Gold Conifers
Color is an essential part of any landscape. It must be considered when working with conifers, possibly even more so than with flowers, since conifers exhibit their colors throughout the year.
Green is the predominant conifer color and has an unlimited number of shades to go with a wide variety of textures. Unfortunately, they can appear to blend together into a green background, especially on cloudy days. The addition of just a few brighter colors can literally transform a landscape into a painter’s palette. The various background shades of green will stand out and become much more apparent.
Blue is the most popular of the conifer colors to be added to a landscape. It is a color that is relatively easy to locate in a wide range of shapes and sizes. Yellows are not as popular as the blues since most people associate yellow with chlorosis. Unfortunately, many people miss an opportunity to brighten a landscape with a perfectly healthy conifer that may exhibit vibrant shades of yellow.
Yellow conifers are interesting because many go through seasonal periods of varying intensity. Many selections will also put on a colorful show of new growth with varying shades of gold, yellow, and even white foliage.
The yellow color appears to be due to a lack of chlorophyll, allowing other pigments to dominate. As more chlorophyll is produced, the yellow pigments are masked by its green coloration. During the summer, leaves/needles will produce more chlorophyll unless genetically prohibited from doing so, causing the gold-flushing conifers to turn green. Golden foliage that is shaded will also turn green as more chlorophyll survives to capture more energy from the reduced light level. Golden conifers in the full sun will often become brighter as the chlorophyll level is reduced. They may become more sensitive to foliage burn with a reduced growth rate.
There are three pigments in plant leaves/needles that are very important. The green one is the chlorophyll—it uses blue and red wavelengths of light for a food production process called photosynthesis. When chlorophyll is produced by the leaf, it lasts for a short time before disappearing. That means the leaf must continuously be producing new chlorophyll.
A second pigment, anthocyanin, is a red pigment and is only visible when the others are not present. It is seldom seen in conifers.
The third pigment in different forms called carotenoids ranges from yellow to orange. It plays an essential role in the leaf. They can use the light wavelengths between red and blue to carry on photosynthesis and supplement the chlorophyll’s work while absorbing some of the sunlight’s energy. They are found with the chlorophyll and extend the chlorophyll’s life span by absorbing some of the damaging chemicals produced in photosynthesis. They can hold up much better in the sunlight than chlorophyll.
Sunlight will gradually destroy the chlorophyll in a leaf. If its intensity increases, chlorophyll is destroyed at a faster rate. If the weather is warm and sunny, the chlorophyll is replaced as fast as it is destroyed, especially if the chlorophyll is in balance with the carotenoids. Suppose the carotenoids are present in smaller amounts. In that case, they may not protect the chlorophyll in a usual manner. The carotenoids will become visible as chlorophyll is destroyed by the sunlight, leading to a conifer with gold foliage. If the carotenoid concentration is too low, then no pigments remain, and the foliage will be white or cream-colored. If a golden plant is shaded, less chlorophyll is destroyed, and the foliage will be greener.
In the spring, a lack of carotenoids would cause a conifer to flush variegated foliage. As time passes, carotenoids’ production would allow the chlorophyll concentration to increase. The variegation would gradually disappear.
Light reduction by haze can also have an effect on the color of a golden conifer. Photosynthesis occurs in chlorophyll when light photons impart energy into the chlorophyll. These photons also destroy the chlorophyll if it is not protected by carotenoids. So it is that a reduction in the rate of photosynthesis will cause a corresponding decrease in the destruction of chlorophyll. Measurements made during studies of the effects of haze upon the tropical forest ecosystem showed some interesting data. On a hazy day in a warm climate, there was a 50% reduction in photosynthetic photons reaching a forest’s canopy.
Haze consists of various substances ranging from pollutants such as sulfates to tiny soot and dust particles. In high humidity areas, solid particles become saturated with water, and the particles tend to be larger. This haze absorbs photons and becomes warmer while decreasing the number of photons available for photosynthesis (and chlorophyll destruction). It is interesting to note that the diffusion effect of haze will direct photons into the normally heavily shaded interiors of conifers, increasing the photosynthesis in this part of the plant.
