Boston's Arnold Arboretum
One of the country's lushest and most varied collections of lilacs
Founded by Harvard College in 1872 from a bequest by James Arnold, Boston's Arnold Arboretum contains one of the country's largest collections of lilacs. As well as a vast array of other plants and trees, lilacs abound on this 265-acre preserve. Between 15 and 20 different lilac species, in about 350 varieties, thrive here in a wide range of colors and scents.
Gardener Steve Schneider led Michael Weishan on a tour of the Arboretum's lilac collection on the day The Victory Garden came to visit, explaining a little bit about these aromatic shrubs, and how to grow and tend them.
The first thing to bear in mind is that from the time you transplant it from the nursery, a lilac will typically take as long as six years to produce blooms. Also, the one or two years it may have spent at the nursery before you acquired it usually can't be deducted from that waiting period owing to the traumatic effects of moving the shrub.
Most of the lilacs at the Arboretum are planted on hillsides. This is worth noting because, as Steve emphasized, lilacs do not do well with "wet feet" meaning they require good drainage, which is aided by a slope. To help prevent the onset of powdery mildew, which can often afflict the leaves, lilacs also need plenty of air flow.
Lilacs also do best in soil that is slightly alkaline. At Arnold Arboretum, as in New England generally, the soil is slightly more acidic, around 6.8. The gardeners use regular applications of lime to keep the soil's pH closer to 7, which is neutral. If your soil is acidic, note that lime takes about six months to activate, so an application in the spring as well as the fall is a good idea.
In terms of rejuvenating old or overgrown lilacs with flowers that have become too high and sparse, Steve recommends cutting the shrub back by one-third each year for three years. In choosing what to prune, look for branches whose flower growth is concentrated at the top, with very little activity lower down. When removing these branches, cut them out right down to the base. You don't want new little branches to grow from larger ones that have been incompletely pruned they'll just cause problems down the road. Proper pruning will help direct more of the shrub's energy toward the base where you want new suckers to grow. Taking out some unessential larger branches will also allow more nourishing sunlight to penetrate to the base.
Maintaining a healthy lilac is a process of give and take, but one well worth the effort for all the enjoyment and beauty it can bring to your garden.
This segment appears in show #2705.