Orchids in the winter

[Lily]

Hi, I have a problem this year.  I have an outdoor green house that works great for my orchids in the spring, summer and early fall.  For the past few years, I have brought my orchids inside during the coldest part of the year.  I live in San Jose, CA so we have some really cold nights in the winter.  My greenhouse is made by Rion and is plastic.  It offers very little protection from the cold.  This year, we are remodeling our house and do not have room to bring all of them inside.  I am looking for ideas for ways to protect the orchids.  I have tried a space heater in the past and it was very expensive to run it.  I have phalenopsis, oncidium. and a few cattleya.  Do you have any suggestions for a heat source that might be less expensive or any other suggestions for winter storage?  Thanks, Lily

[dennis westler]

Dear Lily:

 

Unfortunately, Phalaenopsis absolutely need their night temperatures to remain 60 deg, or only slightly below (except for a brief period which can promote bloom). If they cannot come inside perhaps boarding them for a few months is an alternative. Brookside Orchids, which is not that far away from you does do boarding. Many Cattleyas and Oncidiums  (depending on spacies or parentage) will easily tolerate the occasional night down into the high 40's provided most nights are around 55-58. So doing a little research may determine what part, if any, of your collection can remain in the greenhouse through the winter; especially if you can do some of the things listed below. There are a surprising number of (what used to be called SLCs, SLs and LC's that are surprisingly cold tolerant). )Remember that cooler nights will reduce the watering needs of your plants and that conversly, being on the dry side will reduce stress from cold humid periods, especiall for plants like Oncidiums and Cattleyas that are mostly winter dormant.

 

An additional layer of plastic (like a clear heavy duty tarp) either inside or outside of the greenhouse (with air space between it and the greenhouse walls) should provide some small insulation. Running fans should prevent cold spots during the night, and even out temperature. And a heater with a decent thermostat set at 55 or 58 may reduce heating cost (as opposed to running a small space heater with a minimal ability to be accurately regulated). Sealed black barrels/jugs of water kept below the benches can act as a heat sink, getting warm during the day, and radiating that heat during the night. These things done together can raise the night time minimum. Hopefully you have had a min-max thermometer in the greenhouse and kept records so you know what your winter minimums are, and how they relate to outside temperatures. If you have not, it is a good idea to do so in the future. Hope this all helps! 

 

Sincerely,

Dennis

[Lily]

Thanks Dennis,

 

I have room in the house for some of my orchids.  I will definitely move the Phalaenopsis inside.  I thought about the layer of plastic to provide an air layer for insulation.  I have a cover over the greenhouse to block some of the sun, maybe I could just wrap it in plastic.  I had the black barrels but they did not seem to help much, they just took up space.  I do have a min/max thermometer to monitor the temp but it does get pretty cold here - I live near Mt. Hamilton in the Santa Clara Valley.  I will look for a heater with a thermostat.  That and a fan are probably my best bet after the plastic wrap.  Thanks for the advice.  Lily