A large tree gives a section its character. It frames the house, cools the lawn in January and draws in tui and fantails. What it rarely gives is an easy garden underneath. The space below a mature canopy tends to end up as a patch of tired grass, bare soil and a forgotten bench. With some thought, though, that area can become the most interesting part of the property.
Designing a shade garden around a big tree is mostly about working with three things: light, roots and moisture. Get those right and the plant choices fall into place.
Start by mapping the conditions
Shade is not one condition but several. Spend a few days noting how light moves under the tree at different times. Early morning sun on the eastern edge, dappled light through a thin canopy, and deep, all-day gloom against the trunk each suit different plants.
- Light shade: two to four hours of direct sun or bright filtered light. Most woodland plants thrive here.
- Partial shade: mostly filtered light with little direct sun. Ferns, hostas and many natives cope well.
- Deep shade: close to the trunk under dense evergreens. Only the toughest groundcovers succeed.
Seasons change the picture. Under a deciduous oak or liquidambar, winter and spring bring plenty of light, which suits early bulbs and spring-flowering perennials. Under an evergreen such as a karaka or a camellia, conditions stay much the same all year.
Check moisture as well. Dry, dusty soil under the canopy is very common and rules out plants that need consistent damp.
Protecting the tree’s roots
Most of a tree’s fine feeding roots lie in the top 30 centimetres of soil, spreading well beyond the canopy edge. Any garden built beneath the tree should avoid damaging them.
- Plant small. Use young plants in small pots so planting holes are shallow and narrow.
- Avoid rotary hoeing or deep digging. Work around roots rather than through them.
- Do not raise soil levels by more than a few centimetres. Building beds against the trunk invites collar rot.
- Keep paths permeable. Gravel, bark or stepping stones let air and water reach the roots, unlike concrete.
- Avoid heavy machinery under the canopy, which compacts soil and crushes roots.
If the tree itself is too big or in poor health, the garden plan may need to wait until that is resolved. Large conifers in particular can dominate a section, and removal on tight sites is a significant undertaking. This piece on removing large conifers near lakeside homes explains what is involved.
Layering the planting
A good shade garden mimics the layers of a native forest: a canopy above, a shrub layer, and groundcovers below.
Shrub layer
Choose a few structural shrubs to give height and year-round form. Natives such as kawakawa, coprosma, Pseudopanax and smaller pittosporums handle shade well. In wetter, cooler gardens, rhododendrons, camellias and hydrangeas have long been popular in Bay of Plenty and Waikato gardens.
Perennials and ferns
Ferns are the backbone of most New Zealand shade gardens. Hen and chicken fern, kiokio and the smaller Blechnum species are reliable. Add perennials for colour and texture: rengarenga, Libertia, hellebores, bergenia and native Arthropodium all suit dappled light.
Groundcovers
In the deepest shade and driest spots, rely on tough spreaders such as mondo grass, Acaena, Ajuga and native Nertera in damper corners. Allow them time; most take two or three seasons to knit together.
Paths, seating and practicalities
A shade garden is meant to be enjoyed, so plan a route through it. A simple bark or gravel path that loops around the trunk works well and keeps feet off root zones.
Think about falling debris too. Seats directly under large dead branches or heavy seed cones are not ideal. Have the tree checked for deadwood before you settle on a seating spot.
Some site preparation, such as clearing old stumps, using hired equipment or working at height to lift the canopy, carries real risk. General information on safe practice with machinery, chainsaws and ladders is available from WorkSafe New Zealand, and it is worth reading before tackling anything beyond hand tools.
Watering is the last practical piece. Even shade-tolerant plants need help in their first summer, and tree roots will outcompete them for moisture. A soaker hose laid under mulch delivers water efficiently without wetting foliage.
Mulch, feeding and long-term care
Mulch is the shade gardener’s best friend. A 75 millimetre layer of wood chip or leaf mould retains moisture, suppresses weeds and slowly improves the soil for both tree and plants. Top it up each autumn, and let fallen leaves stay where they land in the planted areas.
Feed lightly with compost or slow-release organic fertiliser in spring.
Frequently asked questions
Can I plant vegetables under a big tree? Most vegetables need at least six hours of sun. Leafy greens like silverbeet and lettuce manage in light shade, but expect smaller harvests.
Will a shade garden harm the tree? Not if roots are protected, soil levels stay the same and digging is kept shallow. Mulch and light planting often improve tree health.
What is the best time to plant a shade garden? Autumn is ideal across most of New Zealand, giving plants winter rain to establish before summer dryness.