Plant now, marvel later: These summer bulbs must be planted in March.

If you want to be standing in front of knee-high blooms, packed window boxes and beds glowing with colour in June, March comes with one clear job. Gardening broadcaster Alan Titchmarsh and plant specialist Sarah Raven agree on the timing: summer-flowering bulbs and tubers need to go into the ground now-leave it too late and the main performance simply won’t happen.

Why March matters so much for summer-flowering bulbs and tubers

March sits in the sweet spot of the gardening calendar. Daylight noticeably increases, the soil begins to warm and thaw, and the sun regains strength-exactly the conditions bulbs and tubers rely on to start rooting promptly.

Planting at this point gives them a head start of several months. During that window they can build a strong root system before high summer turns hot and dry. The payoff is clear: sturdier stems, bigger flowers and a longer flowering season.

One unhurried hour in March can translate into weeks of colour through June, July and August.

Many gardeners reach for the lawnmower or hoe first once spring arrives. Titchmarsh suggests flipping that instinct: set the foundations for colour first-meaning get bulbs and tubers planted-then tackle everything else.

Summer bulbs and tubers to plant now

Summer-flowering bulbs and tubers come in every size and style, from bold dahlias to delicate freesias. The right choices depend on whether you’re filling borders, dressing a patio, or making the most of a balcony.

A simple design tip from the experts: avoid dotting single bulbs around. Plant in small clusters of four to six of the same variety to create “islands” of colour that read well even from a distance.

For tall, dramatic borders and “wow” beds

If you want height and impact in your flowerbeds, these are the standout choices for March planting:

• Lilies: elegant, often scented flowers, typically 60–150 cm tall depending on the variety.
• Gladioli: upright flower spikes that are excellent for cutting and arranging in vases.
• Freesias: refined blooms with a strong perfume, ideal towards the front of a border or in pots.
• Crocosmia: fiery reds and oranges that add movement and energy to a planting scheme.
• Dahlias: from pompon to cactus forms-the classic choice for bold late-summer colour.
• Allium (ornamental onion): spherical flower heads that appear to hover above perennial planting.
• Bearded iris: striking individual blooms, particularly well suited to sunny, dry positions.

For balconies, patios and small gardens

Even with limited space, you can create a surprisingly lush display using pots, troughs and hanging baskets. Titchmarsh is especially enthusiastic about:

• Begonias: long-flowering and happy in partial shade, making them ideal for pots and window boxes.
• Petunias: cascading, flower-heavy plants that quickly fill hanging baskets and balcony containers.
• Verbenas: form dense carpets of blossom and thrive in sunny containers.
• Rudbeckias (coneflower types): tough, reliable bloomers in warm yellows and oranges.

Many of these combine beautifully in one container: taller plants in the centre, trailing varieties around the edge. Done well, you get a “cushioned” look that stays attractive right into autumn.

Planting correctly: depth, spacing and the right position

A useful rule of thumb for bulbs is to plant them at a depth around two to three times their own height. Larger dahlia tubers tend to sit a little shallower, while allium bulbs are often planted a touch deeper.

Plant	Planting depth	Spacing	Position
Lilies	10–15 cm	20–30 cm	Sun to partial shade
Gladioli	8–10 cm	10–15 cm	Full sun
Dahlias	5–8 cm	40–60 cm	Warm, sunny spot
Begonias	3–5 cm	20–25 cm	Partial shade

Before you plant into borders, it’s worth checking the soil quickly. Almost no bulb enjoys sitting in waterlogged ground. If you have heavy clay, open it up with sand or fine gravel to improve drainage. Lilies, in particular, respond well if you add a free-draining layer of sand or grit in the base of the planting hole.

Pot and container planting, done properly

Titchmarsh often opts for large terracotta pots. The drainage hole must be unobstructed so excess water can leave freely. Cover the hole with a broken shard of pot (or a layer of gravel), then fill with a good-quality peat-free compost.

Set bulbs with the growing tip facing upwards, keep sensible spacing between them, cover with compost, and leave a small watering lip at the top. That rim prevents water from spilling over the sides when you irrigate.

