Frost Is Different From Chill

Frost has already stricken some regions.

‘Chill’ could almost be a pleasant euphemism for ‘frost’. Both words describe cool or cold weather that occurs during winter. The obvious difference is that one is good, and one is bad. Chill is a minimum duration of cool weather that some plants require through winter to maintain their schedules. Frost is weather that is cool enough to damage some plants. 

This technical difference is that chill is at or below forty-five degrees Fahrenheit (≤45°F), and frost is at or below thirty-two degrees Fahrenheit (≤32°F). That is a difference of only thirteen degrees Fahrenheit (13°F), just above the freezing temperature of water. Climate and weather are simply not cooperative enough to comply to such precise technicalities.

Climates that provide sufficient chill for many plants that require it are also likely to inflict frost on occasion. Where chill is sufficient for most plants that need it, frost is likely much too severe for plants that are sensitive to it. Climates that lack frost are unlikely to provide enough chill for plants that need just a bit. High chill apples and oranges should not mix.

Of course, just as various chill dependent plants require various degrees of chill, various frost sensitive plants tolerate various degrees of frost. Some orange cultivars can survive frost as cold as twenty-five degrees Fahrenheit (25°F) within climates that low chill apple cultivars are happy with. Angel’s trumpet though, succumbs as soon as ice crystals form. 

It is helpful to know which plants are sensitive to frost, even in frostless climates. Tropical plants might get rather pallid when the weather is too cool for too long, even if frost is not a direct threat. Potted plants are more susceptible to frost damage than they would be in the ground, but can migrate to sheltered situations. Some can be temporary houseplants. 

Frost naturally limits the selection of plants. Various tropical plants that are appropriate to frostless climates are not appropriate for climates with harsh winter weather. That can be confusing with so many distinct climates within such minimal proximity. Coastal, inland, mountain, and all climates are so very different from each other.

The Need For Seed

Seed for some pines is easy to collect as their cones open during warm summer weather. However, some pine cones must be dried or even heated to release their seed.

Lily of the Nile is so easy to propagate by division of congested old plants that not many of us bother to grow it from seed. No one wants to leave the prominent but less than appealing seed pods out in the garden long enough to turn brown and ripen after the blue or white flowers are gone anyway. Besides, only the most basic old fashioned varieties reliably produce genetically similar seed, and even these often revert between blue and white. Yet, collecting seed for propagation is still an option for those who do not mind the risk of genetic variation.

The natural variation of flower color among seedlings of some plants can actually make gardening a bit more interesting. No one really knows if naturalized four o’ clocks will bloom white, yellow, pink or red until they actually bloom. The few types of iris that produce viable seed almost always produce seedlings with identical flowers, but oddities sometimes appear. (Most bearded iris have serious potential for genetic variation, but do not often produce viable seed.)

Cannas are likewise likely to produce seedlings that are indistinguishable from the parents. However, seedlings of many of the fancier cultivars are often variable. Their seed are very hard so should be scarified before sowing. However, I find that I get so many canna seeds that even if less than half germinate without scarification, there are too many anyway! (Scarification involves scratching or chipping the hard seed coat to promote germination. It can be as simple as rubbing the seeds on a file or sand paper, but should not be so aggressive that it damages the seed within.) 

African iris are just as easy to divide as lily of the Nile are, and are as easy to grow from seed as naturalized four o’ clocks are. The difference is that they lack genetic variation, so are always indistinguishable from their parents. The only problem is that they are so easy to propagate that they can soon dominate the garden.

If seed capsules have not been groomed from the various perennials and annuals that can be grown from seed, or if they have been left out in the garden intentionally so that they can ripen, this would be a good time to collect them for their seed. (Four o’ clocks should have been collected earlier though.) Seeds from certain trees, such as silk tree, redbud and the many specie of pine, can likewise be collected. Most seeds prefer to be sown about now to chill through winter, since cold winter weather actually promotes germination when weather warms in spring. However, seeds for annuals and frost sensitive perennials, like cannas, that might germinate early and get damaged by frost, should probably wait until the end of winter to get sown.

Chill Helps Plants Distinguish Seasons

Spring bulbs know what chill means.

The Santa Clara Valley was formerly famous for stone fruit orchards. The San Fernando Valley was formerly famous for citrus orchards. The Wenatchee Region of Washington is still famous for apple orchards. Many variables influence which agricultural commodities grow or grew in each region. Of these, one of the more obvious is temperature and ‘chill’. 

Citrus could not be productive in the Wenatchee Region because it could not survive the chill of winter there. Although productive in home gardens of the Santa Clara Valley, it is not quite as productive as it is where winter is warmer in the San Fernando Valley. Citrus appreciates warmth but not chill. Many tropical and subtropical plants feel the same way. 

