The Importance of Toasting

Celosia ‘Dragon’s Breath’ toasted to a vivid red

Certain plants are promoted with an unusually rich color to their leaves. We are thinking of Celosia ‘Dragon’s Breath’ in this case, but the same is true for a number of other plants we sell: Pepper ‘Black Pearl’, Pennisetum ‘Vertigo’, and others. Their significant feature is that vivid color; however, we are certain you have also seen samples of these plants with muted or washed out tones. “What’s the deal?” you may be asking.

This is toasting—or the lack of it—in action. Toasting is a technique of placing certain cultivars in hot, blazing, preferably full-day sun in order to bring out the famous, foliage color. Let’s take a look under the hood so we can understand what’s going on and what’s going wrong.

Pennisetum ‘Vertigo’ makes a black background for ‘Sunfinity’ Sunflowers

Toasting isn’t fancy—it’s just putting the right plant in the right place. In this case, the right plants happen to be pigment-rich cultivars that are also sun-loving and heat-loving varieties. You can spot them by the unusually deep, rich colors they offer in their leaves, but if you come across them in a shade garden you’ll find them in a more muted state with a heavy green cast to the leaves.

Herein lies the problem. These colorful pigments protect the delicate internal workings of the leaves from the scorching effects of the sun the same way sunglasses protect our eyes at the beach. When we drive through a tunnel on the way home, however, we remove the sunglasses.

 
Pennisetum ‘Fireworks’ cranks up the pigments in full sun

It’s the same with these vivid foliage plants. In the sun, they crank up the pigments to protect the leaves but in shade gardens, they dial back hard to allow the light to strike the chlorophyll. In fact, the heavy green cast is a sign that the plants are getting too much shade during the day. They will become more brilliant if you move them out into the sun. Once they’re in the bright light the plants amp up the drama in about a week’s time.

We know this because all greenhouses, even the clear ones, offer some sun protection. As a result, plants can ship from the greenhouses in their muted form, especially at the beginning of the season before the sun gets too strong. This is normal behavior for the plant. Toasting occurs post-greenhouse, at the garden site. After about a week of soaking up full sun, the foliage brightens right up to provide the vivid results we are expecting.

Alternanthera ‘Little Ruby’—regular watering is as important as full sun

Keep in mind that the sun garden we reference needs to be hot, blazing, and filled with full-day sun to get the brightest, deepest, richest colors the plants can produce. Regular watering is equally important. These plants get rid of heat though evaporation, which doesn’t occur when the water goes missing for a long spell.

As you probably know, not all sun is the same. Morning and evening sun that scoots under a tree canopy is considered gentler. It toasts, but it delivers a light brown version of toasting. Direct noontime sun, like the kind that floods a plaza at lunchtime, delivers a dark brown style of toasting. Building shadows in the morning and evening will tamp down the effect, but not as much.

While the amount of hard sun controls the toasting, individual plants react to it differently. This is something we learn as we use the plants—practice and experience are the best ways to master the process. If you are new to toasting, pick one or two plants that you like. Once you get the technique down you’ll find it transfers over to the other varieties easily.

Black Ipomoeas come with different leaf shapes and vine lengths

We like the drama that striking foliage brings to the garden, so we offer vivid and dark versions whenever we find good ones. Here are some of our current favorites:

• Bronze-leaf Begonias like Cocktail and Bada Boom do just fine in the shade but the harder the sun, the darker the leaves
• Among Pennisetum grasses, ‘Vertigo’ gives us the blackest black and ‘Fireworks’ the reddest red
• Ornamental Peppers ‘Black Pearl’ and ‘Midnight Fire’ have nearly black foliage with fruits that turn bright red—on ‘Black Pearl’ the peppers are button-shaped; on ‘Midnight Fire’ they look like missiles
• Ipomoea has lots of choices among the blacks because the vines have different leaf shapes (heart, serrated, or palmate) and different lengths (mounded, sprawling, or in-between): ‘Blackie’, ‘Bright Ideas Black’, ‘Black Heart’, ‘Ace of Spades’, ‘Spotlight Black’, or ‘Sweet Caroline Jet Black’
• Canna ‘Cannova Scarlet Bronze’ was used as a screen in the Garden by the Street that we reviewed recently; ‘Cannova Orange Bronze’ is another good choice
• Celosia ‘Dragon’s Breath’ has striking vivid reds in the foliage; ‘Dracula’ and ‘Smart Look Red’ have dark and sultry leaves
• Dark-leaf Millets like ‘Prince’, ‘Copper Prince’, and ‘Purple Baron’ create stands as deeply black centerpieces—the differences are in their height and foxtails
• Hibiscus ‘Mahogany Splendor’ is a staff favorite with an unusual maple-like leaf

Ornamental Pepper ‘Black Pearl’ mixed in with Dusty Miller for contrast

For special uses, we have several choices as well:

• For big and tropical we use Colocasia ‘Black Coral’
• For low and dark, we choose from Alternathera ‘Little Ruby’ and ‘Red Threads’, Iresine ‘Purple Lady’, Oxalis ‘Zinfandel’, or Setcreasea ‘Purple Heart’, depending on the texture we want to create
• Coleus ‘Vino’, Coleus ‘Redhead’ and Cordyline ‘Red Star’ are good options for mid-sized dark