Planting design

Planting itself is rarely consented work, but trees near buildings, protected trees and invasive species all carry legal duties.

• On shrinkable clay, keep trees back from foundations by the NHBC zone of influence: high water-demand species (oak, willow, poplar, elm, hawthorn, eucalyptus) at 1.25 × mature height, moderate-demand at 0.75 ×, low-demand (birch, hazel, hornbeam) at 0.5 ×. The calculator applies this automatically once you set the clay band. ^[1]
• Plant trees to BS 8545: pit at least three times the rootball width, no deeper than the rootball, root flare level with finished grade, backfilled with the original topsoil (no organic matter in the base). ^[2]
• Stake low, a single stake to about one-third of the tree's height with a soft buckle-and-spacer tie, and remove it after 2–3 years once the tree is self-supporting. High staking weakens the trunk. ^[2][8]
• Planting near established trees can be restricted by Tree Preservation Orders or conservation-area protections; check with the council before digging within a root protection area. ^[3]
• It is an offence under Schedule 9 of the Wildlife and Countryside Act 1981 to plant or cause to grow invasive non-natives such as Japanese knotweed; some suckering species (Ailanthus, Rhus) are best avoided near boundaries and structures. ^[4]
• Flag toxic and spiny species (yew, laburnum, cherry laurel) where children or pets use the garden, switch on the calculator's “avoid toxic / thorny” filter to exclude them. ^[8]

The rules of thumb behind a border that reads well in every season and knits together within two or three years.

• Think in six layers, canopy tree, sub-canopy/large shrub, shrub, perennial, groundcover and bulbs. Stacking them mimics woodland and fills vertical space (see the layers diagram).
• Right plant, right place: match aspect, soil pH, moisture and hardiness to the plant before anything else, no amount of aftercare fixes a mismatch. The calculator filters the palette on exactly these.
• Aim for roughly 70% structural mass (evergreens, grasses, skeletal shrubs) to 30% loose seasonal flower so the border still reads in winter. At minimum keep 25–30% evergreen structure.
• Plant in odd-numbered drifts, 3, 5, 7, 9, and repeat key species at intervals for rhythm. Even-numbered pairs look static.
• Space at slightly less than each plant's mature spread so they knit with no bare soil, roughly two-thirds of the spread. Triangular (staggered) spacing fits ~15% more plants than a square grid for the same gap and looks more natural (see the spacing diagram).
• Deliver all four seasons: spring bulbs and blossom, summer perennials, autumn berries and foliage, winter bark, evergreen structure and scented winter flowers (Sarcococca, Hamamelis).
• For pollinators choose single, open flowers, double cultivars carry little or no accessible nectar, and spread flowering across the year. Check the RHS Plants for Pollinators list. ^[9]

Establishment is won or lost in the first two years. These are the numbers that matter.

• Test soil pH with a cheap kit before choosing plants (6.1–7.0 suits most species). Don't test within three months of adding lime, fertiliser or organic matter. ^[5]
• Improve beds with 5–10 kg/m² (about half to one bucketful) of well-rotted organic matter forked into the topsoil, not heaped into individual planting holes, where it rots and lets plants sink. ^[6][8]
• Plant bare-root stock November–February while dormant; container-grown is more forgiving but autumn and spring still outperform summer. Never plant into frozen or waterlogged ground. ^[8]
• Set plants to the original soil mark, never proud, never buried. Deep planting starves roots of air and rots the lower stem; it's the single most common establishment failure. ^[8]
• Mulch 7.5 cm (≈75 L/m²) of bark or composted bark over moist, weed-free soil, kept a hand's width clear of stems to avoid collar rot. ^[7]
• Water in well, then give trees and large shrubs 30–50 L/m² (4–6 cans) per week in dry spells through the first 2–3 growing seasons, even in a wet summer. ^[8]
• Keep a weed-free circle at least 1.2 m across around each new tree or shrub for its first three years, grass and weeds out-compete young roots for water. ^[8]
• Leave perennial seed heads standing over winter for birds and overwintering insects; cut back in late February. Divide congested clumps every 3–5 years.

Almost every failed planting scheme in a UK garden comes back to one of these, and none of them are about plant choice alone.

• Planting too deep. The root flare, where the trunk widens into the roots, sits level with the surrounding soil. Bury it and the tree sulks for years or rots at the collar.
• Digging a small square hole in clay. It becomes a sump that holds water all winter. Break the sides and base, and make the pit three times the width of the rootball but no deeper than it.
• Improving the backfill with rich compost. Roots circle in the nice pocket and never move into the surrounding soil. Backfill with the soil that came out, and put the organic matter on top as mulch.
• Spacing at the size the plant is in the pot. Check the mature spread, plant to that, and fill the first two seasons with annuals or short-lived perennials.
• Planting a thirsty tree close to a house on shrinkable clay. The NHBC setbacks exist because subsidence claims are expensive; check the water demand category before you dig.
• Mulching against the stem. Keep mulch 50 to 75 mm deep but pulled back a hand's width from the trunk to avoid collar rot.
• Walking away after planting. New trees and shrubs need 30 to 50 litres per m2 a week in dry spells through their first two summers, and a weed-free circle for three years.
• Ignoring aspect. A south-facing wall and a north-facing border are different climates in the same garden, and no amount of feeding fixes the wrong plant in the wrong place.

Plant prices vary enormously with size, so these are typical 2026 retail and trade ranges for common garden stock.

• 9 cm perennials: roughly £4 to £8 each, and much cheaper by the tray of ten. This is the sensible way to plant a big border.
• 2 to 3 litre shrubs: roughly £12 to £25 each; 5 litre specimens roughly £25 to £45.
• Bare-root hedging such as hawthorn or beech, planted in the dormant season: roughly £1 to £3 per whip, planted at 3 to 5 per metre.
• Container-grown hedging in 3 litre pots: roughly £8 to £18 each, faster to look established but four to eight times the price.
• Feathered or standard trees: roughly £60 to £200, plus stake, tie, guard and a good pit.
• Semi-mature specimen trees: from £400 upward, and they need machine handling and irrigation to establish.
• Soil improver and mulch: roughly £5 to £9 per 60 litre bag, or £40 to £80 per bulk bag delivered, and one bulk bag covers about 15 m2 at 75 mm.
• Planting labour: typically £30 to £45 per hour, or roughly £15 to £25 per m2 of prepared, planted and mulched border.