This must be one of the sillier horticultural names. Tree houseleek, Aeonium arboreum, is neither a tree nor related to leeks. The biggest cultivars can not stand much more than three feet tall. Above that, their succulent foliage gets too heavy for their fleshy stems and fine roots. They perform well as houseplants only within very sunny situations.
Formerly common tree houseleek, with simple green foliage, is not so common anymore. Almost all popular modern cultivars are variegated or bronzed, with wide foliar rosettes. Variegation ranges from bright lemony yellow to creamy white. Bronze ranges from light brown to very darkly purplish. Foliar rosettes are about four to eight inches wide.
Plumply conical trusses of tiny yellow or chartreuse flowers bloom for spring. They are neither numerous nor brightly colorful, but are weirdly interesting. Fresh spring foliage is most colorful and lush. It can fade and partially shed during arid summer weather. New plants propagate very easily from dragging stems or cuttings of pruning scraps.
This is not the genuine licorice of confectionery. This more popular home garden licorice plant, Helichrysum petiolare, is more of an ornamental plant than a culinary herb. Its mild foliar aroma resembles that of genuine licorice, but is very faint. Without disruption of the foliage, the aroma is imperceptible. Since the foliage can be toxic, the flavor is irrelevant.
Licorice plant is popular for its appealingly silvery foliage. Some cultivars are variegated. ‘Limelight’ is strikingly pale silvery chartreuse. The small, rounded and evergreen leaves are distinctly tomentous (slightly fuzzy). The sprawling stems tend to disperse over older growth, and might get deeper than a foot and a half. Mature plants get wider than six feet.
Licorice plant is susceptible to extremes of temperatures. Within more severe climates, it appreciates a bit of partial shade during excessively warm and arid weather. Foliage can roast from harsh exposure. Where winters are cool, foliage appreciates shelter from frost. Roots are susceptible to rot with excessively frequent watering, or inadequate drainage.
There are so many different personalities of Echeveria! This one only slightly resembles the more familiar ‘hen and chicks’ types.
Some but not all of of the many succulent plants known as ‘hen and chicks’ are varieties of Echeveria. Likewise, some but certainly not all Echeveria are known as ‘hen and chicks’. Echeveria are so variable that many do not seem to be related, although all have dense rosettes of succulent leaves. Some have very narrow leaves like miniature yuccas. Others have warty broad leaves. Foliage can be simple green, yellowish, bluish, gray, bronze, bronzy purple or variegated. The edges and tips of leaves of many varieties are blushed with red or purple that is more colorful in winter, or with complete sun exposure. Most Echeveria will tolerate light shade. Propagation is very easy from division of pups, stem cuttings and even leaf cuttings.
Silvery gray that is almost comparable to blue spruce is even more striking from a palm, like the Bismarck palm.
Most palm enthusiasts believe that the distinguished Bismarck palm, Bismarckia nobilis, is rare because it does not like local climates. It can be damaged by frost in winter, and prefers warmer weather in summer. Another concern is that they get too broad for compact urban gardens, since their shady foliar canopies can get more than twenty feet wide. However, a few seemingly happy specimens are sometimes seen about town.
Foliage of this rare palm is strikingly silvery gray. Green Bismarck palms are even more scarce, both because they are less tolerant to frost, and because they are not so striking. The big and rather rounded leaves are more than six feet wide, and maybe up to eight feet wide, on petioles (stalks) about six to eight feet long!
Most coral bells are grown for their colorful foliage.
From Santa Barbara to Vancouver, and also in central Idaho, the humble native coral bells, Heuchera micrantha, is not much to look at, with compact rosettes of relatively small and bronzy rounded leaves with weird tomentum (hairs). In spring and early summer, and sometimes again in autumn, sparse trusses of minute brick red flowers hover about a foot above on wiry and slightly fuzzy stems. Old plants that get bare in the middle can be divided into several small plants in spring or autumn.
Modern cultivars are considerably more interesting, with more substantial foliage in various shades of green, gold, tan, brown, bronze and purplish bronze. The larger and variably lobed leaves can be two inches wide or slightly wider. The flowers stand as much as two feet high, but lack color. Most are pale greenish white. ‘Palace Purple’ has deep bronze or almost purplish foliage. ‘Ruffles’ has deeply lobed and ruffled green leaves. Unlike undemanding wild plants that can grow in cracks in exposed stone, modern cultivars like rich soil. Harsh exposure can scorch foliage, so a bit of partial shade is preferred.
Many coral bells have delightful bloom as an added bonus to their foliage.
Without bloom, the richly vibrant foliar colors of coleus, Coleus scutellarioides, rival floral color of other warm season annuals. Striking foliar patterns are as exquisite as any floral display. Growth is efficient through the warmth of spring. Foliage might last until autumn. Late in its season, spikes of tiny blue flowers can be trimmed off to promote more foliage.
With bright ambient sunlight, coleus is more perennial as a houseplant. However, it may get persistent with pesky bloom as it matures. Some who grow it prefer to let bloom, and then prune it back afterward. Recovery from such pruning can be slow. Vegetative stems, without bloom, root easily as cuttings even in water. New cuttings can replace old plants.
Coleus foliage is intricately variegated with countless combinations of green, chartreuse, yellow, orange, red, burgundy, pink, white and brown. Variegation can be symmetrical or random. Leaf margins may be deeply lobed or just serrate. Modern cultivars might be no better than old fashioned sorts. Mature plants can get as tall and broad as about two feet. Some stay lower.
