How to minimise heat stress and damage in your orchid collection
The secret to minimising heat stress in orchids is to keep transpiration in process. Transpiration is the process of carrying water from a plant's roots to the leaves and the evaporation of water vapour from plant surfaces. This is why I limit fertilising during this time and try to spray each day early in the morning with a kelp extract like Seasol. Generally, I spray everything, though not as much on the root system, as wet roots on a hot day can get severally damaged. Fog the plants as often as you can when the temperature is over 32 degrees. On a cooler day, usually after a change, fertilise and use Seasol again on your plants. The next thing is air movement; I suggest installing a fan to run 24/7. The final thing is humidity. When the humidity level is under 35% keep the floors of the shade house wet. Evaporation of water on the floor reduces the ambient temperature, increases humidity and airflow - all beneficial to your plants.
Benefits of the use of kelp extracts
Just adding that kelp extracts have been used in Tasmania and in Victoria on lucerne crops to produce hay. Just like the rest of the country they have hot periods of low humidity. Experiments by agronomists over the past 30 years have proved that kelp extracts work in keeping transpiration in plants when the temperatures are over 36C and humidity at about the same level. I was introduced to this by Roy Palmer of Condell Park. Roy has a son (Larry) an agronomist who lives and works in northern Tasmania and is one of the pioneers in improving pasture, lucerne, improving the live weight of lambs and calves, as well as improving calving and lambing rates. With lucerne and cereal crops, kelp extracts reduce plant stress during both extremely hot and cold weather. Wilting in hot weather and frost damage during very cold weather is significantly reduced by using kelp extracts within 36 hours of an extreme weather event.
They found out by accident that sheep and cattle that were eating king kelp (for mineral intake) on the shoreline had higher lambing and calving percentages. Kelp is turned into salt blocks and sold thought the country. However the use of kelp extracts has not taken on. As a result 90% of the kelp extracts produced in southern Australia is exported as a food additive to northern Europe.
Modified Hudson Fertigation/Sprayer
from Mark Daniels - Strongrow Orchids
