Graphic shapes with a variety of sizes and bearings, decorative onions enlighten flower beds with their colored heads.
They’re not the first plants we usually think of when filling in a flower bed, pot arrangement or garden box, but decorative onion is as appealing as it is easy!
- Read also: how to grow allium, the ornamental onion
Ornamental onion, pompoms and colors
Depending on the variety, they uphold star-studded sphere-shaped umbels or flat-shaped ones, and come in any of the following tints: mauve, blue, violet, purple, pink, white or yellow (moly allium).
Their tall stem gives them an unusual graphical bearing that is perfectly suited to the most modern designer compositions, for instance in gravel gardens.
Their size also depends on the variety. The smallest ones are around 16 inches (40 cm) high, and are better if your garden is often wind-swept, but larger ones like allium giganteum are true giants that send their bloom over 5 feet (1.5 meters) high!
Allium, grow it directly in the ground or in pots
The planting of allium bulbs is in fall, from September to November. They tolerate all sorts of soil, as long as it is well drained. Plant them in the sun, with the bulb about two or three times as deep as it is tall. Group them together to create a canopy of colored spheres hovering over the garden, or pair them with rose trees, larkspurs, lavender, grasses or iris…
You can also grow them in pots, which is a good option if your garden soil is too heavy. Settle them in a blend of ¾ soil mix and ¼ sand, with a thick drainage layer: like all bulbous plants, they hate stagnating moisture.
Blooming is from May to September depending on the variety and lasts more or less three weeks. The earliest bloomers are Persian onion (Allium hollandicum), whereas Allium senescens blooms last in September. Mixing species will rotate the blooming over the entire summer. Also, take note that these stupendous flowers are edible! Feel free to sprinkle the star-shaped flowers in your dishes and mixed salads!