Q: Is this a good time of the year to plant lilac? And if so, could you please recommend some varieties that don’t grow too large? JK, Dublin
One of the enduring joys of the late spring/early summer garden, this exceptionally long-lived, pollution-tolerant, easy-to-grow, hardy ornamental shrub holds a special place in the affections of many gardeners, who prize it for its intensely perfumed, fleeting blossom.
Many of the oldest varieties of common lilac, or Syringa vulgaris to give it its proper Latin name, slowly grow into substantial shrubs that can eventually reach a height and spread of 5-7m, which would be too big for your purposes. Examples include the mauve-flowered Syringa “Charles Joly”, the ghostly-white S, “Madame Lemoine” and the pale blue, strongly scented S, and “Firmament”, all of which are outstanding heritage French varieties bred by three generations of the Lemoine family between 1876-1953.
Russian breeders have also produced many great lilac varieties over the years, including the wonderful S, “Krasavitsa Moskvy” or “Beauty of Moscow” (pale-pink to white double flowers, height and spread of 5-7m). The American-bred S. Katherine Havemeyer’ is another classic variety that’s also loved by florists.
While none of the above are very suitable for small gardens or container growing, the good news is that new breeding programmes have resulted in a host of compact repeat-flowering varieties that are.
The “Flowerfesta” and “Bloomerang” series of modern hybrid varieties of lilac in particular are useful in terms of their compact but bushy growth habit and disease resistance as well as their greatly extended flowering season, which stretches from late spring intermittently into autumn. Recommended varieties include “Bloomerang Dark Purple”; “Bloomerang Spring Pink”; “Flowerfesta Purple” (pale lilac); “Flowerfesta White”; and “Flowerfesta Pink” (rose-pink).
Just be warned that some gardeners who like their lilacs to flower in traditional lilac season (late spring/very early summer) have criticised these modern longer-flowering varieties for ruining the fleeting magic of the season for them. If that includes you, then instead consider Syringa meyeri “Palibin”, a decorative compact variety of Korean lilac with smoke-pink flowers that appears only in late spring/early summer.
It is also important to point out that although they are compact, none of these varieties make very small shrubs, growing to an average height and spread of 1.25m-1.5m. That said, they will happily grow in a large pot or tub if required, so long as they are given a good-quality growing soil-based compost, kept regularly watered and given an organic mulch and a scattering of slow-release organic fertiliser around the base of the plant in spring. It is also a good idea to deadhead the old blooms as soon as they fade, along with any suckers that appear at the base.
So long as the ground is not waterlogged or frozen, February/early March is a good time of the year to plant lilac. Give it a sunny, sheltered spot and a fertile, cool, moist, but free-draining, neutral to alkaline soil. If your garden’s soil is inclined to be heavy and wet in winter, then make sure to work plenty of coarse horticultural grit into the planting hole but avoid planting into any ground that is prone to winter flooding.
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