Planting summer-flowering bulbs and tubers in March is the difference between standing in front of waist-high blooms, overflowing window boxes and beds that glow in June-and missing the main event altogether. Gardening icon Alan Titchmarsh and plant expert Sarah Raven agree on the timing: if you want a proper summer display, summer-flower bulbs and tubers need to go into the ground now.
Why March is the make-or-break month for summer-flowering bulbs and tubers
March sits in the sweet spot for planting: daylight lengthens, the ground starts to thaw, and the sun finally has some strength. That combination is exactly what summer-flowering bulbs require to begin rooting in good time.
By planting in March, you give plants a valuable head start of several months. They use that period to develop a strong root system before high summer turns hot and dry. The payoff is clear: sturdier stems, larger blooms and flowers that keep coming for longer.
One unhurried hour in March can turn into weeks of colour across June, July and August.
Many home gardeners reach for the lawnmower or hoe as soon as spring arrives. Titchmarsh suggests flipping the order: lay the foundation for colour first-meaning set out bulbs and tubers-and deal with everything else afterwards.
Which summer bulbs to plant now
Summer-flowering bulbs and tubers come in every scale, from the bold dahlia to the delicate freesia. The key is choosing what suits your garden, patio or balcony.
For tall, show-stopping borders
If you want genuine “wow” in your beds, these are the March must-plant options:
- Lilies: elegant, often scented flowers; depending on the variety, around 60–150 cm tall.
- Gladioli: slim flower spikes that are excellent for cutting.
- Freesias: refined blooms with a strong perfume; ideal near the front of a border or in pots.
- Crocosmias: fiery reds and oranges that add movement and energy to planting schemes.
- Dahlias: from ball shapes to cactus forms-the classic choice for a late-summer wall of colour.
- Allium (ornamental onion): spherical flower heads that seem to hover above perennials.
- Bearded iris: striking individual flowers, particularly suited to sunny, dry positions.
Specialists recommend avoiding single, scattered plantings. Instead, place bulbs in small clusters of four to six of the same variety. Grouping creates “islands” of colour that read well even from a distance.
For balconies, patios and small gardens
Limited space doesn’t mean limited impact. With pots, troughs and hanging baskets you can still create a packed display. Titchmarsh is especially fond of:
- Begonias: long flowering, tolerant of partial shade, and ideal for containers.
- Petunias: trailing and floriferous-quickly fill hanging baskets and window boxes.
- Verbenas: form dense carpets of flowers; excellent for sunny pots.
- Rudbeckias (coneflower types): robust, long-flowering plants in warm yellows and oranges.
Many of these combine beautifully: use taller plants as a centrepiece and let trailing varieties spill over the edge. The result is a “cushioned” arrangement that can look good well into autumn.
Planting properly: depth, spacing and position
A reliable rule of thumb for bulbs is to plant them at two to three times the bulb’s own height. Large dahlia tubers tend to sit a little shallower, while allium bulbs usually go slightly 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, do a quick soil check. Almost no bulb enjoys sitting in water. If your soil is heavy or clay-based, open it up with sharp sand or fine gravel. Lilies in particular benefit from a free-draining layer of sand or grit in the base of the planting hole.
Pot and container planting (the professional way)
Titchmarsh often opts for large terracotta pots. Make sure the drainage hole is clear so excess water can escape freely. Cover the hole with a potsherd or a small layer of gravel, then add peat-free compost.
Set bulbs with the pointed end facing upwards, leave enough space between them, cover with compost, and keep a small watering lip at the top. That rim prevents water and compost washing over the edge during watering.
A useful extra: warming the soil without rushing the season
If March is cold where you are, you can still stick to the timetable. In borders, a simple horticultural fleece laid over the planting area for a short period can help the soil warm slightly without forcing growth too hard. In containers, moving pots to a sheltered wall or doorway often makes a noticeable difference-especially for tender summer-flowering bulbs and tubers that dislike lingering chill.
Watering and aftercare to secure a flood of flowers
Right after planting, water thoroughly once so the soil settles around the bulb. In the following weeks, a measured routine is usually enough: water less often but deeply, and allow the compost or soil surface to dry a little between sessions.
Water steadily, not frantically-plants repay that consistency with strong stems and dense flower clusters.
Titchmarsh also likes to prepare tools before the season begins: spade, dibber, watering can, gloves-cleaned, oiled and ready to go. When you’re not rummaging around in the shed in June, you’re far more likely to keep up with small maintenance tasks rather than putting them off.
The overlooked problem inside bulbs: thrips
A surprisingly common issue is a pest hiding inside apparently healthy bulbs: thrips. These tiny insects are difficult to spot with the naked eye. They shelter between bulb scales, lay eggs there, and can survive winter conditions.
The damage often only becomes visible in summer, including:
- stunted buds
- bluish, silvery-looking patches on petals
- brown, scarred areas on leaves
Whether bulbs come from winter storage or a garden centre, inspect them briefly: choose only firm, clean specimens and discard anything soft or mouldy.
Gentle treatment before planting
A straightforward mix can stop thrips before they cause problems. Common recommendations include:
- 1 litre of water
- 1 tablespoon of insecticidal soap based on potassium salts of fatty acids
or a mild soft-soap/Castile-soap solution (in a pinch, a small squirt of washing-up liquid)
Spray the bulbs, let them dry briefly, then repeat the process after three days to catch newly hatched larvae.
Some gardeners also recommend, for gladioli, ranunculus or anemones, a short soak of a few hours in water with a household disinfectant based on oxygen or ammonium compounds. Tulips, daffodils and dahlias tend to be more sensitive to such baths and are best left out.
What to do if you spot damage later
If, in summer, you notice scarred blooms or silvery streaks, you can still limit the impact-provided you act:
- Mist foliage in the evening with a 5% soft-soap solution.
- Hang yellow sticky traps among the plants to catch many flying thrips.
- Remove badly distorted plants rather than letting them limp on.
- Dry stored bulbs thoroughly before winter and keep them at 2–4 °C.
Bulbs that have sat for months in a warm, dusty garage should be checked particularly carefully before planting-otherwise invisible pests can be reintroduced to beds and pots.
Common March mistakes (and how to avoid them)
Most problems with summer bulbs come down to a few repeat errors:
- Planting too late: if bulbs only go in during late April or May, they often don’t have time to build strong roots. Plants stay weaker and the flowering period is shorter.
- Soil that stays too wet: waterlogging quickly leads to rot. If you see a puddle above the planting hole after rain, rethink the spot or improve drainage.
- “Lone wolf” planting: single bulbs get visually lost. Planting in groups creates far more impact, even in small gardens.
How March planting pays off over the long term
Many summer-flowering bulbs and tubers return year after year when they’re happy where they are. Lilies and alliums may even multiply slowly. A well-thought-out March planting plan becomes a dependable framework that only needs topping up occasionally.
A practical tip: sketch each bed on paper and mark where bulbs are planted. It prevents accidental digging when adding perennials later, and it makes it easier to plug late-summer gaps in a deliberate way.
For compact city balconies, another strategy works better: choose a few large containers instead of lots of small ones. Bigger pots hold moisture more reliably, heat up less quickly, and give enough root room for combinations such as dahlias, begonias and trailing plants like petunias-creating genuine mini flower landscapes in just a few square metres.
So if bare beds in March make you hesitate, you’ve got a simple choice: wait-or fill the soil with bulbs and tubers. The plants will get on with their work quietly, and only weeks later will you see just how much that single planting session really achieved.
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