Furniture wax is suitable for indoor furniture maintenance. If the furniture is outside without a roof, it would be wise to maintain it once a year. I use wood oil "Teak oil", but other wood oils are also suitable. Before greasing, sand lightly with sandpaper (sharpness 120) along the tree, the easiest way is to use a porolone sander block. It is easier to grease with cloth. Apply oil as plenty as possible, but it should not be left there. An hour or two after the application the oil, which has not absorbed, must be certainly wiped off. Oil slick that has not been swept shall crepitate. When greasing wear vinyl gloves - liquid oil is harmful to the skin. Oil dries in a few hours and can be touched. It dries completely approximately in one week.
If the furniture is standing directly on the ground, it would be good to put something under the foot, otherwise moisture absorbes into the feet while standing on the ground and the wood shall rot. For the winter it is better to put the furniture under well ventilated roof, but if there is no such possibility, then it is better to preserve the furniture in a snowdrift, than in the basement covered with protective film.