Chris Dalrymple

In the colder months, the requirements of orchids change Lower temperature Less light intensity Shorter days Less evapouration Slower growth

Ref

Average Sunshine Hours per Day Sydney vs Melbourne (which is why we don’t live there) ref

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 PROGNOSISDISMAL MANAGMENTINTENSIVE OUTCOMEKARKED IT THIS IS AN EX-ORCHID, DROPPED OFF THE PERCH, FELL OFF THE TWIG, GONE TO ORCHID HEAVEN RIP

Good growing