Four Soil Prep Steps Before You Plant a Tree

Healthy trees start below the surface. Here are four practical soil prep steps to set your new trees up for strong growth.

Care GuidePlanting GuideSoil PreparationSpring

Healthy trees start below the surface. Whether you're planting a feature Magnolia, a screening Waterhousea, an Olive for a Mediterranean look or a tough Banksia for sandy ground, the soil work you do before the tree goes in sets it up for the strongest possible decade ahead.

Here are four soil prep steps that make the biggest difference.

Soil preparation for tree planting

1. Add organic matter

Compost, well-rotted manure and leaf mould feed soil structure and the microbes that release nutrients to roots. Spread a 5-8cm layer over the planting area and dig it through to 15-20cm depth.

For mulching, apply a 5cm layer of organic mulch around the root zone after planting. Keep it a hand's width clear of the trunk for a healthy collar.

Cover crops like clover or alfalfa work well in larger areas. Dig them in before they set seed and they'll add organic matter as they break down.

2. Open up drainage

Trees love a free-draining root zone. Test drainage with a simple hole test: dig a hole 30cm deep, fill it with water. If it drains within 24 hours, you're set. If it's slower, a few quick wins:

Raised beds or mounds for heavy clay sites
Coarse sand or fine gravel mixed through clay (don't overdo it)
French drains where water pools

Drainage preparation before planting

3. Test and balance pH

Most trees prefer a slightly acidic to neutral pH (6.0-7.0). Pick up a home test kit or send a sample to a soil lab.

Acidic soil (below 6.0): add lime to raise pH
Alkaline soil (above 7.0): add elemental sulfur or aluminium sulfate to lower pH

Native plants like Banksia love lower pH and lean soil. No need to lift the pH for them.

Cercis canadensis Forest Pansy planted in well-prepared soil

4. Aerate compacted ground

Open ground loves oxygen. A garden fork pushed in and rocked back to open holes through the root zone makes a real difference on heavy or trafficked sites. Organic matter then helps hold that improved structure in place.

FAQs

How often should I amend soil with organic matter?
Annually, before each planting season. Mulch breaks down and feeds the soil over time.

Can I improve drainage in established beds?
Yes, with a gentle touch. Work sand, gravel or compost into the top 100mm without disturbing tree roots.

When is the best time to test pH?
Late autumn or early spring, so amendments have time to work before planting.

Get the soil right and the rest of the planting process is much easier. Match the soil prep to the species and your trees will reward you for years.

1. Magnolia x soulangeana (Saucer Magnolia)

A deciduous showpiece for cool to temperate gardens. Saucer Magnolia rewards good soil prep with masses of pink and white blooms in early spring.

Type: Deciduous flowering tree
Height: 4-6m
Width: 3-5m
Growth rate: Moderate
Foliage: Mid green oval leaves, gold tones in autumn
Flowers: Large pink and white saucer-shaped blooms on bare wood, late winter to early spring
Form: Rounded, open habit
Conditions: Full sun to part shade. Cool to temperate climates. Shelter from hot afternoon sun and strong wind.
Maintenance: Low. Mulch annually, water deeply through dry spells, light prune after flowering only if needed.
Best for: Feature tree, front yard, cottage and heritage gardens

Why choose it

Magnolias respond strongly to well-prepared soil. Compost-enriched, free-draining ground gives the dense root system everything it needs to fuel that big spring flowering display.

Perfect pair

Underplant with Camellia sasanqua for layered seasonal flower.

Tips for planting

Dig in compost across a wide area before planting, not just the hole. The feeder roots run shallow and wide.

Get the soil right and Magnolia x soulangeana will deliver a spring show every year.

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2. Olea europaea (Olive)

The classic Mediterranean evergreen. Olive trees handle dry soils and hot sites once established, and reward good drainage with silver foliage and reliable cropping.

