| Temperature Range (˚F) | Days | Nights |
|---|---|---|
| Cool house | 61 | 55-61 |
| Intermediate house | 70-81 | 60-70 |
| Warm house | up to 90 | 70-75 |
Most of your plants will have almost matured their new growths by the end of this month. Care should be taken in watering to assure even distribution of moisture. Maintain good humidity to prevent dehydration of plant growth due to higher temperatures. Frequent misting of plants and floor can be done, but care must be exercised to avoid over watering. You can use a fog nozzle. If you spray leaf areas that have become very hot, the cells will rupture and rot will develop. It is best to water early in the day before it gets hot outside.
When you were repotting did you notice if all of the roots are plump and white? Were some flattened or dried (appearing to consist of only a stringy central core)? Chances are that both kinds were present. These dried root remnants are the result of a normal aging process. Cut them away when repotting, taking care not injure the orchid. This is a smart move, because too many decaying roots soon become “mush” and accelerate the deterioration of the mix.
Did you notice that some of the beneficial, fleshy roots have blackened root tips? This symptom can mean that your water contains an excessive concentration of soluble salts or that the clay pot surfaces are bonding with or accumulating excess salts, either from normal water supply or your regular fertilizer treatments. Some growers, facing the challenges of dealing with poor water quality, have resorted to using deionized water or, better yet, rainwater. Scrub away the visible salt crusts capping the top edges of clay pots before recycling them. Be sure to leach the medium thoroughly once or twice a month.
Snow mold: Another root condition to avoid is the development of snow mold, a white fungus that looks just like what the name implies. Snow mold can appear on the surface of the potting medium, but more likely it will develop in the root zone. An insidious problem, the mold often escapes detection until the root mass has been smothered in a rapidly deteriorating medium. The condition is treatable. Affected plants will not be lost. However, snow mold seems to appear most frequently when media are kept too wet, causing the roots to rot and the substrate to become a soggy mess. Snow mold is a saprophytic fungus that actually works to hasten the potting medium’s decomposition. Monitor watering practices to avoid the problem. Blend a small amount of redwood chips in your potting material to increase the acidity and to deter snow mold. Repot affected plants, and be careful to remove all of the old medium before rinsing the roots in a weak solution of Physan.
As the growths mature you can start alternating with lower nitrogen fertilizer, like 10-30-20, at a rate of 1/2 tsp./gal. to encourage development of bloom spikes. Still continue to use the 30-10-10, but change back and forth. The more growth you can achieve now, the more flowers your orchids can support in their blooming seasons.
During this time when temperatures are warmer, it might be a good time to consider double-lining the greenhouse for insulation for the coming winter months, or perhaps a good general housecleaning; also removing the algae buildup with diluted bleach or Physan on the plastic is in store. You can also inspect your heaters and clean them for fall use. You could also make any other repairs that might be needed.
The pests are most active during the warm months. Inspect the undersides of leaves for undesirable creatures in hiding. Remove dried cataphylls on cattleya pseudobulbs to eliminate a hiding place. Watch your orchids grow, be alert for distress signals and treat them quickly when they appear.
Orchids need all the air they can get this month, and it may take a little ingenuity to provide the cool, moist conditions some of the plants need.
Cattleyas: July is a great growing month for cattleyas. If their flower buds are developing, the plants will need even more water. Even though cattleyas like more light than most orchids, they must be shaded when the sun is hot, and they need frequent misting to keep the pseudobulbs plump.
Paphiopedilum: Good shade and humidity will aid good growth. If you fertilize, do so at one-quarter strength on a regular basis. They are not heavy feeders.
Phalaenopsis: Keep well watered. Continue to fertilize with high nitrogen fertilizer. Continue to keep well shaded. They do love humidity and should be watered often enough so that the potting material never becomes dry.
Oncidium Alliance: If grown on slabs be sure to keep plants well misted daily and fertilize regularly.
Odontoglossum and Masdevallia: The next couple of months will be the supreme test of the cool growers’ effectiveness. These plants will only just tolerate the heat, not enjoy it. Extra shade and constant ventilation will help. Do not repot now.
Dendrobiums: Growth is rapid this month. They need only enough shade to prevent their leaves from becoming scorched. When the terminal leaf appears, decrease the amount of water they are receiving but give them enough water to keep their pseudobulbs from shriveling. Misting helps to keep them fresh.
Miltonias: Miltonias can safely be repotted if necessary. They do not seem to mind being disturbed in warm weather. But they should be kept shaded and moist and be given as much fresh air as possible. The Columbian group will need more shade than the Brazilians, but to be safe keep both kinds shaded from the hot sun.
Odontoglossums: Keep them as cool and moist as possible and mist the leaves frequently. Leafless pseudobulbs are the result of their being too dry during the summer.
Shade early in the morning to counteract the rise in temperature. If repotting has not been completed, hold off until cooler weather. They then will have a better opportunity to develop new roots and growths.
Plants outside: Make sure you keep them well watered and fertilized on a regular basis. Most people tend to forget to fertilize plants when they are set outside in the yard. Check to see the sun is still filtered to some extent. Also check for spider mites.
Information for these culture calendars are taken from The AOS Bulletin, Orchid Digest, a book Orchids and How to Grow Them by Gloria Jean Sessler and some of my own experiences.
Kentucky Orchid Society 