As the vernal equinox approaches, the gardening calendar enters one of its most critical windows. March serves as the strategic bridge between seasons, offering a final opportunity to establish spring-flowering varieties while initiating the growth cycle for a vibrant summer display. For enthusiasts aiming for a high-impact garden, the work beginning this month dictates the success of the landscape through the first frost of autumn.
Understanding the Seasonal Shift
In professional horticulture, “spring bulbs” fall into two distinct categories. Traditional spring bloomers, such as tulips and daffodils, are typically dormant bulbs planted in autumn. However, if that window was missed, gardeners can still achieve immediate results by purchasing plants “in the green.” These are actively growing specimens—specifically snowdrops and bluebells—that are transplanted while in leaf, often yielding better establishment than their dormant counterparts.
Conversely, March is the primary planting season for summer-flowering bulbs, including architectural dahlias, towering gladioli, and tropical cannas. While some varieties can be tucked directly into the earth, others benefit from “starting” indoors to extend their flowering window.
Direct Planting for Outdoor Impact
For those planting directly into borders, several hardy and semi-hardy varieties are ready for the soil as it begins to warm.
- Dahlias: These versatile tubers should be planted 10–15 cm deep and spaced 60–90 cm apart to accommodate their mature size. In cooler climates, it is prudent to wait until late April or keep horticultural fleece nearby to shield emerging shoots from late-season frost.
- Gladioli: To ensure a continuous supply of vertical blooms for cutting, plant corms in two-week intervals from now through May. They require a depth of 10 cm and thrive in well-drained soil to prevent corm rot.
- Crocosmia and Eucomis: For exotic flair, the Pineapple Lily (Eucomis) and the fiery Crocosmia ‘Lucifer’ offer architectural interest. Crocosmia is particularly valued for its ability to naturalize and attract pollinators like bees and hummingbirds.
Maximizing the Season with Indoor Starts
Starting tender bulbs indoors during March provides a significant head start, especially for varieties that demand warmth.
Tuberous begonias should be placed hollow-side up in moist compost at temperatures between 18–21°C. Cannas, which bring a lush, tropical aesthetic to the garden, benefit from a 24-hour warm water soak before being potted up. Dahlias can also be “waked up” in a frost-free greenhouse or on a sunny windowsill; simply place the tubers in pots with the old stem (the crown) just above the soil line and water sparingly until green growth appears.
Best Practices for Healthy Blooms
Success in bulb gardening relies heavily on soil preparation and ongoing maintenance. Professional growers emphasize the “rule of three”: plant bulbs at a depth roughly two to three times their diameter. This provides structural stability and protection against temperature fluctuations.
Drainage is non-negotiable; if gardening on heavy clay, incorporate grit or organic matter to prevent waterlogging. Once growth is established, transition to a high-potassium liquid feed, such as tomato fertilizer, every two weeks. This shifts the plant’s energy from leaf production to flower development.
Vigilance Against Spring Pests
The primary threat to new growth involves slugs and snails, which can decimated emerging shoots overnight. Utilizing biological controls like nematodes or physical barriers such as copper rings is recommended. Additionally, those growing in containers should monitor for vine weevil grubs, which target the root systems of begonias and dahlias from beneath the soil surface.
By taking advantage of the March planting window, gardeners ensure a seamless transition from the delicate hues of spring to the bold, architectural brilliance of a high-summer landscape.