A trough is like any other plant container, except that it’s made from cement.

Finish trough planter

Grow your special and unique plants in a special and unique container.

Photo Credit: Lane Greer

Mixing ingredients

After lining your wheelbarrow with a tarp (and before adding water), mix together the peat, perlite and cement.

Photo Credit: Lane Greer

Put cement in liner

Place the cement mixture into a plastic-lined container.

Photo Credit: Lane Greer

Shape in mold

First shape the bottom, then the sides, making them 2-3 inches thick.

Photo Credit: Lane Greer

Making troughs

“Hey, this is easier than I thought!”

Photo Credit: Lane Greer

Add drainage hole

While your newly shaped trough is still wet, make 2-4 drainage holes in the bottom, then add decorative items along the top.

Photo Credit: Lane Greer

Trough with mix

After the trough has cured, add the appropriate planting mix for the varieties you intend to plant.

Photo Credit: Lane Greer

Trough planting

As with planting any container, plants are placed into the trough and planting mix is filled in around them.

Photo Credit: Lane Greer

“Why do I want a heavy cement container?” you may ask. Primarily because of the fascinating plants you can grow in them – usually rare or unique plants, ones that are so small, no one would ever see them in a landscape garden. Troughs also allow you to create special microenvironments to suit the plants that need them, like cacti or sedums. Alpines and rock garden plants are favorites for troughs, too, because they need excellent drainage, which is easy to provide in a trough. (Plus, concrete planters just look pretty cool.)

What’s more, this is a great shared activity for family and friends. (It’s also easier for two people to mix the ingredients, as well as carry around the finished product.) The materials cost about $50, and you’ll likely have enough material to make two troughs – one for you and one for your assistant.

Here’s what you’ll need:

  • Fine peat moss (or coir) – Peat and coir are packaged in bags from 8 quarts to 3.8 cubic feet. (I would err on the side of having too much, since you can always use peat or coir elsewhere in your garden.)
  • Portland cement, type I or II – Do not use concrete! You can find this cement at home improvement or hardware stores in 50-lb. bags, but often you can’t buy less than 70 lbs.
  • Perlite (You can use coarse sand instead, but the trough will be much heavier.) Buy a big bag – they’re huge, but light as a feather. Home supply stores usually sell smaller bags, so you might want to buy two. (Like the peat moss, you can always use excess perlite later.)
  • Concrete bonding primer – Available at home supply stores in the concrete section
  • Chopped glass fiber or concrete reinforcing fiber – also available at home supply stores in the concrete section.
  • A bucket – 1 or 2 gallons is best.
  • Water
  • A large piece of disposable plastic, like a trash bag
  • A container for molding – A plastic tub with rounded corners works well. It should be at least 8-12 inches deep for good rooting. As for the other dimensions, shoot for a container that’s about 12-18 inches wide and long. If it’s too big, it’ll be extremely heavy; too small means fewer plants.
  • A wheelbarrow or other container for mixing
  • A tarp for lining the wheelbarrow
  • Dust mask
  • Form-fitting, tough, disposable rubber gloves
  • Decorating materials, like tinted ceramic tile mastic, broken china, shells, marbles, cement dye, etc. (optional)

The amount of peat, cement and perlite you’ll need depends on the ultimate size of the trough. It’s the ratio that’s important: Use a 1:1:1.5 ratio of packed peat, cement and perlite, or a 1:2:3 ratio of packed coir, cement and perlite. (Many recipes call for 1 bucket of peat or 2 buckets of coir.)

Directions

  1. Line your molding container with a large piece of plastic. The plastic should have long “tails” hanging over the sides that you can grab later and use to pull out the finished trough.
  2. Line the wheelbarrow with the tarp. (When you’re finished, you can just hose off the tarp, making cleanup much easier.)
  3. Mix the peat and perlite thoroughly in the wheelbarrow with your hands. Make sure to break up any clumps of peat. (Wear your gloves for this. It’s also a good idea to wear a dust mask for this step – especially when adding the perlite.)
  4. Add about two handfuls of chopped glass fibers, breaking it apart as it’s added.
  5. Add the cement. Blend thoroughly.
  6. Add water, then start mixing with a hoe or shovel. I would start with 1 gallon of water, then slowly add a little more as needed. Your mixture consistency should be that of crumbly cookie dough or cottage cheese. Along with the water, add 2 cups of concrete primer for hardening. (And if you’re using concrete dye, add it now.)
  7. After you have workable concrete, place it into your plastic-lined container. Just throw it in by the gloved-handful until you have enough to start shaping the bottom. Spread it up the sides as you go, using your hands. The sides and bottom should be 2-3 inches thick.
  8. Using your gloved finger, a metal tool or bottle lid, make 2-4 drainage holes in the bottom of the container. (The holes should be slightly wider than your finger.) You have about an hour to work with the concrete before it gets too hard and dry. (If the mix is too crumbly, sprinkle it with water.)
  9. If you’d like, add decorative items – like shells or marbles – along the top edge.
  10. After you finish shaping and decorating, cover your molded container with plastic. Place it somewhere very cool, like in a cool garage or basement, to start drying.
  11. After 1-2 days, remove the container from its mold – just grab the plastic tails and pull up! (It’ll slide out easily.)
  12. If you want to do any scraping or shaping of your concrete container, now’s your last chance. You can use a screwdriver or other metal tools to scrape out images into the sides or to make the trough look more like natural rock. (The plastic will leave wrinkles in the trough; these can be enhanced or somewhat eroded by scraping.)
  13. Return the trough to its cool place and allow it to sit for about a month. This will make your new container much harder.
  14. After the trough has cured, you can plant in it. Place a plastic screen or some other permeable barrier inside the container over the drainage holes. (It’s important to keep out worms, which can wreak havoc on plants.)
  15. Fill your trough with potting mix and plant as you would any container. Then water in thoroughly and enjoy your creation!

(Many thanks to Ginny Maffitt, who taught me how to make troughs at the Berry Botanic Garden in Portland, OR, and provided information for this article.)