Lilac (Syringa) with its fragrant flowers is for many inseparable from spring and today adorns countless gardens, mostly in the form of noble lilac. Botanically, the shrub belongs to the Oleaceae family. Almost 30 species and meanwhile countless varieties belong to the genus. The natural range of lilac stretches from Southeast Europe to East Asia. The lilac should not be confused with the summer lilac – despite its similar German name, it is another plant genus that is botanically only remotely related to the lilac.
In recent years the lilac has been avoided by many garden designers, as it did not fit into modern gardens with its rustic garden charm. In addition, garden lovers had to live with the standard assortment for decades, most of which still originates from Lemoine breeding (more details can be found under “Important species and varieties”). The common lilac (Syringa vulgaris), also called peasant lilac, is one of the oldest European garden shrubs. When he – and his numerous hybrids, the so-called noble lilacs – open their long flower panicles at the latest at the beginning of May and exude their unmistakable lilac scent, there is hardly anything more beautiful in the garden. Due to many breeds, the range of robust, easy-care and attractive links for the garden has expanded considerably. Recommended lilac species (and their varieties) are the Chinese lilac (Syringa x chinensis), also known as royal lilac, the dwarf scented lilac (Syringa meyeri), the dwarf shrub Syringa microphylla and the Preston hybrids (Syringa x prestoniae), which are particularly frost hardy.
Appearance and growth
Lilac is a deciduous shrub that over time grows into a large shrub, rarely into a small tree. The growth heights vary greatly by species: While Syringa meyeri is only 1 to 1.5 meters high, the common lilac can reach a proud seven meters. The leaves are opposite, stalked and mostly simple. However, there are also species and varieties with lobed or feathered leaves. They can be oval, roundish to ovoid or heart-shaped. The habitus of the lied itself is very upright and compact. The flower buds usually sit in pairs at the ends of the branches formed in the previous year and, depending on the region, open from the end of April to mid-May. Then the white, yellowish, pink to violet flowers also exude their typical floral scent. After flowering, around the beginning of June, lilac forms fruit capsules containing the seeds.
Location and soil
All lilac species are sun worshippers and tolerate dry heat. They also grow in shady places, but do not form a dense crown and produce considerably fewer flowers. Noble lilacs are also very wind resistant, which is why they are often planted in northern the United States as windbreak hedges. The demands on the soil are different: noble lilac grows best on nutrient-rich, rather dry loam soils with a high lime content, while Preston lilac prefers soils with low lime content and slightly more humid soils. Overall, however, lilac is quite tolerant and can also cope with less favourable soils. However, it does not tolerate waterlogging and soil compaction.
The best time to plant lilacs is in autumn. The planting hole should be about twice the circumference of the root ball. Mix the excavated material with some compost before refilling to improve nutrient supply. Smaller lilac species, such as the dwarf lilac, which are also sold as small stems, can even be cultivated in tubs. Take care to give the plants sufficient space and to avoid waterlogging.
Lilac is extremely easy to care for, because well ingrown plants can do without irrigation even in dry summers. On sandy soils you should provide the flowering shrubs with additional nutrients in the form of horn shavings or slow-release fertilizers. If you apply a thin layer of mature compost to the tree disc every spring, you will enrich the soil with humus and improve its ability to store water and nutrients.
Lilac forms its flower buds already in the previous year. In order not to reduce the flower splendour unnecessarily, you should only carry out smaller pruning measures at the end of May after flowering. If possible, cut back all faded panicles of the lilac using two well-formed side buds. This prevents seed formation and stimulates the shrub to form new flower buds, which then open in the next season. In autumn, you can bring old, aged shrubs back to their former glory by cutting back the main branches to a length of 40 to 60 centimeters (rejuvenation cut). If you want to grow the lilac as a small tree with one trunk, you should cut off all side branches and disturbing side shoots from the young plants as early as possible.
Lilacs are very suitable for single planting, but can also be combined with other flowering shrubs. Ideal are plants that flower at about the same time, for example ornamental apple, Kolkwitzie (Kolkwitzia), Duftjasmin (Philadelphus) or Weigelie (Weigela).
