Trachelium caeruleum is a lesser known genus that is gaining in popularity. Used extensively in the cut flower trade it is gaining in popularity for use as a bedding or container plant. It produces beautiful dome-shaped flower heads that are crowded with tiny, tubular flowers.
The plants have an upright habit and forms an elegant mound of small lance-shaped, serrated leaves from which a large central umbel forms with smaller side umbels or ‘satellites'. The flower stems are topped with large clusters composed of many tiny flowers.
Growing 90 to 120cm (36 to 48in) tall with a spread of 30 to 45cm (12 to 18in), the elegant basal foliage display hues of cordovan purple or deep green, brushed with a purple hue and plum highlights.
Trachelium caeruleum is considered a tender perennial, it is hardy to around 4°C (40°F) and in temperate climates it is often grown as a half hardy annual. They enjoy a sunny spot in well-drained soil and are useful for filing gaps in herbaceous borders.
The plants bloom over a long season, beginning in early summer they are in bloom right through to late autumn. The flowers have a light fragrance and are highly attractive to both bees and butterflies. They produces copious amounts of nectar for and is a boon for building up bees’ honey reserves before winter. The long stems are a popular choice for cut flower production, providing both texture and colour to an arrangement.
Trachelium caeruleum ‘Lake Michigan’ is a cultivated variety, bred to give earlier flowering. It can be sown either in early spring for flowering in late summer, or sown in autumn the seedlings can be overwintered to give earlier flowering plants the following year.
‘Lake Michigan’ is available in a series of four distinct colourways - White, Blue, Wine-red and Purple.
The foliage and stems of White and Blue are mid-green. Wine-red has dark reddish foliage and stems, and Purple has dark green foliage and stems.
- Awarded the RHS Award of Garden Merit
Trachelium caeruleum has been awarded the Royal Horticultural Society’s Award of Garden Merit (AGM).
Sowing: Sow in spring or in autumn.
Trachelium has very small seed so is supplied in pelleted form. This makes sowing much easier and gives better germination results. The seeds can be sown either in early spring for flowering in late summer, or sown in autumn the seedlings can be overwintered and will give earlier flowering plants the following year.
Sow indoors at 18 to 24°C (65 to 75°F). It is not recommended to sow the small seeds directly outdoors.
Sow into pots or trays containing moistened compost. Press the seeds lightly into the surface of the compost but do not cover the seeds with soil as light aids germination.
Expect germination in 15 to 20 days. Seedling growth is comparatively slow, requiring 10 to 12 weeks from sowing to transplanting. Transplant when there are at least two sets of true leaves, do not allow the small plants to become root bound.
Trachelium caeruleum is a light sensitive plant and needs a position with as much sunlight as possible for optimum growth. It also needs a regular water supply so keep the seedlings well watered especially on sunny days.
Once the seedlings have their first pair of true leaves (they come after the seedlings first pair of leaves) and are large enough to handle, Prick out each seedling into larger pots to grow on. Use one plant per 10cm (4in) pot or three plants per 20cm (8in) pot.
Gradually acclimatise the plants to outdoor conditions for 10 to 15 days before planting out in spring, after all risk of frost has passed. Grow in a position with moist but well-drained soil and an area that gets as much sunlight as possible. Plant 30cm (12in) apart and line the planting hole with compost or fertiliser to assist the growth of fuller flowers.
Trachelium is a qualitative long day plant. It needs a period of 15 to 16 hours of daylight to come into flower. Under natural conditions the plant will begin flowering in June. It can be grown under lights to give earlier flowering.
Trachelium require a great deal of water while the plants are actively growing. Do not let them dry out otherwise flower quality will suffer. Once they have bloomed, just water in dry conditions and remove dead flower heads to promote new blossoms.
The plants grow best with low humidity and at temperatures under 25°C (77°F). They are very tolerant of pests and diseases. Stems are stiff and erect, and do not require support.
Trachelium is hardy to around 4°C (40°F), if you have a cold greenhouse in late autumn, the plants can be dug up and placed in a plastic pot to overwinter in frost free conditions. They can then be replanted in spring and will give large clumping plants that will flower early the following year.
For cut flower production a spacing of 23 x 23cm (9 x 9in) on a 4ft. bed produces good yield of high quality stems. First harvest comes about ten weeks after transplanting and continues until early to mid-October.
Trachelium caeruleum is a popular choice with florists for providing both texture and colour to an arrangement. The small flowers are set closely together on an umbel with a diameter of up to 10 to 15cm (4 to 6in). The upright stems grow to a length of around 75 to 105cm (30 to 42in).
The flowers should be harvested when one quarter of the florets are open. For maximum vase life, place trachelium stems in water as soon as possible after cutting. Cut the stems at a 45 degree angle with a sharp knife and remove foliage on the lower third of the stems. Place in sterilised buckets filled with luke warm water.
To condition for immediate use or shipping, place the flowers in warm water, 21 to 24°C (70 to 75°F) containing floral preservatives and leave over night to condition before using. Select a floral preservative which contains sucrose as well as bactericide to facilitate water uptake and inhibit stem plugging.
Trachelium can be shipped horizontally, but best quality is kept when flower stems are shipped upright in buckets of water. Trachelium are not sensitive to ethylene. They have a vase life of 10 to 14 days in water.
Cottage/Informal Garden, Flower Arranging, Borders and Beds, Bees and wildlife.
Trachelium is a small genus of flowering plant belonging to the family Campanulaceae, the bellflower family.
Native to the western Mediterranean its native range includes Algeria, Morocco, Portugal, Spain, and Sicily. It has also become naturalised in a few areas, including New Zealand, the Azores, and parts of mainland Europe.
The genus name Trachelium derives from the Greek word meaning ‘rough throat’. The Greek trachilos, means ‘throat’ and ‘wort’, an old word of either English or German origin, also spelled ‘wyrt’ meaning a plant.
The species name caeruleum simply means ‘blue’ and refers to the colour of the flowers of the species.
The common name of Throatwort again the word ‘throat’ is for the area it was supposed to heal. it was once regarded as an important medicinal plant and used as a gargle for sore throats. It in reality has no medicinal value, the belief to the contrary was due to its throat-shaped corolla which in the supernatural imaginings of the Doctrine of Signatures meant God had given the flowers this shape as a message to humanity to use it to cure throat ailments.
- Awarded the RHS Award of Garden Merit
- Additional Information
Packet Size 25 Pelleted Seeds Seed Form Supplied in pelleted form. Family Campanulaceae Genus Trachelium Species caeruleum Cultivar Lake Michigan Blue Hardiness Tender Perennial often used as an Annual Flowers Blue large clusters Natural Flower Time June to October Height 90 to 120cm (36 to 48in) Spread 30 to 45cm (12 to 18in) Position Full sun for best flowering Soil Reasonably fertile, moisture retentive but well drained soil