Some Plants Need To Chill

41210thumbIt is easy to snivel about the weather when it gets uncomfortable for us. The rain gets too wet. The temperature gets too cool. Even here on the west coast, without the cold of Minnesota, the heat of Arizona, the humidity of Louisiana or the rain of the west coast of Washington, we tend to think about weather by limited human standards. What we fail to consider is that many other organisms rely on a variety of weather conditions for their survival.

Deciduous plants make it obvious that they know how to deal with cool winter weather. What is not so obvious that that many deciduous plants actually need specific wintry conditions to be convinced that it really is winter. If the weather does not get cool enough, or stay cool long enough, some plants do not go dormant long enough to get the rest that they need in order to perform adequately the following spring and summer.

For example, the reason that only a few of the many different varieties of apple can be grown locally is that most have chill requirements that exceed what they get here. A chill requirement is a specific duration of cool winter weather. Only a minority of all varieties were bred for their minimal chill requirements, so that they will produce reliably even where winters are innately mild.

Besides chill requirements, some seeds like to be soaked in moist soil before they germinate the following spring. This lets them know that it is raining, like it typically does in winter. Pecans, for example, can be soaked for a while inside before sowing, bur really prefer to be out in the garden through winter, where they can tell than rain water is actually flowing past them through the soil, and the microorganisms in the soil help to break down their shells.

It is all about timing. Chill requirements get apple trees to bloom in spring, only after they were convinced that it was already winter. If they were not so specific, they might bloom after a brief cool spell in autumn, leaving their blossoms or developing fruit vulnerable to later frost. Pecans germinate and grow only after the danger of frost, but before the weather gets too dry. If they start too early, they may not survive frost. If they start too late, they may desiccate through summer.

Seasonal Potted Plants For Christmas

91218thumb‘Tis the season for seasonal potted plants. These are not well established houseplant or potted plants that live out on porches and patios through the year. Seasonal potted plants are those that are purchased at their prime, allowed to live in our homes and offices while they continue to bloom or maintain their foliage, and then most likely get discarded when no longer visually appealing.

Poinsettia epitomizes winter seasonal potted plants. Florists’ cyclamen, azalea, holly, amaryllis, Christmas cactus and small living Christmas trees are other overly popular choices. All are grown in very synthetic environments designed to force optimal performance, with no regard to survival afterward. They are like cut flowers that are not yet dead. They are true aberrations of horticulture.

Technically, any of them can survive as potted plants, or out in the garden after they serve their purpose as appealing seasonal potted plants. Their main difficulty is that it is not so easy for them to recover from their prior cultivation, and adapt to more realistic environmental conditions. For now, it is best to enjoy them at their best, and try to maintain them at their best for as long as possible.

Eventually, they all experience a phase in which their original growth deteriorates to some extent, while they start to generate new growth that is adapted to the situation that they are in at the time. Christmas cactus are probably the most proficient at adapting, and becoming delightful houseplants. They are even likely to bloom occasionally, although not on any particular schedule for winter.

Holly, azalea and cyclamen can eventually get planted out in the garden. Most hollies grow into large evergreen shrubbery, but do not produce as many berries as they originally did. Azaleas are cultivars that were developed to be seasonal potted plants, so are a bit more finicky than those developed more for landscapes. Cyclamen can be added to pots of mixed annuals and perennials.

Living Christmas trees are not so easy to accommodate. Most are pines that need their space.

Christmas Trees – Dead Or Alive

41203thumbChristmas trees are like vegetables. Really, they are like big vegetables that do not get eaten. They are grown on farms, and then harvested and sent off to consumers. Although they smell like a forest, and they are descendents of trees that naturally grow in the wild somewhere, there is nothing natural about their cultivation. In fact, most are grown a very long way from where their kind are from. Therefore, bringing a cut Christmas tree into the home takes nothing from the wild, and does not interfere with nature any more than eating vegetables does.

