As the ground thaws and the days lengthen, March has arrived as a critical window for gardeners aiming to secure a vibrant summer display. While many associate “spring bulbs” with autumn-planted favorites like tulips and daffodils, horticultural experts emphasize that now is the primary season for planting summer-flowering varieties.
By strategically selecting tubers, corms, and rhizomes this month, enthusiasts can ensure a continuous succession of color from mid-summer until the first frost of autumn. This guide explores the essential techniques for outdoor planting, starting tender varieties under glass, and salvaging the season with “in the green” alternatives.
The Spring Planting Portfolio
The current gardening window focuses on heat-loving species that thrive once the mercury rises. Key varieties to prioritize for outdoor beds include:
- Dahlias: These versatile tubers can be placed directly in the soil in milder regions starting in mid-March. To ensure success, plant them 10–15 cm deep in nutrient-rich, well-draining soil. Because they are heavy feeders that can reach significant heights, experts recommend installing stakes at the time of planting and enriching the soil with organic compost.
- Gladioli: Ideal for architectural height and floral arrangements, these corms should be planted 10 cm deep. To avoid a “one-and-done” bloom cycle, gardeners should plant batches every two weeks through May to stagger the flowering period.
- Crocosmia and Eucomis: For those seeking exotic flair, Crocosmia offers fiery hues that attract pollinators, while the Eucomis (Pineapple Lily) provides a unique tropical aesthetic. Both prefer full sun and high-drainage environments.
Maximizing the Season with Indoor Starting
In colder climates, or for varieties with particularly long growing requirements, starting bulbs indoors is a professional secret for an extended flowering season. Tuberous Begonias and Cannas benefit significantly from a warm start in a greenhouse or on a bright windowsill.
Tuberous begonias should be placed hollow-side up in moist compost, while Canna rhizomes thrive after a 24-hour soak in warm water to break dormancy. Once these indoor starts have developed robust root systems and the threat of frost has passed in late May, they can be hardened off and moved to their permanent outdoor positions.
The “In the Green” Loophole
For those who missed the autumn deadline for spring-flowering bulbs, garden centers currently offer “in the green” options. Unlike dormant bulbs, these are plants lifted while actively growing or just after flowering. This is the gold standard for establishing snowdrops and bluebells, as they transplant with a much higher success rate than their dry counterparts.
Professional Maintenance and Protection
Success in the summer garden relies on more than just planting depth—which should generally be two to three times the bulb’s diameter. Drainage remains the most significant factor in bulb health; heavy clay soils should be amended with grit to prevent rot.
As growth emerges, a high-potassium liquid feed, such as tomato fertilizer, should be applied every fortnight to prioritize bloom production over foliage. Gardeners must also remain vigilant against late-season frosts, keeping horticultural fleece ready to shield tender new shoots. By managing pests like slugs and vine weevils early in the season, you can ensure your March efforts result in a spectacular, healthy landscape come July.