September To Do List

  • In spite of the day length becoming shorter in September, this month can still produce very warm days for continued growth of your plants.  Watch them carefully and provide adequate water and fertilizer before tapering off when warm days begin to wane.
  • Some cattlyeas and other genera (dendrobiums, oncidiums) are still in active growth mode so take the opportunity to repot those you may have missed before month’s end to allow enough growth before the onset of cooler weather and initiation of the dormancy period.
  • Maintain good hygiene practices to minimize transmission of pests and viruses, particularly during the warm summer months when pests and diseases can proliferate very quickly and spread throughout the collection. Carefully inspect plants for scale and aphids and treat early to minimize spread.
  • More details on specific genera can be found on the AOS website

Indoors and Greenhouse

  • Carefully monitor greenhouse temperatures as higher summer and early fall temperatures can easily cook plants. Make sure fans and automatic vents are in good working order.  Mist plants to increase humidity and cool down temperatures.
  • Continue to provide good air circulation for indoor plants to discourage diseases and pests such as mealy bugs and scale. Treat early to avoid spreading to other plants. More info on pests and diseases can be found at the AOS website.
  • Maintain increased watering and fertilizer to accommodate growth during this period. Avoid over fertilizing to minimize root damage and growth of soft growths. Keep to one half to one fourth the recommended amount on the package.


  • Continue to monitor and control snails, slugs and pests during this period. They can do considerable damage to plants in short order.
  • Cattleyas should be coming into the fall blooming season as well as hardening off of growth produced in the spring and summer.  Maintain watering frequency and cut back on fertilizer as growths mature. 
  • Early blooming cymbidiums should be developing spikes so switch from high nitrogen fertilizer to one with higher phosphorus and potassium (Hi Bloom such as 10-30-20) to initiate and stimulate spike production.  See also the AOS website for more information.
  • Catasetums/cycnoches should begin their fall blooming period during this month.  Continue to give them warm temperatures, high light and fertilize well at each watering until you see them begin their dormancy period by the yellowing and dropping of leaves. Cut back on water and fertilizer as suggested by Fred Clarke on his website.
  • To induce your phalaenopsis to re-bloom, subject them to 1-2 weeks of night temps of around 50 °F, but bring them in when night temps go below 50 °F as they are sensitive to cold.  If you grow them in the house, put them in a cool room or near a window to obtain the lower night temps for spike initiation.


The monthly To Do list is a collaboration of several POS members. We appreciate any and all comments, suggestions, and feedback on our new feature. Please send them to!