However, many of the numerous cultivars of apple that are so famously productive in the Wenatchee Region would be unproductive in the Santa Clara Valley. Only a scant few of these might produce relatively meagerly in the San Fernando Valley. Unlike citrus, which dislike chill, apple trees need chill for production. Some cultivars need more than others.

Chill regulates the schedules of many plants that are originally endemic to climates with cool winters. It confirms the occurrence of winter, which is a convenient time to finish one annual cycle and begin another. Some plants require only a minimal chill. Those that are from climates with harsh winters require coercion by more significant and sustained chill.  

One of the primary reasons that spring bulbs are available for planting early in autumn is that some benefit from spending winter in a cool and damp garden. Although, most bulbs are chilled prior to marketing. Some previously chilled spring bulbs bloom splendidly for their first season, but then bloom unsatisfactorily if chill is inadequate for them afterward.

Most plants that need more chill than they can get locally are simply not available locally. Some are available online though. A few locally popular plants that are marginal for mild climates get confused by the seasons. This is why some flowers such as torch lily, bloom randomly or out of season. Daphne and some late winter flowers may be blooming now, and could get damaged by frost later.

Tropical plants make a smooth transition as houseplants

Houseplants live outside somewhere.

Hibiscus, bougainvilleas, philodendrons and so many of the tropical and subtropical plants that we can enjoy in our gardens can only survive through winter in greenhouses in most other climates in America. Many of our tropical houseplants though, seem to be the same everywhere. Houseplants are generally grown in our homes not because they can not survive in our gardens, but because they ‘can’ survive in our homes.

Yes, houseplants are merely any plants, tropical or otherwise, that we grow in our houses. Yet, most and perhaps almost all of the plants that are best adapted to surviving as houseplants happen to be tropical plants. Tropicals do not need the seasons that they would get outside. Because many are native to dense and very competitive tropical forest environments, they are adapted to the sort of shade that they get in our homes, and survive on minimal volumes of soil that they have available while potted.

Nonetheless, they miss their tropical lifestyles. They only tolerate dry interior air, but would prefer more humidity. They would likewise prefer to be rinsed of dust more often than they can be in indoors. A regular supply of fresh organic debris to supply nutrients would be nice. However, if merely fertilized instead, tropicals are sensitive to salts and other toxins that eventually accumulate in the soil.

This is why some of the more resilient houseplants like to be brought outside for a gentle rinsing during a mild rain. As long as it is not too cool or windy, gentle rain rinses dust from the foliage and toxins from the soil. Plants can be brought out in the morning and brought in late to get as much time out in the rain as possible, but should not be left out overnight when it may get too cool. Even though they do not need any more moisture, plants can be watered by hose a few times to allow water to rinse freely through the soil.

Plants in overly decomposed potting soil are easier to repot with fresh soil while they are outside. Those that do not need to be repotted might still like getting grungy and potentially toxic mineral deposits scrubbed from their pots and drainage pans.

Christmas Trees Dead Or Alive

Live Christmas trees can get huge.

Poinsettias, Christmas cacti, cyclamen, various forced bulbs and several other seasonal potted plants are again becoming popular. It happens annually prior to Christmas. Heath, heather, rosemary, English holly with berries, and delightful compact conifers have been gaining popularity for many past years. Seasonal potted plants are increasingly diverse.

Unfortunately, few survive for long after Christmas. Forced bulbs exhaust their resources. Cyclamen are likely to rot after a month or so. Very few retire to a garden. Poinsettia gets too lanky in the garden to be a favorite. Most seasonal plants simply succumb to neglect. After their primary performances, they are no longer interesting enough to justify tending.

In reality, some of these seasonal potted plants are little more than cut flowers with roots. These roots allow them to live longer than cut flowers, but their ultimate fate is the same. Wreaths, garlands and various seasonal cut greenery likewise serve a purpose, but only temporarily. Without roots, it all lacks any potential to retire into a garden after Christmas.

Christmas trees are really not much different. Although there are several different sorts of Christmas trees, they fit into similar categories as cut foliage and seasonal potted plants. Obviously, they are seasonal. They need not last much longer than Christmas. Although, some have a potential to do so, few survive or function for more than a few Christmases.

Contrary to popular belief, and their expense, cut Christmas trees are generally the most practical Christmas trees. They are essentially a very substantial sort of cut foliage. They grow on farms like any other foliage and vegetables. After such a tree serves its purpose, it resigns to compost or green waste recyclery. A freshly cut tree can replace it next year.

Large potted Christmas trees may seem to be more practical, but require maintenance to remain as appealing as they are now for another year. Despite the expense, few last that long. They want to get out of confinement, so that they can grow as trees. Pre-decorated small trees are Italian stone pines. They grow much too big for contained home gardens.

