Thoughts on resting orchids and winter growing

This is a photo taken today of one of our young plants of Epidendrum centrapetalum which shows its very active root growth to match its top growth which got me thinking about winter and resting orchids.

It my opinion there are four kinds of orchid species at this time of year.

  1. Orchid that come from strongly seasonal climates with dry cooler winters. e.g. Dendrobium aphyllum, Coelogyne cristata
  2. Orchids that come from strongly seasonal climates with warm dry winters e.g. Thunia alba
  3. Orchids that come from cool climates without strong seasonal differences
  4. Orchids that come from warm climates without strong seasonal differences

This sounds like a nightmare for anyone growing a mixed collection but usefully your plants will give you clues to their preference.

Any plants that are clearly in active growth now with long green root tips and growths are not from winter dry habitats – examples are most of our pleurothallis, masdevallias and other species from year round cloud forests – many of these species positively love our winters with even cool temperatures and none of the summer heat stress.

Seasonal plants tend to do all their growing in the summer – almost all of our cattleya species – they now have mature growths and are thinking about flowering (any time from now until April) and then it will be rapid growth time again in the summer. Many of our dendrobiums are similar – our Dendrobium aphyllum plants are losing their leaves. Dendrobium densiflorum plants have all made up their new bulbs and are now sitting, waiting to flower in late spring. Some of our seasonal plants are already losing their leaves so that they can sit out a really dry period – stenoglottis species, Calanthe vestita and Thunia alba for example.

As regulars will know our greenhouse sections are divided geographically but not down to the minutiae of micromate.

In our cool Americas section most species keep growing all winter apart from a few species from particularly dry winter habitats – Cuitlauziana pendula for instance.

In Cool Asia all the plants have something of a winter rest especially with the heating rarely coming on (minimum 7-10C) but these cool habitats tend to have frequent mists and even rain in the dry season so do not let bulbs shrivel.

Warm Asia ia a challenge as some plants from near the equator (such as plants from our recently visited Sarawak) experience very little seasonal difference in the year, while others (such as plants from the Himalayas) have a dramatically different climate summer and winter. We move many of the seasonal plants to the roof of Cool Asia or Coll Americas for a dry cool three months to make management easier.

Warm Americas is similar with some plants wanting to keep growing while many rest – again using the roof for resting plants naturally keeps them dryer, and brighter to mimic deciduous forests.

Good luck with your own plant this winter – more tips at the Orchid Christmas festival on Dec 3rd – Zoom link https://zoom.us/j/97501868004 at 6.30pm



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