Setting up a large wooden planter.
We have been given a beautiful wooden (pine maybe?) planter. It is about 5 ft long and 3 ft across and is on a stand about waist high. I am so thrilled with it that I really want to try to look after it so that it lasts as long as possible. It has had 3 good coats of linseed oil and seems to have absorbed as much as poss. There are some drainage holes in the central bottom plank but am wondering about putting in a layer of gravel now or even, don't laugh, a disposable child's night time bed sheet. They let moisture out one way only. Is that a ridiculous idea or would it go some way to keeping the timber drier?