As the vernal equinox approaches, the horticultural world turns its attention to the foundational work that defines a vibrant summer landscape. March serves as a critical bridge in the gardening calendar, offering a final opportunity to secure spring color while initiating the growth cycle for summer’s most dramatic floral displays. Whether working in the open soil or utilizing a protected greenhouse, gardeners can now take specific steps to ensure a continuous bloom from July through the first frosts of autumn.
Navigating the “Spring” Bulb Distinction
Confusion often arises regarding the term “spring bulbs.” Traditionally, spring-flowering varieties like tulips and daffodils are installed during the autumn. However, for those who missed the October window, garden centers currently offer “in the green” bulbs—plants sold while actively growing. These are particularly effective for establishing snowdrops and bluebells, as they transplant with higher success rates than dormant bulbs.
Conversely, the current month marks the primary planting window for summer-flowering bulbs, including dahlias, gladioli, and lilies. These heat-loving species require the warming soil of March and April to establish the robust root systems necessary for their mid-year peak.
Outdoor Essentials: Dahlias, Gladioli, and Exotic Varieties
For gardeners in milder climates, Dahlias can be transitioned into the ground starting in mid-March. To ensure success, plant tubers 10–15 cm deep in nutrient-rich, well-drained soil. Because these plants can reach significant heights, experts recommend placing support stakes at the time of planting to avoid piercing the tubers later in the season.
Gladioli offer a structured, architectural elegance to borders. To extend the flowering season, practitioners should employ “succession planting”—placing corms every two weeks from now until May. This technique prevents a singular, short-lived bloom and ensures a steady supply of cut flowers throughout the summer.
For those seeking a unique aesthetic, the Eucomis (Pineapple Lily) and Crocosmia are becoming increasingly popular. The Eucomis thrives in sunny, sheltered spots, producing exotic spikes by late summer, while Crocosmia varieties like ‘Lucifer’ provide fiery displays that act as magnets for pollinators.
The Indoor Advantage: Starting Early for Better Blooms
In cooler regions, starting tender bulbs indoors is a strategic move to bypass the risk of late frosts. Begonias and Cannas benefit significantly from this head start.
- Tuberous Begonias: These should be placed hollow-side up in moist compost at temperatures between 18–21°C. They are the ideal solution for North-facing gardens or shaded balconies.
- Cannas: These tropical giants require a 24-hour soak in warm water to break dormancy before being potted and kept at a minimum of 18°C.
- Dahlias: Starting these in pots on a windowsill or in a frost-free greenhouse in March results in much earlier flowering once they are hardened off and moved outside in May.
Best Practices for Healthy Growth
Success with summer bulbs relies on three pillars: drainage, depth, and defense. Most bulbs will rot in waterlogged earth; heavy clay soil must be amended with grit or organic compost to improve aeration. As a general rule, bulbs should be planted at a depth of two to three times their own diameter.
Once green shoots appear, the plants become “heavy feeders.” High-potassium fertilizers, such as tomato feed, should be applied fortnightly to prioritize flower production over leaf growth. Gardeners must also remain vigilant against pests. Slugs and snails are particularly fond of tender new shoots, while vine weevils can threaten container-grown begonias. Utilizing biological controls like nematodes in early spring can provide a proactive shield against these underground threats.
By acting now, gardeners can transition from the quiet of winter into a season of architectural heights and saturated colors, ensuring the landscape remains a blooming sanctuary well into the cooler days of October.