Preston lilac

Preston lilac: how do you recognise it?

Habit

Sturdy, upright, dense shrub about 3 m tall and wide.

Leaves

Large, broadly oval, about 8–15 cm, opposite, dark green.

Flowers

Long, narrow, nodding panicles of pink to purple flowers, in June.

Scent

Sweet and pleasant, especially on warm days.

Roots

Fibrous and branching; it may form some suckers.

Flowering: June · Plants: March–April and October–November · Pruning: June–July

Why grow it?

• Late flowering in June, when common lilacs have finished.
• Long, nodding, scented panicles, lovely to cut for a vase.
• Extremely hardy, even after the harshest winters.
• Bees and butterflies visit the flowers.
• Tough and easy, with little maintenance.

Preston lilac: where does it grow best?

• Sun to partial shade; it flowers best in sun.
• Rich, well-drained soil: sand, loam or clay, best neutral to chalky; add a little lime on acid soil.
• Normally moist soil; no standing water.
• Plant it where you will smell it, near a terrace or window, or as a loose hedge.
• Allow 2.5–3 m of space per plant.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

3 m tall, 3 m wide

Hardiness

Hardy (to -40 °C)

Goes well with

• Peony: Flowers at the same time in June and fills the space in front of the shrub.
• Rose: Shrub roses flower in June too, in pink, white or red.
• Cranesbill (hardy geranium): Blue or purple flowers fill the space under the shrub.
• Foxglove: Tall flower spires in June among the shrubs.

Preston lilac: when and how to plant it?

Plant in March–April and October–November.

1. Plant in March–April or in October–November, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and mix in compost.
3. Set the shrub at the same depth as it stood in its pot and firm the soil well.
4. Keep 2.5–3 m away from other shrubs and buildings.
5. Water in well straight away, even if it is raining.
6. Spread a layer of compost or bark around the base, without covering the stem.

Care

Water

Weekly in dry spells in the first year. After that rain is enough, except in long dry summers.

Feeding

In spring, a spadeful of compost or organic fertiliser. Too much nitrogen gives plenty of leaves and few flowers.

Mulching

A layer of compost or bark keeps the soil cool and moist.

Spent flowers

Cut off the faded panicles straight after flowering; this keeps the shrub tidy and gives new flower buds room.

Liming

On acid soil, scatter a little lime every few years.

Tip: Plant it next to a common lilac: they flower a few weeks apart, so you enjoy the scent for longer. Cut off the faded panicles straight after flowering.

Preston lilac: when to prune it?

Pruning months: June–July.

When: Straight after flowering, in June–July.

How:

• Cut off the faded panicles just above the first pair of leaves or young shoots.
• Remove dead, weak and crossing stems right at the base.
• A shrub that has grown too tall can be shortened by a third after flowering.
• Every few years, take a few of the oldest stems to the ground to keep the shrub young.

Caution: Lilacs flower on old wood: the flower buds form in summer. So never prune in winter or spring, nor after mid-July, or you will cut off the flowers.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Softwood cuttings

In June–July: 8–10 cm cuttings from young shoots in moist cutting compost under plastic. Results vary, so take several.

Layering

In spring, bury a low stem and pin it down; separate it after a year.

Suckers

In autumn, lift a rooted sucker. On grafted shrubs the sucker comes from the rootstock and is not the same as the plant.

Preston lilac: how does it get through the winter?

Hardy to −40 °C.

• Very hardy, down to about −40 °C: one of the hardiest ornamental shrubs, in Belgium it never needs protection.
• Next year’s buds are already on the branches, so do not prune in winter.
• In a pot: stand it against a wall and wrap the pot in hessian so the roots do not freeze.

Diseases and pests

• Powdery mildew: White powder on the leaves from late summer. Usually harmless; ensure air and space, water at the base and thin a dense shrub.
• Bacterial blight: Black spots on leaves and young shoots and dying tips in a cool, wet spring. Cut affected wood back into healthy wood, clear the prunings and avoid too much nitrogen.
• Few or no flowers: Too much shade, too much nitrogen fertiliser or pruning too late. A young shrub sometimes flowers only after two to three years; give it time and prune only after flowering.
• Aphids: On young shoots in May–June. Ladybirds usually clear them; otherwise rinse off with water.

Through the year

• March: Plant or transplant. Give compost.
• April: Apply mulch. Water young plants.
• May: Buds swell. Watch for aphids.
• June: Flowering. Cut off faded panicles. Prune after flowering.
• July: Take softwood cuttings. Water in dry weather. No more pruning after mid-July.
• August: Watch for powdery mildew. Water in dry weather.
• October: Plant. Lift suckers.
• November: Plant. Clear fallen leaves.
• December: Dormant. Next year’s buds are already on the branches.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• Isabella Preston was an English-born Canadian plant breeder who crossed lilacs and lilies in Ottawa; this group is named after her.
• These lilacs were developed for the harsh Canadian climate and are known for their extreme hardiness.
• Next year’s flower buds form as early as summer and spend the winter on the branches.