The haze effect’s net result decreases the gold coloring in golden conifers while allowing the whole plant’s overall photosynthetic rate to remain at an unchanged level.
During the fall, cooler temperatures slow chlorophyll production in a typical conifer. Still, the green color remains because the chlorophyll/carotenoid balance remains in place. The rate of photosynthesis becomes very low as the quantity of chlorophyll decreases. Suppose there is a reduction in the carotenoids, upsetting the chlorophyll/carotenoid balance. In that case, the chlorophyll may not be replaced as fast as it is destroyed. The primary pigment remaining is the carotenoid, producing a yellow foliaged plant. If the temperatures get even colder, the carotenoids become more visible as the chlorophyll suffers even more loss.
An example would be a conifer such as Pinus contorta ‘Chief Joseph’, which turns bright gold in the winter. Another would be Pinus strobus ‘Hillside Wintergold’, which becomes more brilliant as the temperature becomes colder. The length of daylight plays no role in this process. Conifers that are gold in the winter turn green when placed in a heated greenhouse, even though the length of daylight has not changed.
White foliage is uncommon in conifers since it is due to a lack of any pigmentation. It affects the plant’s survivability. Most commonly, it is expressed as variegation throughout the foliage of the plant, sometimes in a pattern through each leaf/needle and other times as patches throughout the foliage. Some conifers have a white frosted appearance, while others produce white growth in the spring that eventually develops pigmentation. The variegation may also range in color from cream through yellow to bright gold. The color variations are due to the relative quantities of pigments within patches or layers of cells, determined genetically.
Variegation is often unstable and can vary in several ways. Sometimes a branch will lose its variegation and is referred to as a reversion even though it is just a return to what was normal. Banded variegation can vary seasonally or even climatically. Variegation due to genetic variation occurs when one or more cell layers have a low quantity of carotenoids. Such a deficiency prevents chlorophyll from becoming established, and a patch or a band of yellow or white results. For example, when a leaf grows in the spring, layers of carotenoids-poor cells will cause the leaf/needle to be banded as in the ‘Oculus Draconis’ types of pines.
All kinds of people visited our Lehighton, Pennsylvania home to see Coenosium Gardens and purchase some little plant treasures. If an ‘out of towner’ had trouble finding us, just about anyone in town could direct him to the house with ‘weird looking’ plants all around it. Those ‘weird looking’ plants were a magnet for conifer collectors from many parts of the country. A wide variety of plants with many different shapes, sizes, textures, and colors were located throughout our gardens. One group which attracted considerable comment was the golden group. To the uninitiated, these plants appeared sick or dying, a fact that all collectors have come up against. For example, we had two golden oriental arborvitaes (Platycladus orientalis ‘Conspicua’) flanking the entrance to our house. Every winter, we were questioned about their bronzed appearance as visitors wondered what was happening to these plants.
After we moved to the Northwest, our collection grew so that it filled almost three acres with a wide range of conifers in all colors. The blues and golds added variety and interest to the planting. They provided a bright contrast to the basic greens, especially on cloudy days.
Gold conifers used for landscaping gardens are not the dull, chlorotic golds of sick plants. Instead, they are the bright, vibrant golds and yellows of very healthy plants. These are golds present throughout the year, varying in brightness with the season or golds that are seasonal, becoming bright at certain times of the year while green the rest of the time.
Golden conifers are the Dr. Jekylls and Mr. Hydes of the conifer world. They are the gaudiest of the conifers. When used correctly, they add allure and elegance to the landscape. A source of bright color throughout the year, once used, they are often considered indispensable. Most people enjoy a splash of color in the garden. Flowers add such color but only ephemerally so. On the other hand, selected conifers serve the same function for extended periods.
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