Firs, particularly Douglas fir, are the most popular of Christmas trees. Pines are probably the second most popular. Redwoods, spruces, cedars, cypresses or even Junipers can also work. They each have their own distinct color, texture and aroma. Healthy and well hydrated trees that continue to get watered as needed should have no problem lasting through Christmas. Ultimately though, cut Christmas trees are not good for much after Christmas, and eventually get composted or otherwise disposed of.

Living Christmas trees might seem like a better option to cut Christmas trees because they dispel any unfounded guilt associated with cut Christmas trees, and initially seem to be less disposable. The problem is that they have problems of their own. Simply purchasing one is a big expense. Even the big ones are smaller than cut trees, but much heavier and unwieldy. Contrary to popular belief, only a few types that grow slowly, such as some spruce, can actually live in a tub for more than one or two years, and even they can be finicky.

The main problem is where to plant a living Christmas tree when it outgrows its container. Conifers innately do not like to be confined for too long. Yet, in the ground, most grow into substantial trees. The common little Christmas trees that are already decorated are actually the worst since they are juvenile Italian stone pines or Canary Island pines, which grow big and fast. Potted trees can not be planted out in the wild because their confined roots need to be watered until new roots can disperse. Even if they could survive, non-native trees should not go into natural ecosystems.

Winter Berries Are Showing Color

91211thumbNothing lasts forever. Spring flowers fade. Summer fruit gets eaten. Fall color falls from the trees and gets raked away. Berries and other small fruits that ripen to provide a bit of color through late autumn get eaten by birds and squirrels through winter. Every type of berry and every season is unique. It is impossible to predict how long particular berries will last through any particular season.

It would be presumptuous to believe that colorful berries should remain uneaten in our gardens until they decay. After all, they are produced specially for the birds and rodents who consume them. Their visually appealing bright colors are more culinarily appealing to overwintering wildlife. It is no free lunch though. Well fed wildlife is expected to disperse the seed within the berries they eat.

It is an ingenious system. Wildlife might think that they exploit the inanimate flora who produces the berries and small fruit for them. The associated flora could think that they exploit the mobility of the wildlife who eats their seed laden fruit. Those of us who grow plants who utilize this technique get to enjoy the color of the fruit while it lasts. Some of us prefer to enjoy the wildlife attracted to it.

Firethorn (pyracantha), toyon, cotoneaster and English hawthorn are the best for colorful red berries in late autumn and winter. All are of the family Rosaceae, and produce similar clusters of small bright red or maybe reddish orange berries. Yellow firethorn is rare here. Cotoneaster can be tall shrubbery, sprawling shrubbery, or groundcover. Only English hawthorn is a deciduous small tree.

The many species and cultivars of holly are unrelated to the family Rosaceae. In other regions, some are famous for producing seemingly similar berries. However, those that are the most prolific with berries are unpopular here. Those that are somewhat popular produce only a few berries due to a lack of pollinators. (They are dioecious, so female plants must be pollinated by rare males.)

This is the time of year to appreciate the colorful berries while they last.

Colorful Autumn And Winter Berries

41126thumbBefore the colorful foliage of autumn falls and gets raked away, a few types of berries and fruit start to provide a bit of color to last into winter, or at least until birds and other wildlife eat them. Technically, the most colorful berries are actually intended for the birds, both those that overwinter and those that migrate south for the winter. The berries are designed by the plants that produce them to both entice birds, and to reward them for dispersing the seeds within.

Pyracantha (or firethorn) is the most colorful of the berries. Cotoneaster is similar, but not quite so prolific. Toyon and English hawthorn, which can grow as small trees, produce open clusters of similar bright red berries. Of these, only English hawthorn is deciduous, and can defoliate before the berries disappear. Although such fruit is abundant, it is not often messy because it gets devoured before it reaches the ground. However, the birds can be messy.

