Ornamental garlic (Allium), which belongs to the Allioideae subfamily within the Amaryllis family (Amaryllidaceae), is undoubtedly one of the most varied bulb flower genera. Approximately 940 persevering types count to the type Allium today – with it, it is one of the biggest types among the bulb-flowers. In addition, there are some hybrids that have been created by crossing different species, as well as various varieties. In former times the genus was assigned to the family of the lily family (Liliaceae). However, molecular genetic investigations led to a change in plant systematics.
The use of leeks distinguishes between ornamental and useful plants. The genus Allium includes, among others, onions (Allium cepa), leeks (Allium ampeloprasum), garlic (Allium sativum) and chives (Allium schoenoprasum). Species such as wild garlic (Allium ursium) are cultivated both for ornamental purposes and for consumption in the garden, while star-spotted leek (Alllium christophii) is cultivated as a purely ornamental plant. The leeks are found almost all over the world, with most Allium species occurring in the northern hemisphere. The bear’s garlic is one of the few species native to our region. It has its natural occurrence in beech forests. Many of the ornamental species planted are steppe and mountain plants from Central Asia. There are about 35 different ornamental leek species and hybrids available in nurseries, with Iran leek (Allium aflatunense), star ball leek (Allium christophii) and the Allium hybrid ‘Globemaster’ among the best known.
Appearance and growth
Depending on the species, ornamental garlic reaches a growth height of 12 to 150 centimetres. For example, the blue tongue leek (Allium nevskianum) grows to a height of between 12 and 15 centimetres, while many hybrid varieties, but especially the giant leek (Allium giganteum), impress with their impressive height. The flowering season is between April and September, with the most frequently planted species flowering between May and June. The individual flowers stand in umbels, which in many species have a spherical shape and can reach a diameter of 25 centimetres. Violet tones predominate as flower colour, but there are also white, yellow, pink, red and even blue flowering species. The strong flower stalk is usually leafless. After the fertilization of the flowers, capsule fruits develop which contain black ovoid to spherical seeds. The long, narrow leaves of the bulbous plant are stalked and the ornamental leek can be distinguished between the two vegetation and resting phases typical of bulbous plants: In spring the leaves and the flower shaft sprout from the underground storage organ. After flowering and subsequent seed ripening, all parts of the plant above ground die off, while the bulb survives until next spring. Neither root growth nor the formation of daughter bulbs take place during this resting phase. For many Allium species, the vegetation period lasts only three to four months. They are thus optimally adapted to the summer droughts of their home countries.
Location and soil
Like almost all bulb flowers, the various Allium species grow predominantly in extreme locations that can only be colonised by a few plants. Their habitats are often steppes and rocky mountain slopes, which are blessed with sufficient precipitation only for a few months of the year. The bulb allows the ornamental garlic species an extremely short vegetation period, because the entire plant, including the flower, is already planted in it and rests in the soil until the soil temperature and humidity allow it to sprout. When the first green tips of the various Allium species penetrate the soil surface, it only takes a few weeks until the plants are in full bloom. After pollination by insects and the onset of seed maturation, most Allium species wither quite quickly and store all important nutrients back in their bulbs – the entire growing season rarely lasts longer than three to four months and therefore enables the plants to survive in summer-dry regions. However, this also means that most ornamental garlic species, like tulips, react very sensitively to damp, impermeable garden soil. Under permanently damp conditions, the onions rot sometimes very fast.
Onions are planted from September to November, when the soil is frost-free, even into December. The soil should be permeable, the location predominantly sunny. On loamy soils, you should bed the onion on a shovel load of coarse-grained construction sand so that the rainwater can seep away well. An early planting is preferable with most types, so that the bulbs can still root before the winter. With the hybrid variety ‘Purple Sensation’, however, an early planting date leads to a very early shoot in spring, which is then at risk of frost. Planting is not recommended before November. The planting depth depends on the size of the bulb. As a rule of thumb, the planting hole should be three times as deep as the bulb is high. Tip: It is best to mark the planting sites with thin bamboo sticks so that you do not damage the late sprouting Allium species in spring when working the soil.
In many ornamental garlic species, the leaves turn yellow quite early in the year, sometimes even at flowering time. If they should interfere optically, they can be removed. Otherwise one waits until after the bloom the above-ground plant parts wither and then cuts them off. The bulb flowers are fertilized during the spring shoots, a suitable organic fertilizer is a complete fertilizer.
Wintering or winter protection
Some Allium species are not completely hardy in our latitudes. In an unprotected position, you need winter protection in the form of a cover made of fir brushwood, straw or leaves. Alpine species in particular must be protected from the interaction of frost-thaw frost.
The tall Allium species and hybrids can be well combined in the sunny bed with many flowering shrubs, for example with perennial peonies (Paeonia), cranesbill (Geranium) and catnip (Nepeta). They are the right choice for the romantic garden as well as for gardens in the country house style – here they also make a good figure as rose companions. In modern facilities, characterised by architectural forms, the large spherical inflorescences can be very well staged, for example between grasses. Short-stalked species such as the blue-tongue leek or the gold-leek (Allium moly) are suitable for the rock garden. Bear’s garlic is the right choice for large, near-natural plantations under deciduous trees.
Important species and varieties
Anyone who has ever been to a garden show will have come across various Allium species, because garden designers love ornamental garlic. No wonder: especially with large flowered species like the giant leek ‘Globemaster’ or the star ball leek great bed designs can be realized. During the main visiting season in May and June, the plants are usually in full bloom and seem to float with their large purple spheres over the bed. Ornamental garlic species are often combined with bed roses and medium-high summer shrubs such as phlox, catnip, gorgeous cranesbill and steppe sage. The star ball leek is also an excellent bedding partner for ornamental grasses and late summer perennials such as coneflower, stonecrop and aster, because its golden yellow, withered inflorescences set great accents at the end of the season.
In addition to the larger Allium species for bedding, there are a number of smaller species that feel at home in the rock garden. Most prefer calcareous gravel soils, but are quite adaptable in pH as long as the soil is permeable. The winter hardiness of the onions also depends strongly on the permeability of the substrate: Low winter temperatures are no problem, especially for the Central Asian ornamental garlic species, because even in the continental climate of their homeland the temperatures can drop far below freezing. It is only important that the soil is airy and dry, because the onions do not tolerate wet cold. By the way: A rock garden is ideal for hobby gardeners to live out their Allium collecting passion – in view of the diversity of species, however, it should not be too small.
Picture gallery: Ornamental garlic variety
The ornamental garlic species usually form daughter bulbs, which can be separated from the mother bulb and replanted in autumn. Species such as wild garlic spread strongly on their own. Plants that are too dense can be excavated and replanted in late summer. Many species are reproduced by sowing. The plants are cold germ buckets, which means that the seeds need a cold effect of several weeks after sowing with temperatures around the freezing point so that they rise.
Diseases and pests
Ornamental garlic can be infested by aphids, otherwise pests and plant diseases do not play a major role.
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I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.