Extra step that helps (often overlooked): in colder parts of the UK, keep some fleece or an upturned pot handy. If a sharp late frost is forecast after you’ve planted, a quick overnight cover can protect emerging shoots in containers, which cool down faster than garden soil.

Watering and routine care to secure a flood of flowers

After planting, water thoroughly once so the soil settles snugly around the bulbs or tubers. In the following weeks, a steady approach works best: water less often but more deeply, and allow the compost or soil surface to dry slightly between watering sessions.

Water consistently rather than frantically, and the plants repay you with firm stems and dense flower clusters.

Titchmarsh also likes to prepare his tools before the season properly gets going-spade, dibber, watering can and gloves-cleaned, oiled and within easy reach. When you’re not hunting in the shed in June, you’re far more likely to keep up with small jobs and not postpone essential care.

Feeding (a useful addition once growth starts): when shoots are established, a balanced liquid feed every 10–14 days can make a noticeable difference in containers. For border plantings, a spring mulch and a light top-dressing of a general fertiliser supports steady growth-especially for dahlias and lilies, which are naturally hungry plants.

The hidden pest inside bulbs: thrips

A surprising number of apparently healthy bulbs can harbour a pest you can barely see: thrips. These tiny insects hide between the bulb scales, lay eggs there and can survive the winter unnoticed.

Damage often only becomes obvious in summer, showing up as:

• stunted buds
• bluish, silvery-looking flecks on petals
• brown, scarred patches on leaves

Whether bulbs come from overwinter storage or a garden centre, it’s worth giving them a quick inspection. Choose only firm, clean specimens and discard anything soft or mouldy.

Gentle treatment before planting

A straightforward spray mix can help stop thrips before they cause trouble. Recommended ingredients are:

• 1 litre of water
• 1 tablespoon of insecticidal soap (potassium salts of fatty acids)
  or a mild solution made with soft soap/Castile soap, and if you’re stuck, a small squirt of washing-up liquid

Mist the bulbs, allow them to dry briefly, and repeat the treatment three days later. That second pass helps catch newly hatched larvae.

For gladioli, ranunculus or anemones, some gardeners also advise a short soak of a few hours in water with a household disinfectant based on oxygen or ammonium compounds. Tulips, daffodils and dahlias are much more sensitive to this kind of bath, so it’s safer to avoid treating those in that way.

What if you spot damage later in the season?

If summer arrives and you notice scarring or silvery trails, all is not lost-but you should respond quickly:

• In the evening, mist leaves with a 5% soft-soap solution.
• Hang yellow sticky traps among plants to catch many flying thrips.
• Remove severely distorted plants rather than letting them linger and spread problems.
• Dry lifted bulbs thoroughly before winter storage and store at 2–4 °C.

Bulbs that have sat warm and dust-dry in a garage for months are especially worth checking before planting. Without that inspection, unseen pests can end up right back in your beds.

Common March mistakes-and how to avoid them

Most setbacks with summer-flowering bulbs and tubers come down to a few repeat errors:

• Planting too late: if bulbs go in during late April or May, they often don’t have time to develop strong roots. Plants stay weaker and the flowering period is shorter.
• Soil that’s too wet: waterlogging quickly leads to rot. If you can see a puddle lingering above the planting spot after rain, improve drainage or choose a better site.
• Singles scattered through borders: isolated bulbs look lost. Planting in groups creates far more impact, even in compact gardens.

How March planting pays off in the long run

Many summer bulbs and tubers will return year after year if they’re happy where they are. Lilies and alliums can even multiply gradually over time. With a little planning now, you can build a dependable framework that only needs occasional topping up.

A practical method is to sketch each bed on paper and note where each bulb cluster sits. That prevents accidental digging when you’re adding perennials later, and makes it easier to target late-summer gaps deliberately.

For small city balconies, a different strategy often works better: choose a few large containers rather than lots of small ones. Bigger pots hold moisture longer, heat up less in sunshine, and provide enough space for combinations such as dahlias and begonias with trailing plants like petunias-turning a few square metres into a genuine mini flower landscape.

So if bare beds in March make you hesitate, you have two options: wait-or fill the soil with bulbs and tubers. They’ll get on with the work quietly underground, and weeks later you’ll see exactly what that one planting session was worth.