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.

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.

Six on Saturday: No Flowers – Again

These pictures seemed to be interesting when I took them. Only now I notice that there are no flowers here. Actually, there are not many flowers in the landscape where these pictures were taken anyway. Until last year, the facility associated with the landscape was used mostly during summer; so most flowers were selected to bloom during summer. Winter can be quite bland.

Also, for such a mild climate, winter can be surprisingly cool in some cooler exposed locales. Mild frost is normal. On rare occasion, if the weather is just so, puddles can get a thin layer of ice.

1. Lemon ripens this time of year. This pale greenish yellow color will become brighter yellow soon. I suspect that these are ‘Eureka’ lemon, but they crop very heavily in season, like ‘Lisbon’.

2. Flowering cherry will be spectacular in spring, but looks horrid now. This particular tree does not defoliate completely until just prior to bloom. It does this annually. This tree is ‘Kwanzan’.

3. Silver wattle is an an aggressively invasive exotic species locally. Fortunately, there is not much within the landscapes here. Now there is even less. I know it will regenerate from its roots.

4. Argyle apple is a silly name for this Eucalyptus cinerea. It grew from the lignotuber of an overgrown tree that was discarded from a retail nursery in Los Osos. The silver foliage is striking.

5. Lawson cypress also has strikingly silvery foliage. It is not as silvery as that of Argyle apple, but is slightly more bluish. The color of both species seems to be more striking through winter.

6. Ice is rare here, but possible. Of course, it is not as bad as it looks. It is very thin. Winter weather is innately mild here, which limits cultivation of apples and pears than require more chill.

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/

Jack Frost Nipping At Foliage

Yuck! Freezer burn!

It is impossible to deny that the weather has been unusually cold when tough perennials like ligularia and farfugium express symptoms of frost damage. Late autumn and winter are expected to be cold, but not as cold as it has been recently. Ligularia, farfugium and most tough perennials should recover as if nothing happened. Cannas will naturally die back or need to be cut back to the ground later, but their resilient rhizomes should be safe, and regenerate later as winter ends. Unfortunately, sensitive perennials like pelargoniums may have been killed if frost damage extended too far into lower stems and roots.

The best way to protect plants from frost is to grow only plants that are not so vulnerable to frost. The problem with this technique is that it is too limiting. Abstaining from the few most sensitive plants like bananas and angel wing begonia probably would not be a problem for most of us. However, avoidance of moderately sensitive plants would involve familiar plants like bougainvilleas, lemons and split leaf philodendron.

Many of the smaller sensitive plants like angel wing begonia, can be grown in containers that can be moved to more sheltered spots if and when necessary. They can be brought inside or moved onto covered porches. If they only need to be protected for a few days during the coldest weather, they can be moved into garages. The problem with this technique is that many plants get too big for containers.

Bougainvilleas eventually get big, and do not like to be grown in containers anyway. They should be planted in warm spots in the garden not only because their foliage can be damaged by frost in winter, but also because they like warmth during summer. A south facing wall with an eave above provides a nice warm exposure, a bit of protection from frost above, and a slight bit of ambient warmth from the building behind it. Even if the foliage gets frosted, the main stems within should be safe.

During the coldest nights, sensitive foliage can be protected by burlap, paper, plastic or any sheeting suspended above by stakes or any light framework. With this technique, only exposed foliage or foliage that touches the sheeting will be damaged. It is unfortunately not practical to tent large plants like giant bird-of-paradise.

Even though it is unsightly, unprotected foliage and stems that get damaged by frost should not necessarily be pruned away immediately. This damaged foliage insulates and protects sensitive stems below. Besides, such early pruning can stimulate new growth that will be even more sensitive to frost later.

Six on Saturday: Frozen II

Contrary to popular belief, there is a bit of chill during winter here. I was surprised by how many were surprised by my pictures of slight frost last week. The stone fruit that used to grow in the Santa Clara Valley could not have produced without adequate chill. Some deciduous trees color well for autumn, and all defoliate. We do not use much firewood, but some of us use some.

It may not look much like autumn to outsiders. Nonetheless, I find the local climate to be more than satisfactory for what I grow. In some regards, I find it to be ideal. Rhody just stays in by the stove.

1. Sycamores are trashy. Because of anthracnose, they dropped leaves in spring. They dropped more after the Fire. Now they are defoliating for winter. A bulldozer is used for all the leaves.

