ZONE ENHANCER GUIDE
Here you'll find how to squeeze the extra few zones out of your yard...
PLAN(T)ING FOR A FREEZE
Aclimitizing
Acclimitization certainly favors the chance of survival. Especially, palms tend
to become hardier with age as most plants do. One technique proposes to rapidly
grow the plant to a decent size in a greenhouse where minimum temperatures are
kept above 50 deg. F. in order to avoid winter dormancy. For palms, grow a small
stem which will protect the central growth bud from the cold. As a rule of thumb,
grow a five-gallon-pot plant which is root bound or approx. 90% of the pot is filled with
roots. Then, the plant is slowly adapted to the outdoor climate: Inicially move
it outside only during warm summer days but protect it against sun burn with a
screen. After a few weeks transplant the plant in its permanent location:
Don Tollefson suggests POT PLANTING:.
When you plant a palm in the ground, leave it in the container. No slitting
the sides or cutting open the bottom of the container. Traditional planting, i.e.
removing the pot, will send the plant into trauma and setback. For palms usually
one to three years after that it will resume regular growth or die. Hardly the
condition you want for your palm when you test it in its first winter. With pot
planting, however, the palm will display an initial spurt of growth followed by steady
growth. A root-bound plant has 'binded' in the pot which is essential for vigorous
growth. Keeping this environment in place with pot planting will avoid shock. As the
palm sends out exploratory roots through the drain holes and finally burst the container,
there is absolutely no setback. In fact, pot planting has shown a doubling in size
within two years for Licuala ramsayi.
In so.Cal., many growers are able to avoid the 1 to 2 year period of
no new above ground growth by planting the palm and the bucket, into the ground.
Our summers are very dry and warm, and the method helps retain moisture in the root zone.
In addition to pot planting,
I top with mulch and fertilizer the palms, which seems to continue or speed up the
growth rate. Growers in moist/humid climates have stated that they do not notice any
benefits from pot planting.
See more information on when to plant a palm.
Planting Medium - Sand vs. Clay
In the S.E. US sandy soil is much preferred over clay soil for growing
tropicals. Winters are generally mild but are subject to spells of cold weather.
However, these periods are usually very short-lived. During these periods clay soils are very slow to warm up afterwards. Certain species
(Sabal palmetto, Serenoa repens, Washingtonia, Butia and Phoenix) can often tolerate
these cold spells if planted in sand. If planted in clay they seem to be much more
sensitive. NOTE: Mixing a lot of sand into your clay soil might not work if you experience
extended periods of freezing temperatures.
Find/Create a Microclimate
A microclimate is usually an area in your yard where temperatures are at least a few degrees warmer during a freeze.
Most common are sites where:
- Wind is blocked i.e. by a S.W.facing wall of a house.
- Heat radiation is blocked by an overhead cover i.e. under large trees(canopy) or a roof extension.
- The sun's rays accumulate and radiate back at night. i.e. a large stone mass, near a lake or pond.
- Artificial heat i.e. heat leaks from the house, fireplace, a ventilation system, an underground sewer pipe.
Locate these sites and plant your tropicals here first. Then try the same species in other places
too.
AVOID: Low spots where cold air drains or open solitary positions.
NOTE: A sunny location during winter might dry out evergreens and desicate the plant if not enough
water is artificially added. Possibly a location away from the winter sun might be safer even
if it is colder (see Selecting A Species).
A Microclimate's H2O Factors
WATER
The winter rain season (i.e. N. Europe) might help keep minimum temperatures up and provides the
necessary moisture in areas where dry winds desiccate the ground and the leaves of evergreen
tropicals (i.e. Brahea). So, if you have an area in your yard that stays moist, it might give you
the same effect as a nearby lake.
SNOW
At first snow sounds awful, but actually insulates perfectly from cool winds and heat radiation.
Also the plant and the ground can still exchange oxigen for vital functions. However, be careful
when snow sitts for a few days on large tropical leaves. The weight of the snow can crush or
badly bend the leaves. Solution: Wipe off excess snow.
ICE
Ice, however, is bad. It's insulating property is questionable and is best washed off with a
garden hose. Especially bad is that it blocks perspiration between ground and plant. This
is definitely a killer. So, avoid sites where your yard accumulates ice.
Hungry Winter Pests
Depending on the part of the world you live in you have to fight off predators of various sizes
and sometimes a pesticide just won't do. If you live in the continental US there's a good
chance you will encounter hungry rodents which love to eat the starch rich root systems and corms
especially on bananas. These rodents come in all sizes; from tiny voles to large nutrias.
Unfortunately, all are deadly to your plants. So, contact your local government's wildlife
protection branch for information. For gophers, pot planting has been used by John Tallman,
former President of the S. CA Palm Society. Be also aware of other hungry winter animals, i.e
birds or dear, which can do a lot of damage to the tender new growth of cycads and smaller
palms. See more information on Rodent Prevention.
FALL PREPARATIONS
- Avoid heavy pruning in late fall. This encourages tender new growth that can
be damaged by an early cold.
