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.

Rainy Season

 

 

As I mentioned this morning, the first storm since spring delivered a bit more than an inch and a half of rain before dawn on Wednesday, ending the fire season. The second storm is here right now. It is expected to be followed by a continuous series of storms that will provide rain through Monday, showers through Thursday, more rain on Friday, and showers . . . forever!

It is now the rainy season.

The video above shows what rain does. It gets things wet. It is, after all, composed of water. It falls mysteriously from the sky, which, as you can plainly see, is occupied only by a mostly monochromatic gray cloud cover. Seriously! There is nothing else up there. There is no one on the roof with a hose or anything of the sort. All that water just falls from the cloud cover above.

I could not get video of individual raindrops falling. They are too small and too fast. Only a few can be seen indirectly in the video, falling in front of the water cascading from the rusted out gutter. The spots on the video are raindrops that landed on the lens, so were no longer so animate. The cascading water is, of course, an accumulation of many raindrops that fell on the roof.

Besides ending the long fire season, rain also disrupts the slim fall color season, when foliage of certain deciduous trees turns color as the weather cools in autumn. There is not much to brag about anyway. Only a few native trees are moderately colorful. More colorful exotic trees are not very popular because they do not color as well as they do where autumn weather is cooler.P91130K

Before the rain, these birches were a nice clear yellow, but were already defoliating. Their fallen leaves were as pretty on the ground as they were in the trees, but unfortunately needed to be blown. By now, there is likely more on the ground than there is in the trees, but it will need to be blown too. At least it gets to stay on the open ground in the rest of the casual landscape.P91130K+

The only tulip tree here got cool enough to defoliate before the birches this year, but not quite cool enough to color well first. It is a grand tree nonetheless. We do not expect exemplary color in autumn in our splendidly mild climate anyway. The sweetgums will compensate. They are only beginning to color, and should hold some of their foliage rather well through the weather.P91130K++

Six on Saturday: First Storm

 

The first storm since spring came through Tuesday night. It was cool enough for a bit of snow on the summits of the Diablo Range, including Mount Hamilton, east of the Santa Clara Valley. The fire season is now over. More storms are forecast. More will continue through the remainder of winter and into spring. Even chaparral climates eventually get a seasonal ration of rain.

1. An inch and a half of rain is generous for a first storm. It is more than 10% of what my garden in town got annually. This side of the Santa Cruz Mountains gets about three times as much.P91130

2. My reflection in the rain caught in this ‘tote’ is not as artistic as it was in the green bucket last year. I tried. A flash would have added interest. I do not really know how the camera works.P91130+

3. Cyclamen, even the common florists’ type, deserve more than to be grown as cool season annuals, and then discarded in spring. I can rant about that later. For now, they sure are pretty.P91130++

4. After the rain, even a close up of this seriously abused juniper is pretty. It was recycled from one site into another, only to be removed again. It is now canned and waiting for a new home.P91130+++

5. Storms are messy. There was not much wind with this storm. Nonetheless, rotten limbs get heavier and softer as they get soaked by rain. This one broke apart more as I dragged it away.P91130++++

6. What is worse than runoff from the road washing away some of the yellow birch foliage dislodged by rain, is that it likely took away some of the amaryllis seed tossed out here earlier.P91130+++++

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/

Almost RAIN!

P91123KThere have been only three hints at precipitation since last spring.

The (sideways) picture above shows the same dampened hood of a Chevrolet that provided the illustration for a post on another blog on September 30.

The picture below shows a similarly dampened but different windshield from that which provided the illustration for a post on November 16, regarding a bit of precipitation two days prior, on November 14.P91123K+

All four pictures here were actually taken just after a very brief rain shower that happened just after midnight on November 19. I tried to be artistic with them, but I am not a photographer.

The picture below demonstrates how difficult it is to hold the camera steady while getting a close up picture of rain dripping from a lumber rack at night. Do digital cameras automatically extend exposure to accommodate for the darkness? Is it blurred or merely ‘abstract’?P91123K++

The rain shower was very brief, lasting only a few minutes, but dropped dozens of individual raindrops, maybe more than a hundred! In fact, there were enough of them to collectively flow from one of the roofs, accumulate in a gutter, and flow down this downspout and onto the pavement below! (I really do not know why a diverter is needed on pavement, but there it is.)P91123K+++

I bet that if all the precipitation than fell from the sky during these last three incidents could have been collected, there would have been more than a pint! As excellent as it was, it was not even the best of it. For the first time since last spring, a storm is predicted to move in and start RAINING about noon on Tuesday, November 26! Showers should continue afterward.

