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Frosted Foliage Is Ugly Foliage

Frosted foliage can be removed now.

Weather is variable everywhere. Climates and seasons are imprecisely regulating. They merely define predictable ranges of the elements of weather, such as temperature, wind, humidity, precipitation and cloudiness. As unusual as weather sometimes seems to be, it generally conforms. Winter weather is mild here, but sometimes leave vegetation frosted. 

Frost was sneaky this winter, by occurring during nights between pleasantly warm days. All elements of the weather were within ranges that are normal for local climate, but their chronology was deceptive. Frost seemed unlikely after such springlike daytime weather. Some foliage was frosted only because protection from frost seemed to be unnecessary.

Frost is now unlikely for most local climates so late in the season. Only climates that are at significant elevation or significantly inland might still experience frost. Coastal and low elevation climates are generally past their last frost dates. Some climates experience no frost at all. Except for within the coolest situations, no more vegetation should be frosted.

Therefore, it is generally safe to prune and groom away unsightly frosted vegetation. It is no longer helpful to insulate undamaged vegetation below. Any new growth that pruning of this nature may stimulate or expose should be safe from frost. Within climates that lack frost, vegetation that gets shabby from chill might also appreciate pruning and grooming.

Pruning and grooming of frosted vegetation can be challenging. Many frosted plants are already actively growing in response to warmer weather. Their new growth mingles with their damaged growth that must be removed. Efficient separation of the two requires a bit of effort and persistence. Fresh and tender new growth is innately vulnerable to damage. 

For example, small new shoots of angel’s trumpet break away very easily if bulky frosted stems fall onto or through them in the process of removal. New shoots of several types of canna emerge from the soil among old shoots while it is too early to cut the old shoots to the ground. Grooming is easier where it can happen earlier, or for cannas that grow later. 

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Frost Damage Is Not Cool

Frost damage is a cold reality.

Frost happens. It may not happen every winter. It may not happen everywhere. For a few of the mildest climates, it may not be a major concern. For some climates though, it might have potential to cause significant problems. The best means to avert frost damage is to avoid plants that are vulnerable to a degree of frost that is normal for a particular climate.

Of course, that is not as simple as it sounds. Even in mild climates, angel’s trumpet might get shabby from chill that is not cold enough for frost. Where weather gets cooler, familiar plants such as bougainvillea, avocado, lemon, fuchsia and pelargonium may experience frost damage. Such plants necessitate certain precautions, and must assume innate risk. 

Some plants that are susceptible to frost damage can live in portable pots that can move to sheltered situations prior to frosty weather. Some might be houseplants that live in the garden for part of the year, but come inside at least for winter. Eaves, particularly if above walls of heated buildings, may be adequate protection for marginally susceptible plants.

Plants that are susceptible to frost damage, but live in the ground or are too big to move, may need temporary protection from frost. Such protection might consist of tarps, burlap, old sheets, plastic trash bags or cardboard, suspended above by stakes and string. Thin materials, such as sheets or trash bags, can freeze through, so should not touch foliage.

Protective tenting materials should not remain over sensitive foliage for too long. Ideally, they should be in place immediately prior to frost, and then gone immediately after. Since frost occurs at night here, protection is useful only overnight. During daytime, it obstructs sunlight, but collects heat to stimulate new growth that is more sensitive to frost damage.

Many plants are too big to protect. Fortunately, bigger plants are less susceptible to frost damage than smaller plants. If possible, outer foliage that succumbs should remain until the local last frost date. Although unsightly, it shelters inner growth. Moreover, premature removal of frost damage stimulates new growth that is even more susceptible to subsequent frost damage.

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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.

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Six on Saturday: No Theme

There was a theme when I assembled these six pictures. I just can not remember what it was now. I am very happy with the three species from Del Norte County, #3, #4 and #5. #6 is my favorite though. It was so unfortunately necessary to remove the venerable old trees. It was necessary to remove their suckers too. I combined the two unpleasant tasks in a rather satisfying manner. There was absolutely no indications that the original trees were grafted. I looked for unions. I was informed that the suckers were visually identical to the original trees. I hope that the suckers that I transplanted within the centers of the decayed trunks will grow into trees that are new copies of the original trees!

