The allium family of plants contains around four hundred species that includes the familiar onion, garlic, and chives.
Allium aflatunense; also known as ornamental onions, are grown for their showy flower heads that come in a wide range of colour and sizes.
The flower heads which can be 25-150mm (1"-6") in diameter (subject to variety) come in shades of blue, purple, white and yellow, and flower from late spring to late summer.
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When the plants die back, the dried flower heads look attractive if left in the garden, or they can be cut for indoor flower arrangements.
They prefer a sunny, sheltered spot, in a light well-drained soil, although some varieties will tolerate dappled shade.
Depending upon variety plants can grow to a height of 300mm-1200mm (12"-48") high,producing blue, purple, white or yellow coloured star like flowers that appear in June.
They prefer moderately fertile, well-drained soil in full sun or partial shade, but not cold, exposed or waterlogged areas.
They will grow in heavier soils, providing a layer of horticultural grit is added to the planting holes.
For stability; bury them to three or four times their own depth or a minimum of 75mm (3") deep whichever the greater.
Alliums look at their best if the bulbs are planted out in groups of three or more set at 200mm (8") apart.
The smaller varieties can be closely planted for impact.
Leave undisturbed until the clumps are overcrowded, then lift, split, and replant immediately.
The leaves should be allowed to die back and not removed until completely brown.
It is also possible to grow alliums in deep outdoor containers.
It is a matter of choice but it is probably best to use lower growing varieties in containers.
Pests & Diseases;
As mentioned above Alliums are closely related to culinary onions, and may occasionally suffer from related problems, such as white rot, downy mildew and onion fly.
Therefore it is advisable not to plant them in a spot where onions have been grown in previous years.
Cultivation;
Week 2; Sow commercially purchased seed in trays of seed compost and germinates at a minimum temperature of 16°C (60°F)
Germination should take 2-3 weeks.
Week 7; Prick out seedlings sown the previous year (circa week 27)into 70mm (3") pots and place in a cold frame until ready for planting out.
Week 10 - 11; Prick out seedlings if large enough to handle into 70mm (3") pots and place in a cold frame until ready for planting out the following year.
Note; it can take two or three year to get to flowering stage.
circa week 18; As new growth appears; top dress the border/bed with a general fertilser to the manufacturers specification.
Week 27; Collect seed after ripening and sow them immediatly in pots in a cool greenhouse or coldframe to produce flowering bulbs.
Alternatively; store in a fridge and sow in spring at about 13°C (55°F).
Sow the collected seeds thinly and grow on for a year, then prick them out into pots/boxes or nursery bed and grow on for at least one more year.
Seeds should germinate within 10-12 weeks.
Note; Being hybrids; they may not necessarily come true to the parent plant from this method, plus they will take several years to reach flowering size.
Some alliums produce aerial bulbils in the flower head.
These should be carefully removed, separated, and either placed 25mm (1") apart and 10-12 mm (½")deep in a nursery bed or in pots of gritty compost and grown on in a coldframe.
They then can be treated as described under seed sown varieties.
Week 40-42; Plant out; in well prepared fertile soil,covering the bulbs to three or four times their own depth, min 75mm(3"), and leave untouched for several years.
Plants may need staking, especially on exposed sites.
Week 40; If required; from now and until March divide large clumps and replant immediately.
Many species produce offsets, these should be detached and planted out immediately.
Smaller offsets can be placed in pots of gritty compost and grown on in a coldframe until planting out time the following year.
