Wallflower: complete guide

Overview

The wallflower (Erysimum x cheiri) is one of those spring garden classics that gardeners fall in love with once and never quite want to give up. That warm, clove-like fragrance drifting across the garden on an April afternoon, the dense clusters of flowers in gold, orange, crimson and burgundy, and the cheerful reliability of a plant that asks for almost nothing in return: that is the wallflower in a nutshell. Native to rocky cliffs and old walls in Greece, it has naturalised across most of Europe over centuries of cultivation. Today it is equally at home in a Belgian cottage border, a Dutch courtyard trough or an English terraced front garden. Gardenworld (gardenworld.app) lists the wallflower among the top spring-flowering plants for small front gardens, and for good reason.

Appearance and bloom cycle

Erysimum x cheiri forms a bushy, semi-woody plant reaching 30 to 60 cm tall, depending on the variety. The stems become slightly woody at the base, which is why the plant is technically a short-lived perennial or sub-shrub, though most gardeners treat it as a biennial. Leaves are narrow, lance-shaped and dark green, holding through mild winters. The four-petalled flowers, typical of the Brassicaceae family, are carried in dense terminal clusters. The colour range is remarkable: from the classic golden-yellow through rich orange, blood-red and mahogany to soft cream and purple. Popular named varieties include 'Blood Red', 'Cloth of Gold', 'Primrose Bedder' and the mixed 'Persian Carpet' series.

Flowering runs from March to May, sometimes extending into June in cool, cloudy weather. Plants are visited intensively by early bumblebees, honeybees and various solitary bees - making the wallflower one of the best early-season pollinator plants available. After flowering, long narrow seed pods develop. If you want to collect seed for next year, leave a few pods to ripen fully before shaking them out.

Ideal location

Wallflowers need a sunny to lightly sheltered spot. Full sun produces the most flowers and the sturdiest growth. The plant's Mediterranean heritage explains its preferences: dry, warm conditions with sharp drainage and some shelter from biting north and east winds. Against a south-facing wall is ideal. In colder parts of northern Europe, this south-facing aspect makes the difference between a plant that sails through winter and one that struggles.

Wallflowers are famously comfortable growing in the cracks of old stone walls, between pavers and in rocky outcrops. These spots offer exactly what the plant wants: sharp drainage, reflected warmth and lime-rich substrate. If your garden has an old wall with mortar joints, pop a few seedlings in and watch them flourish.

Soil requirements

Good drainage is the single most important factor. Wallflowers hate waterlogged soil: wet roots in cold weather lead quickly to rotting and death. Sandy loam or free-draining stony soil is best. Heavy clay should be broken up with grit and coarse sand before planting. Work in some mature garden compost for structure, but do not over-feed: too much nitrogen produces lush leafy growth at the expense of flowers.

Soil pH should be neutral to slightly alkaline - between 6.5 and 7.5. If your soil is on the acidic side, incorporate a handful of garden lime or crushed limestone when preparing the bed. Avoid planting wallflowers where other brassicas (cabbages, broccoli, rocket) have grown recently, as clubroot disease can affect them too.

Watering

Once established, wallflowers are quite drought-tolerant. During the first few weeks after autumn planting, water regularly to help them settle in. After that, reduce watering through winter: soggy soil in cold weather is far more dangerous than a little dryness. During the spring flowering period, water during prolonged dry spells, but always allow the top layer of soil to dry out between waterings.

In containers, use a free-draining compost mix - a standard multipurpose compost with added perlite or horticultural grit works well. Make sure pots have generous drainage holes. Container-grown wallflowers dry out faster than ground-planted ones and will need checking every few days during dry spring weather.

Pruning

Deadheading spent flower clusters promptly - cutting back to just above a healthy leaf - can encourage a second, lighter flush of bloom in June. This works best on young, vigorous plants in their first flowering year. Older, woodier specimens rarely produce a worthwhile second show.

If you are treating wallflowers as biennials (which gives the best results), pruning is largely irrelevant: pull them out after flowering and compost them. To collect seed, let a few clusters fully ripen: the pods will turn brown and dry, and the seeds inside will be dark brown. Collect into a paper bag and store in a cool, dry place until sowing time in June or July.

Maintenance calendar

January - February: Check young plants for frost damage after cold spells. Ensure drainage has not been compromised by frozen ground. Move container plants under cover if prolonged hard frost is forecast.

March: Early varieties begin to open. Apply a thin top-dressing of well-rotted compost around plants to retain moisture and add nutrients. Begin watching for slug damage on emerging shoots.

April - May: Peak flowering. Enjoy the fragrance and the pollinators. Water during dry periods. Do not feed with high-nitrogen fertiliser at this point.

June: Flowering winds down. Collect seed from selected plants. Remove spent plants from the border and replace with summer bedding.

July - August: Sow seed for next year's display. Sow thinly in seed trays or modular trays with fine, free-draining compost. Germination takes 7 to 14 days at 15 to 18 degrees Celsius. Prick out when large enough to handle.

September - October: Plant out young seedlings at 25 to 30 cm spacings. Water in well. Choose a sunny, sheltered position with good drainage.

November - December: Plants should be well established by now. Apply a mulch of coarse grit or garden compost around the base if severe frosts are expected. Do not water unless conditions are unusually dry.

Winter hardiness

Wallflowers are hardy to around -8 to -10 degrees Celsius (USDA zone 7), provided the soil is well-drained. Persistent wet and cold together is what kills them: the roots simply rot. In USDA zone 6 and colder regions, a protective mulch of straw or bracken over the root zone in November helps, as does a sheltered south-facing position.

In the UK and most of northwest Europe, wallflowers have been grown outdoors for centuries without issue in average winters. Very cold winters - sustained below -15 degrees Celsius - can cause losses even in sheltered spots. Because they are relatively inexpensive and easy to raise from seed, most gardeners simply resow each summer and do not worry too much about losing a few plants to frost.

Companion plants

Wallflowers are among the most versatile spring companions in the border:

• Tulips are the traditional partner. Plant wallflowers between late-flowering tulips in harmonising or contrasting shades. The wallflower provides a warm, fragrant carpet from which the tulips emerge.
• Forget-me-nots (Myosotis) provide a cloud of sky-blue that sets off orange and yellow wallflowers perfectly.
• Primroses and polyanthus flower slightly earlier but tall primula species overlap well with early wallflowers in March-April.
• Sweet William (Dianthus barbatus) can be planted nearby as a summer follow-on, giving continuous interest from spring into summer.
• Pansies and violas work well as low-growing underplanting, filling gaps between wallflower plants at ground level.

For ideas on how to incorporate wallflowers into a complete front garden design, visit gardenworld.app.

Final thoughts

The wallflower rewards the gardener who plans ahead. A few minutes spent sowing in July means weeks of golden, fragrant beauty the following April and May. There are few spring plants that combine such vivid colour with such powerful fragrance, and few that feed early pollinators as generously. Give it a sunny wall, good drainage and a little patience, and the wallflower will not disappoint.