Dream couple: Lilac (left) and ornamental apple (right) bloom in a duet
Also windbreak hedges made of lilac are useful and a real feast for the eyes during the flowering season in May. Small species like the dwarf scented bush (Syringa meyeri ‘Palibin’) can be kept on the terrace as hardy tub plants with a height and width of only 1.2 metres. Since the shrubs form a very dense root network and often also runners, planting underneath in the garden is not easy: choose different bulb flowers or robust shrubs that can withstand drought, such as Brandkraut (Phlomis russeliana), Waldanemone (Anemone sylvestris) or Balkanstorchschnabel (Geranium macrorrhizum). Tip: Lilac also does very well in the vase, although it withers quickly there. Its scent can fill entire rooms. A nice side effect: If you regularly cut a few bouquets during the flowering period, you will automatically prevent the crown from growing old and paying for itself.
Important species and varieties
An Austrian envoy brought the lilac from Turkey to the Viennese court in 1565. From there, the flowering shrub finally found its way into Central European gardens. Especially in the Lemoine tree nursery in Nancy/France at the end of the 19th century, intensive breeding resulted in a large variety of varieties. These noble lilacs already mentioned helped the shrub to its final breakthrough as a garden plant. In England, the common lilac and its cultivars still bear the name “french lilac” (“French lilac”) today, but as far as variety is concerned, much has changed in recent years, as already mentioned: In the meantime, there are current varieties of the noble lilac with significantly improved characteristics. They are more robust and usually somewhat more compact than the old varieties. Their flowers often look two-coloured because the bracts of the buds are darker than the petals. All noble lilac varieties can grow up to four to six metres high and can also be grown as small flowering trees with one stem. They can reach a very high age and occasionally form runners.
The so-called Preston hybrids (Syringa x prestoniae) play an increasingly important role. They are also available under the German name Kanadischer Flieder. These are varieties which originated around 1920 in Canada from crosses between the Bogen lilac (Syringa reflexa) and the Zottigen lilac (Syringa villosa) which is hardly known in this country. They are very frost hardy, carry particularly long, filigree flower panicles and flower somewhat later than the varieties of the Edel-Flied. Preston hybrids are the first choice for smaller gardens in particular, as they are barely taller than three metres. The varieties ‘Minuet’ (light violet) and ‘Redwine’ (purple red) have been awarded ‘Excellent’ in a tree classification in the Netherlands.
Noble lilacs used to be propagated mostly by grafting, which means that the roots of the plants originate from the common lilac. However, this tends to the runner-formation and drives wild fliederschösslinge loudly with it. Nowadays more and more noble lilacs are grown “root true” from cuttings or by meristem propagation in the laboratory: On the one hand, root-true noble varieties form fewer runners, on the other hand, these are variety-true. Buy therefore with the noble lilac if possible root-true varieties.
If you want to propagate lilacs yourself, the easiest way to do this is to use root runners, which are pricked with a spade in spring or autumn. But beware with noble song varieties: They are often grafted on seedlings of the wild species, which means that your offspring is a “wildling”. The Chinese lilac, the bow lilac (Syringa reflexa) and the Hungarian lilac (Syringa josikaea) can be multiplied by cut wood. Dwarf lilacs are propagated exclusively by cuttings. Sowing is also possible with wild species. Simply harvest the dry fruit in October, shake the seeds out and put them in growing boxes with sowing soil. These can then remain outside until January, but should not dry out completely during this time. Then they come covered into an unheated greenhouse, where the seeds begin to germinate. In spring the seedlings can be pricked into individual pots, in autumn they are placed in the garden.
Diseases and pests
A typical pest that can occur on lilacs is the lilac miner moth or lilac moth. They recognize an infestation by brown leaves in May. As a rule, it is sufficient to pick the larvae by hand as soon as they appear. Aphids and powdery mildew may also occur, but do not cause major damage.
In an interview with our store editor Dieke van Dieken, plant doctor René Wadas reveals his tips against aphids.Credits: Production: Folkert Siemens; Camera and Editing: Fabian Primsch
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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.