Lettuce and other greens (chard, spinach, etc.) are supposed to be fairly easy to grow in raised beds, but our results have been less than spectacular. Slugs and aphids take their toll, but the biggest problem seems to be flea beetles. This year we decided to try gutter and PVC gardening in order to get the lettuce up out of the raised beds and it's working out very well so far. Gutter gardens can be hung from wire, tied to a fence or attached to the side of a building, but since none of those options worked for our situation, we opted to build a free standing Gutter Garden Trellis which holds six half-sections (5' long) of gutter.
There are two materials for gutters - metal and vinyl, and both are usually ten feet long. Metal gutters seemed stronger than vinyl but since the gutters were cut in half, the decreased strength of the vinyl wasn't an issue. If you're going to keep the sections ten feet long you might want to go with metal gutters instead of vinyl. Another reason for choosing vinyl gutters is because metal gutters might conduct heat and cold more readily than vinyl, and with such a short growing season here in the Northeast the vinyl seemed the better option for better temperature stability.
One ten-foot section of gutter and four endcaps yields two five-foot sections of gutter garden. Each five-foot section of gutter can hold up to six lettuce plants. The ten foot section of gutter cost $3.99, and the endcaps were $3.43 each, so two five-foot sections cost a total of $17.71 plus tax . The five-foot sections of gutter are easy to work with and fit inside our coldframe in case the temps drop below freezing at night in early springtime. Our two gutter garden trellises hold six five-foot sections (three each) so the total cost for all six five-foot sections of gutter garden was $53.13. The image below shows two vertical garden trellises and three of the six half sections of gutter:
The gutter endcaps fit snugly on the gutters, but a bead of caulk was applied in order to keep water loss to a minimum, because gutter gardens tend to dry out very quickly due to the shallow design. There are five or six 3/8" drainage holes along the bottom, but the holes should be kept closer to the edges, not the center of the gutter. The number of drainage holes will depend on the drainage properties of your soil so drill a few holes and see how well it drains. You can always drill more holes or make the holes larger, but if you drill too many and the water pours out, you're stuck. The vinyl gutters are cut the same way as metal gutters - either with a hacksaw or tin snips.
Even though it raises the cost a bit, the best results so far have come from mixing potting soil with the native soil. The ratio changes each time but it's about one-third potting mix and the remainder is soil. If your soil has a lot of clay you may want to add even more potting mix in order to retain good drainage. Some of the soil is lost when the plants are harvested, but most of the mix gets reused for several successive planting with new mix added as needed.
Like all containers, the soil in the gutter dries out faster than in-ground plantings so they need to be checked often if there's no rain. A thin layer of mulch helps to keep the lettuces hydrated, and straw works well because it's not as bulky as other mulches. Lettuce grows quickly so the only fertilizer application is usually one dose of Neptune's Harvest Fish and Seaweed fertilizer about a week after the lettuce is transplanted into the gutter. If you're using potting mix, check to see if any fertilizer is already in the potting mix before applying more fertilizer.
The first lettuces grown were Magenta, Bergam's Green, and Deer Tongue, and they all did very well (the gutters are in the cold frame in the above image). The Mizuna was grown in a PVC garden which I was experimenting with alongside the gutter garden. (You can read more in the PVC Gardening post.) All the lettuce plants were grown from seed in cell packs, then transplanted. None were direct seeded. So far we've only grown lettuce but will try some chard, kale, and herbs next.