March Flower Planting Tips: The Best Blooms to Grow in the UK

March Flower Planting Tips: The Best Blooms to Grow in the UK

As winter loosens its grip and days start to lengthen, March marks a pivotal moment for UK gardeners to breathe new life into their outdoor spaces. The soil begins to thaw, daylight hours extend, and many flower varieties are primed to take advantage of these conditions. Whether you’re eager for an early pop of colour from hardy annuals or aiming for summer splendour with bulbs and tubers, March provides a strategic window for planting. This guide delves into the best blooms to grow in early spring and offers practical tips to help each seed, bulb, or cutting thrive in the UK’s often unpredictable early-season weather.

1. Introduction: Why March is Ideal for Planting

The arrival of March often comes with moderate temperatures and more reliable daylight—two vital factors for germinating seeds and establishing young plants. Although sudden cold snaps remain a possibility in the UK, many hardy flower species handle occasional frosts well, and half-hardy varieties can gain an early start under protection. By harnessing spring’s energy, you can secure a strong root system and vigorous growth before late spring and summer’s peak demands. The result? A garden bursting with blooms across the warmer months and a head start on your seasonal planting goals.

2. Check Your Garden: Soil, Light, and Frost Risk

Before deciding on what flowers to plant, analyse each corner of your garden to ensure optimal conditions:

Soil Characteristics
- Clay: Rich but prone to waterlogging. Improve drainage with grit or compost.
- Sandy: Drains well, warms quickly, but may need added organic matter to hold moisture and nutrients.
- Loamy: The ideal mix, balancing fertility and drainage for most flower varieties.
Sunlight Exposure
- Full Sun (6+ hrs): Perfect for many spring annuals, bulbs, and sun-loving perennials.
- Partial Shade (2–4 hrs): Suits woodland or shade-tolerant perennials and certain annuals.
- Full Shade: More limited, but select species thrive in low-light environments.
Frost Pockets
- Identifying: Look for dips in the landscape or poorly drained spots that remain cooler overnight.
- Protective Measures: Cloches, fleece, or cold frames can shield tender seedlings and half-hardy flowers from late frosts.

3. Hardy Annuals: Early Spring Colour

3.1. Calendula (Pot Marigold)

Why Grow: Simple to cultivate, providing bright orange and yellow blooms that persist through spring and summer.
Sowing Tip: Direct sow in prepared beds. Lightly rake seeds in and keep soil moist until germination.

3.2. Cornflowers (Centaurea cyanus)

Why Grow: Iconic cottage-garden favourites with vivid blue petals; pollinator-friendly.
Sowing Tip: Sow outdoors in well-draining soil. Thin seedlings to allow proper spacing.

3.3. Sweet Peas (Lathyrus odoratus)

Why Grow: Delightful fragrance, climbing habit, and long-lasting cut flowers.
Sowing Tip: Germinate seeds in root trainers or small pots indoors. Harden off before planting in sunny beds with support.

3.4. Nigella (Love-in-a-Mist)

Why Grow: Airy foliage topped with delicate blooms in soft blues, pinks, or whites.
Sowing Tip: Best sown direct; lightly scatter seeds in open borders and gently cover with fine soil.

4. Perennials and Biennials for March Planting

4.1. Lupins

Trait: Tall, spiky flower clusters that add vertical interest.
Planting: Start seeds indoors or opt for nursery plugs. Prefers full sun and fertile, well-drained soil.

4.2. Delphiniums

Trait: Towering flower spikes in blues, pinks, or whites; a show-stopper in borders.
Planting: Sow in modules indoors or transplant established seedlings. Stake mature plants to prevent wind damage.

4.3. Foxgloves (Digitalis)

Trait: Bee-friendly tubular blooms, commonly a biennial but often self-seeds.
Planting: Scatter seeds under partial shade or transplant seedlings. Keep consistently moist soil for best results.

4.4. Aquilegia (Columbine)

Trait: Nodding, intricate flowers in various hues; self-seeds to form natural drifts.
Planting: Sow seeds directly or place young plants in moderate shade, watering well until established.

5. Bulbs and Tubers: Laying Groundwork for Summer Blooms

5.1. Dahlia Tubers

Timing: Pot up indoors in March if frosts linger. Transition outdoors once conditions warm.
Placement: Choose a sunny spot with well-draining soil. Pinch out main shoots for bushier growth.

5.2. Lily Bulbs

Timing: Plant in March for summer flowering.
Tip: Ensure adequate drainage; some lilies thrive in partial shade, but most prefer plenty of sun.

