V. Arjuna x V. insignis
August in Your Orchid Collection
August Climate Data
Average high: 90.6
Average low: 76.5
Average mean: 83.6
Average rainfall: 8.63"
July and August are the two most similar months in South Florida. Most of the advice on watering, disease and pest control in last month's calendar still apply but subtle changes are taking place. Although it may not seem so, as temperatures climb into the low nineties most afternoons, summer is in retreat: each day a little shorter, each night a little longer. With shorter days the importance of watering as early in the morning as possible comes to the fore. With less hours of sunlight to dry the plants, extra care should be taken in choosing when to water. Back to the basics of the classic saying: If a Vanda looks like it needs water, water it; If a Cattleya or Oncidium looks like it needs water, water it tomorrow. If a Paph or a Phal looks like it needs water, you should have watered it yesterday. If plants retain water even from an early morning watering, allowing them to dry a bit harder before the next watering is always a good idea. An extra day of drying rarely does harm.
August should provide numerous opportunities to dry each orchid to its desired level of dryness. Take the opportunity to dry your orchids "hard" at least once but preferably twice in August. This will give your orchids a leg up on their mortal enemies, the fungus, before the drizzle of September switches the advantage to our adversaries. August is definitely not the month to over indulge in water. September, the soggiest of months, is next up. The corollary to this calculated drying is the concept that when watering in August above all water thoroughly. If watering is necessary be sure that the roots and medium are totally saturated with the application. The drizzling rains of September are so detrimental precisely because they keep the foliage of the plants wet unduly long. We want our plants which are still growing to receive plenty of water but also plenty of drying time.
Good air circulation and proper watering are the keys to disease prevention. Remember that your plants will have increased considerably in size by this point in the growing season. They have added extra growths and extra leaves across the summer. August is a good time to evaluate the spacing of our plants. Remember the old Florida saw that one needs a cat to grow good orchids because when properly spaced a cat should be able to navigate the benches between plants without knocking them over. While we can not recommend specific chemicals, the county agent recommends Banrot, a convenient combination of Thiophanate-methyl and Truban which controls a number of leaf-spotting diseases and soft rots, for home owner use. A combination of Thiophanate-methyl and mancozeb has also been recommended. This can be found pre-packaged as Duosan. If one can overcome the aversion to chemicals and can learn the safe application of them, they are valuable tools to better orchid growing. An ounce of prevention is worth a pound of cure especially before the soft, slow drizzle of September sets in.
Lengthening nights in August mean cooler nighttime temperatures. Many sympodial orchids are reaching the end of their growing cycle and require less nitrogen. Cattleyas and oncidiums have maturing bulbs. Genera that become deciduous in winter like nobile dendrobiums, calanthes and catasetums should be given much less nitrogen in August to prevent them producing an unwanted off season growth and perhaps forgetting to flower. Substitute an additional application of potassium nitrate and Epsom salt (1TBS each per gal) instead of the balanced 20-20-20. Vandas will respond well to this also, as several of the parental species of our hybrids produce blooms on shortening day lengths and lower levels of nitrogen in their fertilizer seems to egg them on. As explicated in the last chapter, modern research indicates that orchids require less phosphorous than previously thought. This concept should lead us to more judicious use of phosphorus. Fertilizer high in phosphorus may still be of some value at the end of the growing season, perhaps not so much as stimulus as shock. One or two heavy applications in succession, a week or so apart will certainly provide all the phosphorus and all the stimulus (or wake up shock), our plants require to bloom.
Snails can be somewhat of a problem in August too, but left to multiply they will be in their full glory when those slow unrelenting rains of September set in. Control them with baits in pellet or liquid/paste form. Remember, these are baits; the pests are drawn to them. Therefore apply lightly, but frequently. Because they wash away in the heavy rains, baits should be reapplied every two weeks. One pellet every two to three feet will do the job, but one application will not. Given a choice, the smallest pellets baits are best. They keep us from over applying and also pose much less threat to neighborhood pets. A small bait pellet in a Vanda crown is a nuisance, a large bait pellet can be a disaster.
If you have been waiting to make cuttings of the terete vandas or reed stem epidendrums, you can wait no longer. The potting season is drawing absolutely to a close. Pot up those overgrown Phals, before they even think of spiking. Re-set those strap leaf vandas early in August whilst they still have just enough time to re-establish themselves in the September humidity and before the cool weather arrives and their root growth slows or stops. As in all seasons, be sure that the plants are firmly set in their containers. There is no "wiggle room" this late in the growing season to restart tender roots that have been chafed off a loosely set plant. As the cooler weather approaches try to give plants that have been repotted late more protection from the first cold snaps.