Thorn Hedge Planting Spacing: Closing the Gaps in a Living Barrier Before Its Second Winter

A thorn hedge is a fence that grows, and its weak years are its first ones, when the whips stand in a row of separate bushes with walk-through gaps between them. This study models shrub spread as r(t) = 0.18 + 0.22 t metres from stated values, and computes when neighbouring canopies meet at each planting spacing: at 0.9 m spacing the hedge closes in 1.23 years, at 1.5 m spacing it takes 2.59 years, a full extra growing season and more spent as a dotted line rather than a barrier. Crossing delay at maturity, computed from a stated stem density, is 40 seconds for a single 0.6 m row at 0.9 m spacing and 80 seconds for a double staggered row of 1.2 m depth. Planting cost at 0.9 m spacing is 12 plants per 10 m. The rule is to plant thorn hedging at 0.9 m or closer in a double staggered row where the ground allows, accepting the plant cost as the price of closing the barrier before its second winter, and to protect the young hedge with a temporary fence rather than pretending it is already a barrier. SIMULATED, NOT MEASURED.