2. Bald cypress colors well by simple local standards, even if it is merely orangy brown. Bald cypress is rare here, perhaps because of the climate, or perhaps because of its buttressing roots.

3. Dogwood fruit is messy through winter. Surprisingly, wildlife is not particularly interested in it. I should make jelly with it for competition at the Harvest Festival next year (if it happens).

4. FreeBay is how we refer to small piles of bay firewood left on roadsides for neighbors to take away. Vegetation management has become a priority, and generates firewood as a byproduct.

5. Canna behave as outsiders expect them to here. They try to continue blooming until they eventually get frosted. The minor frost they experienced so far was insufficient to stop them yet.

6. Minor frost seems to evaporate as readily as it thaws when exposed to sunlight. This sure looks like autumn. I somehow sort of believe that this is what autumn looks like in other regions.

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/

Frost!

Fire and Ice! Frost becomes a concern at about the same time that fire season ends here. Like the article about fire yesterday, this article is from three years ago, in fact, at about the same time.

Tony Tomeo

P71208+K1Yes, we get it too. It took a while, but we finally got it just like most of everyone else in North America and the Northern part of the Norther Hemisphere. It is not much to brag about, but it is enough to melt the big feral pumpkin vine that I wrote about earlier ( https://tonytomeo.wordpress.com/2017/12/03/too-late-for-pie/ ). It has actually been frosting for a few nights. I just got around to getting this picture this morning.

Now that the foliage is melting and collapsing, a leak is now visible in the exposed valve manifold that was obscured in the previous picture. It did not get cold enough to freeze the pipe, so the water was dripping freely. This confirms the earlier theory about where the pumpkin vine was getting water from.

Two pumpkins are also exposed by the collapsing foliage. They were not visible earlier. Unfortunately, they are too under-developed…

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Six on Saturday: Frozen

It was unusually cool yesterday morning. Deciduous trees are a bit more colorful. Some are defoliating. It is looking more like autumn. The soil is still damp from a little bit of rain more than a week ago. Although there is no more rain in the forecast, this rainy season could start at any time now. This is the time for autumn planting, and will soon be the time for dormant pruning.

As much as I like enjoy this weather and this time of year, I can understand why people get annoyed by it in climates where it starts sooner, lasts longer, and gets significantly cooler.

1. Frost on the windshield is not uncommon during winter. It is uncommon prior to winter though. It is also uncommon in the relatively warm (less cool) area where this vehicle was parked.

2. Frost on the roofs is a bit unexpected so early as well. It had covered this roof thoroughly, but is melting now that the sun is coming up. The weather really did not ‘feel’ as cold as it looked.

3. This contraption does not seem so ridiculous now. It insulates an exposed water main, to hopefully protect it from freezing. Water pipes seldom freeze here. Nonetheless, it is a possibility.

4. Dogwood colors well for autumn, even when the weather is not so cool. The species does not perform so well in the Santa Clara Valley, just a few miles north. Notice the frosty roof beyond.

5. This young birch is already defoliated! Actually, it is a formerly canned specimen that is a bit distressed from planting on November 8. Other birches are still wearing bright yellow foliage.

6. Turkeys return annually, precisely on the morning after Thanksgiving, after disappearing for about two or three weeks. Who knows where they go? Their stupidity might be exaggerated.

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/

Mild Weather Is Still Problematic

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Minimal frost delayed certain spring blooms.

It is amazing that so many orchards are so productive in California, and that so many similar orchards had formerly been productive in the urban areas in which so many of us now live. Nowadays, it takes so much work to care for just a few fruit trees in home gardens. Horticulture is not what it used to be.

Diseases and pests get transmitted all over the world at a rate unlike at any other time in history. It is just too easy to buy and sell infected plants online, and get them delivered without adequate inspection. Many varieties of plants that are so easily imported may not perform as reliably as the more traditional varieties.

Modern landscaping does not make fruit production any easier. Most deciduous fruit trees do not get pruned adequately or properly. Many get too much water. Almost all must live in crowded landscape conditions where diseases and pest proliferate. Sanitation (removal of infected plant parts) is rarely as efficient as it should be.

