Erysimum allioni, Cheiranthus allioni

Cheerful deep orange blooms cover the Siberian wallflower from spring, right through to early summer. They are very easy to grow and combine well with other plants; indeed wallflowers demand companions and set the mind racing regarding potential planting combinations.

Tulips are traditional bedmates, and a vibrant scheme can be had with hot coloured orange or red tulips. A cooler effect can be created by interplanting with clouds of taller, blue forget-me-nots.
Try combining them with the coloured spring foliage of herbaceous perennials. These can either be planted with the wallflowers in autumn, or the wallflowers can be inserted into more permanent herbaceous plantings. Imagine how good they would look among mounds of purple-leaved Heuchera ‘Plum Pudding’, Sedum pulchellum ‘Purple Emperor’ or swathes of Salvia officinalis ‘Purpurascens’.

English and Siberian wallflowers can be distinguished botanically by differences in their fruit and stigma. From the gardener’s perspective, the most significant difference is in flower colour. Siberian wallflowers are only ever orange, apricot or yellow and are at their best in early to mid-May. English wallflowers have a broader range of colour, looser flower heads and peak about two weeks’ earlier in mid to late-April.

Sowing:
Sow in late summer to early winter for spring flowering or late winter to early spring for autumn
They prefer temperatures of 21°C (70°F) days and 10°C (50°F) nights and can flower in moderate heat at a maximum temperature of 27°C (80°F).
Plants require 70 to 80 days to flower from sowing and will start flowering when they are 10cm (4”) tall. Start in pots or sow direct in mid August.flowering

Starting in Pots:
Surface sow in pots or containers containing good quality seed compost (John Innes or similar) Cover with a fine thin layer of compost or vermiculite.
The compost should be kept moist but not wet at all times. Seed germinate in seven to 10 days at 20°C (68°F).
Prick out each seedling as it becomes large enough to handle, transplant into 7.5cm (3in) pots. Gradually acclimatise to outdoor conditions for 10 to 15 days before planting out after all risk of frost.

Sowing Direct:
Seeds may also be sown outdoors directly where they are to flower or in a reserve bed in a sheltered position. Prick out to 15cm (6in) apart and transplant in October.

Cultivation:
Plants are usually disposed of after flowering, but they can be cut back hard for a flush of flowers later in summer or to produce shoots for cuttings taken in July.
Deadheading prolongs their bloom, but let some of them go to seed. They are often generous self-sowers, or you can gather the seed and resow it yourself.
All parts of the plant are poisonous. specially the seeds. Plant contains Cheirotoxin that has similar but lesser toxic effects as Digitalis does...

Plant Uses:
Plant in rock gardens, large containers, beds, and borders.
They are pleasant by paths and doorsteps. Wallflowers will bloom all winter in a cool room in sunlight. They make good cut flowers, too.

Identity crisis:
Erysimum cheiri (English wallflower) is not in fact English, but native to the eastern Mediterranean, whereas E. x marshallii (Siberian wallflower) is not Siberian but a hybrid first raised in England.
Cultivated wallflowers have suffered their fair share of identity problems. Most were previously assigned to the genus Cheiranthus, but modern authorities now place them all in Erysimum.

Nomenclature:
Erysimum x marshallii is better known by the illegitimate name E. allionii (syn. Cheiranthus allionii), but the correct name predates this and honours its raiser John Marshall who, in 1846, crossed E. perofskianum with the species now known as E. decumbens.