5.3. Begonia Tubers

Timing: Ideal for starting indoors or in a greenhouse, then transferring to beds or containers.
Note: Prefers partial shade, keeping soil consistently but not excessively moist.

5.4. Gladiolus Corms

Timing: Plant in batches from March onward for staggered summer blooms.
Depth: Bury at least 10–15 cm, positioning in sunny, sheltered beds. Consider staking tall varieties.

6. Sowing Strategies: Indoors vs. Direct Outdoors

Indoors/Under Cover

Advantages: Germination is easier to control in heated propagators or on sunny windowsills. Half-hardy species gain an early edge.
Disadvantages: Extra step of hardening off before final planting; limited indoor space.

Direct Sowing

Advantages: Fewer transplant shocks, simpler overall approach.
Disadvantages: Germination can stall if temperatures dip; must monitor moisture and weeds diligently.

For a balanced approach, sow hardy types like calendula or cornflowers directly, while using indoor setups for more tender, half-hardy species (e.g., certain marigolds, cosmos, or zinnias).

7. Essential Planting and Care Techniques

Soil Preparation
- Add Organic Matter: Mix compost or manure to improve drainage and fertility.
- Rake Level: Remove stones or debris for even seed placement and germination.
Watering Routine
- Initial Soak: Water thoroughly right after sowing or transplanting.
- Frequency: Keep the topsoil moist, particularly when seeds are germinating. Avoid waterlogging.
Fertilising
- Light Feeding: Many seed-starting mixes have baseline nutrients. Introduce balanced fertiliser once plants show stable growth.
- Mulching: Conserves moisture, moderates soil temperature, and reduces weeds.
Pest Management
- Watch for Slugs and Snails: Common in damp spring weather; use organic controls or physical barriers.
- Aphids: Spot-treat with soapy water or insecticidal solutions as needed.
Hardening Off
- Process: Gradually expose indoor-grown seedlings to outdoor conditions, increasing their resilience.
- Timeline: Usually 1–2 weeks, placing seedlings outside for progressively longer periods each day.
Support for Taller Blooms
- Stakes or Cages: Prevent top-heavy plants (delphiniums, lupins, sweet peas) from flopping in wind or rain.

8. Conclusion

March heralds a key turning point in the UK gardening calendar—daylight is on the rise, the ground is softening, and many flower species are primed to flourish in cool-to-mild conditions. Whether you opt for hardy annuals direct sown into garden beds, half-hardy plants begun indoors, or summer bulbs tucked away for later splendour, this month’s efforts will repay you with weeks (and even months) of dazzling colour and fragrant blooms. Attend to soil health, practice mindful watering, and remain vigilant against pests, and your early-spring ventures will transform your garden into a celebration of seasonal vitality.

9. Top 10 Questions and Answers

Q: Can I plant annuals outdoors in March if I live in a colder UK region?
A: Yes, for hardy species like cornflowers or nigella. For half-hardy plants, start indoors or protect with cloches until frosts subside.
Q: How do I know if my soil is warm enough for direct sowing?
A: A soil thermometer is handy—aim for at least 7–10°C. Alternatively, wait until the soil no longer feels icy or wet to the touch.
Q: When should I begin fertilising newly sown seeds?
A: Many seeds have enough nutrients in the seed-starting mix. Start a gentle feeding regime once seedlings form true leaves and steady growth.
Q: Do dahlia tubers require staking?
A: Often, yes. Tall dahlia varieties benefit from support to prevent stems from breaking under their heavy blooms.
Q: Are lilies suitable for containers?
A: Absolutely—use a free-draining potting mix and ensure containers have enough depth. Position them where they get adequate sun.
Q: Which short perennials can I plant for immediate spring colour?
A: Pansies, violas, and some primulas offer quick bursts of colour. Many are available as ready-to-plant blooms.
Q: Can I use leftover compost from last year for seed starting?
A: If it’s free of pests or diseases, rejuvenate it with fresh compost or a slow-release fertiliser. Sterilisation can help if contamination is suspected.
Q: How often should I water newly planted bulbs in March?
A: Water lightly but regularly, ensuring soil is moist but never soggy. Adjust during prolonged dry spells or heavy rains.
Q: Is deadheading necessary for spring annuals planted in March?
A: Yes. Removing spent blossoms on species like calendula or pansies encourages more prolific blooms.
Q: Will a late cold snap destroy all progress?
A: Hardy plants withstand mild frosts, but half-hardy ones need protection (fleece or temporary relocation indoors) until temperatures stabilise.

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