The rainy season will likely begin with this first storm. That is how the weather typically operates here.

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

Not Quite Rain

P91116KMost of us here agree that the minimal bit of precipitation that fell from the sky on Thursday was not real rain. There are a few different theories about what it actually was though. It could be considered to have been drizzle. It alternatively could have been heavy fog or mist. Some of us make up silly names for what it was, such as fine rain, dusting, spritzes, sprinkles or mizzle.

Is it just me, or do those last three sound like inane kitten names? ‘Dusting’, sounds dirty and dry, which it was not.

Whatever it was, it was the second occurrence of such precipitation since the rainy season ended last spring. Something similar happened on the last day of September. I wrote about it in my other blog, with a picture of it on the hood of a parked car, rather than the windshield. I think it was more of a surprise then because it was earlier, and the chance of precipitation was slim.

This weather pattern is still within what would be considered normal here. The rainy season typically starts a bit earlier, even if with just a single primary storm passing through, followed by a long pause before more follow. There is no strict schedule though. We know that the rain will eventually start, and that rainy seasons that start late tend to provide significantly more rain.

Rain is likely just as uncomfortable here as it is everywhere else. Perhaps it is even dirtier, because it rinses off dust and crud that has been accumulating since spring. No one wants to work in their garden while it is wet. Nonetheless, because there is no rain for nearly half the year, the first storm of a season is something to be celebrated. The forecast predicts no celebration yet.

Six on Saturday: Light Duty Autumn

 

Autumn is mild here. There has been no rain yet. None is in the forecast. Nights are only beginning to get cool. A thermometer outside claims that it has been cool enough for frost, although none has yet been observed. As pleasant as such mild weather is, it can be boring in the garden. The few deciduous trees that develop good color are only beginning to do so, and in no rush. Some chores that rely on chill or rain get delayed.

1. 32 degrees! Does this qualify as frost? This is the same thermometer that said it was 96 degrees last week. I do not believe everything it says, although cold is not as easy to fake as heat.P92202

2. Krispy Kritter had a bad day. It is not from frost though. This formerly exemplary Heavenly bamboo succumbed to warmth and aridity, . . . . and unintended disconnection of irrigation.P92202+

3. California buckeye defoliated through the warmth of summer, and should foliate for early winter, only to defoliate as winter gets cooler. I knock these big seeds out because they look silly.P92202++

4. African iris, Morea bicolor, got split early where it crowded a walkway. We did not want to plug it until the rain starts, so soaked it in a bucket of water, where the roots started growing!P92202+++

5. Mrs. Pollock zonal geranium, Pelargonium hortorum ‘Mrs. Pollock’, likewise needed to be pruned back prematurely. I was able to process cuttings from the scraps, and plug them directly.P92202++++

6. Such intricate variegation is genetically unstable. Mrs. Pollock zonal geranium often gets less variegated mutant growth that must be plucked. Well, . . . . I sort of plugged some as cuttings.P92202+++++

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/

Mediterranean Climate Is Something Special

90925thumbThe climate here is pretty cool, at least in winter. Right now, it is pleasantly warm. It does not often get uncomfortably cold or hot, and when it does, it does not stay like that for too long. In between the warmest days of summer, the nights typically cool off nicely. In between the coolest nights of winter, the days typically warm up nicely. Humidity is normally minimal. Rain is adequate in season.

We have here what is known as a ‘Mediterranean’ climate. Obviously, it is similar to many climates of the Mediterranean Basin. Beyond the Mediterranean region, there are not many other places in the World that enjoy such reliably temperate weather. Most of such places are in southern and southwestern Australia, the Western Cape of South Africa, central Chile, and evidently, right here.

