In the last week, two people in our local online gardening forum have asked for help identifying the mystery shrub blooming in their yard:
Recognize it? Most people are familiar with lilacs. (I can only assume that these two are newbie gardeners!) And how can you help but love these impressive flowers, with their memorable scent? If there’s any downside, it’s that for most of the year lilacs are either dormant and leafless, or a plain green blob. But when those blossoms appear in May, all is forgiven. Lilacs are an old favorite, and Colorado is an ideal place to grow them.
Lilacs are easy to identify. Look for a large shrub with opposite branching—a trait they share with maples, dogwood, ash trees, and honeysuckles, among others. This branching carries over into the flowers, which appear as twins. The bright green leaves are a classic “leaf-shape” with a point at the end. And those flowers come in not just purple, but also pink, blue, red, white, and yellow.
Lilacs are amazingly forgiving. We had several planted in un-amended dirt (I hesitate to call it soil), where they only received any irrigation during periods of severe drought. We purchased them as fifty cent seedlings from the US Forest Service, and by the time we moved, twenty years later, they towered over my head and were covered with abundant purple flowers every spring. I miss them!
Sure, they’d prefer fertile soil and regular watering, but the only mandatory requirements are full sun, good drainage, and significant winter chill. (The smaller Korean Lilacs are a better choice for areas with milder climates.)
Pruning isn’t essential, but some thinning of dense shrubs can help prevent powdery mildew. Flowers bloom on old wood, so pruning in the spring can eliminate the show for that year. Some people prune off spent flower heads, mostly for cosmetic reasons. A few varieties are repeat bloomers, and deadheading will increase the second flush of blossoms. If the shrub becomes old and overgrown, try cutting off a third of the oldest stems at ground level. Repeat over the next two years to you’ll have a completely rejuvenated plant.
Along with the aforementioned powdery mildew, lilacs can be subject to several other pests and diseases, but healthy plants shrug off most problems. I get a kick out of the neat, circular cut-outs left by the leaf-cutter bees, especially as I know they won’t do any harm. Possible nasties include Cecropia and Great ash sphinx moths (which chew leaves), black vine weevils, lilac leafminer, bacterial blight, and rust. More concerning are lilac borer (Podosesia syringae) and scale. Still, most lilacs thrive problem-free. Don’t let this list deter you.
Syringa vulgaris isn’t the only lilac species. We have a Japanese Tree Lilac (Syringa reticulata) planted next to our driveway, chosen for its pretty clusters of fragrant white flowers and lack of fruit drop. (The original plan called for a Canada Red Cherry, which would have dropped red chokecherries all over the pavement, not to mention the dining, and pooping, birds it would have attracted. No thanks.) This small-to-medium sized tree also does well in Colorado. It prefers consistent moisture, but it can tolerate drier conditions, along with alkaline soils and very cold temperatures.