Cattleya Alliance Plants
In most areas of the country, higher light and higher temperatures require more fertilizer and water for Cattleyas. If you are in one of the areas with extremely high temperatures cut back on the fertilizer since your plants will be stressed from the heat and will go into a period of very little growth until the temperatures moderate in the fall. Be sure to watch for fungal diseases as well as scale since both proliferate in higher temperatures.
Phalaenopsis or Moth Orchids
Phals are one of the warm growing orchids and as such are happiest during our summer months. They should be fertilized every week during these months so that they can achieve maximum growth to support spikes in the fall. Very high temperatures (over 90 degrees Fahrenheit or 32 Centigrade) will cause leaf loss. So if possible try to keep your plants in areas where they are not exposed to these high temperatures. Be very careful of water in the crowns of plants to avoid rot and provide good air circulation.
Paphiopedilums or Slipper Orchids
Paphs generally like a little cooler temperatures than some of the other orchids. Even the so-called "warm growers" will not like temperatures above about 85 degrees Fahrenheit or 29 degrees Centigrade. Good air circulation is a must for these plants especially during warmer weather. Make sure that they do not dry out and that high humidity is provided if the plants are in warm areas.
Watch for fungal infections
Fungus infections are especially prevalent during the hot and humid summer months, especially on thin leafed orchids. If you notice spotting on the leaves of your plants, spray with a good fungicide such as Physan or Consan to keep the problem from getting worse. Be sure to spray both the bottom and the top of leaves for best results. Increase your air circulation around that specific plant if possible since poor air circulation is one of the causes of fungal infections.
Watch for new growth and stake inflorescences
Stake new inflorescences on most of the summer growing orchids such as Epidendrum, Dendrobium, Brassavola, Oncidiums and Phrags. It is a good idea to put in the stake as soon as you notice the inflorescence so that you can keep track of where it is and stake when the growth has reached about 4 inches. Be careful not to pinch the inflorescence because all the growth and flower development is nourished through the stem.