Autumn Weather Prompts Foliar Color

91127thumb(alternate)Mild climates allow more flowers to bloom through autumn and winter here than in most other parts of America. That is why cool season annuals like pansies and violas are so popular. Cyclamen can be planted now too. None will be obscured by snow. By the time cool season annuals start to fade, warm season annuals will be replacing them. There is something to bloom in every season.

There are a few disadvantages to mild climates, though. Many plants rely on significant winter chill to stay on schedule. Inadequate chill limits the cultivars of apples and pears that are productive here. Not many spring bulbs will naturalize. Prior to winter, some deciduous plants are hesitant to resign to dormancy until they experience a chill that is cool enough to convince them it is autumn.

Some deciduous plants recognize a specific temperature as credible evidence of a change of seasons. Others want a specific temperature to be sustained for a specific duration or repeated for a few nights. Shorter days and longer nights are taken into consideration by species who want to confirm what they deduce from the weather. Different plants use different methods of observation.

That is why deciduous plants who develop foliar color before defoliating in autumn do so on their own terms. Weather conditions that promote excellent color among birches may not be the same that cause flowering cherries to color well. Warmth and minimal humidity that sometimes prompt premature and blandly colored defoliation of sycamores might enhance later color of sweetgums.

Sweetgum, Chinese pistache, flowering pear and ginkgo are the most reliable trees for foliar color in autumn. Ginkgo turns only brilliant yellow. The others exhibit an excellent mix of yellow, orange and red. Crape myrtle can be about as colorful, but is not always as reliable.

Of course, there is more to these and other deciduous trees than their colorful foliage in autumn. After all, they are trees. Their particular characteristics and appropriateness must be considered before adding any of them to a landscape.91127thumb

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Slow Color

P91110Autumn is not much to brag about here. It supposedly got just cool enough at night for the minimal requirement of frost, at 32 degrees, but no one noticed. It has been getting to the low 80s during the day. There has been no rain yet, and none is in the forecast. As bland as such weather seems, it is not at all out of the ordinary. Autumn often arrives later than it does elsewhere.

Consequently, autumn foliar color is not much to brag about either. There are only a few trees that reliably develop good color, such as sweetgum, pistache, flowering pear, crape myrtle and maidenhair tree (ginkgo). As reliable as it is, maidenhair tree provides only bright yellow, without the oranges and reds that the others exhibit. None are exhibiting significant color just yet.

There are several other trees that have potential to develop good color, but are not as reliable about doing so. Birch can get almost as brilliant yellow as maidenhair tree does, but does not do it every year. Red oak may turn brilliant orange with a bit of brownish red mixed in, but only every few years or so. On rare occasion, even London plane (sycamore) shows off burnt orange.

Every species has a distinct personality. They each respond differently to different variables. Weather conditions that stimulate good color among flowering cherries may not stimulate good color for bigleaf maples. Dogwoods that colored so well at about the same time last year as the tulip trees, are already nearly bare after minimal color, while the tulip trees are mostly green.

Every few years, if mildly but suddenly chilled, these cottonwood develop a brighter yellow, with less blotching. With slower and drier chill this year, they are deteriorating and falling without much yellow at all.P91110+

Dyckia

91023It is easy to mistake various cultivars of Dyckia for diminutive relatives of Agave or Yucca. They form stout rosettes of rigid leaves with wickedly sharp terminal spines. Their comparably nasty but incurved marginal teeth resemble those of most species of Agave, but are generally more abundant. Surprisingly though, Dyckia are instead related to bromeliads. They just happen to be xeric.

Dyckia do not bloom much, but when they do, the tall and arching floral stalks really are more typical of bromeliads. As they bloom late in spring or in summer, the many small individual flowers on each stalk are collectively colorful enough to be delightfully popular with hummingbirds, butterflies and bees. Bloom is most commonly rich reddish orange, but some cultivars bloom red or yellow.

No one seems to mind that Dyckia does not often bloom. The foliage is remarkably striking alone. Many cultivars form dense mounding colonies of pups that, although unpleasant to handle, can be divided for propagation. A few toothless cultivars, armed only with terminal spines, are easier to handle. Individual rosettes can be as tall and broad as a foot. Dyckia do not need much water.

Hedges – Living In The Background

90918thumbPretty soon, as autumn weather starts to get cooler, some deciduous plants will develop brilliant color before defoliating for their winter dormancy. Throughout the rest of the year, evergreen plants with gold, silver, bronze, bluish, purplish, reddish or variegated foliage are more colorful than common green foliage is. A few deciduous plants with colored foliage turn different colors in autumn.

