The last several nights have threatened frost, even down here in the mid-lowlands of my garden in the southern section of Pasadena.  While the end of January is the average last frost date for our area, I haven’t worried much about it for quite a few years since we haven’t had even a light frost in more than a decade.  But the possibility is always there at this time of year, especially for more highland gardens than mine.  So, here are some thoughts to help you understand the possibility/probability in your locale.
 
Why Frost Happens
     Frost – or indeed any “bad” thing – actually happening in our gardens is the result of several factors that I’ve adapted from the Plant Pathology “Disease Triangle.”

1. Pathogen – the “disease” – or “pest” or “frost” mechanism. While diseases and pests are pretty much always around in our gardens during their particular life cycles, frost conditions exist only during our winters. But whether or not they result in damage in your garden depends on the other two factors.
2. Environmental Conditions. For pests, this means the temperature, humidity and other elements that they consider close to ideal and so they may thrive. For frost, this means not only being close to 32 degrees Fahrenheit freezing temperatures but also whether the soil is hydrated (our rains confirmed that), the wind is blowing (lowering the freeze factor or keeping the frost from settling), where the plant is located (next to a wall or out in the open), etc.
3. Host Plant Susceptibility. Is the plant more likely to attract the pest or be damaged by frost?If the plant is healthy and of a resistant variety, it’s less susceptible to a particular pest; if it’s worn out from a season’s growth or not resistant to that pest, it’s more susceptible. Regarding frost, if it’s a tender begonia, it is definitely more open to frost damage; but if it’s a deciduous plum tree that’s already dormant, frost is less of a potential problem.

     All three of these conditions must be met for the pest or the frost to affect the plant.  If any of the three isn’t existent, then chances are there’ll be no damage.  Also, time is a limiting factor – long enough for all the conducive conditions to be in effect for the pest or frost to actually inflict damage.
 
How to Protect Against Future Frosts
     You can change a couple of the environmental conditions to preclude frost damage.  First, recognize that frost falls straight down on still nights.

1. Move container plants under eaves so they’re shielded by the roof above.
2. Provide top covering for plants in the open. For example, if you’re still nurturing old tomato plants for those last few slowly-ripening (or at least coloring-up) fruits, provide cover above the plant that extends out just beyond the foliage. Unless you also get freezing winds, no need to wrap the plant entirely; the top protection is most critical.
3. A caveat regarding using plastic, however – don’t let it touch the plant leaves, since this will literally transmit the chill damage directly where it touches.Let there be some open air to act as insulation between the plastic and the plant foliage.
4. Keep plants hydrated. With all of our wonderful rains so far, plants may be fine for at least a couple more weeks before needing irrigation or more rain.

 
If Some of Your Plants Have Already Been Nipped
     You may not know for several days whether a plant has been damaged by frost, since the foliage may not go limp and shrivel for a while. 
     When you do see damage, it’s best to not trim it off immediately, even though this may offend your sense of aesthetics and desire to keep plants neatly trimmed.  The dead foliage will serve as protective interference for the tender interior of the plant from further damage from later frosts.
      Although it may take a month or so for new growth to appear, it will define precisely how far the dieback actually occurred on each branch – sometimes considerably less than you would have guessed when first observing wilted leaves. 

     I hope you haven’t been stomping around your garden during or following all of these wonderful mini-downpours we’ve been having.  This is certainly the best way for rain to sink into our depleted soil – little, then more, then little, then a couple of days’ reprieve for all the water in the air-pore spaces to thoroughly moisten the soil particles and then drain down further into the soil profile.  But that process takes days, and it’s critical for you to not be walking on the soil, compressing it just with your weight, during that time. 
     This is because your weight presses the water out of the pore spaces, compacting the soil particles together.  The problem is that they don’t decompress after you’re done walking there – it’s a permanent compression.  As it dries, what’s left is a squished-out solid brick that can no longer absorb any moisture.  Even in pathways, this isn’t a good thing because it lessens the available surface area open to any moisture.
     This is the time I make a point of doing other garden-related activities, like sorting my seeds that I’ll be sowing later, preparing my seed tray supplies, repotting container plants, cleaning and sharpening tools, perusing garden catalogs, or anything else not in the garden.
     Great time to visit your favorite nurseries to purchase plants you’ll plant later, after they’ve had a week or so to acclimate to your garden’s microclimate.  Even bareroot roses you can purchase and submerge the roots into water overnight to get them thoroughly hydrated before planting.
     Even for my pruning tasks – roses and fruit trees – and certainly planting bareroot roses and fruit trees – I’ll put these off until there’s been no new rain for several days.  After all, we really don’t have to do these tasks until mid-February at the latest.  That’s usually the time when really active growth starts happening – buds swell, color-up, and begin to open – so consequently is an excellent time to be able to see what’s happening and therefore which choices to make in pruning.
    
