What Flowers to Plant in March in the UK: A Comprehensive Guide

What Flowers to Plant in March in the UK: A Comprehensive Guide

March marks the transition from winter dormancy to early spring in the UK, bringing milder temperatures, longer days, and the first signs of new life in the garden. For many gardeners, it’s the perfect month to sow seeds, plant bulbs, and set out young plants that will flourish as the season warms. This comprehensive guide will help you choose what flowers to plant in March, explaining the varieties best suited to the UK climate, offering step-by-step planting tips, and covering key considerations for nurturing a vibrant, colorful garden all spring and summer long.

1. Introduction: Why March is an Ideal Month for Planting

In the UK, March typically signals the start of an upswing in temperature and daylight hours. While unpredictable weather—occasional frosts or chilly nights—can still be a concern, this month often offers the first realistic window to begin planting outside. Early to mid-spring planting confers several advantages:

Milder Frost Risk: Although late frosts remain possible, the harshest winter temperatures usually abate by March, reducing the likelihood of plant damage.
Extended Growing Season: Planting early gives annuals and perennials a head start, leading to stronger root systems and more robust blooms later in the season.
Improved Soil Conditions: Thawed and slightly warmer soil in March is generally more hospitable to germinating seeds and rooting transplants.

Whether you’re seeding hardy annuals directly into garden beds, transplanting young perennials, or tucking away bulbs for a summer display, March offers a chance to reinvigorate your outdoor space with fresh colour and foliage.

2. Assessing Your Garden Space and Soil

Before diving into specific flowers, take stock of your garden’s microclimates, soil type, and available sunlight:

Soil Type
- Clay: Rich in nutrients but can be dense, retaining water. Consider adding compost or grit for better drainage.
- Sandy: Drains quickly, often needing extra organic matter to retain moisture.
- Loam: A balanced mixture of clay, silt, and sand—ideal for many flowers.
- Chalky or Alkaline: May require ericaceous compost or soil amendments for acid-loving plants.
Sunlight and Shade
- Full Sun: Areas receiving 6+ hours of direct light are perfect for many annuals and sun-loving perennials.
- Partial Shade: Receive a few hours of direct sun or consistently dappled light—select plants labeled “part shade” or “partial sun.”
- Full Shade: Less common for annual flower beds, but certain bulbs and perennials adapt well to minimal sunlight.
Temperature and Microclimates
- Sheltered Spots: Walls or hedges can create warmer, protected areas. Early planting is often safer here.
- Frost Pockets: Low-lying areas may still be prone to cold snaps, so watch for the risk of frost damage.

A quick soil test (pH and nutrient content) combined with observation of light patterns helps guide your flower choices and fosters stronger, healthier growth.

3. Top Annual Flowers to Plant in March

Annuals complete their life cycle in one growing season, offering fast, often prolific blooms. The following hardy and half-hardy annuals can be started in March under the right conditions:

Sweet Peas (Lathyrus odoratus)
- Why Plant: Highly fragrant climbers with delicate, pastel-coloured blooms.
- How: Sow seeds indoors or in a greenhouse. Harden off seedlings before transplanting outdoors in April.
Cornflowers (Centaurea cyanus)
- Why Plant: Vibrant blue petals attract pollinators, making them cottage-garden favourites.
- How: Hardy enough for direct sowing once the soil warms, or start seedlings under cover.
Calendula (Pot Marigold)
- Why Plant: Easy-growing and cheery orange or yellow flowers; also beneficial for pollinator-friendly gardens.
- How: Sow seeds directly in well-draining soil or start in modules for transplanting.
Nigella (Love-in-a-Mist)
- Why Plant: Misty foliage with striking blooms in blues, pinks, or whites. Self-seeds freely.
- How: Direct sow seeds in a sunny spot; lightly rake in and water. Thin seedlings as they appear.
Pansies and Violas
- Why Plant: Cold-tolerant, offering bright splashes of colour early in spring.
- How: Often sold as plug plants ready to go outdoors in March; ensure soil is workable and not waterlogged.

4. Perennials and Biennials Worth Considering

Perennials return year after year, while biennials require two seasons to bloom. Planting them in March establishes their root systems in time for the growing season:

Lupins
- Trait: Eye-catching flower spikes in varied hues.
- Planting: Can be sown indoors in pots or transplanted from nursery-grown young plants. Require sunny, well-draining beds.
Delphiniums
- Trait: Tall spires of blue, purple, or white blooms—dramatic garden centrepieces.
- Planting: Sow indoors or set out established seedlings in a sunny spot with nutrient-rich soil.
Digitalis (Foxgloves)
- Trait: Towering tubular flowers adored by bees, typically biennial but often self-seeds to create perennial-like displays.
- Planting: Sow in modules or place young plants in partial shade with moist, well-draining soil.
Aquilegia (Columbine)
- Trait: Intricate blooms in various colours, perfect for cottage gardens.
- Planting: Sow seeds or place small plants in semi-shade; deadhead spent flowers to prevent excessive self-seeding.