Potted Plants Need Work Too

Most potted plants would prefer to be in the ground, . . . if possible.

Potted plants can be a problem any time of the year. Some want more water than get. Most get too much water or do not drain adequately. Large plants get constricted roots if pots are too small. The roots of some plants get cooked in exposed pots that collect too much heat from sunlight. Besides, too many pots just seem to be in the way in otherwise useful spaces on decks, patios and anywhere else trendsetting landscape designers want to put them.

Now that the weather is getting cool and rainy, potted plants are not as active as they were during warm weather. Many are dormant. Although few demand the attention that they got during warmer weather, plants still need to be tended to appropriately through autumn and winter.

Cool season annuals, which are also known as ‘winter’ annuals, should get groomed as long as they are performing in the garden, just like warm season annuals get groomed through summer. Deteriorating flowers should be plucked from pansy, viola, primrose, Iceland poppy, calendula, dianthus, stock, chrysanthemum and cyclamen because they can mildew and spread mildew to developing flowers and foliage. Unplucked cyclamen and calendula can develop seed which diverts resources from bloom.

Pots that are out in exposed areas will not need to be watered while they get enough water from rain. The problem is that many that do not drain adequately can get too much water from rain and stay saturated. Dormant and defoliated plants do not need much moisture at all. Even evergreen plants do not need as much as they do while active during warm weather, because cool and humid weather inhibits evapotranspiration (evaporation from foliar surfaces).

Potted plants under eaves also need less water while the weather is cool and humid, but need to be watered nonetheless because they are sheltered from rain. Plants in hanging pots typically drain and dry more efficiently, so probably want a bit more water. Even a few sheltered small plants in the ground may occasionally want to be watered during rainy weather if they do not extend enough roots where they can get moisture from rain beyond the sheltered area. Sheltered plants are actually the most likely to be neglected because watering does not seem so important when it is raining.

Chimney Clearance Must Be Maintained

Modern homes lack old fashioned fireplaces.

Even as autumn weather cools, smoke rising from a simple old fashioned brick chimney is a rare sight nowadays. A smoking stovepipe is rarer. Modern building codes forbid the installation of new fireplaces or wood stoves within most municipalities here. Modern air quality ordinances severely limit the use of existing fireplaces and wood burning stoves.

Furthermore, existing fireplaces and wood stoves are neither as popular nor as common as they had been. After an earthquake, a faulty chimney is likely to justify removal rather than repair. An unused wood stove wastes too much space. Old orchards that generated inexpensive firewood as they relinquished their space to urban development are extinct.

There are a few advantages to these modern trends though. Modern homes consume so much less energy for heating than older homes because of efficient insulation. Insulation of older homes retains heat that fireplaces generate, so that less wood is needed. Almost every surviving chimney has a spark arrestor. Modern roof materials are noncombustible.

Nonetheless, vegetation that gets too near to a chimney that is in use can be hazardous. Even if clearance was adequate last winter, trees, vines and large shrubbery grew since then. It does not take long for such vegetation to overwhelm a chimney, or encroach a bit more than it should. It does not take too much vegetation to be hazardously combustible.

Clinging vines like English ivy and Boston ivy sometimes climb up and then over the top of a chimney. Although not especially combustible, they will burn directly over a fireplace or wood stove. Just like gutters do, vines can accumulate leaves that fall from deciduous trees to become more combustible. Birds or rodents can build combustible nests in them.

Evergreen trees and big shrubbery are similarly combustible over a chimney. Deciduous trees are generally not as hazardous. Conversely, cypress, pine, cedar, eucalyptus, large junipers, and ungroomed palms are very combustible. Eucalyptus foliage will burn while fresh, if it gets hot enough. The other trees tend to accumulate very combustible detritus.

Dormancy And Defoliation Are Advantageous

Hostas go dormant and defoliate for winter, and regenerate for spring.

Many plants are deciduous in autumn and winter, which means that they defoliate or die back, and then refoliate or regenerate in spring. Many others are evergreen, which simply means that they are always foliated through all seasons. What many people do not realize is that evergreen plants replace their foliage just like deciduous plants do. They just do not do it in such distinct phases of defoliation, dormancy and refoliation.

Tropical plants like cannas and some of the various begonias really have no need for formal defoliation, since they are from climates that lack winter. In the wild, they continually and systematically shed old stems as they produce new stems. Locally, they tend to shed more than they grow during late autumn and winter. The large types of begonias tend to keep their canes for so many years that it is not so obvious. Where winters are colder, cannas freeze to the ground, only to regenerate from their thick rhizomes as winter ends.

Zonal geraniums may seem rather tired this time of year for the opposite reason. They expect late autumn weather to include frost that would kill them back to the ground where they would stay relatively dormant until warmer weather after winter. Just because their foliage is instead evergreen through winter does not mean that it should be. It lingers and often becomes infested with mildew and rust (fungal diseases) that proliferate in humid autumn weather.

