How should I seal/coat/paint my trellis for a vine or a rose? Is coating necessary? What colour tones are possible? These questions apply to classic trellises as well as to modern trellises. Wooden climbing supports will take on a grey patina over the years, but this effect is not necessarily to be considered a defect, as it can give a rustic and natural effect. The three hardwoods-- robinia (black locust), oak, and chestnut can be but need not be painted (coated). All other types of wood should be given a protective coating outdoors. The edges of the lattice laths will need to be lightly sanded for the coating to hold properly (otherwise, expect the dreaded 'edge curling' of the coating).