Orchids in Winter
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Transcript Orchids in Winter
Chris Dalrymple
In the colder months, the requirements of orchids
change
Lower temperature
Less light intensity
Shorter days
Less evapouration
Slower growth
Ref www.worldweatheronline.com
Average Sunshine Hours per Day
Sydney vs Melbourne (which is why we don’t live there)
ref www.livingin-australia.com
How you approach winter will depend on
What orchids you grow
Whether you have heat
The potting medium and pot
The air flow
Overhead coverage
Frost
Wind protection
These factors are interconnected
What orchids you grow
Do they need a temperature drop to initiate flowering?
Do they require/tolerate drying of the root zone
between watering or need some degree of constant
moisture?
What are their conditions in their natural habitats?
What are their light requirements?
Are they potted or mounted?
Some warm growing orchids may be grown cold if kept
dry in winter months
Potting medium
Bark will hold moisture for some days; coconut husk for
longer
The larger the particle size, the larger the air spaces and
the faster the drying
Perlite/inert media generally dry faster
Polystyrene dries rapidly
All the above depends on air flow ie. the more airflow
the faster drying of any mix of media
Know what your potting medium does
The pots
The wider the pot, the slower it will dry
The deeper the pot, the slower it will dry
Most orchid pots now have excellent drainage
Basket ‘net’ pots and square ‘vanda’ pots have even
better drainage and will dry faster
How do you judge how rapidly the mix is drying?
Have different sized pots of your mix with no orchids
in them, watered at your usual frequency with
everything else
You can tip them out without disturbing a plant to see
what is happening in the pots, winter or summer
Not absolutely accurate as no orchid organic matter in
the pot but is indicative
Airflow
Always desirable for growing orchids
The faster the flow, the faster the drying
What are your prevailing winds in summer vs winter?
Wind temperature is important in winter – orchids do
not like cold wet roots
Do you require improved airflow in winter?
Fans in closed houses +/- heat when vents are shut
Bulb rot secondary to waterlogged roots
Overhead cover
Solid cover allows control of exposure to rain
Winter rain, particularly Sydney rain, is cold
Rarely protection from hail
Will decrease light intensity depending on material used
It can be removed for summer
Frost
Close to the coast, rarely a problem
Inland may be a major problem
Can be devastating to a collection
Be aware of your frost patterns, usually at lower
elevations
Occurs when there is no air movement
Protect by physical coverage or improved airflow
Wind protection
While some airflow is desirable, strong winds may cause
damage to a collection either potted or mounted
Colder winds will cause more damage when pots remain
wet
Increased risk of fungal infections in these conditions
Note that winds may dry mounted and hanging plants
very quickly
Light intensity
Will depend on the aspect of the orchid house and
ambient conditions eg tree coverage
As a general principle, the more light in winter the
better
Adjustable factors such as removing denser shade cloth
used in summer
Adjuvant lighting may be considered in some situations
Adjust watering habits
Will depend on whether orchids are potted or mounted
Morning watering only
Decreased frequency depending on ambient conditions
ie. no watering when cold and raining, wait for a clear
day
Clear days will have colder nights so the earlier the
better
Adjust watering habits
Have a strategy to cope with a mixed collection
Misting vs watering for humidity
Be aware of hanging plants dripping onto pots below
Where possible avoid leaving the foliage wet which may
result in leaf damage, lessened by good airflow and early
watering
Leaf water damage
Adjust your collection
Group similar plants together
potted vs mounted
those requiring some constant moisture vs those
tolerating a dry interval vs those deliberately kept dry
over winter
similar potting mixes
do not be afraid to omit waterings
This will simplify watering the collection
Fertiliser
Fertilising should be decreased or ceased completely in
the colder months
The plants do not require much food when not growing
Costs money for no advantage to the plant
Watch your plants
Pots remaining heavy between waterings
Signs of drying with shrivelling of pseudobulbs
Signs of fungal infection with root/bulb rot
Signs of secondary infection by scale or mealy bug
Be ready to alter your watering regimen or adjust
conditions if you detect any problems
If a plant shows a problem, change something
or you will need
DEATH CERTIFICATE
THE ORCHID
GENUS:
SPECIES:
PRESENTED TO
CONDITION
POOR
PROGNOSIS
DISMAL
MANAGMENT
INTENSIVE
OUTCOME
KARKED IT
THIS IS AN EX-ORCHID, DROPPED OFF THE PERCH,
FELL OFF THE TWIG, GONE TO ORCHID HEAVEN
RIP
Good growing