However, zonal geraniums need not be pruned back just yet. Even if they eventually get damaged by frost, pruning should be delayed so that the already damaged older foliage and stems can shelter the even more sensitive new growth as it emerges below. They can get cut back after frost would be likely.

Evergreen pear can get very spotty once the warm weather runs out because the same damp and cool weather that inhibits its growth also promotes proliferation of the blight that damages and discolors the foliage. The damaged foliage eventually gets replaced as new foliage emerges in spring, but will remain spotty and discolored until then. Photinia does not get as spotty, but holds blighted foliage longer into the following summer. Ivy can be temporarily damaged by a visually similar blight.

Dried Floral Material Worth Recycling

Yucca bloom produces interesting floral stalks.

Gardens might be colorful throughout the year here. There is not much time between the latest of the autumn flowers and the earliest of the spring flowers. Winter flowers are glad to compensate for the lapse. Of course, there are plenty of flowers in spring and summer. Nonetheless, dried flowers are more popular now that there are fewer flowers for cutting.

The quantity of flowers blooming within a particular season might not be proportionate to the quantity of flowers available for cutting. Flowers that bloom through winter, even if as abundant as spring or summer flowers, do not develop as fast. Harvesting too many bird of Paradise flowers depletes the limited supply before something else can replace them.

Deciduous foliage that provides spectacular color through autumn is no substitute for cut flowers. Nor is the majority of colorful bark that becomes more prominent through winter. Some colorful berries can function like cut flowers, but only if there are plenty to spare in the garden. Conventional dried flowers that grew last summer may be useful about now.

For the venturesome and resourceful, unconventional dried flowers and other dried plant parts can also be fun. Such items, unlike statice, straw flower, lavender and other familiar dried flowers, might be byproducts of gardening. They might be derived from detritus that should otherwise go to compost or greenwaste. Some might even be products of weeds!

Pampas grass, both garden varieties and the invasively naturalized type, produces bold blooms that dry quite well. Because the leaves can cause such nasty paper cuts, flowers might be easier to harvest from a distance, with a pole pruner. Hair spray can contain the fuzz, so that it does not disperse indoors. Cat tails, if still intact, are compatible with them. 

Floral stems of lily of the Nile, New Zealand flax, and some species of Yucca are striking even after bloom. After deadheading, they can become flowerless dried flowers. Fruiting structures are no problem to remove. If within reach, some palms may provide distinctive bloom trusses. Floral design can be as imaginative as gardening and landscape design. 

Dried Flowers Last All Year

With proper processing, hydrangea bloom can be dried.

Statice, strawflower and globe thistle continue to bloom later than most other summer annuals, and hold their flowers longer. Even after bloom, the flowers are so stiff and ‘crispy’ that they remain intact and colorful until they succumb to exposure to weather. If cut and brought in from the weather soon enough, they will last as dried flowers at least until fresh flowers start to bloom in the garden next spring.

Strawflower and larger globe thistle tend to wilt and droop from the weight of the bulky flowers, so should be tied in small bunches and hung upside down to dry. Perennial statice (which has larger blooms than annual statice) tends to flop to the ground, but the stems often bend only at the base so that the rest of the stem length stays somewhat straight. Smaller globe thistle and annual statice often dry standing up while still out in the garden.

Yarrow and English lavender can be dried as well, but lose most of their color. Lavender dries naturally in the garden. Yarrow can likewise be allowed to dry in the garden, but probably keeps a bit more color if cut while still fresh and hung upside down. Because yarrow blooms are so wide, they should be hung individually or in small bundles. Queen Anne’s lace has even wider blooms that curl inward as they dry, so they really should be hung individually.

Old hydrangea flowers that are only beginning to fade can dry surprisingly well if cut and hung individually before they deteriorate too much or start to rot. Some varieties retain color better than others. Some fade almost completely to an appealing brown paper bag.

There are not many roses this time of year, but when they do bloom, even they can be cut and dried while beginning to unfurl. Only a few small and tightly budded roses can be dried when completely open. Because they droop right below the blooms, roses should be hung upside down to dry. Dark colored roses get very dark as they dry. White roses turn tan. Pink and yellow are probably the better colors.

Cat-tails and pampas grass flowers are big, bold and dated cut flowers. Yet, for situations where big flowers fit, they are just as practical now as they were in the 1970s. Because pampas grass flowers shed, and cat-tails can explode (to disperse their seed), they should be sprayed with hair spray or another fixative to keep them contained. Pampas grass foliage has dangerously serrate edges that can give nasty paper cuts, so should be handled carefully, and displayed out of the way.