to grow and bloom. Scatter larkspur seeds over prepared soil 6 weeks or so before your first fall frost, so they can germinate in comfortably cool soil. Larkspur germination can be further improved by chilling seeds in the freezer for a week before sowing them.
Even when chilled, larkspur seeds take three weeks or more to germinate. To keep the seeded bed from drying out, cover it with a double thickness of row cover (garden fleece) spread over the seeded soil. A few weeks after they sprout, larkspur seedlings develop deeply lobed leaves that make them easy to distinguish from weeds. Larkspur is poisonous to people and livestock, so the plants are seldom bothered by browsing animals.
Don’t Forget Forget-Me-Nots
Little pollinators love cool blue forget-me-nots, which bloom for weeks in late spring from plants started in the fall. Common forget-me-not (Myosotis sylvatica) is a sure winner when allowed to mingle with late-blooming bulbs, or you can make the blue pop by pairing forget-me-nots with bold orange wallflowers. For rock gardens or walls, look for the more petite alpine forget-me-not (M. alpestris), which is Alaska’s state flower. Water forget-me-not (M. scorpoides) is at home in a moist woodland garden or along the edge of a half-shaded water garden.
Like their borage cousins, forget-me-nots have noticeably hairy leaves that set them apart from winter weeds and make them unpalatable to most critters. Common forget-me-nots are willing reseeders which deserve watching cool temperate climates (like the Upper Midwest region of the USA), where it can quickly go weedy. Elsewhere, every found forget-me-not is a treasure, worthy of replanting or sharing with a friend.