Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
August, 2007
Regional Report

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Concrete castings of hosta leaves brighten a shady bed.

Making a Leaf Casting

I've always loved big-leaved plants for the drama they lend to a garden, the way they hold onto water droplets and catch the sunlight. The intricate network of veins is remarkably showy on the huge leaves of rhubarb, gunnera, hosta, ligularia, rodgersia, to name a few. So when a friend recently asked if I'd like to learn how to make leaf castings out of cement, I grabbed a pair of disposable gloves and some work clothes and spent a hot summer afternoon in the cool of a barn, creating garden art out of leaves and cement.

First, a note about semantics: cement is the raw material consisting of clay and limestone; concrete is the final product that results when cement is mixed with sand and water.

The basic process of making a leaf casting involves covering the back side of a leaf with a cement/sand/water mixture, letting it dry and harden, then removing the leaf to reveal the shape and design of the leaf in concrete. Leaf castings can be utilitarian, serving as birdbaths or platform bird feeders. They can be eye-catching ornaments amidst low-growing plants or at the foot of a tree. With extra support added, they can guide your steps in the garden.

I'll share with you the recipe and process we used for making leaf castings, but know that there are many variations on the recipe and different techniques as well. Since there's no mold, every casting is unique, and, of course, coloring the casting involves endless possibilities. It's is a creative and exciting project, and the results can be stunning.

Here's the process we used:

* Portland cement type 1 (grey or white)
* sandbox sand
* Silpro liquid acrylic sealer
* acrylic or latex paint
* tile sealer
* water
* plastic tub without corners (where cement can hide) for mixing cement
* thin plastic bags for making castings
* large, thick sheet of plastic for covering container of cement
* waterproof rubber or latex gloves, thick ones for mixing cement, thinner ones for making casting
* face mask for mixing cement
* goggles for mixing cement
* freshly cut leaves to cast. Choose ones with pronounced veins and interesting margins, such as hosta, rhubarb, Dutchman's Pipe, ligularia, gunnera, rodgersia, and elephant ears.

1. Set up a work table in a cool, well-ventilated area out of direct sun. Cover the table with a sheet of plastic. Mix some sand with enough water to dampen it, and make a mound of sand on the table that's larger than your leaf. Cover the sand with a thin plastic bag such as a dry cleaner bag.

2. Cut off the stem of your leaf to about 1 inch, lay the leaf upside down on top of the plastic-covered sand and gently move the sand around underneath the leaf so it supports all parts of the leaf. You may need to remove the leaf a couple of times to form the sand into a mound that will better support the leaf. Make the bottom tip of the leaf point upward so when the casting is finished and turned over, the tip will have a natural-looking downward curl.

3. To mix the cement, don face mask and thick gloves and mix 3 parts Portland cement and 3 parts sandbox sand in the plastic tub. Mix 1/4 cup Silpro into 1 cup of water and add to the cement/sand mixture a little at a time. Continue adding plain water until cement is the consistency of toothpaste. The mixture should hold together if you squeeze it. If you add too much water, add more cement -- not sand -- to thicken it. Mix slowly to avoid incorporating air, which will make bubbles in your casting. Keep the mixture covered to keep it from beginning to set in the container.

4. With your hands protected by thin gloves, scoop a small blob of the mixture at a time, forming it into a thin patty, and pressing it onto the back of the leaf, starting at the midrib and working outward. Aim for a thickness of about 1/4 to 3/8 inch over the entire back, making the midrib extra thick to give the leaf support. Stop just short of the outer edge of the leaf (so you can peel the leaf away.)

To get a more finished edge, use a small paintbrush to brush the cement mixture towards the edges. Just don't make the edges too thin or they may break off.

For large castings that need more strength, you can sandwich a layer of overlapping drywall mesh tape in between two layers of cement mixture. I haven't tried this but you can find directions online.

5. When you're finished, cover the casting with a plastic bag or plastic wrap to hold in the moisture so it will dry more slowly.

6. Immediately wash the concrete tub outside with a garden hose so the cement mixture won't set and ruin the tub.

7. Let the leaf casting sit for a few days. The longer the curing time, the stronger the final concrete casting will be. Since the concrete will dry faster at warmer temperatures than at cool temperatures, anything you can do to keep the temperature down can help.

8. Small leaves may be dry after only 2 days, larger leaves will take longer. The concrete will turn light colored when it's dry. Then gently lift the casting off the sand and turn it over. Let it sit another couple of days before handling it. The real leaf will be stuck to the casting, so peel it off, using needle nose pliers, if needed, to carefully remove the leaf from deep veins without chipping the casting.

9. I used acrylic paint on the leaves, adding different colors in layers. Try different techniques. Watered down paint makes a wash that leaves hints of color. You can apply the paint with an almost dry natural sponge, or apply it with a paintbrush and then wipe it lightly with a damp sponge. You can use a tiny paintbrush to add color to the veins, or sponge on color so it seems into the veins and then lightly wipe the leaf with a damp sponge to remove most of the color on the raised portions of the leaf. Let the creative juices flow.

10. If you're keeping the casting outdoors, it's a good idea to paint a sealer product used for tile over the entire surface -- top and bottom.

Other Techniques To Try
I've read that you can get a smoother surface by mixing a small amount of a more watery slurry of cement and spreading that over the leaf first, then adding the thicker cement. You can also use this slurry to fill in any bubble holes that appear in the finished casting. You'll find other ideas online and in garden craft books.

Another tip: Smallish leaves and those with rounded margins are best for learning. Deeply lobed margins are trickier because there's more risk of the edges breaking or chipping. But, of course, they make the most interesting castings!

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