This particular region of Mediterranean climate is quite large, and extends into northern Baja California. Native plants know how to live here, and many of those that are adaptable to landscapes and home gardens can survive quite nicely with little or no irrigation. Some exotic (non-native) plants want climates with more warmth in summer, more chill in winter, or more rain through the year.

The best, as well as the worst, exotic plant species for local landscapes are those that are native to other Mediterranean climates.

The worst are those that are so happy in the local climate that they naturalize and become invasive to native ecosystems. Without pathogens or competing species that inhibited their proliferation within their respective native ranges, many naturalized species are detrimentally aggressive in ecosystems that they invade. Pampas grass, broom and Acacia dealbata are familiar examples.

The best exotics are not so threatening. Australian fuchsia, kangaroo paw, coprosma, westringia, bottle brush, grevillea, dracaena palm and eucalyptus originated from Australia. Lemon verbena, mayten and some salvias are from Chile. African iris, lily-of-the-Nile, bird-of-Paradise and all of the aloes came from South Africa. Olive, oleander, cistus, and all the lavenders are Mediterranean.

Pasadena Windstorm

P90727K

The weather in the parts of California that most of us are familiar with is generally rather mild. Some of the hottest temperatures every recorded were in the Mojave Desert, but not many of us even know how to get there. Some of the heaviest snowfall ever recorded was near Tahoe, but many of us think of that as almost Nevada. San Jose, Los Angeles and the most populous regions enjoy mostly comfortable weather throughout they year.
‘Drought’ is often an inaccurate description of the naturally prolonged dry chaparral and desert weather, as if it is abnormal. There would be no chaparral or desert if it rained here as much as it does in other climates. What is considered to be normal rainfall in some regions would be disastrous to regions that do not normally get so much precipitation. Drought does happen here sometimes, but it is not as common as outsiders believe it to be.
Once in a while, we get something that really is strange. The floods and mudslides of the Winter of 1982 were disastrous. The wicked frosts of late 1990 were the worst in recorded history, even though they would not have been much of a problem in most other climates farther inland. On the morning of December 1 in 2011, Pasadena and the surrounding regions of the San Gabriel Valley experienced historically strong and destructive winds.
When I went to Los Angeles shortly afterward, I was amazed to see that pieces of the glass facades of some of the skyscrapers had been stripped away. Thrashed fronds of queen palms hung limply as if a hurricane had gone through. My colleague got these startling pictures of destroyed Canary Island date palms, which are famously resilient to wind, in Leimert Park, about fifteen miles southwest of Pasadena.

P90727K+

Summer Turns Up The Heat

90626thumbDoes the heat seem to have come on suddenly this year? There was all that rain through winter, then a quick but delightful spring, and now it is suddenly over a hundred degrees in some places! What happened?! There is certainly nothing abnormal about such warmth in the middle of June. It just comes as a surprise when it arrives so suddenly after such pleasantly mild spring weather.

At least warm weather here is not as dreadful as it is in other climates. It cools down a bit overnight. Humidity is typically (although not always) low. There is typically at least a bit of breeze by late afternoon, just after the worst of the warmth. We need not contend with the sort of dankly humid heat, that lasts all day and into the night without even a slight breeze, that so much of America gets.

Of course, that is no consolation now. By our standards, it is hot. Gardening is no fun, and some of it gets neglected. We become more aware of where shade trees should have been planted. We might also notice wilted or pallid plants that are not getting enough water. Pruning that was delayed while new spring growth matured may need to be delayed a bit longer, until the weather cools.

Unfortunately, the minimal humidity and occasional breezes that make the weather more comfortable for us make it more uncomfortable for the plants in the garden. Plants can realistically tolerate more heat than we can, but prefer it to be in conjunction with humidity. Otherwise, they can lose too much moisture to evapotransipiration (evaporation from foliar surfaces), and wilt or desiccate.

Automated irrigation obviously needs to be adjusted accordingly. Potted plants need more of an increase than those in the ground. Those that are overgrown, in hanging pots, or exposed to the typical evening breezes will be the most consumptive. It is not always easy to know how much they need, but one can be certain that if they are wilting, they need more than they have been getting.

Pots exposed to sunlight can get uncomfortably warm. If cascading or bushy growth does not shade the south sides, smaller potted plants can.