Planting a thuja hedge – trench, spacing and soil

Mark positions and count the plants

Check boundaries, required setbacks, underground services and room for the mature hedge. Choose spacing for the cultivar and plant size using the nursery's guidance. Measure centre to centre.

Count example: if the distance between the first and last plant centres is 10 m and the chosen spacing is 0.5 m, there are 20 spaces and 21 plants. Both endpoints contain a plant.

If 10 m is instead the whole available line and the example leaves 0.25 m at each end, the outer plant centres are 9.5 m apart. At 0.5 m spacing that gives 19 spaces and 20 plants. These figures are arithmetic assumptions, not universal spacing or setback rules.

Mark the actual positions before purchase. If the length does not divide evenly, adjust the layout within the nursery's spacing guidance rather than simply rounding the division.

Check the soil and allow for the root balls

Look for persistent wetness along the line and unsuitable material in the rooting zone. Suitable excavated soil may be reused for backfilling. Adding better soil or more water does not automatically solve a wet trench.

Size the trench or holes for the actual root balls and ground conditions. Allow for the balls and the selected backfill approach rather than following one fixed trench width and depth.

Choose a planting time when the ground can be worked and establishment watering can be provided, following local nursery advice. Do not transfer a northern-hemisphere calendar directly to Australia.

Separate trench volume from bought soil

Separate trench example: 10 m × 0.4 m × 0.4 m = 1.6 m³. Width and depth are calculation assumptions.

Root balls and suitable soil returned from the excavation also occupy the trench. Buy growing medium for the part they do not fill. There is no universal percentage to deduct: use the actual ball sizes and the reusable soil available.

Ask the supplier how the selected growing medium settles and what delivery quantity will produce the required finished fill.

Set planting height before backfilling

Confirm the nursery's instruction for the top of the root ball relative to the finished surrounding ground. If the instruction is ground level, set the ball to that level, not to a trench edge or temporary heap. Do not bury the stem while backfilling.

Check the line, spacing and height before completing the fill. Use the selected soil strategy and planting instructions. If a ball does not fit at the intended height, adjust the hole rather than concealing the height error with soil over the top.

Water in and move to establishment care

Water at planting according to the nursery's instructions. Follow moisture in both the root ball and surrounding soil. Wet roots do not automatically need more water because the foliage looks poor.

If mulch is used, keep it clear of the plant bases and follow its spreading instructions. Before finishing, check positions, heights, backfill and the water route. Ongoing watering and establishment care belong in the thuja-care guide; completing the planting is not proof that the hedge has rooted.