How to Plant a Conifer So It Never Needs Moving

Give it the width it will actually reach

The single most common planting mistake with conifers is spacing for the plant in the pot rather than the plant in twenty years. Broadleaf shrubs forgive this because they regrow from old wood when you cut them back. Conifers largely do not. A spreading conifer planted three feet (90 cm) from a path will eventually reach across the path, and the only remedies are removing it or cutting into bare wood that will stay bare. Decide the width now.

Work from the annual growth rate rather than from a stated mature size. A spreading form adding twelve inches (30 cm) of width per side each year needs at least ten feet (3 m) of clear ground for a decade of growth. A dwarf globe adding two inches (5 cm) a side will be comfortable in three feet (90 cm) for the same period. Measure the space you actually have, divide by the annual growth, and you know how many years you are buying.

For hedges and screens the calculation runs the other way. Space upright forms at roughly half to two-thirds of their intended final width so they knit into a continuous face, typically 24-36 in (60-90 cm) apart for a screen you want dense within a few years. Planting tighter than that does not make the hedge dense faster; it makes the plants shade each other at the base and lose their lower branches, which is the one fault a conifer hedge cannot recover from.

Drainage decides survival

Most garden conifers die of wet roots rather than of cold, drought or pests. Their fine roots sit in the top twelve to eighteen inches (30-45 cm) of soil and need air in that layer year round. Ground that stays saturated for days after rain will kill them slowly, and the symptoms, browning from the inside and a general dull color, look exactly like drought, which leads people to water more and finish the job.

Test the site before you dig the final hole. Dig a hole about twelve inches (30 cm) deep and wide, fill it with water, let it drain, then fill it again and time the second draining. Under four hours is fine. Four to twelve hours is workable if you plant on a slight mound. Longer than twelve hours means you should either plant on a raised bed six to twelve inches (15-30 cm) above the surrounding grade or choose a different position entirely.

Soil pH matters less than drainage for most conifers, and the majority sit happily anywhere from slightly acid to slightly alkaline. What they dislike is compaction. If the site has been driven over, walked hard or scraped during building work, break up a wide area rather than digging one deep hole, because a deep hole in compacted ground behaves as a bucket.

Planting step by step

The best planting windows are early autumn, when the soil is still warm and the roots have months of cool moist conditions ahead, and mid-spring once the soil has warmed but before summer heat arrives. Avoid planting into frozen ground or into hot dry soil in high summer, when an evergreen with a full head of foliage cannot replace the water it loses.

1. Soak the root ball first Stand the container in water until bubbles stop rising, usually fifteen to twenty minutes. A conifer root ball that goes into the ground dry often stays dry, because the peat-based mix repels water once it has shrunk away from the pot wall, and rain then runs around it into the surrounding soil.
2. Dig wide, not deep Make the hole two to three times the width of the root ball and no deeper than the root ball itself. Firm ground under the base so the plant cannot sink. Conifers planted even two inches (5 cm) too deep suffer stem rot at the collar and decline over several seasons for no visible reason.
3. Tease out circling roots Root balls that have sat in a pot too long carry roots circling the outside. Cut through them in three or four places with a knife and pull the outer roots outward. Left circling, they eventually girdle the trunk and the plant fails suddenly after years of apparently healthy growth.
4. Set the collar at or just above soil level Lay a cane across the hole to check. The point where the trunk flares into roots should sit level with the surrounding soil, or an inch (2-3 cm) proud on heavy ground so it settles level rather than sinking below.
5. Backfill with the soil you dug out Do not fill the hole with rich compost. A pocket of soft material surrounded by heavier soil keeps the roots inside the pocket and holds water. Mix in a little compost if the ground is very poor, but the backfill should be recognizably the same material as the surrounding soil.
6. Water in heavily and mulch Give five to ten gallons (20-40 liters) slowly, enough to settle the soil around the roots and remove air pockets. Then mulch two to three inches (5-8 cm) deep over the whole planting area, keeping the mulch two inches (5 cm) clear of the trunk itself.

Support and shelter in the first two years

Large uprights and anything over about four feet (1.2 m) need staking on exposed sites, but stake low. A single stake driven at an angle into undisturbed ground, tied at roughly a third of the plant height, holds the root ball still while letting the top flex. Flexing is what thickens the trunk. High staking produces a plant that stands only because the stake does. Remove ties after two growing seasons and check them every few months in the meantime, because a tie left in place cuts into the bark and eventually strangles the stem.

Wind is the other first-year risk, and it does its damage in winter rather than summer. Evergreen foliage keeps losing water through cold weather while frozen or cold soil stops the roots replacing it, and the result is brown scorched foliage on the windward side. A temporary screen of mesh or hessian on the exposed side for the first two winters costs little and prevents damage that on a conifer never grows out.

Record the planting position, the date by season, the height at planting and the direction of the prevailing winter wind. Two years on, when one plant in a row is browning and the others are not, that record usually explains why, and it tells you where to put shelter for the next planting.