Caring for ornamental onions, planting, fertilizing & more

Height: 15-20cm

Special feature: tongue-like, blue-green leaves
Flowering period : May, June
Flower color: white to gray fading to pink

Botanical name: Allium oreophilum
Height: 15 cm
Special feature: for rock gardens, also suitable for dry soil
Flowering period: May, June
Flower color: purple

Botanical name: Allium amethystinus
Height: 50-100 cm
Special feature: cut flower, for beds
Flowering period: July
Flower color: red

Botanical name: Allium Nectarosscordum siculum
Height: 50-100 cm
Special feature: flowers are bell-shaped
Flowering period: July, August
Flower color: cream/pink

Botanical name: Allium christophii
Height: 50 cm
Special feature: for naturalising
Flowering period: May, June, July
Flower color: violet

Worth knowing Location Planting time Planting Care Watering Fertilizing In the tub Species Pests & Diseases FAQ

Ornamental onion is one of those bulbous flowers that need to be planted before winter in order to bloom with an inflorescence and numerous individual flowers in late spring and summer. Allium looks best in combination with perennials, ground cover or annual flowers. The bulbs are hardy and can sprout again for many years. Roots are only formed if planted in good time and the giant leek can develop magnificently. In addition, ball leeks must be sunny. Ornamental onions belong to the group of autumn bulbs that will delight in the garden for many years and require little maintenance. Ball leeks come in many varieties and shades of color.

Botanical name: Allium giganteum
Other names: ornamental leek, giant leek, ball leek, giant leek, star ball leek, allium
Use: ornamental plant, cut flower, insect plant, for naturalising in the garden, for borders, rock gardens and perennial beds
Origin: Near East, Central Asia
Planting time: each depending on the species from August to early December
Flower colours: violet, lilac, blue, light blue, white
Flowering period: April, May, June (depending on the variety)
Special features: There are over 900 known botanical species and varieties worldwide. All members form an onion as a storage organ.

At which location does the ornamental onion feel most comfortable?

All ornamental onion varieties prefer humus-rich, well-drained soil without waterlogging. You should improve loamy and moist soil with some sand before planting, sandy soil needs some potting soil for better water storage. The location should be as sunny as possible. In partial shade and shade, the color of the flowers is not as intense and the size of the balls is smaller. A pH value of 6 to 6.5 is advantageous for the leek.

Our gardening tip: If the water drainage is not guaranteed, it can quickly rot. If the soil is too sandy, the onion flowers get too little water and root development is inhibited.

When is the right planting time for Allium

The onion of the giant leek must be planted in autumn. Planting in September and October is ideal. With sufficient soil temperature and moisture, the storage organ forms new roots and the shoot tip develops. Low temperatures in winter do no harm, so ornamental onions stay in the garden all year round. In the spring, the sprouting and the formation of the stalk take place. If planted in spring, only leaves would form and there would be no flowering. Therefore, ball leeks must be planted before winter.

How do I plant my Allium giganteum in the garden

Before planting the ornamental onion, you should loosen the location in the garden, remove all weeds and improve them if necessary (add sand for heavy soil and add humus for light sandy soil). The planting depth depends on the bulb size. As a rule of thumb, the planting hole should be three times as deep as the bulb is tall. Ornamental onions that are set too low sprout with difficulty. It is optimal if you mark the location so as not to cause damage when hacking.

Planting in 5 steps:

  • Dig a planting hole.
  • Put good quality potting soil in the planting hole.
  • With organic flower bulb power you can stimulate and support soil activity. Put this soil activator in the planting hole before planting or sprinkle it on the surface and work it in.
  • Now the storage organs are placed in the planting hole with the tip pointing upwards.

Finally, cover loosely with excavation or potting soil. Depending on the soil conditions, you can water after planting. If you have planted Allium in containers, regular watering is necessary.