5. Bulbs, Tubers, and Corms for Spring Planting

While many spring bulbs (like daffodils and tulips) are typically planted in autumn, a few bulbous plants prefer or tolerate early spring planting:

Lily Bulbs
- Timing: Plant in March for early-to-mid summer blooms.
- Method: Choose well-drained soil; bury bulbs three times their height. Water sparingly until growth appears.
Dahlia Tubers
- Timing: In milder areas, you can plant dahlias in pots or under cover this month. Transplant outdoors when frosts have passed.
- Method: Position tubers horizontally; cover with soil and water lightly. Pinch out tips for bushier growth.
Begonia Tubers
- Timing: Start indoors in March; transplant outside in late spring once frosts are unlikely.
- Method: Plant tubers shallowly in moist, well-aerated potting mix.
Gladiolus Corms
- Timing: From late March into April for mid-to-late summer flowering.
- Method: Plant corms approximately 10–15 cm deep in sunny spots, spacing well for airflow.

6. Seed Sowing Indoors vs. Direct Sowing

Indoors/Under Cover

Advantages: Offers control over temperature and humidity; seeds germinate faster, especially for half-hardy annuals.
Method: Use seed trays or modules in a greenhouse, cold frame, or on a bright windowsill. Keep compost moist but not waterlogged. Harden off before transferring outdoors.

Direct Sowing in Beds

Advantages: Less transplant shock; no need for additional indoor space.
Method: Prepare a fine tilth by raking the soil, then lightly press seeds in. Water gently and thin seedlings once they sprout to avoid overcrowding.

Choosing an Approach depends on the flower’s cold tolerance, your available indoor space, and the reliability of March weather in your specific UK region.

7. Essential Planting Tips and Techniques

Soil Preparation
- Organic Matter: Incorporate well-rotted compost or manure for improved drainage and fertility.
- Raking: Break up clods, remove stones, and level the surface before sowing or planting.
Depth and Spacing
- Seeds: Follow packet guidelines for recommended sowing depth; most small seeds need only light coverage.
- Transplants: Dig a hole slightly larger than the root ball, keeping the plant at the same soil level it had in its pot.
Water Management
- Initial Soak: Water newly planted seeds or transplants gently.
- Monitoring: March can be unpredictable; water thoroughly during dry spells but avoid soaking waterlogged soil.
Hardening Off
- Process: Gradually expose indoor-grown seedlings to outdoor conditions over 1–2 weeks to reduce transplant shock.

8. Aftercare: Feeding, Watering, and Pest Management

8.1. Fertilizing

When: Begin light feeding once seedlings or transplants show active growth.
Type: A balanced, slow-release general-purpose fertilizer often suits most flowers.

8.2. Mulching

Why: Retains soil moisture, suppresses weeds, and stabilizes soil temperature.
Materials: Compost, bark chips, or well-rotted manure. Keep mulch slightly away from plant stems to avoid rot.

8.3. Watering Schedule

Timing: Typically 1–2 waterings per week if rain is scarce. Adjust frequency based on local conditions.
Method: Soaker hoses or watering at the base minimize leaf wetness, reducing fungal risks.

8.4. Pest and Disease Control

Prevention: Healthy, well-spaced plants are less susceptible to problems.
Observation: Check leaves and stems for aphids, slugs, snails, or fungal spots. Prompt action—like organic slug pellets or insecticidal soap—prevents widespread damage.

9. Conclusion

March is a dynamic month for UK gardeners—winter’s chill recedes, and the promise of new life beckons. By carefully selecting hardy annuals, early perennials, and late-season bulbs suited to your garden’s light and soil conditions, you can enjoy a garden brimming with blossoms well into summer. Sowing seeds indoors or directly in prepared beds, maintaining healthy soil, and keeping a keen eye on watering and pests are all pivotal to success. With these detailed tips in mind, you’ll be able to greet the warmer days ahead with a vibrant and flower-filled outdoor space—one that’s a testament to the power and joy of spring planting.

10. Top 10 Questions and Answers

Q: Is it too early to plant flowers outdoors in March in the UK?
A: Generally, hardy annuals and certain perennials tolerate cool conditions. However, always check local frost dates; consider sowing half-hardy annuals under cover first.
Q: What’s the difference between hardy and half-hardy annuals?
A: Hardy annuals can withstand cooler temperatures and light frosts, while half-hardy annuals need warmer conditions and often require indoor sowing until frosts pass.
Q: Can I plant my summer bulbs like lilies directly in the ground in March?
A: Yes, if the soil is workable and frost risk is minimal. In colder regions, start bulbs in pots indoors or in a greenhouse to protect them initially.
Q: Do I need to fertilize newly planted flowers right away?
A: Typically, a lightly fertilized seed starting mix suffices at sowing. Begin more robust feeding once seedlings or transplants establish roots and show active growth.
Q: How do I protect early-sown seedlings from unexpected frosts?
A: Use cloches, fleece, or row covers to insulate tender plants. Harden them off gradually if started indoors.
Q: Is direct sowing or indoor seed starting better?
A: Indoor sowing gives more control over germination conditions. Direct sowing is simpler but riskier in case of cold snaps. A mix of both methods can be optimal.
Q: How do I ensure my flowers don’t become leggy when grown indoors?
A: Provide ample light—ideally a sunny windowsill or a grow light. Keep temperatures moderate and avoid overwatering.
Q: Which plants are best for shady UK gardens in early spring?
A: Try shade-tolerant options like foxgloves, aquilegias, and certain varieties of pansies or violas.
Q: How soon should I mulch after planting?
A: Once transplants or seedlings are in place and well-watered, mulching can be done immediately to lock in moisture and discourage weeds.
Q: Should I pinch out seedlings to encourage bushier growth?
A: Yes, for certain annuals like sweet peas, pinching out the top can lead to branching and more blooms. Follow the plant’s care instructions for best results.

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