Planting summer bulbs in March: seven stars for a long flowering season

Picking up a spade and a box of bulbs in March gives your summer garden a genuine head start. The soil is gradually warming up while remaining pleasantly moist – precisely the conditions many summer-flowering bulbs enjoy. With suitable varieties and well-judged timing, flowering can continue from June right through to October.

Why March is the ideal time to plant summer bulbs

Although the garden often still looks wintry in March, plenty is already happening beneath the surface. Rain over the previous months has thoroughly moistened the soil, while temperatures edge upwards a little each week.

“Planting summer bulbs in March gives them time to establish a strong network of roots – making them more resilient later on during heat and dry spells.”

The right planting time varies slightly by location:

• Mild areas / wine-growing climates / suburban locations: Planting can often begin as early as the start of March.
• Central Germany: Mid to late March is generally the most suitable time.
• Cooler areas / higher ground: It is better to wait until early April, or start them under glass in pots beforehand.

Where late frosts are likely, cover young shoots with garden fleece in the evening. A light mulch of leaves or bark chippings also helps to soften fluctuations in temperature.

How to plant flower bulbs properly in March

Before planting, inspect the bulbs or tubers carefully. Firm, plump specimens without rotten patches or mould will get off to a far better start than those that are soft or shrivelled.

Choosing the right position and soil

Summer-flowering bulbs generally prefer the following conditions:

• Loose, free-draining soil: Waterlogging is harmful, particularly in spring.
• Nutrient-rich ground: Mature compost used as an initial feed can make a remarkable difference.
• Plenty of sun: Species with especially striking flowers, in particular, need many hours of light.

Improve heavy soils with sand or fine grit. If puddles remain after rainfall, the site is unsuitable for bulbous plants.

The simple depth rule that nearly always works

A straightforward rule of thumb makes planting depth easy to remember:

“Planting depth = roughly 2.5 to 3 times the height of the bulb.”

For example, a bulb measuring 5 centimetres high should be planted 12 to 15 centimetres deep. Position it with the pointed end facing upwards. Firm the soil lightly after planting, then water thoroughly once.

Tall varieties with long flower stems benefit from a support cane inserted at planting time. This prevents shoots from snapping in the wind or collapsing in rain.

Seven bulb stars that really shine in summer

These seven varieties can be used to create a bed that delivers colour from June into autumn – without requiring daily watering.

Dahlias: an explosion of colour until October

Dahlias are among the favourites of many amateur gardeners. Depending on the variety, they flower from high summer well into late autumn. Planted in free-draining soil during March or April, they grow into vigorous bushes covered in countless blooms, from simple flowers to pompon forms.

• Position: Full sun and sheltered from wind.
• Spacing: 40 to 80 centimetres, depending on the variety.
• Tip: Regularly removing faded flower heads encourages fresh buds.

In frost-prone areas, it is worth starting the tubers indoors or in a greenhouse in pots. Once the final frosts have passed, the plants can be moved outside.

Lilies: elegant fragrance and strong vertical interest

Lilies add structure to perennial borders. Their flowers usually emerge between June and August, releasing a fragrance that may be subtle or intense depending on the type. Plant the bulbs deeply so they remain cool and firmly anchored.

• Position: A bright site, ideally with their “feet” lightly shaded by low-growing perennials.
• Planting depth: Usually 15 to 20 centimetres.
• Tip: A little sand beneath each bulb helps to prevent rot.

Lilies work particularly well in mixed borders, rising above a base layer of perennials and grasses.

Tuberous begonias: vivid colour for shade

Tuberous begonias are specialist plants for partially shaded and shaded spots. In places where other summer flowering plants struggle, they add colour to window boxes, containers and border edges, usually from July into autumn.

• Position: Partial shade to shade, sheltered from wind.
• Use: Ideal for window boxes, hanging baskets and shaded front gardens.
• Tip: Start them indoors in pots in March, then put them outside from May.

