When to plant lilacs in spring or autumn

Plant bare-root common lilac while it is dormant. Early spring, after the ground becomes workable and before the buds open, is usually the simplest opportunity. Autumn can also work after leaf fall if the soil can be worked and freezing is still some way off. A well-rooted container shrub gives you more flexibility. Its new site still needs drainage and you need a way to water it through establishment. Check what the nursery is sending before choosing a planting day.

Finding the spring window

For a shrub shipped without a root ball, look for the interval after the ground thaws and before the buds start opening. Dig a little in the actual planting spot, to the depth the roots will occupy. The soil should break apart reasonably easily. If it smears across the spade or the test hole fills with water, wait for it to become workable. An unusually warm afternoon tells you very little about deeper ground.

Later in spring, new leaves and drying wind complicate the handling of bare roots. If you have not ordered yet, look for lilac that is already growing well in its pot, or ask the nursery to deliver during a better window. If the shrub arrives before you can plant, cover and protect the roots from sun and wind immediately. Follow the nursery's storage directions rather than leaving a bare-root plant open in a warm room while you get the garden ready.

When an autumn planting makes sense

Look for natural leaf fall and the end of active growth. Check local soil and the forecast before committing. A light frost on the surface is different from frozen ground at root depth. If the ground is already frozen where you need to dig or rain has left it saturated, delay planting and ask the nursery how to handle that stock. Buying early can make delivery easier to arrange without leaving you to hold bare roots until the weather changes.

On an exposed Ukrainian plot where the ground cools quickly, the autumn opportunity may be brief. A sheltered garden in southern Ukraine may have a longer workable interval but still need irrigation through a dry autumn. On a low plot in Polissia or a site with heavy soil in western Ukraine, check drainage before fixing the date. These are examples of site conditions to look for. A regional name alone cannot tell you whether the bed is ready.

Identify the nursery stock before buying

Bare roots and roots wrapped for delivery

A lilac may be sold without soil or with its bare roots wrapped in damp packing. That wrapping helps keep the roots moist in transit. Treat either type as bare-root stock. Open the package in shade with the planting hole ready. If you find a substantial amount of dried or rotten root material, photograph it and contact the seller before planting. Keep the roots covered and out of direct wind while you assess the problem.

A shrub grown in its container

The roots of a well-established container plant hold the medium together when the pot is gently removed. If the compost collapses immediately, find out how recently the shrub was potted. Watch for thick circling roots at the edge of the pot, too. Loosen accessible roots carefully and ask the nursery how to address a densely bound mass. Preserve the healthy root ball as far as possible while giving the perimeter roots a way into the surrounding soil.

Own-root and grafted lilacs

Ask whether the named cultivar grows on its own roots or was grafted onto different stock. A shoot arising from below the graft can differ from the cultivar you bought. Ask the nursery to identify the graft and give the planting level for its particular stock. Find out before covering the base with soil. Several stems at ground level cannot by themselves tell you which kind of plant you have.

Choose a position for the grown shrub

Common lilac performs well in a sunny position with air movement and soil that drains. Check the shade cast by walls, fences and neighbouring trees when they are in leaf. Look up the mature spread of your particular cultivar and measure the space from the intended centre of the shrub. A small plant looks as if it will fit beside a gate, but a grown shrub can take up much of the passage.

Inspect the area after rain. A puddle below a downpipe or a wet layer beneath a dry surface can matter more than the colour of the topsoil. Compare the location with nearby higher ground. Where water repeatedly stands, move the planting or solve the drainage before buying. A gravel layer at the bottom of a planting hole gives trapped water no outlet through compact ground.

Plant with the base at the right level

1. Open a hole wide enough for the root system to fit without being folded. Use the previous nursery soil level as your guide. For grafted plants, check the supplier's instruction about graft position separately.
2. Spread bare roots over soil in the hole or lower the container root ball into place. View the stems from the side. Lay a straight stick across the hole if judging the height by eye is difficult.
3. Backfill without leaving large voids and water to settle the soil around the roots. Check the height and the position of the shrub again afterwards. Avoid trampling wet soil to force it into place.
4. Mulch the root area and leave space around the stems. Keep the graft clear and visible where the supplier says it should be. Leave the base easy to inspect after rain or watering.

Check the root ball after planting

Feel the moisture in the original root ball and the soil next to it. An open nursery medium and heavy garden soil can dry at different rates. Watch where water goes when you irrigate. If mulch covers the ground, pull it aside briefly to inspect the soil. A damp patch beside one stem does not tell you whether water has reached the rest of the roots.

After heavy rain, check whether the soil drained and whether the shrub sank as the ground settled. In drying wind, check sooner even if a nearby established shrub still looks fresh. A recently transplanted lilac draws from a much smaller volume of soil. In a shaded position, see how long the soil holds moisture before using the same watering pattern as the sunny side of the garden.

Judge establishment by the condition of the whole shrub over the season. Flowers also depend on cultivar, maturity, available sun and past pruning. Before cutting back healthy stems, see when lilacs flower and where their buds form. Use the separate guide to choosing a yellow lilac if flower colour and cultivar choice are your main concern.

Decide whether to feed separately

After planting, get the moisture right and confirm that the soil around the base is still at the right level. A lilac growing normally may not require routine fertilization. If growth is weak, compare the light and soil conditions with healthy shrubs nearby. Assessing the soil before choosing a fertilizer helps you establish whether feeding is useful. Use the shrub group on the appropriate product and keep the separate rate for young trees out of this decision.

Granules for deciduous shrubs

Complex fertilizer universal granular

If the soil and shrub condition indicate a need to feed, the deciduous tree and shrub row applies to common lilac. The figure below belongs to that plant group.

It is recommended to loosen the soil before applying; for trees and bushes, apply to the root zone.

Leafy trees and buches: 45 gr/m²

The product page lists 3 and 5 kg bags and a 4 kg canister. Compare the pack weight with the root-zone area you actually intend to treat and read the complete directions before ordering.

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