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Type:Shrubs and Trees
Pruning season:After flowering
Weediness:Can sucker aggressively

Lilacs (Syringa) are a genus of about 20 species of flowering plants in the family Oleaceae (olive), native to Europe and Asia. The genus name Syringa is derived from syrinx meaning a hollow tube or pipe, and refers to the hollow state of the younger shoots in some species. The name "pipe tree" is occasionally used.


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Lilacs range in size from large shrubs to small trees, 2-10 m tall. The leaves are opposite (occasionally in whorls of three), deciduous, and in most species simple and heart-shaped, but pinnate in a few species (e.g. S. laciniata, S. pinnatifolia). The flowers are produced in spring, each flower about 1 cm diameter, white, pale pink or more generally purple, with four petals. The flowers grow in large panicles, and in several species have a strong fragrance. Flowering starts after 80-110 growing degree days.

Growing conditions

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Lilacs are popular shrubs in parks and gardens throughout the temperate zone. In addition to the species listed above, several hybrids and numerous cultivars have been developed. The term French lilac is often used to refer to modern double-flowered cultivars, thanks to the work of prolific breeder Victor Lemoine.

The wood of lilac is close-grained, diffuse-porous, extremely hard and one of the densest in Europe. The sapwood is typically cream-coloured and the heartwood has various shades of brown and purple. Lilac wood has traditionally been used for engraving, musical instruments, knife handles etc. When drying the wood has a tendency to be encurved as a twisted material, and to split into narrow sticks. The wood of Common Lilac is even harder than for example that of Syringa josikaea.

Purple lilacs symbolise first love and white lilacs youthful innocence.


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Lilac in flower (a white flowered cultivar

Lilacs flower on old wood, and produce more flowers if unpruned. If pruned, the plant responds by producing fast-growing young vegetative growth with no flowers, in an attempt to restore the removed branches; a pruned lilac often produces few or no flowers for one to five or more years, before the new growth matures sufficiently to start flowering. Unpruned lilacs flower reliably every year. Despite this, a common fallacy holds that lilacs should be pruned regularly. If pruning is required, it should be done right after flowering is finished, before next year's flower buds are formed. Lilacs generally grow better in slightly alkaline soil.


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Pests and diseases

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Crown Gall

Bacterial Blights

Powdery Mildew

Leaf Spots

  • Cercospora lilacis
  • Macrophoma halstedii
  • Phyllosticta porteri
  • Phyllosticta syringae
  • Phyllosticta syringella
  • Ploeospora herbarum

Leaf Blights

  • Cladosporium herbarum
  • Heterosporium syringae

White Mold


  • Physalospora obtusa


Shoot Blight

  • Gloeosporium syringae

Thread Blight

  • Pellicularia koleroga

Stem Girdles

  • Hymenochaete agglutinans

Wood Rots

  • Polyporus versicolor (vectored by the lilac borer)

Mushroom Rots




  • Witches’ Broom (LWB)


  • Root Knot

Climate-related Issues

  • Frost injury (causes flower bud failure)
  • Pollution injury (causes leafroll)
  • Susceptible to graft incompatibilities










  • Leafcutter Bees


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  • Flora Europaea: Syringa
  • Flora of China: Syringa
  • Flora of Pakistan: Syringa
  • Christopher Brickell and Judith D. Zuk (1997). The American Horticultural Society A-Z Encyclopedia of Garden Plants. DK Publishing. pp. 993–995. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  • Staff of the L. H. Bailey Hortorium (1976). Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Cornell University Press. pp. 1090–1091. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  • Pirone, Pascal P. (1978). Diseases & Pests of Ornamental Plants (Fifth Edition ed.). John Wiley & Sons, New York. pp. 492–497. {{cite book}}: |edition= has extra text (help); Cite has empty unknown parameter: |coauthors= (help)
  • Cranshaw, Whitney (2004). Garden Insects of North America: The Ultimate Guide to Backyard Bugs. Princeton University Press. p. 622. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  • Pippa Greenwood, Andrew Halstead, A.R. Chase, Daniel Gilrein (2000). American Horticultural Society Pests & Diseases: The Complete Guide to Preventing, Identifying, and Treating Plant Problems (First Edition ed.). Dorling Kindersley (DK) Publishing, inc. p. 196. {{cite book}}: |edition= has extra text (help); Cite has empty unknown parameter: |coauthors= (help)CS1 maint: multiple names: authors list (link)