English holly really should produce more berries than it does, but there are not enough pollinators out there. (Hollies are dioecious, which means that plants are either male or female. Female plants need male pollinators to produce fruit.) Decades ago, when horticulture was taken more seriously, male pollinator plants were marketed with female plants. Some other types of holly somehow make a few more berries, especially as they get older.

Loquat, mahonia, pomegranate and some flowering crabapples try to produce colorful fruit, but are not quite as colorful. Pomegranate fruit can be impressive in its own way, but are just rusty reddish brown on the outside. Strawberry tree produces a few red berries throughout most of the year. Many types of pittosporum develop fruit, but most are about as green as their foliage. The sticky amber seeds are ‘interesting’ when the fruit splits open, if anyone happens to look that closely.

Oranges, lemons, grapefruits, mandarins and other citrus will be colorful later in winter, even though they do not care if they attract any birds. For now, persimmons are the biggest and most colorful fruits out in the garden.

Division Renovates Tired Old Perennials

91204thumbAutumn is a time for planting partly because it is when many plants are beginning their winter dormancy. They are, or will soon be, less active than they would be at any other time of year. Some may not start to grow again until after winter ends. Others will want to secretly disperse their roots through the rainy winter weather, while merely appearing to be dormant from above the soil level.

That is why autumn is also the best time for division of many types of perennials. Such perennials should be adequately dormant to not be bothered by the process of getting dug and divided into smaller parts, then replanted. They actually prefer to get it done sooner than later, so that they can slowly disperse their roots through cool and rainy winter weather, and be ready to grow in spring.

Divisions is often done to renovate bulky perennials that have become overgrown, shabby, or too crowded with their own growth to bloom well. Some of the more vigorous perennials may benefit from division for renovation every several years or so. Many complaisant perennials may never benefit from division. Of these, some might be divided merely for propagation of more of the same.

Japanese anemone, bergenia and other perennials that bloom in autumn and winter should get divided later, after bloom. Like perennials that get divided now, they tend to recover and efficiently disperse roots before spring. However, they may need to be watered a bit more than typical if the weather gets warm and dry early next year. Their schedules do not coincide with local climates.

Lily-of-the-Nile, African iris and New Zealand flax can be divided into individual shoots, even if a few shoots get planted together in clumps. Entire plants do not need to be dug if it would be easier to merely pluck a few outer shoots from the perimeters of congested parent plants. Black-eyed Susan and Shasta daisy can be divided into clumps of several dormant basal rhizomes and roots.

‘Pups’, or sideshoots, of agaves and some types of yuccas can be carefully pried from their parent plants without disturbing them.

Arborists Specialize In Tree Horticulture

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Why is it so difficult to believe that there are so many different kinds of horticultural professionals? No one is ever surprised that surgeons, cardiologists, dermatologists, ophthalmologists and pulmonologists are all physicians. Yet, those who do not know better consider all horticultural professionals to be ‘gardeners’. This is actually more insulting to real professionals than outsiders can imagine, because the gardening industry is more dominated by non-professionals than any other horticultural industry.

Nurserymen, landscapers and florists are also horticultural professionals. Each of these basic categories can be divided into more specialized professions. For example, production nurserymen grow nursery stock or other horticultural commodities, while retail nurserymen maintain plant material only long enough to sell it. Maintenance gardeners are probably the most familiar of horticultural professionals because so many of us use their services around our home gardens.

Arborists are the horticulturists who specialize in trees, and really should be more familiar than they are. The only landscapes that have no possible use for their services are those that are devoid of trees. Even the most proficient of maintenance gardeners should not be expected to maintain large trees or diagnose potential arboricultural problems, not only because arboriculture is so specialized, but also because maintenance gardeners have their own specialties to be concerned with.

Because trees are the most substantial features of a landscape, and they have the potential to cause proportionate problems if not maintained properly, it is very important to have them maintained by qualified arborists. Those who are certified by the International Society of Arboriculture, or ISA, have passed an exam of their expertise, and maintain their certification with regular involvement with the ISA. Such involvement includes attendance to arboricultural seminars and classes.

