Over the two years we've featured our pallet planters out in the gardens, we've had lots of questions regarding their construction, set-up and utilization. While we're taking a year off from using this unique vertical planting opportunity in 2014, this set-up does allow for a fun way to grow lots of plants in a very small "foot print". Shipping pallets are used to help move heavier objects/supplies as they allow for a fork lift or other equipment to unload and relocate them efficiently. At the gardens, much of our bulk potting soil, new containers and other supplies come in on these pallets and their re-purposing for a planter, while not a new idea, was a great way to demonstrate another use for these pallets. The question has come up about using these pallets for planting vegetables and if it is safe considering some of the implications on how wood is treated for insect protection. It is important to check the stamping label on the pallets and look for a HT which indicates Heat Treated. HT pallets are safe for use with growing vegetables and other edibles. Those with a MB stamp indicate treatment with methyl bromide which should not be used for a planter that will contain edibles. Regardless, knowing your pallet is important. The average pallet is roughly 4' x 4' which is 16 sq. ft. Imagine two of these back to back now allowing 32 sq. ft. of planting space plus the sides and the top adding another 10 square feet or so. Taking up minimal space, this vertical opportunity can provide significant planting space with the minimal use of traditional ground area. Note the general steps that we've utilized below for construction of the pallet planter.
a typical pallet (on end)
When building our pallet planters, we put two of these back to back and secure them together. While ultimately the slats will be the openings for plants, we do take the liberty in widening some of the openings and creating larger planting pockets (see directly above), particularly on pallets that have narrow gaps between the slats. However, before securing the two pallets together with screws and additional supporting lumber along the sides (as needed, see below), line the inside of the planter entirely with landscape fabric (see directly below). We tack this fabric liner in with a staple gun. This will help contain the potting soil and ultimately plants will be installed in little slits created at the time of planting.
As seen above, we created some supports to help keep the planter upright but ultimately also included some stakes on both sides of the planter out in the final location. Don't fill these with soil until they are set in place. We use a combination of light weight potting soil (2/3) with compost (1/3) and after mixing this medium together and adding a slow-release fertilizer, we fill the secured pallet planter (located in its final destination) and water it well to settle the soil. We'll top this soil off once it settles. It is then just a matter of selecting plants keeping in mind that while they don't mind rooting in sideways, you now have to accommodate their height which can billow out and over adjacent plants. We try to select all plants/varieties under 12" in height or plant the larger selections at the top. We'll start at the bottom of the pallet planter and plant the "tallest" selections and taper up to the shorter ones at the top of the planter to minimize plants "shadowing" or overgrowing neighbors beneath them. This will happen to a certain degree regardless but keep in mind that shorter stature plants will lend themselves to a compact display and will be less prone to wind damage and breakage. These pallet planters are quite heavy when the plants have matured and the soil is wet. The examples seen in this posting are well over 400 lbs so proper securing is vital. There is more good information on the internet regarding this vertical option so have fun with it!