Lilac shrub root-bound and not growing


I have a lilac bush in a container. whicvh i had planned to put into the ground this year. but it is not doing well.. the other lilacs are way ahead with their growth and leaves and flower heads forming. what can i do. i took it out of the container and it appears root bound. can you advise me will try to send photo. thank you.


Lilacs (Syringa) come in many sizes. Common lilac shrubs (Syringa vulgaris) are seen along Ontario country roadsides in fragrant bloom mid-spring. Lilacs are a resilient Zone 3 shrub and are considered a non-native invasive plant in the U.S. and Canada. In natural settings, they tend to dominate shallow limestone areas.

Smaller varieties can be grown in pots with well-drained soil and medium moisture. Dwarf Korean Lilac (Syringa meyeri ‘Palabin’) has a small, rounded form suitable for containers. However, a plant that is severely root bound indicates it is a larger variety and requires more space. Being confined and root-bound in a container is causing stress and diminished growth in the plant.

Below is a detailed article on how to box-cut the root ball so the roots mix more freely when planted in soil. University of Minnesota technicians tried three different methods with encircled roots: 1) use a knife to slice cuts into the sides and bottom; 2) box cut with pruning saw into a square and 3) leave roots as is. After five years of growth, they dug up the samples and found box cut roots most successfully spread into the soil.

Planting the tree to the proper depth is key to its survival. Instead of planting it at the same level as in the container, it is suggested that the top soil be removed until the first large root (1/4 inch thick) appears. This root should be planted level or just above soil level.

Toronto Master Gardeners website has an excellent Garden Guide for tree planting:

Hopefully the lilac will rebound and flourish in your garden.

May 4, 2022