Plant Summer Bulbs in March: Alan Titchmarsh and Sarah Raven’s Advice

Anyone hoping to see metre-high flowers, overflowing window boxes and brilliantly coloured beds in June has a clear job to do in March. Garden legend Alan Titchmarsh and plant expert Sarah Raven agree: summer-flowering bulbs and tubers need planting now, or the spectacular display will not materialise.

Why March matters so much for summer-flowering bulbs

March falls within the ideal planting period. Days are lengthening, the soil is thawing and the sun is becoming stronger again. Those are precisely the conditions summer-flowering bulbs need to establish roots in good time.

Planting at this point gives the plants a lead of several months. They can develop a robust root system before the height of summer brings heat and dry conditions. In turn, this produces sturdier stems, larger blooms and a longer flowering season.

“One unhurried hour in March can determine whether June, July and August are filled with colour for weeks.”

In spring, many amateur gardeners reach first for the lawnmower and hoe. Titchmarsh suggests a different order of priorities: create the foundation for colour first by planting bulbs and tubers, then deal with everything else.

Summer bulbs to plant now

Summer-flowering bulbs and tubers come in every scale, from bold dahlias to delicate freesias. The important factor is choosing plants that suit your garden or balcony.

For tall, dramatic beds

For a real “wow effect” in garden beds, these are the main varieties to plant in March:

• Lilies: Elegant, often fragrant flowers, reaching 60 to 150 centimetres depending on the variety.
• Gladioli: Slim flower spikes that are perfect for cutting and displaying in a vase.
• Freesias: Delicate, strongly scented blooms, ideal near the front of a bed or in pots.
• Crocosmias: Fiery red and orange shades that add movement to planting schemes.
• Dahlias: From ball-shaped to cactus forms, these are the classic choice for walls of colour in late summer.
• Allium (ornamental onion): Rounded flower heads that appear to float above perennial borders.
• Bearded iris: Striking individual flowers, especially suited to sunny, dry positions.

Experts advise against planting these individually. Instead, use small groups of four to six bulbs of the same variety. This creates islands of colour that make an impact even from a distance.

For balconies, patios and compact gardens

Even with limited room, pots, planters and hanging baskets can deliver a remarkable display. Titchmarsh is especially enthusiastic about:

• Begonias: Long-flowering plants that also tolerate partial shade, making them ideal for boxes and pots.
• Petunias: Trailing, floriferous plants that quickly fill hanging baskets and window boxes.
• Verbenas: They form dense carpets of flowers and work well in containers in sunny spots.
• Rudbeckias (coneflower varieties): Tough, long-flowering plants in warm yellow and orange tones.

Many of these can be planted together: arrange taller plants in the centre of a pot and trailing varieties around the edge. The result is a genuinely “cushioned” arrangement that remains attractive into autumn.

How to plant: depth, spacing and position

The basic rule for bulbs is to plant them around two to three times as deep as the bulb is tall. Large dahlia tubers should sit more shallowly, while allium bulbs generally need a slightly deeper planting depth.

In a border, it is worth carrying out a quick soil check. Almost no bulbous plant will tolerate waterlogging. Dense, clay-heavy soil can be opened up with sand or fine gravel. Lilies in particular benefit from a free-draining layer of sand or horticultural grit in the planting hole.

Planting in pots and containers like a professional

Titchmarsh often chooses large terracotta pots. The drainage hole at the base must remain unobstructed so watering can drain away freely. Place a piece of broken terracotta or some gravel over the hole, then add a layer of peat-free compost.

Position the bulbs with their tips facing upwards, allow adequate space between them, cover with compost and leave a small watering gap at the top. This prevents water from overflowing later.

Watering, aftercare and securing a mass of flowers

Water thoroughly once straight after planting so that the compost settles around the bulb. Over the following weeks, a measured routine is usually enough: water less often but deeply, allowing the growing medium to dry out between waterings.

“Water consistently, but without panic, and the plants will reward the effort with strong stems and dense clusters of blooms.”

Titchmarsh likes to prepare tools before the season begins: spade, dibber, watering can and gloves, all oiled, cleaned and ready to use. Anyone who does not have to search the shed in June is more likely to keep to a routine and avoid delaying essential jobs.

Thrips: the overlooked enemy inside bulbs

Many apparently healthy bulbs can conceal a pest that is barely visible to the naked eye: thrips. These tiny insects settle between the scales, lay eggs there and survive the winter as a result.

The consequences are often not visible until summer:

• 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 before planting. Use only firm, clean specimens and discard any that are soft or mouldy.

Gentle treatment before planting

A simple mixture can stop thrips before they cause damage. The recommended ingredients are:

• 1 litre of water
• 1 tablespoon of insecticidal soap based on potassium salts of fatty acids
  or a mild soft-soap or Castile soap solution; if necessary, a small squirt of washing-up liquid

Spray the bulbs with the mixture, leave them to dry briefly, then repeat after three days. This also targets larvae that have only just hatched.

For gladioli, ranunculus or anemones, some gardeners also recommend soaking them for a few hours in water containing a household disinfectant based on oxygen or ammonium. Tulips, daffodils and dahlias are considerably more sensitive to these baths, so should not be treated this way.

What to do when damage is already visible

If scarred flowers or silvery marks appear during summer, all is not lost, but action is needed:

• Mist the leaves in the evening with a five per cent soft-soap solution.
• Hang yellow sticky traps among the plants, as they attract many flying thrips.
• Remove severely distorted plants rather than keeping them going.
• Dry stored bulbs thoroughly before winter and keep them at 2–4 °C.

Bulbs that have spent months in a warm, dust-dry garage should be inspected particularly carefully before planting. Without that check, unseen pests can simply return to the border.

Common March mistakes – and how to avoid them

Most issues with summer bulbs stem from straightforward causes. Three mistakes occur time and again:

• Planting too late: If bulbs are not planted until late April or May, they often lack time to make strong roots. Plants are weaker and flower for a shorter period.
• Soil that is too wet: Waterlogging can quickly cause rot. If rain leaves a puddle above the planting hole, reconsider the site or improve the soil structure.
• Single plants in a border: Individual bulbs become visually lost. Group planting produces far greater impact, even in a small garden.

How March planting pays off in the long term

Many summer bulbs return year after year when they are given the right position. Lilies and alliums can even multiply gradually. Planning wisely now creates a reliable framework over time that needs only occasional additions.

One practical tip is to sketch each bed on paper and mark where every bulb has been planted. This prevents accidental digging-up later when planting perennials, and makes it easier to fill late-summer gaps with precision.

A different approach suits small urban balconies: choose several large containers rather than lots of small ones. They retain water more effectively, heat up less and provide enough room for combinations of dahlias, begonias and trailing plants such as petunias. Even a few square metres can then become a miniature flower landscape.

So, when bare beds prompt doubts in March, there is a choice: wait, or fill the soil with bulbs and tubers. The plants will then get on quietly with their work, and only weeks later will the true effect of that single planting session become clear.