Foliar color is not limited to autumn. Some deciduous plants display colorful foliage from spring to autumn. Then, some of these change color for autumn. Some evergreen plants display colorful foliage through the year. Variegation of foliage can be more colorful than associated bloom. So can unvariegated bronze, purple, red, yellow, blue or gray foliage.
All sorts of plants exhibit variegation or other variations of color of their foliage. They can be annuals, perennials, shrubs, vines, trees, or houseplants. Although many are popular primarily because of their foliage, some provide appealing bloom as well. Blue and gray foliage is a natural advantage in harsh climates. Other colors are selections of mutations.
Because variegation deprives portions of foliar surface area of the chlorophyll needed to perform photosynthesis, it inhibits growth. This can be an advantage for plants that grow too vigorously otherwise. However, many variegated plants occasionally develop growth that is not variegated. If not removed, it can overwhelm and displace desired variegation.
New Zealand flax, dracaena palm (Cordyline australis), gold dust plant, euonymus, coral bells and hosta are some of the many plants that are more familiar with colored foliage or variegation than without. If simple unvariegated coleus, croton or caladium are available, they must be notably rare. Blue spruce is always blue. Purple leaf plum is always purple.
Although both gold and gray junipers are popular, the most common are green. Bronzed and variegated cannas are likewise not quite as popular as those with simple lush green foliage. Pittosporum tobira is so much more vigorous without variegation than with it, that the two distinct types of this same species perform different functions within landscapes.
Golden honeylocust supposedly produces lighter shade than darker green honeylocust. ‘Ruby Lace’, a bronze cultivar of honeylocust, supposedly produces faintly darker shade. Some golden or variegated foliage is more susceptible to scorch; although sun exposure enhances foliar color and variegation. Fresh new spring growth gets the best foliar color, but is likely to fade through summer.
Wispy billows of pinkish or tan blooms through June and July are what the smoke tree, Cotinus coggygria, is named for. It probably should have gotten more recognition for brilliant foliar color in autumn. It reliably turns bright yellow and orange, and if the weather is right, it can turn rich red and even purplish. Until then, the popular modern varieties have either dark purplish or light yellowish foliage. Some of the older plants have slightly bluish green foliage. The nearly circular leaves are about two or three inches long. Yellowish varieties tend to be shortest. Those with purplish or bronze foliage get larger. Old fashioned green plants are the largest, and can get twelve feet tall and broad. Smoke tree can be large shrubbery, or pruned up as small trees. Aggressive pruning in winter promotes better foliar color through spring and summer, but inhibits smoky bloom. Slightly distressed plants have better color in autumn. Plants that are watered too much are likely to succumb to disease within only a few years.
Flowers get all the credit for color. They certainly are the most colorful features in the garden, as well as the most fragrant. However, foliage can do so much more than simply provide green. It can be hued with yellow, red, blue, purple, bronze, gray, or variegated with white or yellow. Plants with colorful foliage can range in size and function from small annuals and perennials to shrubbery, vines and even trees.
Hydrangea, hosta, ivy, English holly and various pittosporum are some of the more popular plants for white variegation, and are often variegated with yellow. Euonymus can conversely be variegated with white, but is usually variegated with yellow. New Zealand flax can be variegated with pink, bronze, brown or gold. Box elder is a good sized deciduous tree that can be variegated with white, or alternatively frosted uniformly with gold as new foliage emerges in spring. There is even a variety that has slightly purplish or smoky colored new foliage.
Silver mountain gum, silver Mediterranean fan palm, lamb’s ears, artemesia and the various dusty millers have remarkably silvery foliage. Silver mountain gum can grow into a mid-sized tree with a stout trunk. Lamb’s ears is a low perennial. Olive trees, some junipers and the various lavenders have gray foliage. Colorado blue spruce and some agaves have striking blue color.
Various purple leaf plums and Japanese maples are famous for their purplish foliage. Smoke tree and some beech have even darker purplish foliage. Some New Zealand flax and cannas can be just as purple or comparably bronze.
Actually, New Zealand flax and cannas, as well as junipers known for blue or gray foliage, can alternatively be bright yellow. Golden arborvitae, golden honeylocust and golden Monterey cypress really stand out nicely against darker green.
Colorful foliage tends to be most colorful as it develops freshly in spring, and tends to fade somewhat through summer. Gold junipers can actually fade to basic green by autumn. Shade inhibits most types of coloration, but can show off variegation better. There really is so much variety with colorful foliage that it is impossible to generalize.
Coral bells can bloom again in autumn. (This is not my picture.)
From Santa Barbara to Vancouver, and also in central Idaho, the humble native coral bells, Heuchera micrantha, is not much to look at, with compact rosettes of relatively small and bronzy rounded leaves with weird tomentum (hairs). In spring and early summer, and sometimes again in autumn, sparse trusses of minute brick red flowers hover about a foot above on wiry and slightly fuzzy stems. Old plants that get bare in the middle can be divided into several small plants in spring or autumn.
Modern cultivars are considerably more interesting, with more substantial foliage in various shades of green, gold, tan, brown, bronze and purplish bronze. The larger and variably lobed leaves can be two inches wide or slightly wider. The flowers stand as much as two feet high, but lack color. Most are pale greenish white. ‘Palace Purple’ has deep bronze or almost purplish foliage. ‘Ruffles’ has deeply lobed and ruffled green leaves. Unlike undemanding wild plants that can grow in cracks in exposed stone, modern cultivars like rich soil. Harsh exposure can scorch foliage, so a bit of partial shade is preferred.
Most coral bells are grown more for their colorful and low foliage than for their bloom. (Both pictures here were obtained online. I can not find my pictures.)
Tony Tomeo 