Lilac shrubs or trees (Syringa vulgaris) are loved for their heavenly fragrant flowers in spring and summer. In autumn their heart shaped leaves change colour, before they lose their leaves for winter.
Lilacs do best in cool to mild weather and a spot that gets full sun to part shade. The soil should be able to drain well. Depending on the cultivar you’ve chosen, they can grow from 2-4 metres tall.
Lilacs are prized for their incredibly fragrant blooms that perfume the garden in spring. However, these classic shrubs require specific growing conditions to thrive Heavy clay soil can be problematic for lilacs, but with a few adjustments, you can still enjoy their beauty and fragrance
Follow this complete guide to learn techniques for planting lilacs in clay soil. With good preparation and aftercare, your lilacs will flourish despite the challenging soil environment.
Why Lilacs Dislike Wet Clay Soil
Lilacs have roots that need good drainage and air circulation. Compacted clay soils easily become waterlogged after rain. Excess moisture surrounds the roots, suffocating them by depriving them of oxygen. This leads to root rot and other detrimental effects.
Standing water also increases the risk of soil-borne fungal diseases taking hold. Over time, consistently soggy soil severely weakens lilacs, stunting their growth and reducing bloom production.
Additionally, clay soil is dense with few large pore spaces. This prevents proper root expansion and penetration. The fine particles cling tightly together, making it difficult for roots to ramify outward.
For these reasons, heavy wet clay must be amended prior to planting lilacs. The goal is to create a loose, well-draining soil environment the roots can thrive in.
Preparing Clay Soil Before Planting
When prepping a clay soil planting site for lilacs, focus on these important steps:
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Test drainage – Dig a hole 12″ deep and fill with water. If it takes more than 12 hours to drain, the site drains poorly.
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Loosen the soil – Rototill or double dig to break up compacted clay. Remove rocks and debris
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Add organic matter – Incorporate 2-3 inches of compost, aged manure, leaf mold or peat moss per square foot of soil.
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Mix amendments thoroughly – Blend into at least 8 inches deep, and up to 12 inches for optimal results.
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Consider raised beds – Building raised beds creates excellent drainage for lilac roots.
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Improve texture – Adding materials like gypsum, calcined clay or sharp sand gives clay soil better granularity.
With plenty of organic material worked into the heavy clay soil, it will improve drainage and provide the loose consistency lilac roots need.
How to Plant Lilacs in Clay Soil
When planting lilacs in clay, follow these tips:
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Dig an extra wide hole at least 2-3 times the width of the root ball.
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Rough up the sides and bottom of the hole with a fork to promote outward root growth.
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Partially backfill the hole with the amended soil mix.
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Carefully place the lilac in the hole, positioned upright. Top of root ball should be level with the ground.
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Fill remaining space with amended soil, tamping gently to remove air pockets.
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Water thoroughly until moist, then add mulch. Avoid piling mulch on stems.
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Stake the shrub for support if needed while establishing.
Caring for Lilacs in Clay Soil
Keep your lilacs thriving in clay soil by providing attentive care:
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Water 1-2 times per week during the first year, avoiding heavy soakings.
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Replenish mulch annually to retain moisture and suppress weeds.
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Fertilize in early spring with a balanced 10-10-10 or rose fertilizer to encourage flowering.
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Prune immediately after blooming by removing spent blooms and any weak or dead branches.
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Monitor for signs of fungal issues like powdery mildew and treat organically at first onset.
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Aerate compacted areas around the roots in fall with a fork to improve drainage before winter.
With proper preparation and ongoing care, those fragrant lilac blooms you love can thrive in clay!
Choose Lilac Varieties Suited for Clay Soil
Certain lilac varieties are better able to cope with heavy soil than others. Look for these clay-tolerant types:
- Common lilac (Syringa vulgaris)
- ‘Charles Joly’ – Large reddish-purple double blooms, French hybrid
- ‘Miss Kim’ – Compact Korean dwarf lilac, lavender blooms
- ‘Sensation’ – Single purple with white edges, heavy bloomer
- ‘Josee’ – Reblooming dwarf, deep pink blooms
- ‘Bloomerang’ series – Reblooming dwarf hybrids in various colors
When shopping for lilacs, let your nursery know you’ll be planting them in dense clay. They can further recommend suitable varieties to give you the best chance of success.