Then there is all this crazy weather! First, the winter does not get as cool as it should. Then, it does not get warm enough in spring. It is all so difficult to keep track of. Many plants do not know how to respond. Those that stay dormant through cool weather got an early start. Those that like warmth in spring started late.

The unfortunate deciduous fruit trees that need both a good chill through winter and nice warm spring weather are really confused. Early blooms were ruined by brief late frosts or brief rain showers. Some delayed blooms were not synchronized with pollinators. Some of the minimal fruit is developing slowly.

Even the fruitless or ‘flowering’ relatives of the deciduous fruit trees are annoyed by the weather. Many flowering cherry trees that should have bloomed profusely prior to foliation delayed bloom until lower foliage started to appear. However, both bloom and foliation are so slow and sporadic that upper stems stayed bare quite late.

Flowering crabapple trees, which generally bloom after flowering cherries, actually bloomed more reliably, and were not delayed as much. Hopefully, fruiting apple and pear trees, although late, will be more productive than so many of the cherry, apricot, plum, peach and nectarine trees will be this year.

Frost Is Now Old News

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Minor frost can cause major damage.

Frost was something of a nonissue for some of us this winter. For those of us in milder climates, in rarely is. Those who limit selection of what grows in their gardens to species that are resilient to frost need not be concerned with it. Those of us who enjoy gardening a bit too much are more likely to grow a few marginal species that would prefer to be somewhere with milder winter weather.

Protection from frost might have been a concern prior to the onset of cold weather. Then, there was more concern for the few plants that might have been damaged by frost. Grooming and pruning of damaged foliage and stems needed to be delayed until after the threat of subsequent frost. Now that it is so late in the season, subsequent frost is very unlikely. It is safe to clean up any mess.

Pruning and grooming of foliage and stems that were damaged by frost is delayed for two main reasons. Firstly, the damaged material, although unsightly, helps insulate undamaged foliage and stems below it from subsequent frost. Secondly, premature removal of damaged material stimulates premature development of new foliage and stems that are more sensitive to subsequent frost.

Not only is it now safe to prune and groom frost damaged plants, but such procedures should not be delayed while affected plants recover. The same frost damaged material that provided a bit of protective insulation earlier would now interfere with the healthy development of new stems and foliage. Pruning can now promote new growth that was preferably delayed through colder weather.

Because the weather has been so pleasantly mild for quite a while already, new growth may already be developing among some frost damaged plants. Damaged material should be removed as carefully as possible to limit damage to such new growth. Many perennials that were not damaged this year might be pruned as if they were, to remove tired old growth, and promote new growth.

Many of the dormant spores of fungal and bacterial pathogens that overwinter in old foliage will be removed as such foliage gets groomed away.

Some Annuals Are Not Annual

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Some summer annuals can survive winter.

So many annuals are actually perennials. They just get dug and replaced because they are not pretty enough during their off season. For warm season annuals, winter is the off season. For cool season annuals, summer is the off season. However, if left alone, many annuals that are actually perennials go dormant so that they can survive through their off season to regenerate and perform again for another season, or several seasons

Cyclamen and various primroses are cool season annuals that are in season now. Cyclamen will go dormant and defoliate as the weather gets warm in summer. Primroses do not defoliate, but get rather runty through warm weather. If planted with other light duty warm season perennials that take over for them, no one notices. For example, primroses are colorful enough now to distract from tired fleabane. By the time primroses fade, the fleabane takes over.

Chrysanthemums are among the flashiest of perennial annuals, but also have a short season. They typically get planted while blooming in autumn, but finish their bloom cycle before winter. After all the rain and cool weather . . . and then a bit of warm weather, some are already dying back to the ground; but closer examination might reveal new growth already emerging from the roots!

Nasturtiums can obscure regenerating chrysanthemums nicely. If the frost sets them back, they recovery quickly. They will bloom more colorfully by spring, and continue until summer gets too warm. By that time, the chrysanthemums should be filling out nicely to bloom by autumn. As the chrysanthemums finish, the nasturtiums will have sown their seeds, so that the process can start over again. Neither chrysanthemum nor nasturtium need to be removed while out of season. They only need to be pruned back and groomed accordingly.

Coleus, impatiens, fibrous begonias and maybe even polka dot plant that were only moderately damaged by frost might be salvageable if they can stay put long enough. That is the advantage of growing them in pots with other small perennials that will cover for them when they die back or need to be pruned back.