25 Mar Herbs, not ammo: Vertical gardening with ammunition cans

It’s a powerful thing when an object associated with damage and destruction takes on a new, life-giving incarnation. (Emphasis on carnation.)

If you’ve checked out our garden or follow it on Instagram, you might have noticed that we use ammunition cans as planters for two vertical gardens. Under an east-facing eave, we suspend ten ammo cans as herb containers inside a redwood frame. On our south-facing fence, we hang ammo cans as planters for our collection of flowering cacti. They’re low profile, they’re sleek, they’re strong, and with a few quick modifications, ammo cans make excellent garden planters for small-space vertical gardens.

Ammo Can Vertical Herb Garden by Ryan Benoit Design

Our collection of flowering cacti. We’re in late March and bloom season is just beginning. Follow us on Instagram to see the fireworks this spring.

Blooms, not bullets: We planted this rat tail cactus (Disocactus flagelliformis) in September 2014, and it’s now flowering!

Cartouche boxes were made for the safe transport and storage of ammunition, and when their rubber gasketed lids are clamped down, they’re airtight, watertight and stack well. Ammo cans have long been repurposed for the dry storage of valuables at home and protecting food, maps, cell phones, et cetera while camping. They’re also a great dry environment to store seeds, as Garden Betty demonstrates.

The boxes are readily available at most military surplus stores and also from online sources like Amazon and eBay. We purchased our boxes at our local swap meet and military surplus stores, where we’re able to inspect the condition of the boxes.

Ammo cans come in an array of different sizes.  The most common sizes are .50 caliber (6 x 12 x 6.75 inches) and .30 caliber  (10 x 3.5 x 6.5 inches). Prices vary from $7 to $30 per can. Most are for sale in their original olive color (touch-up paint here). The yellow or white stenciled labels are often scrubbed off or spray-painted over. We had to search through dozens and dozens of cans to find some with stenciled labels still visible. 

Can you spot the drip irrigation system? All ten planters are watered daily for one minute through a concealed 1/4″ tubing system. Draining water cascades down to the planter below.

Things to consider:

– A note about toxicity. Harmful chemicals leaching into the soil should be a concern when working with repurposed materials whose backstory might not be entirely clear. Because ammunition and older paints contain lead, we recommend using lightly used or brand-new cans, and always wash before use. Plus some cold comfort: According to studies like this one from the University of Minnesota, “in general, plants do not absorb or accumulate lead.” But it is possible, and in the leafy parts of plants more so than in fruits. (And then there are the “bioremediators”/”phytoremediators” like sunflowers, plants the practically vacuum up heavy metals from the soil, cleaning up polluted areas.) When it comes to lead in soil, the biggest risk comes from ingesting the soil itself, so washing crops is key. If any of this gives you pause, grow ornamental plants in your ammo cans instead.

– Ammo cans are constructed of painted steel which means they will rust.  We expect ours to last between five and ten years before it’s too corroded to use. The rust will start forming around the drainage holes where the protective paint is compromised. Our planters have held up very well over the past two years with regular waterings.  There is some minor surface corrosion on the inside of the boxes, but most of the paint is still intact.

This is the largest ammo can (5 gallon) that we’ve converted into a planter. It’s our young pitaya plant’s temporary home. The can is also a relic with a date stamp of 1955. Older cans should be carefully scrubbed clean with soap and water as there is chance that older paints contain lead. We washed our container and kept the paint intact to minimize the possibility of paint dust potentially contaminating the soil.

Lids can be saved for a future project or used as shelves as seen above. If you aren’t comfortable planting edibles in painted metal containers, you could always use them as cachepots, i.e. decorative containers that hold the plant’s actual pot.

We can see some surface rust on the inside of the box after two years. We’re hoping our boxes last five to ten years before completely rusting out.

The rust is most prevelant around the holes and edges of the planter.

Converting the ammunion can into a planter:

1. Remove the lid. The lid easily detaches from the box at the hinge. Save for a future upcycle project.

2. Wash can with soap and water.

3. Mark and drill the drain holes. We marked and drilled four 1/4-inch drain holes on the large .50 cal cans. Good drainage is critical for most plants, so drilling drain holes is a must. Corrosion will start at the drain holes, so too many drain holes will cause the bottom to rot sooner. Four to eight drain holes are sufficient on the .50 cal cans. Two to six drain holes are sufficient on the smaller .30 cal cans.

4. Optional: Paint the ammo cans. We recommend only repainting new cans where there is no risk of exposure to lead paint. Lightly sand the entire can, inside and out, to prepare surface. Apply primer and paint to all surfaces with a brush and roller, or spray. Apply two coats. We chose to keep our ammo cans in their original olive drab color.

5. Design and assemble the mounting hardware. We drilled holes in the sides of the ammo cans to secure mounting bolts for the vertical herb garden installation. We drilled holes in the backside of the ammo cans to secure custom aluminum brackets for the flowering cactus wall. We used stainless steel nuts, bolts and washers to secure the mounting hardware.

6. Add soil. We added a mesh screen barrier at the bottom of each planter before adding the soil to improve drainage and prevent holes from clogging.

7. Add plants or seedlings. Besides epis and herbs, we think ammo cans could make healthy and stylish planters for wax and lipstick plants, and of course, small succulents.

8. Mount or set the planters.

Ammo boxs come with removable lids.

Lids slide apart from the box at the hinge for easy removal.

Ammo cans make great table top planters. Water soil with planter in sink.

For a while we grew moneyworts in ammo cans. These low-profile ammo cans are perfect for sills.

We needed a way to mount the ammunition planters on our cedar slat fence.

We designed and fabricated custom brackets out of aluminum.

The aluminum mounting brackets hook onto the slats and allow us to move the planters around.

July of 2014.

March of 2015. We still have some vacancies that we’re excited to fill.

We transplanted our struggling ric rac cactus (Selenicereus anthonyanus) into an ammo can where it is now much happier.

Rat tail cactus (Disocactus flagelliformis) planted in September 2014.

Building the ammo can vertical herb garden back in July 2013.

Preparing six large .50 cal ammo cans and four smaller .30 cal cans for their new role as herb planters.

A little lovage (Levisticum officinale) goes a long way.

Here you can see the drip irrigation supplied to each box.

Chives on scrambled eggs. A must.

We brought yerba buena into the top planter last fall as it can survive in part shade. The top planters are always the toughest planters for growing herbs because they receive the least sun. (Most herbs are full sun-lovers.) We’ve had our best luck with tarragon, oregano, thyme, mint, cilantro, parsley and chives.

And now for the grand finale, whose ready for a vertical garden disco?

We installed controllable LED colored light strips in the sides of our redwood frame. We normally keep the color on purple in the evenings, but sometimes blue or green more fits our mood.

Check out more designs at Ryan Benoit Design.