Type: Evergreen fruiting tree
Height: 4-8m
Width: 3-6m
Growth rate: Moderate
Foliage: Silver-grey lance-shaped evergreen leaves
Flowers: Small cream flowers in spring followed by fruit
Form: Open, rounded crown with characterful trunk
Conditions: Full sun. Sharp drainage essential. Tolerates 30°C and above, drought, coastal exposure.
Maintenance: Very low. Light prune in winter for shape. No need for rich feeding.
Best for: Mediterranean and dry gardens, driveways, courtyards

Why choose it

Olives sulk in wet feet. Improving drainage with sand, gravel or raised mounds before planting is the single biggest factor in long-term health.

Perfect pair

Pair with a Laurus nobilis Bay as the hedging companion to its feature form.

Tips for planting

Skip the compost-heavy mix. Olives prefer lean, free-draining soil.

Get drainage right and an Olive will live for generations.

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3. Banksia integrifolia (Coast Banksia)

A tough Australian native that thrives in sandy, well-drained soils. Coast Banksia handles wind, salt and poor ground better than almost anything.

Type: Evergreen native tree
Height: 6-15m
Width: 4-8m
Growth rate: Fast
Foliage: Dark green leaves with silver undersides
Flowers: Golden cylindrical flower spikes, autumn to spring
Form: Upright, open habit
Conditions: Full sun. Sandy, well-drained, low-phosphorus soil. Coastal tolerant.
Maintenance: Very low. Avoid phosphorus-rich fertilisers.
Best for: Coastal gardens, bird-attracting plantings, low-input landscapes

Why choose it

Banksias are sensitive to over-rich soil. Skip the compost in the planting hole and improve structure with coarse sand instead. They want lean, free-draining ground.

Perfect pair

Pair with a Waterhousea floribunda hedge for contrast against this open feature form.

Tips for planting

Use a low-phosphorus native fertiliser - Banksias are sensitive to phosphorus-heavy mixes.

Match the soil to the species and Coast Banksia will thrive for decades.

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4. Waterhousea floribunda (Weeping Lilly Pilly)

Fast-growing Australian native with dense weeping foliage. Outstanding hedge or screen when planted into well-prepared soil.

Type: Evergreen native screening tree
Height: 6-10m (can be pruned to desired height)
Width: 3-5m
Growth rate: Fast
Foliage: Glossy dark green weeping foliage with pink new growth
Flowers: Small fluffy cream flowers in summer
Form: Weeping, dense
Conditions: Full sun to part shade. Moist, well-drained, organic-rich soil. Frost tender when young.
Maintenance: Trim 2-3 times a year to maintain hedge form. Mulch and water through summer.
Best for: Hedging, screening, privacy planting

Why choose it

Waterhousea rewards rich, moisture-retentive soil. Improve clay and sandy ground with compost so the dense root mat can support rapid growth.

Perfect pair

Plant a Magnolia x soulangeana as the feature tree in front of this dense hedge.

Tips for planting

Mulch 50mm deep, keep clear of the trunk to avoid collar rot.

Good soil prep upfront and Waterhousea will deliver a dense hedge in two seasons.

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Compare at a glance

Cultivar	Height	Width	Form	Foliage	Best if you…
Magnolia x soulangeana Saucer Magnolia	4-6m	3-5m	Rounded, open habit	Mid green oval leaves, gold tones in autumn	Feature tree, front yard, cottage and heritage gardens
Olea europaea Olive	4-8m	3-6m	Open, rounded crown with characterful trunk	Silver-grey lance-shaped evergreen leaves	Mediterranean and dry gardens, driveways, courtyards
Banksia integrifolia Coast Banksia	6-15m	4-8m	Upright, open habit	Dark green leaves with silver undersides	Coastal gardens, bird-attracting plantings, low-input landscapes
Waterhousea floribunda Weeping Lilly Pilly	6-10m (can be pruned to desired height)	3-5m	Weeping, dense	Glossy dark green weeping foliage with pink new growth	Hedging, screening, privacy planting