Receive a Gift Amaryllis?
     Amaryllis that's just finished blooming can be grown as an evergreen, indoors or out, through the fall, and encouraged to bloom again next winter.  The bloomed-out stalk can be cut off about an inch above where it emerges from the bulb or allowed to dry up naturally -- this allows the plant to reabsorb the energy and store it for the next bloom.  
     Set the plant in a warm, sunny place, water generously, and fertilize regularly through August. 
     Then, let the plant rest a bit, with no fertilizer and only enough moisture to keep the soil barely moist.   Be sure to not let the plant dry out at any time, however, or the growth cycle will be upset and perhaps skip or delay the next round of bloom. 
     In September, move the plant to a spot that's sunny but where daytime temperatures are in the 70's and nightime temperatures are above 55.  Begin watering and fertilizing -- with a high phosphorus and high-potash food (the last two numbers of the N-P-K trio) -- and watch for buds.  You may even have two or three separate bloom stalks.
     The first year, you may not have any blooms because the plant is readjusting to its new conditions and light schedule.

     What a great way to end 2016 and begin 2017 – with LOTS of rain!  Yay!  So glorious to relish each gentle drop over long hours so the soil was able to absorb all the goodness…and then have those downpours that really filled the soil's air pores so the moisture could sink deeply down into rootzones.  Love it!  With the promise of more on-and-off-again showers at least through the coming week, I’m definitely looking forward to continually happy trees and plants!
     Yesterday, I went up the hill to document all the wonderful color and lush edibles flourishing in the chill.  The glory of living in Southern California was so apparent.  Sharing it all with you here!
      
Pruning Tasks Through Mid-February
     The big tasks of the month – really through about mid-February when tree fruit blossoms start opening – are planting bareroot fruit trees and roses, and pruning to guide new growth.
     If you can, attend as many of the various workshops available at botanic gardens and nurseries as you can to increase your comfort level in dealing with your own plants.  See the “Upcoming Events” on my homepage, and also the “Botanic Gardens…” listing on the “Events” menu item page. 
     Truly, try not to get too worried about ruining your plants with your first attempts at pruning.  The plants want to grow, so chances are they’ll survive whatever you do to them.  And then you’ll observe what the results were and consequently how to alter your efforts next time around. 
     In addition, with more recent recommendations to accomplish “summer” pruning – which really means pruning to guide growth throughout the year – you needn’t feel that you have only this one chance each year to do it correctly.  What a relief! Allow yourself to learn as you go, and your trees will reward you...maybe not this year but certainly after that!
      I'll discuss all of this in more detail in upcoming blogs, but for now, here're the basics to get you started:

Overall Guidelines

• Remove broken, crossing, or diseased branches
• Keep height within desired range for easy harvesting

 
Roses

• Trim just above outward-facing buds.
• Cut out slender twiggy growth so energy reverts to strong canes.
• Height is your choice – 12 inches, 18 inches, 3 feet, whatever you prefer relative to the strength of the plant.
• Leave stub of no more than one-quarter of an inch. More will cause dieback that may extend further down the stem.

 
Perennials

• Trim down to bottom-most new buds.

 
Deciduous Fruit Trees

• Object is to keep new growth limited to about six feet tall and wide for easy harvesting.
• Cut back branches with buds about half way.

 
“Summer” Pruning Year Around

• Trim back after flowering plants blossom, or trees fruit.This will encourage new growth that you can again cut back for fuller plant foliage and blossoming or fruiting within your desired height range.