Growing in a wooden barrel in my backyard now is some arugala and lettuce - red oak leaf, and a local variety called Anuenue, a kind of Manoa lettuce. Looks like the light rains and cool temps we're having in Hilo are the creating the perfect conditions for a flourishing crop.
Living on the windward side sometimes presents unique growing conditions. Take my friend living in a rainforest in Volcano Village, for example. He has installed window boxes around the deck and filled them with a premium potting mix and an organic fertilizer to grow greens. Although there appears to be adequate sunlight, his plants are rotting from the roots up. What is the problem? Possibly too much water.
Commercial potting mixes tend to be high in peat, which is excellent for retaining moisture. However, in high humidity locations, you should add perlite or fine cinder to the mix to improve drainage. Incorporating perlite also has the advantage of making hanging planters lighter in weight. A plastic container sometimes can have an attached saucer or tray that compounds the drainage problem. If you don’t have to worry about water spilling out onto the area below it, remove the container’s attached catchment by simply pulling it off – usually it’s a snap-on piece.
Rat lungworm infection is a concern for many salad-lovers these days, especially in East Hawai'i. Growing greens in containers can make slug and snail control much easier – the critters are easier to spot and hand-pick, and you can use a non-chemical control measure such as copper tape barrier around the container. Instead of a metaldehyde-based snail bait, use one made from iron phosphate, such as Sluggo, which is more earth-friendly and breaks down into nitrogen, plus it isn’t attractive to pets and wildlife. Also, if you’re growing your greens high up off the ground the snails are less likely to find it. No matter how you grow your greens, however, always inspect and wash them carefully for safety’s sake.