LONDON — As March brings the first consistent signs of spring, gardeners are entering a critical window for floral success. While many associate the season with emerging tulips and daffodils, the current weeks represent the prime period for planting summer-flowering bulbs. Horticulture experts emphasize that the actions taken now—from starting tender tubers indoors to preparing outdoor beds—will dictate the vibrancy and longevity of garden displays from midsummer through the first frosts of autumn.
Navigating the “Two Springs” of Bulb Planting
Understanding the distinction between spring-flowering and summer-flowering bulbs is essential for seasonal timing. Spring-flowering varieties, such as alliums and crocuses, are typically established in the autumn. However, those who missed the autumn window can still find “in the green” plants at nurseries—actively growing specimens, such as snowdrops and bluebells, that can be transplanted immediately.
The current priority, however, is the summer-flowering category. This group includes garden staples like dahlias, gladioli, and begonias. These varieties require the warming soil of March and April to establish the root systems necessary for their dramatic warm-weather displays.
Establishing the “Big Three”: Dahlias, Gladioli, and Cannas
Dahlias remain the centerpiece of the summer border. In milder regions, tubers can be transitioned directly into well-drained, rich soil at a depth of 10–15 cm. Expert growers recommend installing support stakes simultaneously with planting to avoid piercing the tubers later. For those in colder climates, starting dahlias in pots indoors at approximately 15°C ensures a head start against a shorter growing season.
Gladioli offer architectural height and are prized for floral arrangements. To avoid a “one-and-done” bloom cycle, gardeners should practice succession planting—tucking corms into the soil every two weeks from March through May. This technique guarantees a continuous supply of fresh spikes throughout the summer.
Cannas provide a tropical aesthetic with bold, paddle-shaped foliage. These heat-loving plants should be started indoors now. A professional tip for success involves soaking the rhizomes in warm water for 24 hours prior to potting to break dormancy and accelerate the sprouting process.
Strategic Solutions for Shade and Texture
For gardeners dealing with limited sunlight, Tuberous Begonias are the ideal solution. These should be started indoors by pressing the tubers, hollow-side up, into moist compost. Once the threat of frost has passed in late May, they can be moved to hanging baskets or shaded corners.
For exotic flair, the Eucomis, or Pineapple Lily, is an underutilized gem that performs well in sunny, sheltered spots. Meanwhile, Crocosmia—specifically the vibrant ‘Lucifer’ variety—is a hardy choice that multiplies quickly, providing excellent value and attracting pollinators like bees and hummingbirds.
Essential Maintenance and Protection
To ensure optimal growth, gardeners should adhere to a few professional standards:
- Drainage is Paramount: Bulbs are prone to rot in waterlogged conditions. Heavy clay soils should be amended with grit and organic matter, or diverted into raised beds and containers.
- The Depth Rule: Most bulbs should be planted at a depth roughly two to three times their own diameter to protect against late-season temperature fluctuations.
- Nutritional Support: Once green shoots are established, apply a high-potassium liquid feed (such as tomato fertiliser) every fortnight to prioritise flower production over foliage.
- Pest Vigilance: Emerging shoots are highly vulnerable to slugs and snails. Utilizing biological controls like nematodes or physical barriers such as copper rings can prevent significant damage during the early growth stages.
As the garden transitions through April and May, the focus will shift from planting to hardening off indoor starts. By planning a phased approach now, enthusiasts can ensure a resilient, high-impact landscape that thrives long after the spring blooms have faded.