As the vernal equinox approaches, the gardening calendar enters its most critical window. March serves as the ultimate bridge between seasons, offering a final opportunity to secure spring color while laying the groundwork for a lush summer display. For enthusiasts looking to transform their outdoor spaces, the current weeks are vital for both dormant tuber preparation and “in the green” transplanting.
Professional horticulturists categorize spring bulb activities into two distinct tracks: salvaging the spring bloom and initiating the summer cycle. While traditional spring-flowering bulbs like tulips are typically settled in autumn, those who missed the window can still find success by purchasing plants “in the green.” These are actively growing specimens, such as snowdrops and bluebells, lifted while in leaf. Experts prefer this method for establishing woodland colonies, as they transplant with far higher success rates than dry bulbs.
The Foundation of a Summer Display
The primary focus for March, however, is the summer-flowering category. This includes architectural heavyweights such as dahlias, gladioli, and lilies. These varieties require a warm start to ensure they reach their full potential by July.
Dahlias and Gladioli
Dahlias remain the centerpiece of the summer border, though they require strategic handling. In milder regions, tubers can be transitioned directly into rich, well-drained soil at a depth of 10–15 cm. However, in cooler climates, starting them in pots indoors is recommended to avoid late frosts. To ensure a continuous harvest of cut flowers, gardeners should plant gladioli corms in two-week intervals from now through May. This “succession planting” prevents a single, short-lived bloom window and provides color well into autumn.
Exotic Additions
For those seeking visual impact, the Eucomis (Pineapple Lily) and Canna offer tropical aesthetics. While Eucomis is surprisingly hardy once established in a sunny, south-facing spot, Cannas require a head start indoors. Soaking Canna rhizomes for 24 hours before potting them in a warm environment (18°C+) is a proven professional technique to break dormancy early.
Professional Indoor Starting Techniques
Starting tender bulbs indoors in March significantly extends the flowering season. For tuberous begonias—the gold standard for shaded balconies—tubers should be placed hollow-side up in moist compost. Maintaining a temperature between 18°C and 21°C is essential for root development.
When moving any indoor-started plant to the garden, “hardening off” is a non-negotiable step. Gradually acclimatizing young shoots to outdoor temperatures over a week prevents transplant shock and foliage scorch.
Maintenance and Protection
Success in the summer garden is often determined by the quality of the soil and the vigor of the feeding regimen. Horticulturalists recommend the following “best practices” for spring planting:
- Drainage and Depth: Always plant bulbs at a depth of two to three times their diameter. If working with heavy clay, incorporate grit and organic matter to prevent bulb rot.
- Nutritional Support: Once green growth is established, switch to a high-potassium liquid feed, such as tomato fertilizer, every fortnight. This prioritizes flower production over leafy growth.
- Pest Management: Emerging shoots are highly vulnerable to slugs and snails. Utilizing biological controls like nematodes or physical copper barriers in early spring can save a season’s work from overnight destruction.
By acting now to balance indoor propagation with outdoor bulb placement, gardeners ensure a seamless transition from the delicate whites of spring snowdrops to the fiery reds of late-summer Crocosmia. The work done in the cool damp of March is the direct architect of the vibrant, sun-drenched garden to come.