Place the tuber shallowly, with the slightly hollow side facing upwards. A loose growing medium that never becomes completely waterlogged prevents rot.

Gladioli: spectacular flower spikes for cutting

Gladioli are the classic cut flowers of grandmother’s garden – and they are now enjoying a comeback. Their tall flower spikes make a bold statement in borders and cottage gardens.

• Position: A sunny, sheltered site.
• Successional planting: Planting fresh corms every two weeks extends the flowering period.
• Tip: Push in a support cane at the same time as planting.

Because gladioli are prone to wind damage, they are best placed in front of walls or hedges. In narrow borders, they can also be concealed behind low perennials, leaving only their flower spikes visible.

Cannas: tropical flair beside the patio

Cannas, also known as Indian shot, immediately bring a holiday feel to the garden with their broad, often vividly patterned leaves and large blooms. They are especially impressive in substantial containers.

• Position: Full sun, warmth and a wind-free location.
• Soil: Nutrient-rich and evenly moist, but never wet.
• Tip: Start them indoors in pots during March, then move them outdoors after the last frosts.

In cooler regions, overwinter the rhizomes somewhere frost-free, such as a cellar or garage. The following spring, they can be divided to produce new plants.

Crocosmia: fiery arches for late summer

Crocosmia, often sold as montbretia, stands out for its arching flower stems in shades of orange, red or yellow. It brings movement to borders and suits naturally styled gardens particularly well.

• Position: Sun to partial shade.
• Planting: Plant in groups for the strongest colour effect.
• Tip: A light winter covering of leaves helps during severe cold spells.

Its fine foliage and curved stems create an attractive contrast with compact perennials or grasses.

Agapanthus: spherical blooms for enthusiasts

Agapanthus, commonly called African lily, produces large rounded flower heads in white or blue during summer. It is grown in containers in many gardens because it is not reliably hardy everywhere.

• Position: Sun, preferably beside a warm house wall.
• Container growing: Closely packed roots encourage more prolific flowering.
• Tip: Overwinter somewhere bright and frost-free, watering sparingly.

Those living in mild regions can also plant hardy varieties in borders. Free-draining soil and winter protection are essential there.

Combining the seven varieties for a long flowering display

To ensure your garden stays interesting for months rather than producing only a brief burst of colour, it helps to plan a broad flowering sequence. One possible arrangement is:

Month	Typical flowering plants from the selection
June	Lilies, early gladioli, first agapanthus varieties
July	Dahlias, begonias, gladioli, cannas, agapanthus
August	Dahlias, cannas, crocosmia, begonias
September/October	Dahlias, late begonias, remaining flowers on cannas

For a harmonious border, position tall varieties such as dahlias, gladioli and cannas towards the back. Crocosmia and lilies occupy the middle layer, while begonias and smaller agapanthus varieties take the foreground.

Practical essentials: feeding, watering and common mistakes

Summer bulbs are among the more forgiving garden plants when a few basic principles are followed:

• Water moderately but thoroughly: A deep soak less often is better than a little water every day.
• Nutrient boost: One application of organic fertiliser or compost in spring is usually sufficient.
• Remove faded blooms: This directs more energy into new buds rather than seed production.

Common mistakes include overly wet soil, planting outdoors too early in frost-prone locations and setting plants too close together. Ignoring the spacing recommended on the packet increases the risk of fungal disease and weak growth.

What amateur gardeners should know before the next season

Many summer-flowering bulbs and tubers are not fully hardy. In harsher regions, for example, dahlia tubers, cannas and some gladiolus varieties should be lifted from the soil in autumn and placed in boxes filled with slightly moist growing medium. Stored in a cool, frost-free, dark place, they will keep until the following spring.

From a gardening perspective, this small amount of extra work is worthwhile: once purchased, most of these varieties will accompany you for many years. Each season, you can divide them, move them and try new colour contrasts – gradually shaping your own summer garden, which begins on paper, and in the border, as early as March.