Download Orchids in Winter - Orchid Society of NSW

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