Lilacs, the fragrant, flowering shrubs of the genus Syringa, are a beloved sign of spring, but the question of “how long they last” has three different answers depending on the context. The duration can refer to the life of the entire perennial plant, the brief, intense period of its annual bloom, or the fleeting vase life of the cut flowers. Understanding these three distinct timeframes allows for the best care and appreciation of these classic garden plants.
The Lifespan of the Lilac Shrub
The lilac shrub itself is remarkably long-lived. Under suitable conditions, many common lilac (Syringa vulgaris) varieties can survive for a century or more, with some historical specimens dating back to the 1870s still thriving today. This impressive longevity is supported by planting the shrub in a location that receives at least six hours of direct sunlight daily and ensuring the soil is well-drained.
For the plant to maintain vigor and abundant flowering over decades, a specific technique called rejuvenation pruning is necessary for older, overgrown shrubs. This process involves the systematic removal of the oldest, thickest stems over a period of two to three years. Since the most productive flowers grow on younger wood, removing a third of the oldest canes each year encourages new, healthy shoots to emerge from the base, effectively renewing the plant.
The Duration of the Annual Bloom
The seasonal display of lilac flowers is relatively short, typically lasting between two to four weeks, though this can vary by species and local environment. The bloom time is heavily influenced by climate, as lilacs require a period of cold winter dormancy, known as chilling hours, to set their flower buds. Once spring arrives, cooler temperatures tend to extend the bloom duration, while a sudden heatwave can shorten the flowering period considerably.
Gardeners can strategically extend the overall lilac viewing period in their landscape by choosing cultivars with varying bloom times. Planting a combination of early-season varieties, like Syringa x hyacinthiflora, with mid-season common lilacs and late-season types, such as the Japanese Tree Lilac (Syringa reticulata), can provide continuous flowering for up to two months. Some modern cultivars, like the Bloomerang series, have been bred to rebloom sporadically in the summer and fall, further stretching the seasonal enjoyment.
Maximizing the Life of Cut Lilac Flowers
Once cut, lilac stems have a naturally short vase life, often lasting only three to seven days, which makes proper post-harvest care crucial for maximizing their display. The ideal time to harvest blooms is in the cool part of the morning, after the dew has dried but before the sun is strong, when the stems are fully hydrated. When selecting stems, they should have at least half, but not all, of their individual florets open, as the flowers open very little once they are cut.
Immediate immersion into a bucket of water is required, and all foliage that would sit below the waterline must be stripped away to prevent bacterial growth and water loss through the leaves. Lilacs have woody stems that are prone to sealing, which prevents water uptake, so the stem ends must be prepared to allow for maximum hydration. A common technique is to make a fresh cut on a slant, then immediately split the bottom inch or two of the stem vertically or crush the stem end with a hammer.
After preparation, the stems should be placed in water containing a floral preservative, or a homemade solution, and conditioned in a cool, dark place for a few hours before arranging. The preservative can be created using a mixture of:
- Water.
- Sugar (as a food source).
- A few drops of household bleach (to inhibit bacteria).
- A slight acid, such as lemon juice (to help the water travel up the stem).
Keeping the arrangement away from direct sunlight and heat sources, and changing the water daily, will help the delicate blossoms remain fresh for the longest possible time.