Misting System

A misting system is a line of small nozzles that splits water into droplets so fine they hang in the air rather than falling as a stream. It runs in short bursts of a few seconds rather than continuously. It is used for three jobs: keeping the leaves damp on cuttings that have no roots yet, holding the air in a growing space moist, and cooling that air as the droplets turn to vapour.

The pressure behind the nozzle decides which of those jobs a system can actually do. At about 2 to 4 bar (30 to 60 psi) the droplets are heavy enough to land and wet the leaf. That is what an unrooted cutting needs: with no roots to draw water up, the film on the leaf takes the sun's heat instead of the water inside it, so the cutting does not wilt while it roots. Cooling asks for the opposite - droplets of ten to twenty microns, fine enough to evaporate in mid-air before they reach anything, which takes roughly 55 to 85 bar (800 to 1200 psi) and a far stronger pump. Equipment sold as fog but plumbed at mist pressure wets the crop instead of cooling it. How much cooling arrives depends on how dry the air already is, and in humid air even a well-built system delivers little.

Most of the upkeep is keeping the nozzles open. Minerals in the water leave scale inside the pipe and the tiny openings, and grit, algae and silt block them outright, so the supply passes through a strainer matched to the water and cleaned when the pressure across it drops rather than on a set day. The other failures come from too much water, or none. Mist running too long rots cuttings in a bed that does not drain freely, and a stuck valve, a failed sensor or a power cut on a hot afternoon can kill a bench of rootless cuttings within hours. Lines are drained before a freeze. A misting system is never a structure in its own right; it sits inside a nursery, greenhouse or shade house, and shade and ventilation do most of the cooling before mist is asked to finish.