1. Brugmansia X candida ‘Double White’, angel’s trumpet is a copy of the specimen at el Catedral de Santa Clara de Los Gatos. It somehow got frosted! Frost happens even here.

2. Yucca recurvifolia or Yucca gloriosa var.(iety) tristis, pendulous yucca is blooming at an unoccupied residence where only a few neighbors see it. It tastes like iceberg lettuce.

3. Abies grandis, grand fir was brought by another horticulturist here, from the extreme northwest corner of California, literally on the coast, barely south of the Oregon border.

4. Picea sitchensis, Sitka spruce got collected with the grand fir above and the bear grass below. I am very pleased with these species, but do not know where to plant more trees.

5. Xerophyllum tenax, bear grass came with the two tree species above, but will be easily incorporated into landscapes here. I am unfamiliar with it, and intent to get acquainted.

6. Prunus serrulata ‘Beni Hoshi’, flowering cherry was so severely decayed that only the outer shell of its stumped trunk remains. The twig in the center is its own rooted sucker! 

This is the link for Six on Saturday, for anyone else who would like to participate:

https://thepropagatorblog.wordpress.com/2017/09/18/six-on-saturday-a-participant-guide/
Posted on by tonytomeo · 5 Comments

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.

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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.

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Cold Winters Have Certain Advantages

Winter frost can improve spring bloom.

Even in May, damage from the frosts of last winter is still evident among some of the more sensitive plants. Lemon trees and bougainvilleas that have not yet been pruned may still display bare stems protruding above fresher new growth. Some bougainvilleas did not survive. Those that are recovering will bloom later because replacement of foliage is their priority for now.

However, peonies, although rare, are blooming better than they have since 1991, right after one of the worst frosts in recorded history. Earlier, some lilacs, forsythias and wisterias likewise bloomed unusually well. While so many plants were succumbing to cold weather, many others were enjoying it.

The reason that peonies typically do not seem as happy locally as they are in severe climates is that they really prefer more cold weather while they are dormant through winter. Without it, they may not go completely dormant, or may not stay dormant long enough to get the rest that they need; and then wake up tired in spring. Cold winter weather promotes more adequate dormancy, which stimulates healthier growth and bloom this time of year. It all makes sense considering that peonies are naturally endemic to colder climates.

A preference for cooler winter weather is also why so many varieties of apples and pears that are grown in other regions do not perform well here. The good news is that as the fruit of local apple and pear trees matures through spring and summer, it may be of better quality that it has been for many years. Trees that typically produce sparsely may produce more abundantly this year. The weather that damaged tropical and subtropical plants was an advantage to others.

Nothing can restore cherries, apricots, peaches and any other early blooming fruit that was dislodged by late rain, but any fruit that survived may be just as unusually good as apples and pears. Not only is the best place for gardening, but minor weather problems can have certain advantages.

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The Spring Rush Is On

Pittosporum can be pruned aggressively now.

It is safe to say that any remaining frost damage can be pruned away. Frosted foliage and stems were only left through winter to help insulate inner stems from more damage by subsequent frost, and to avoid stimulating new growth that would be even more sensitive to frost. Now that there is no threat of subsequent frost, and surviving but damaged plants are growing anyway, there is no reason to retain unsightly frosted foliage. The few plants that do not regenerate probably did not survive.

Spring is the busiest time of year for most plants. By now, most have either bloomed or will be blooming soon. Early spring bulbs have already finished. Later bulbs will be blooming soon enough. Deciduous plants that were bare through winter are developing new foliage. Evergreen plants are likewise growing new foliage to replace older foliage that will get shed later in the year.

If necessary, flowering cherry, flowering crabapple, lilac, forsythia and mock orange (Philadelphus) can be pruned as they finish bloom. Flowering cherry should not need much; but flowering crabapple might be in need of aggressive structural pruning. Some of the older canes of lilac, forsythia and mock orange can be pruned to the ground, where their replacement canes are probably already emerging.