Such colorful foliage is generally appealing in the garden. However, there are reasons why not all plants in the garden are so colorful. There really is the potential for too much of a good thing. If all foliage was always colorful, landscapes would look cluttered. Flowers would not be so prominent. There are many situations for which plain and simple evergreen foliage is likely the best choice.

That is why simple evergreen hedges of the various species and cultivars of pittosporum, privet, holly, arborvitae and laurel are still so popular. Some are formally shorn. Where space is sufficient, others are informal screens in which the shrubbery is more or less allowed to assume its natural form and size. The various boxwoods are useful for smaller evergreen and formally shorn hedges.

Most contiguous hedges and screens are intended to separate spaces or obscure fences or buildings. Some sporadic sorts might only expected to disrupt the expansiveness of large buildings or partially deflect prevalent breezes. What they have in common, is that they are in the background. Some are behind or next to lawns, patios or decks. Others are behind more prominent plants.

Shearing hedges that are adjacent to lawns, patios and decks is of course much easier than shearing those that are behind other plants. Screens or hedges behind rose gardens, dahlias, flower beds, or anything that might be damaged by the process of shearing a hedge, should be of the sort that do not need to be shorn regularly. Nor should they be so colorful that they steal the show.

If possible, maintenance of hedges should be scheduled to coincide with the off season of plants in their foreground.

Delta Maidenhair Fern

90904Some of us might remember Delta maidenhair fern, Adiantum raddianum, as a houseplant that was popular for terrariums in the 1970s and into the 1980s. Although quite happy in terrariums, it eventually gets big enough to crowd other plants in such tight spaces. It prefers to be potted on a porch, or in a regularly watered and sheltered spot in the garden. It tolerates quite a bit of shade.

Regular watering is important to keeping the foliage well hydrated, particularly among potted plants that are unable to disperse their roots into surrounding soil. The stolons bellow the foliage are not so sensitive, so can regenerate new foliage if partly desiccated old foliage needs to be cut back. They want good rich soil or potting media, and appreciate occasional application of fertilizer.

Individual fronds (leaves) have the potential to get as long as a foot, and half as wide, although they are mostly significantly smaller, and might be only half as long. Each frond is intricately divided into many small leaflets that are almost triangular, except that their out edges are curved and scalloped. Foliage is lighter green than that of most other ferns. Rachi (leafstalks) are black and thin.

Ferns Are Delightful Without Bloom

90904thumbMany of the most popular plants are expected to bloom to add color and fragrance to the garden. Many others are grown to produce fruit or vegetables. Some are appreciated for their foliar color in autumn. Big trees are grown for shade. Turf grasses are grown as lawn. Evergreen shrubbery makes hedges. It seems that all plants perform particular tasks in the gardens which they inhabit.

Ferns only need to provide rich foliage. They do so very efficiently, with remarkably stylish and distinctive textures, and deep green color. Most ferns are evergreen, so only need to be groomed of their old foliage as it gets replaced by new foliage. Most of the few deciduous ferns are bare only briefly during their respective dormant seasons. Some can grow wild without any grooming at all.

Many ferns are famously tolerant of partial shade that is too dark for many other types of plants. Many are tolerant of confinement, so are happy in pots, planters and small atriums, or under stairs. Some ferns that are tolerant of both shade and confinement are popular as houseplants. Those that get too big or their situations are generally easy to dig and relocate, or divide into more plants.

There are only two species of tree fern that are common here; the Australian tree fern, and the New Zealand tree fern. Australian tree fern is taller with leaner trunks. Tasmanian tree fern is short and stout. These and more rare tree ferns are the only ferns that leave the ground as they develop ‘trunks’ of tightly bundled fibrous roots dispersed through the decayed remains of their rhizomes.

Their rhizomes are just their thick herbaceous stems. Those of tree ferns do not branch into more than a single terminal bud, so can not be divided. Rhizomes of most other ferns split into clumps of a few or many individual budded rhizomes, which can be divided if they get too crowded. Leaves that grow from the rhizomes are known as fronds. The fronds of almost all ferns are divided into smaller leaflets known as pinnae, which are suspended by leafstalks known as rachi.

Colorful Foliage Fades Through Summer

P90713Autumn foliar color is not the concern yet. It develops later as deciduous plants defoliate for winter. Purplish, reddish, yellowish, bluish or gray foliar color that can be seen now is provided by plants that are colorful while actively growing. Almost all of this sort of foliage is most colorful when it is young and fresh, early in spring. Then, through summer, some of the best foliar color fades.

