Lilac tree in bloom
image by Dorian Bianco:commons.wikimedia.org
Lilacs are the visually stunning and sweetly scented harbingers of summer. Grown in either shrub or tree form, lilacs can be used in the garden as hedging, foundation plantings and ornamental specimen trees. As deciduous flowering shrubs, lilacs can easily be pruned during dormancy to present in a tree configuration. The tree structure is best established when the tree is young and yearly maintenance pruning is sufficient to maintain this form.
Maintain a well drained, evenly moist but never consistently wet soil for your young lilac tree. Establish a watering regimen by feeling the soil with your finger an inch or two down into the soil every few days for a few weeks. You will quickly be able to determine the average time that water will be required, what kind of uptake your young tree has and how much is enough to keep it moist between waterings. Lay down a blanket of organic mulch to assist in retaining moisture and to keep down competition from weeds. Consider using shredded bark, leaf mold or cocoa hulls applied at least an inch thick around the root ball out to the drip line of the tree.
Prune your young lilac shrub to establish a structural tree shape in the dormant season in late winter just before new growth appears. Cut away the lower hanging branches on the trunk and select three to five main branches to serve as the structure for the lilac tree canopy. Prune away the others and remove any branches that cross or abrade one another.
Apply a layer of well aged manure and compost around the root ball of the tree and till it in lightly and water it in. This should be your only fertilizing on young lilacs. They are light feeders and even mature lilac trees only require feeding every 3 years or so. The manure and compost will gently boost the nutrient value of the soil. Hold off on using a chemical fertilizer until the tree is at least a few years old and when you do make it a low nitrogen formulation.