As the vernal equinox approaches, seasoned gardeners recognize March as a pivotal transition point in the horticultural calendar. While the ground begins to thaw, the window for spring-flowering bulbs closes just as the opportunity for summer-flowering varieties opens. This month serves as the critical bridge for establishing a garden that will remain in peak condition from midsummer through the first frosts of autumn.
The Duel of the Seasons: Knowing Your Bulbs
In professional gardening circles, “spring bulbs” is an umbrella term that can lead to confusion. Historically, spring-flowering varieties like tulips and daffodils were planted in the autumn. However, missing that window doesn’t preclude a vibrant spring display; garden centers are currently stocked with “in the green” bulbs—plants already in active growth—which can be transplanted immediately.
The primary focus for March, however, is the summer-flowering category. This group includes architectural favorites such as dahlias, gladioli, and lilies. These bulbs, tubers, and corms are planted now to ensure they have the necessary lead time to develop robust root systems before the heat of July.
High-Impact Varieties to Plant Outdoors
For many UK and temperate-climate gardeners, the dahlia remains the crown jewel of the summer border. In milder regions, these tubers can be sited directly in the ground from mid-March at a depth of 10–15 cm. Because varieties like the apricot-hued ‘David Howard’ or the dark-foliaged ‘Bishop of Llandaff’ can reach significant heights, experts recommend placing support stakes at the time of planting to avoid piercing the tubers later.
Gladioli offer a different strategic advantage: verticality. To avoid a “one-and-done” blooming period, professional growers suggest successional planting. By putting corm batches in the ground every two weeks from March through May, gardeners can enjoy the architectural spikes of varieties like ‘Plum Tart’ for several months rather than just a few weeks.
For those seeking exotic flair, Eucomis (the Pineapple Lily) and Crocosmia are essential. Crocosmia ‘Lucifer’ is particularly valued for its ability to attract pollinators with fiery red blooms. These species are generally hardy, though they prefer well-drained soil to prevent winter rot.
Giving Tender Varieties an Indoor Head Start
Certain summer staples, such as begonias and cannas, are highly sensitive to frost. To maximize their flowering window, start them in a controlled environment this month.
- Begonias: These are perfect for shaded corners. Place tubers hollow-side up in moist compost at roughly 20°C. Once roots establish and shoots emerge, they can be potted on.
- Cannas: Known for their tropical foliage, canna rhizomes benefit from a 24-hour warm water soak before being potted and kept in a frost-free greenhouse or windowsill.
- Dahlias: Starting these indoors in trays of moist compost allows for earlier blooms and provides protection from early-season slugs.
Professional Maintenance and Protection
Success in the summer garden is often determined by the quality of the soil and early-season vigilance. Most summer bulbs are “heavy feeders.” Once growth is established, a high-potassium liquid feed—such as tomato fertilizer—should be applied fortnightly to prioritize flower production over foliage.
Furthermore, drainage is non-negotiable. If working with heavy clay, professionals recommend amending the soil with grit and organic matter. Because young shoots are highly vulnerable to slugs and late-season “snaps,” keeping horticultural fleece and organic pest controls like nematodes on hand is vital during the unpredictable weeks of April and May.
By taking these steps in March, gardeners move beyond reactive planting and toward a proactive, professional-grade landscape that ensures a lush, color-rich environment for the second half of the year.