Frost protection: cold frames, mulch and the trees that need neither

Not every tree on the bench needs the same protection. A species hardy to zone 5 shrugs off a night at −10°C that would kill a tropical ficus outright — check the care plan's winter line before reaching for fleece. For the trees that do need it, the cheapest protection is placement: against a house wall, under a bench, or grouped with other pots so the mass holds warmth. A cardboard box or a layer of straw mulch over the soil surface covers the rest. Reserve a proper cold frame or unheated shed for the tenderest stock and for the coldest week of the year, not for every frost night — a tree that never feels cold never hardens for the next one.