How do I properly care for my ornamental onions

In addition to the right location, little care is required for ball leeks in your own garden. If necessary, you can support tall varieties with a stick against wind breakage, but the giant leek Allium is usually stable in the bed and does not need any support. The giant ornamental onion plants bloom for many weeks and even after they have faded they are decorative with a distinctive inflorescence. The flower can be cut off, but it doesn’t have to be. If you want to get seeds, leave the dry inflorescence on the plant. The flower can also be used as a dried flower.

How do I water my ornamental onions correctly

Alliums are easy-care and robust plants, but waterlogging is not tolerated. Therefore, watering is only necessary in completely dry locations. Leeks in the flower pot are also only poured carefully and, especially in winter, are protected from too much rain. Dry leaves after flowering are not a sign of a lack of water. This is a natural process where leafy greens are transferred to the storage organ and a resting phase begins.

How do I fertilize my ball leeks properly

Allium bulbs that are planted in the fall and will delight with colorful blooms in the spring tend to grow in the same spot for many years. Fertilization is necessary to ensure that the giant leek remains vigorous and blooms lushly. Start fertilizing as soon as the leaves have grown about a hand’s breadth out of the ground. Heavy consumers such as daffodils, imperial crowns, tulips, lilies and hyacinths require a higher fertilizer content. Depending on the type of fertilizer, one or more fertilizer applications may be necessary. Only fertilize until the bulb flowers start to bloom, because after flowering the bulb matures for summer dormancy and the fertilizer is no longer absorbed.

What is the best way to plant my Allium in a pot

Ornamental onions can grow well in containers. As with other plants, it is important that there is maximum volume of soil. Varieties with a growth height of 30 to 40 cm are particularly suitable for tubs. The giant leek stays outdoors all winter. Make sure that there is never any waterlogging.

9 tips for planting in containers:

    • Choose vessels with a water drain.
    • Provide a drainage layer at the bottom of the jar.
    • Fill the container with high-quality potting soil.
    • Plant so densely that the allium bulbs are just touching each other.
    • Fill in the cavities with soil.
    • Pour penetratingly.
    • Leave the pots outside, because the cold is necessary for flowering.
    • Make sure that it never gets waterlogged in winter.

At low temperatures, protect the vessel with fleece or special winter protection material.

What pests and diseases can ornamental onions get

With the right site conditions and optimal care, Allium giganteum are robust and floriferous. The leek plants bloom and delight with large flowers on sometimes tall stalks. There are no known problems caused by diseases and pests worth mentioning.

FAQ — Frequently asked questions about ornamental onions

Which plants are suitable for combination with Allium giganteum?

      • Perennials that prefer a sunny location are ideal
      • The plants should have similar water requirements as the bulbous plants

Beautiful combinations with the large flower balls result with cranesbill, lady’s mantle, rock roses or catnip.

Why do the leaves turn yellow in summer?

At the end of the growth phase, the onion plants withdraw the nutrients contained in the leaves. As a result, these aerial parts of the plant turn yellow and wither. The onions store the reserves. It is a natural process that usually has no serious causes.

How do I properly care for my Allium giganteum after flowering in summer?

Immediately after flowering, cut off the stems. In this way, no unnecessary energy is wasted in the formation of seeds. It is important that you protect the foliage and leave it on the bulbous plant in its entirety until it has yellowed and dried up. This process is essential for the flower bulb and influences the budding in the next year. Gently loosen the soil around the bulbs and remove any weeds that may be present.

Can giant leeks be propagated by seed?

If you leave the inflorescence on the plant, seeds will form. This germinates and, with a lot of patience, can grow into ball leek bulbs after a few years. As with most bulbous plants, propagation is basically done by separating small daughter bulbs.

Are alliums good for insects?

Almost all varieties, like chives, are ideal for bees, bumblebees and other insects. The heyday of the leek family coincides with a time when there are few flowers. Fruit trees, rapeseed, linden trees and many spring flowers have faded. Star bulb leeks and other varieties attract numerous insects and offer honey and wild bees a rich supply of pollen and nectar.


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