This process is perfectly natural. It does not imply that anything was done improperly, or that plants were not given what they need. In fact, most plants with colorful foliage would rather be green. They are mutants that were reproduced specifically for their distinctive color. Some try to revert back to green by producing greener shoots that grow faster because they have more chlorophyll.

Photinia is an odd one. By now, The rich green foliage shows no clue that it was rich reddish bronze when it developed early in spring. The foliage did not really fade. It merely matured. Then there are the newer cultivars of purple leaf plum, which maintain their color from spring to autumn. It is amazing that such darkly colored foliage that seems be devoid of chlorophyll can photosynthesise!

Some plants maintain their color better than others. Gray or bluish foliage is always gray or bluish; but admittedly, blue spruce and blue junipers are not quite as striking now as they were earlier. If red fountain grass and bronze aonium fade, it will be too slight to notice. Stems of bronze, gold or striped cannas that fade after bloom get pruned out in favor of more colorful unbloomed stems.

‘Forest Pansy’ redbud, ‘Summer Chocolate’ silk tree and ‘Sunburst’ honeylocust are notorious for fading. By now, the formerly richly bronzed redbud and silk tree merely seem to be stained with coffee. Golden honeylocust might have been bright yellow in spring, but now just looks sickly. Gold tipped and silver tipped deodar cedars can likewise be a bit pale. Bronze elderberries hold color well, but golden elderberry might now be chartreuse.P90713+

Giant Bird Of Paradise

60720Unlike the common bird of Paradise that is grown for striking bright orange flowers, the giant bird of Paradise, Strelitzia nicolai, is grown for strikingly lush foliage. The big rich green leaves get nearly six feet long, and flare outward from leaning trunks that can eventually reach upstairs eaves. Foliage is healthiest if sheltered from harsh sunlight (such as hot reflected glare), wind and frost.

Bold white blooms with contrastingly delicate blue streaks are a rare surprise on older trunks. The navy blue floral husks with nectar dripping from them look like the beaks of drooling seagulls; but the flared flowers above look like the crests of parrots.

Foliar Color Long Before Autumn

51104The best and brightest color in the garden is obviously still provided by flowers. Autumn color can be spectacular, but only amongst relatively few deciduous trees, shrubs and vines that turn color reliably in mild climates, and only if the weather is conducive to coloration. The next best option for color beyond green is the sort of colored foliage that does not wait for autumn to materialize.

Foliage can be shaded with varying degrees of yellow, red, pink, purple, bronze, grayish blue or gray, or variegated with white, yellow or silvery gray. Plants that display such colorful foliage can be as small as flowering annuals, or as substantial as shade trees. Many are deciduous plants that also turn color in autumn. Most of the best are actually evergreen, so hold their color through winter.

Color tends to be richest as new foliage emerges in spring, and fades more or less through summer. Gold junipers only start out gold, but then fade to green within only a few months. The purplish foliage of ‘Forest Pansy’ redbud fades to coffee stained green. Yet, bronze New Zealand flax is always bronze. Dusty miller is always gray. Some plants are more reliably colorful than others are.

Exposure is important too. Most blue or gray foliage, whether juniper, agave, spruce, eucalyptus, olive or silver Mediterranean fan palm foliage, will be significantly greener if shaded. However, white variegation of English holly, hydrangea, ivy, hosta and pittosporum have better contrast if partly shaded. Colorful Japanese maples color better with good exposure, but roast if too exposed.

Many plants with colorful foliage are notorious for developing greener mutant growth known as ‘sports’. Because sports have more chlorophyll, they grow more vigorously than more colorful growth does, and can overwhelm and replace the more desirable colorful foliage if not pruned out. Many types of white or yellow variegated euonymus, as well as the more intricately variegated New Zealand flax, can revert to monochromatic green within only a few years.

Holly Fern

60601This is one of those perennials that has mixed reviews. Although relatively tough once established, holly fern, Cyrtomium falcatum, is susceptible to rot and fungal leaf-spot. It likes to be watered somewhat regularly, but rots if the soil is constantly saturated. Leaf-spot is not as dangerous as it looks, but can be unsightly. Too much fertilizer (to correct the damage) can burn the foliage too.

Individual fronds might get as long as a foot and a half, with half a dozen to a dozen pairs glossy and irregularly toothed pinnae. Foliar texture (remotely) resemble that of some types of holly. Because they disperse their roots so efficiently, mature specimens do not like to be transplanted. Small plants can grow as houseplants for years, but eventually want to get out into the garden. Holly fern likes a bit of shade, and will tolerate rather dark shade.