- Avoid applying fall fertilizers which are high in nitrogen. The nitrogen can promote new
foliage that is easily burned by an early frost.
- Apply a fertilizer that has a high potassium content in the fall to strenghten existing foliage at least 45 days in advance of a prospective freeze.
- A 3 to 6 inch layer of mulch will help to protect tender feeder roots which are close to the surface.
- Apply a sunscreen about 2 to 3 times for best results in order to shield tender leaves against cold winds.
- To reduce the pain of watching your favorite plants turn black and mushy,
try to shelter the tender plants in a greenhouse which is the most reliable protection
when you want the whole plant - including leaves - to survive.
- If you planted it permanently outside use a minigreenhouse, a coldframe, a wrapping, a cage, or a blanket. Unfortunately,
you need to make a judgement call here: See the cold protection designs.
- Use modern chemistry for hardier plants and increase the freeze tolerance.
KEEP TUNED-IN TO CURRENT WEATHER
DAY-BEFORE-THE-FREEZE PREPARATIONS
- Check the predicted low for your area:
- Water all plants well to eliminate air pockets in the soil that could become
filled with cold, damaging air.
- When freezing temperatures are predicted for a certain night, cover plants
with blankets, paper, plastic, or the like. Plants covered with materials that do
not breathe (plastics, polyethylene sheeting) should be uncovered first thing in
the morning. If the plastic is not removed, heat and moisture will create a
suffocating environment around the plant and will cook or steam the foliage.
- If you wake up to a heavy frost on your plants, you can prevent permanent
damage by rinsing the foliage with water before the sun’s rays strike the foliage. Water provides energy in a moist situation before the sun comes up. The sun provides energy in a dry situation but may cause dehydratuion damage so the water can prevent this damage.
- To add heat to an area of the yard, leave a sprinkler running all night.
The water temperature in the ground will be much warmer than the air temperature.
AFTER THE FREEZE
- After the last freeze is over start to clean up. Cut off broken or damaged leaves.
Also remove leaves that are completely brown or white. If possible, have at least
two leaves remain that are shooting from the bud.
- Pull periodically on the central growth bud(spear) to see if you can pull it out. Then, poor
a fungicide into the bud two or three times weekly (repeat after a rain). If you are left with a
substantial hole where the central growth used to be and it always fills up with rain water;
drill a drain hole from the side (upward-inside sloping) into the stem to just above the growth center. Then apply the fungicide which must be repeated periodically and after a rain until a new spear apears.
- Fertilize with a balanced slow-release granular fertilizer.
- Make sure the palms have enough water during the dry spring season.
Timing of Freeze Damage Recognition
Sometimes leaf burn is seen immediately after a freeze and the plant appears to be a survivor.
However, sometimes the leaves have no apparent burn but the invisable part of the central
growth bud (which is more cold sensitive) has been badly damaged. This is usually not
obvious until temperatures rise and the bud is killed by its own growth or fungus. Some injuries take
even years to discover like the loss of outer trunk (see
picture).
Watch out for the different stages when freeze damage becomes apparent and take apropriate action:
- During a freeze:
- Species of Caryota may exhibits a nutrient deficiency i.e. yellowing of the leaves.
- Species of Trachycarpus will look dried up and leaflets are folded together as if there was a drought.
Both, yellowing and drying/folding will revert after temperatures rise again.
- Right after freezing temps are over i.e. 1st day after, only some spotting or no damage may be visible. Here especially the spotting is suspect for imminent problems the folling days;
- A few days after a freeze, or when temperatures warm a little let's say around 50°F, the real leaf damage will surface i.e. major sections of the leaves will turn brown.
- A few weeks later, in spring, when temperatures induce growth:
- many palms will lose the spear i.e. Trachies. Action: Pull on the spear every day. If you can rip it out without much force, do so and remove it. Poor fungicide into the cavity (repeat after rain) until a new spear appears. If necessary drill a hole sideways through the stem so all water will drain from the cavity and above the growth bud.
- some palms will destroy their own damaged growth center with their own growth i.e. Sabal. Action: certainly fungicide will help...but not save the palm by itself. So try your best and experiment...
- Still another type of damage exhibits Butia: The wood around a lost spear and rotten growth center will harden and even cover up the remaining live cells in growth bud. New growth will stall and the palm dies. Action: Physically cut back the excess hard wood and force an opening to the growth center. Treat with fungicide.
For more info read the Treating Cold-Damaged Palms by the University of Florida.
Freeze Damage Look-A-Likes
Often winter-freeze damage is apparent in palmate leaves i.e. Trachycarpus; the first leaf in the season will sometimes show a symetrical line of brown dead tissue across the leaf. However, if you did not have any freeze at all and your juvenile plant (no stem) exhibits such damage, it is likely you had either a flood from a nearby creek, lake etc. or simply water from the surrounding soil drained
into the growth center; causing fungus to do some damage i.e. in Sabal umbraculifera. Once such a palm will devellop a stem the problem disapears. Action: again apply preventive treatments of fungicide and try to add additional drainage to the surrounding soil or plant it in a raised bed from the beginning.
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