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Cold Weather Arrives Suddenly
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Greetings!
Again, thanks for the feedback. In the last week several of you commented that the text of this newsletter needs more contrast and size. Since the cost of changing the text is zero, your wishes are granted. This also allows me to type without squinting.
It appears that the chances of warm weather before the end of the year is fleeting. I am expecting 2010 to end up being the coolest year on record for Orange County. I doubt we had more than 6 weeks of temperatures above average for the whole year. Most of the tropical plants in my garden didn't grow much.
This issue will center on protecting your sensitive plants from the cold. The weather has changed so suddenly that I even feel sorry for the plants that normally thrive in it.
I mentioned earlier that I was considering selling the organic product CONCERN WEED PREVENTION PLUS with corn glutein. The 25 pound bags will cover up to 1500 square feet of grass, but is my favorite all-purpose fertilizer that also happens to prevent weed seeds, actually almost any seed, from germinating for up to 5 weeks. A substance normally present in corn seeds is responsible. It is the most impressive lawn fertilizer that I've used and feeds for up to 6 months. The fertilizer analysis is an ideal 8-2-4. The cost is $35 per bag.
We will be selling WEED PREVENTION PLUS at The Great Park Farmers Market on Sunday. For those of you in southern Orange County we will also be at the farmers market that opens at 2pm on Fridays at the Lowe's parking lot in Santa Margarita. (corner of Santa Margarita parkway and Avenida de las Flores)
I have also ordered Blueberry plants which we should receive in a week or so. We will then be able to offer them to you at both farmers market locations.
This winter or early spring, we would like to provide our customers with citrus plants that will perform. To do this we must order them from a commercial orchard supplier. Here's a list of varieties that we usually can offer.
Lemons-Meyer, Lisbon, Variegated Pink
Limes-Mexican, Bearss, Sweet
Mandarins & Tangerines-Satsuma, Clementine, Golden Nugget, Tango, Shasta Gold
Tangelo-Minneola
Oranges-Washington Navel, Cara Cara Navel, Valencia, Smith's Red Valencia, Moro Blood
Grapefruits-Star Ruby, Oroblanco, Melogold
Pummelo-Chandler, Mato Butan
Kumquats-Meiwa, Nagami
Miscellaneous-Yuzu, Calamondin, Kaffir lime,
If you e-mail us with varieties you would be interested in for the coming year, I will see what we can do.
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Keep Your Plants Warmer
Most of your evergreen, broadleafed plants would be happier if summer lasted year round. Generally tropical plants do fine if temperature stay above 55 degrees F. This month I'm expecting night temperatures to hoover between 35-45 degrees F. We may even drop lower. The all-time cold temperatures were recorded in December 1990 when Lake Forest hit 23 degrees F. and San Juan Capistrano dropped below 20 degrees F. During that cold spell Escondido hit 13 degrees and San Francisco wasn't much warmer. We saw birdbaths capped with a layer of ice that persisted until noon! The record setting cold severely damaged avocado and banana trees and many palms leaves turned brown. Quite a few Plumeria turned to mush.
Other plants that are quite tender include Adenium obesum (DESERT ROSE), Hibiscus (especially the more tropical HOTBISCUS), Evolvulus (HAWAIIAN BLUE EYES), Impatiens, Catharanthus roseus (VINCA), PINEAPPLE, PAPAYA. In a real nasty frost you'll also see damage on Syzygium paniculatum (BRUSH CHERRY), Carissa grandiflora (NATAL PLUM), Coprosma repens (MIRROR PLANT), Agave attenuata (FOXTAIL AGAVE), and Calliandra haematocephala (PINK POWDER PUFF). I'm generally not overly concerned until temperatures drop below 28 degrees F.
The coldest nights typically are very still (windless) and clear. Tender plants freeze when the heat stored in them is lost to the cold black night sky. Overhead objects (tree branches, house eaves, clouds) will reflect some of that heat back. Bare, moist soil absorbs the sun's energy during the day more efficiently than lawns, dry soil, or soil covered by mulch. Concrete, rocks, and bodies of water also absorb energy efficiently and heat the air at night. Cold air sinks and tropical plants will stay warmer in raised planters or on a slope. Cold air will cause more damage if it becomes trapped behind a solid wall. In neighborhoods, the homes high on a hill will suffer less frost damage than homes at the bottom of a hill or especially gardens in a steep canyon or along river beds.
I live at the top of a hill along Trabuco creek. My plants look fine except for a few leaves on my Plumeria. In a garden near the bottom of the hill, the banana leaves and Hibiscus leaves have already been blackened by the frost. The temperature does drop gradually as the altitude increases due to decreasing pressure (fewer molecular collisions) at the rate of about 1 degree for every 200+ feet increase.
