Foliar fertilizing promotes better growth
During the peak growing months of summer use a very dilute foliar fertilizer (half normal strength) with 1/2 teaspoon per gallon soap as a wetting agent so that the fertilizer will stay on the leaves long enough to allow the plant to absorb the nutrients. Be sure to spray early in the morning before the sun gets to the plants and provide excellent air circulation to allow for rapid evaporation to prevent rots. Be very careful with the crowns of Phals and Paphs.
Increase your watering for outdoor plants
Outdoor or greenhouse plants will need additional water during the warmest months of the year. In most areas this is their peak growing season. In the hottest areas they will almost go into a hibernation period. Watch out for under watering signs such as wrinkled pseudobulbs, especially on Oncidiums and Cattleyas. I put extra sphagnum moss around those plants that appear to have problems with the heat and then spray early in the morning making sure that the moss gets some water. You increase your humidity this way and the plants will pull water out of the moss if they need it.
Phalaenopsis or Moth Orchids
Phals can still be in full bloom by the middle of the summer. If you want them to re-flower next year, cut back the inflorescences around the middle or end of July even if they're still looking good. This will allow the plants to concentrate on growing and gathering energy to flower next year. If repotting is necessary, go ahead and repot now. If you bought new plants make sure you repot. Many Phals are sold in straight sphagnum moss and this medium is too soggy for most plants for long. Repot in coconut husk or bark mix.
Paphiopedilum and Slipper Orchids
Phragmipediums will need constant moisture during the hot summer months. I grow mine in a saucer of water year round to provide this moisture. Semi-hydroponic culture is even better. They need lots of light in order to produce flowers. Paphiopedilums also like warm temperatures, but require low light so as to keep the leaves from burning. Check the pots often during warm months to make sure that the moisture they need is provided at all times.
Cattleya Alliance Plants
Watch for roots on your fall blooming Catts and when the roots are about 1/2 inch or 2 centimeters long, repot them if necessary in appropriate medium. Watch your plants for over- and under-watering problems and rots during this growth period. A monthly application of fungicide will help reduce the chances of all kinds of rots.