It is ironic that some of the least familiar of horticultural professionals need to stay so dedicated to the maintenance of their credentials. Certified arborists can be found at the website of the ISA at isa-arbor.com.

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

Keep Vegetation Clear From Chimneys

51028thumbFireplaces simply are not what they used to be. Building regulations in many municipalities do not allow for the construction of new fireplaces, except only for pellet stoves. Fireplaces that get damaged by earthquakes are commonly removed instead of repaired. Now that urban sprawl has replaced so many of the rural areas and defunct orchards, firewood is more expensive, even if purchased from a tree service. When a tree needs to be cut down, no one seems to have the time to cut and split the wood.

Modern heating systems are so much more reliable, efficient and just plain easy. Their fuel can actually be less expensive than firewood, and is not nearly as polluting. There is no smoke to offend the neighbors. There are no potentially dangerous sparks. There is no dirty chimney that needs to be cleaned. There is no need for firewood occupying space in the garden. Yet, with all the advantages of other heating systems, many of who still have fireplaces like to use them now that the weather is getting cool.

Because so much heat and a few sparks go out through the chimney, it is extremely important to keep trees and vines away from the top of the chimney. Cypress, pines, cedars, large junipers, eucalypti and fan palms that are not groomed of their dried old leaves are very combustible. Vines like wisteria, bougainvillea, creeping fig and Boston ivy are not unusually combustible, but have a sneaky way of overwhelming chimneys and accumulating debris (and sometimes rat or bird nests!). Any vegetation will be combustible if it gets hot enough. Sparks from burning foliage above can easily ignite old fashioned cedar shingles.

Trees should also be pruned away from roofs, gutters, fences and anything else that can be damaged by the abrasive motion of the stems and foliage in the wind. Stems of deciduous trees lose weight as they defoliate, and may even lift off of roofs that they had been leaning onto just a few weeks ago, but should be pruned accordingly anyway. Branches that have been leaning on a roof for quite a while may have accumulated a bit more debris than would be expected. Gutters and downspouts should be cleared of debris before the rain starts, and may need to be cleared again later where deciduous trees fill them up through autumn and winter.

Evergreen Trees Drop Leaves Too

IMG_20141004_153228As the deciduous trees that will soon be coloring for autumn defoliate for winter, the evergreen trees will become more prominent. Some evergreen trees will drop some of their foliage along with deciduous trees through autumn and winter. Many drop some of their old foliage as new foliage develops in spring, or later in summer. All are on distinct schedules, but are never completely bare.

That certainly does not mean that evergreen trees are not messy. To the contrary, some happen to be significantly messier than some deciduous trees are. They are only evergreen because they do not drop their old foliage until it is replaced by new foliage. Whether individual leaves last just slightly longer than a single year, or for several years, they eventually shed and fall to the ground.

In fact, evergreen trees may shed small but pestering volumes of foliage for a few months or even constantly throughout the year. Some deciduous trees defoliate so efficiently within a very limited time once the weather gets cool, that all of their fallen leaves will be raked away within only two or three weeks. Of course, some trees, both deciduous and evergreen, drop flowers or fruit or both.

Not only do most evergreen trees shed for a longer time than most deciduous trees do, but most shed foliage that is not so easy to rake away. Cypress shed minute and finely textured leaves that are impossible to rake from lawns, but toxic if they accumulate. Juniper and arborvitae are easier to accommodate only because the trees are smaller. Fir, spruce and cedar have bigger needles.

Broadleaf evergreen trees are very different from coniferous trees. Their leaves are considerably easier to rake. They are generally more substantial than those of deciduous trees though. Some may not decompose so readily in deep groundcover. Southern magnolia leaves are notably slow to compost. Instead of producing cones, some broadleaf trees drop acorns or other messy seed.

Nonetheless, where there are compatible with their landscapes, evergreen trees are as practical as deciduous trees are.