There are a few things that can easily be done to create and/or store heat. Transparent plastic tarps will trap the warmth beneath them either as a soil cover (like on strawberry fields) or suspended over the entire plant (like a greenhouse). For best results don't let the plastic touch the leaves. Be careful to remove the plastic during warm winter days to avoid overheating and damaging the leaves. Lights, such as strings of holiday lights, can be placed under the plastic or just wrapped around the plant to keep it warm. Water stores energy very efficiently. Large covered containers (covered to prevent evaporation from cooling the contents) or bags of water placed around plants will absorb daytime energy and release it at night. Individual plants can also be kept warm with heating pads and heating coils available at some garden centers.
You probably know that piles of compost can create and give off substantial heat. Unfortunately there is a severe lack of oxygen in the middle of the pile that can suffocate roots of plants. You can place a container full of warm compost near a plant, but don't cover its soil deeply with loose compost. You can place potted plants on top of a thick bed of compost to keep them warm. This method is often used in cold frames in the colder parts of our country.
On some farms (especially in Florida) sensitive crops are continuously sprinkled with water when temperatures are just below freezing. Water turning to ice releases energy to the crop. (Most crops can go a few degrees below freezing before damage occurs.) On some farms in California the irrigation water is heated before being applied to the field. Many farms have tall wind machines that blows the warmer air (cold air hugs the ground) downwards. These are often combined with heaters. A few farms are experimenting with bright lights, believing that light rays transfer energy more efficiently. All of these methods can only raise the crop's temperature a few degrees and severe cold spells cannot be protected against.
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After the Freeze
When woody trees and shrubs freeze, it's difficult to tell what parts of the plant won't recover. The U of California did research in orchards after the 1990 freeze to see if selective pruning helped the damaged trees recover faster. They found that 6 months following the freeze the untouched orchards all recovered significantly better than the pruned orchards. Apparently even skilled workers cannot determine what is alive and what is dead. Remember also that any pruning that damages live tissue will consume energy to close the wound. This is energy that could otherwise have been used to grow new foliage. Their conclusion was to wait until summer to prune.
With many plants it is easy to tell when they are dead. They turn to limp "mush". Impatiens, Vinca rosea, Plumeria, Desert Rose (Adenium), Papaya, Pineapple, and Foxtail Agave can look like steamed cabbage after a frosty night. When it's totally slimy you know it's dead. If the plants were there more than a few months be sure that you follow the rules of crop rotation if you replace them.
Pygmy Date palms have long leaves that freeze at temperatures below 26 degrees F. The trunk is undamaged and new fronds appear in spring. When this happened 20 years ago, my father sprayed green dye of the dead leaves to disguise them until the new spring growth made an appearance.
Bermuda, St. Augustine and Zoysia lawns will most likely turn straw colored this winter and recover by April. In the mean time you can spray on a green lawn dye (just like they use on sports fields) to mask the problem. Green lawn dye is available at landscape supply stores like Orange County Farm Supply. Some homeowners will plant rye grass seed to keep the area green with a temporary cool season grass until spring.
Even cool season grass lawns (like Marathon) can turn brown following a nasty frost. In my neighborhood I observed that some lawns would turn browner than others, even though they were all Marathon. It turns out that the most damage was seen on lawns where the most compost was incorporated (higher priced landscapes). I've seen this on my own lawn. Most of my original lawn area was heavily amended. A few small parts were not. To this day (nearly 2 decades later) the unamended areas are more dense and grow faster. More compost in the soil consumes oxygen at a higher rate. Underground plant tissue requires oxygen to thrive. The heavily amended soil creates a very shallow lawn, less insulated from the cold (and heat stress). With lawns the damage is minor; all lawns recover from Orange County frost, but with tender tropical plants a shallow root system can be lethal.
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Dreaming of Spring
Cool winters result in a bumper crop of stonefruit, apples and pears.
Warm winters result in a bumper crop of tropical fruit.
Fruiting plants from temperate climates have a requirement of exposure to a certain amount of winter chill to wake up, flowers and fruit properly. This is called their minimum chill requirement (MCR). Most of the temperate fruit varieties sold and grown locally have MCR's of 400 hours or less. This is their exposure during winter to temperatures between 34 degrees F and 56 degrees F (heavily weighted toward the lower end). Temperatures higher than 70 degrees F quickly subtract from the total chill.
Currently we are accumulating about 50 hours per week and as long as we don't have any extended heat waves should reach the fruitful 400 hour mark before spring.
This last year 2009-10 was warmer than average and we only received about 275-300 hours of chill. Unfortunately spring was so cool, that tropicals didn't produce well either. Figs did well, as they do nearly every year.
In the winter of 2007-8 we accumulated around 500-700 hours and even my Honeycrisp apple tree (developed for Minnesota) produced decently. That year we drowned in apricots, nectarines, peaches, plums and pluots.
KEEP DREAMING!
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26285 Verona Place
Mission Viejo, California 92692
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