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.