Overgrown or disfigured oleander, photinia, bottlebrush, privet, pittosporum and juniper that need restorative pruning can be pruned now. They recover most efficiently in early spring, and have plenty of time to develop plenty of new growth before they slow down again next autumn. If pruned much earlier, they would have stayed bare longer, since they would not have grown much through winter. Besides, almost all pittosporum are susceptible to disease if fresh pruning wounds are exposed to rainy weather.

Seed can be sown for any of the warm season vegetables and flowering annuals, such as zucchini, corn, okra, nasturtium, lupine and sunflower. Tomato, pepper, eggplant, petunia, marigold and busy Lizzie (Impatiens) can likewise be grown from seed, but are easier to grow from small cell pack plants. Cuttings of jade plant, iceplant, sedum and all sorts of succulents, as well as divided pups of aloe, agave and yucca, really get going well this time of year.

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Last Frost Dates Help Scheduling

Frost is unlikely until next autumn.

Frost is not as much of a concern here as it is in other climates. It is very rare in some of the coastal climates of Southern California. The potential for frost damage increases farther inland, farther north, and at higher elevations. Regardless, it is generally tolerable locally. Even if it is necessary to protect a few marginal plants prior to frost, the ‘average last frost date’ gets little consideration.

The average last frost date designates the end of the frost season for a particular region. Although a specific date, it is an average of dates of the last frost of previous years. It includes minor frost that caused no major damage. Damaging frost, although possible, is unlikely afterward. It becomes more unlikely as the season advances. The process reverses after the average first frost date.

Obviously, average last frost dates are as variable as climates. They are irrelevant for climates without frost. Climates with cooler winters generally have average last frost dates later than those of milder climates. For most of us on the West Coast of California, the average last frost date happens before we are aware of it. Nonetheless, it is helpful to know the date for our particular regions.

Warm season vegetable and bedding plants should be safe in the garden after the average last frost date. Directly sown seed should get all the warmth it needs to germinate. Young plants will not likely experience damaging frost. The weather will continue to get warmer. The days will continue to get longer. Cool season vegetable and bedding plants will relinquish their space as necessary.

Plants that sustained damage from earlier frost can now be pruned and groomed. Damaged foliage that remained in place to insulate inner stems is no longer necessary. Pruning and removal of ruined vegetation stimulates new growth while it will be safe from frost. Aggressively pruning and grooming damaged plants that are already regenerating fragile new growth may be complicated.

Most local climates are beyond their respective average last frost dates. Soon, the others will be too.

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Good Weather Can Be Bad

This should be the rainy season.

As if the lack of rain is not serious enough, the lack of cool winter weather will also cause problems for gardening. Warmth is certainly not as bad as drought, and makes gardening and other outdoor activities more pleasurable, but it interferes with the schedules and cycles that we and the flora in our gardens rely on. Something as natural as the weather should not be so unnatural.

The earlier unseasonably cold weather convinced plants that it really was winter. The problem is that the weather then turned unseasonably warm, and has stayed this warm long enough for plants to believe that it is spring! Some established (not freshly planted) narcissus and daffodils that should bloom as winter ends are already blooming, and some that are naturalized where they get no supplemental watering are already fading from the lack of moisture.

Buds of dormant roses are not staying so dormant, and may soon pop and start to grow. Buds of dormant fruit trees could do the same. When the rain finally starts, it will likely damage and spread disease among freshly exposed rose foliage and newly developing buds. Fungal and bacterial diseases that get an early start will likely proliferate more than they normally do through the following spring. Rain can likewise damage and dislodge fruit blossoms.

The many plants in the garden fortunately have a remarkable capacity for adaptation to weird weather. Bulbs, roses, fruit trees and other plants should eventually recover and get on with life as if nothing happened. The weather is actually more of a problem to those of us who want an early and healthy abundance of roses and an abundance of fruit in summer.

It is still a bit too early to know how the weather will affect what happens in the garden this spring, but fruit production of many types of fruit, as well as bloom of some types of flowers is expected to be inhibited.