September in Your Orchid Collection

by Motes Orchids in


  • Average high: 89.0
  • Average low: 75.7
  • Average mean: 82.4
  • Average rainfall: 8.38"

Excerpted from Florida Orchid Growing: Month by Month by Martin Motes. All rights reserved.

September looms as the only truly dismal month in South Florida. Even without the prospect of the unspeakable ‘H’ word, September disheartens since it is easily the dampest, dullest month in the year. Although more inches of rain fall in June, more hours of rain occur in the often slow, seemingly endless drizzles of September. Frequently a day or two can pass without so much as a solid hour of truly bright sunshine to lift our spirits and dry out our plants. Days are growing much shorter also, with long nights when our plants are wet from the frequent rains. Coming at the end of the rainy season when disease pressure has been building, September presents the maximum opportunity for fungal and bacterial diseases to take hold of our orchids. Hopefully careful watering practices and the judicial use of fungicides (as recommended last month) will have diminished the potential for disease in our collections. But even in the best managed collection, September calls for extra vigilance. Keep a close eye out for problems and remove immediately any plant that shows the first sign of fungus to a dry location to prevent the disease being spread by splashing rain drops. Good hygiene is particularly important this month. Clean up growing areas and remove any dead leaves, twigs or other organic debris from the plants and the ground. In September numerous diseases that linger in decaying plant material find the ideal conditions that allow them to jump to the living tissue of our prize orchids. Such problems can develop more quickly in September than in any other month. September is a month to stay home and be there for your orchids. Look at every plant, every day.

    September, above all, is the month that the old Florida growers’ adage that "One needs a cat to grow good orchids," holds true. By leaving enough space between plants on a shade house bench for a cat to walk around without knocking them down, one provides the good air circulation which is absolutely essential in periods of protracted wet weather. Well spaced plants are much less likely to encounter disease problems this month. Remember that your plants will have grown considerably over the summer and that the space they occupied comfortably in the Spring has now been filled by their own growth as well as their neighbors. Space them out. Now is perhaps the time to decide to hang some of the larger ones where they will dry much more quickly. The small cute ones left behind on the bench will be very appreciative of the extra air and light.

  Another excellent way to increase air circulation and enhance rapid drying is by trimming excess (particularly vertical) branches from all trees which support orchids or are near to orchid growing areas. By increasing the light and air flow one will also garner the benefit of reducing the possibility that such trees will be knocked down in a severe storm. Trees trimmed to permit proper air circulation and light for orchids were frequently the only ones which survived upright after Andrew. As there is rarely time to do such pruning when storm warnings are actually posted and creating extra debris is not then wise, now is the time to protect both your orchids and your trees. Days are shortening quickly now and more hours of rain and overcast skies mean that your orchids will benefit from all the additional light that they can get. Beginning the process of “hardening off” our plants by allowing more light to reach them will give them a leg up on the coming cool weather as well.
    As orchids grown outside are so frequently wet in September, it is often difficult to apply fertilizer or fungicides to the plants because they are already damp. Catch 22! — the plants need extra protection because they are wet and because they are wet one can’t apply chemicals to protect them. In these circumstances, many growers find Quaternary ammonium compounds useful. Sold as Physan, Consan, Greenshield or Triathalon these disinfectants dissolve totally in water and can be applied to wet plants. Strengths vary so follow the label. Although Federal regulations say they should not, many growers substitute the cheap and readily available pool algicide which contain the same active ingredient. Home Depot sells a brand called ‘‘Pool Time’’ which could be purchased legally to disinfect walks and pathways at the rate of 1 to 2 tsps. per gallon and would certainly do no harm at that rate, if it came into contact with the orchids no more frequently than every 7-10 days.

    This month when those brief periods of dry weather permit growers to think of applying other pesticides, they are tempted to think of giving their starving charges fertilizer as well. This is generally not a good idea with any fertilizer containing phosphorous (the second in the numerical series of three numbers). Phosphorus changes the PH of water and tends to interact with many other chemicals reducing their effectiveness. In September we need as much fire power from our chemical arsenal as we can get. A much better strategy in general to add some nutrients employs potassium nitrate (KNO3) 13-0-43 at a rate of 1 tbs per gallon of water. One should ask for the type usually referred to as ‘‘spray grade’’. In general sympodial orchids are reaching the end of their growth cycle as September progresses so a reduction in nitrogen from the potassium nitrate substitution or a missed fertilizer application usually does little harm to orchids grown outside in South Florida. Soft cane dendrobiums of the “Nobile” types will actually benefit from the reduction in feeding. It’s time to wean these deciduous types before cutting them off entirely from the grub next month. Vandas and Phalaenopsis on the other hand can be fertilized as often as weather permits and will bloom all the stronger for this extra attention in the coming months. 
    Snails can also be a problem again in September. Even if you earlier used the ‘‘lightly, frequently’’ baiting suggested in July, snails can travel long distances on wet ground in the dull, dark weather of September. Chances are your neighbors have not been as good as you on snail control. So, once more with feeling: snail bait "lightly, frequently" to give a warm welcome to any recently arrived mollusks. With an eye to the heavens (or at least to the TV screen), removing any old boards, empty pots or other debris that might fly about in a storm will also render the humble snails homeless. An opportunity to re-double your virtue and save some precious moments in the face of the storm that we hope never comes!