With some thoughtful preparation and care, you can have vibrant, fragrant lilacs brightening your yard despite challenging soil conditions. Try these techniques for planting in clay and you’ll be rewarded with armloads of beautiful, sweet-smelling blooms each spring.
Planting in the garden
Prepare the soil and dig a hole twice as wide and as deep as the pot. This is where you will plant your lilac. Gently remove the lilac from the nursery pot and tease the roots lightly if they’re compact. Plant into the hole and backfill around the plant. Water in well. Put mulch around the base of your lilac to keep it moist and keep weeds away, but don’t put mulch on the main stem.
Lilacs that are smaller or grafted can be grown in large pots or planters that drain well. Pick a pot that is at least 50–60 cm wide and the same depth. Fill your pot or planter with Scotts Osmocote Premium Potting Mix. Gently remove the lilac from the nursery pot and tease the roots lightly if they are compact. Plant the lilac into the potting mix and backfill around the plant. Add a lot of water and mulch over the top of the potting mix to help it stay moist. But don’t put mulch on top of the plant’s main stem.
Lilacs are easy to take care of. To keep them happy, you only need to fertilize them once a year in late winter with Scotts Osmocote Controlled Release Fertilizer: All Purpose. Every spring, put down a new layer of compost and mulch around the plants’ drip zone to help keep the soil moist and keep weeds from growing. If you live somewhere that doesn’t get much rain in the summer, you will need to water your lilac often when it’s dry. During the off-season, cut away any dead wood and suckers that have grown at the base of your lilac. When lilac plants are young, cut off the spent flowers. But when the plants are tall and established, don’t bother with them as much.
Lilacs are very hardy and generally pest and disease resistant, especially once they are established. Slugs and snails may attack younger lilacs and new plants. If this happens, put beer traps (shallow saucers filled with beer) at the base of your lilac or sprinkle Defender Slug and Snail Pellets around it. When to Plant Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec.
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Top 5 steps to growing lilacs
- Choose a full sun to part shade spot
- Before planting, work Scotts Osmocote Compost Premium Soil Improver into the soil and add dolomite lime if the soil is too acidic. Lilacs like soil that is more alkaline.
- Make sure the tree or shrub has plenty of room to grow. Before planting, always check the label to see how tall and wide the plant will get when it’s fully grown.
- When it comes to soil, lilacs like it when it drains well. They won’t do well in heavy clay soils or soils that stay wet a lot.
- Lilacs come in different shades of white, mauve, pink, and purple. Pick one that goes with the rest of your garden’s colors.
Lilacs prefer a moist, yet free draining soil that has been enriched with organic matter. Before you plant, get the soil ready by mixing Scotts Osmocote Compost Premium Soil Improver and Scotts Osmocote Controlled Release Fertilizer: All Purpose together.
How to plant lilac tree and improve your clay soil
FAQ
What bush grows well in clay soil?
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Arborvitae
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Aronia
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Buttonbush
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Cotoneaster
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Dogwood
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Diervilla
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Flowering Quince
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Forsythia
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Honeysuckle
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Lilac (well drained clay only)
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Ninebark
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Potentilla
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Rose of Sharon
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Smooth hydrangea (well drained clay only)
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Spirea
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What is the best place to plant a lilac bush?
What is the best month to plant lilacs?
What kind of soil is best for lilacs?
How do you plant a lilac tree?
Plant the lilac: Dig a hole that is twice as wide and deep as the root ball of your lilac. Gently loosen the roots and place the plant in the hole, making sure that the top of the root ball is level with the soil surface. Backfill the hole with the amended soil and lightly firm the soil arund the plant. 4.
Can Lilacs grow in clay soil?
To improve the growing conditions for lilacs in clay soil, it is recommended to amend the soil with organic matter such as compost or well-rotted manure. This will help to improve the soil structure, increase drainage, and provie essential nutrients for the lilacs. Additionally, adding perlite or sand to the soil can also help to improve drainage.
What kind of soil do lilac plants need?
Specifically, lilac plants will want a neutral or slightly alkaline soil with a pH of somewhere around 7. If you have clay soil, it’s best to amend it with humus, compost or similar organic material for it to be aerated. Unfortunately, a lilac shrub sitting in too much water is a recipe for disaster.
How do you grow a lilac plant in a container?
Dig a hole that’s both deep and wide enough for a container-grown lilac plant’s roots; the top of the root ball should be level with the soil. Backfill and gently firm the soil around the plant then water in the well. Add mulch to retain moisture in the soil and to cut down on weeds.