May To Do List


  • Increases in day length and drastic changes in light levels this month may require repositioning of plants to avoid overexposure to sun. Although cattleyas, dendrobiums and cymbidiums thrive in high light levels, phalaenopisis, miltonopsis, masdevallias and other lower light plants can easily burn. For most orchids, one wants to have light grassy green leaves.  Dark green leaves suggest too little light, while yellow colored or red tinted leaves usually indicate too much light.
  • Increasing winds result in additional dust build up on your orchid leaves. This provides the perfect environment for harboring mites. Treat accordingly.
  • As your flower spikes grow taller avoid changing the orchids orientation to the light to avoid flowers being twisted on the stems. For paphs, do not stake to early or the stems will not be as strong and flower will be in "nodding" position.
  • May should be the height of growth and repotting season as new roots emerge from pseudobulbs or fans. Try to repot when roots are small and just beginning to emerge in order to minimize damage to soft tissues and avoid transplant shock, giving plants a head start in the growing season.
  • Repot when orchids have begun to over grow their pots and/or when media has started to break down.  Also consider repotting plants that have been in pots for 2 or more years and are existing, but not thriving. Repotting can revitalize and provide new vigor to such plants.
  • The repotting process can be overwhelming so set aside plants and repot a few every day to ease the process.
  • As you repot and divide your plants, set aside any extra divisions as donations for the POS auction or for silent auction at the meetings. It will prevent overcrowding of your benches and make someone else happy to get a piece of your prized plant.
  • Follow good hygiene practices as outlined last month to minimize transmission of pests and viruses.
  • During warm weather, pests and diseases can proliferate very quickly and spread throughout the collection. Carefully inspect plants and treat early to minimize spread.
  • Cautiously use any pesticide, fungicide or chemical.  Always use the lowest prescribed dose and avoid spraying flowers and buds. Recommended dosing for orchids can sometimes be found on the manufacturer’s website or on various orchid forums (such as The Orchid Source
  • More details on specific genera can be found on the AOS website

Indoors and Greenhouse

  • Address higher light levels by adding shade cloth or painting with shading compound to avoid burning sensitive plants.
  • Continue to provide good air circulation for indoor plants to discourage diseases and pests such as mealy bugs. Treat early to avoid spreading to other plants.
  • Increase watering and fertilizer to accommodate the growth spurt 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.
  • If you grow  your plants inside and have outdoor growing space, move your plants outside for the warm season. Do this especially if your plants are crowded together or your hanging plants drip on the plants below when you water. The humidity and larger temperature differential between day and night are beneficial for your plants.


  • Continue to monitor and control snails, slugs and pests during warm weather. They can do considerable damage to plants in short order.
  • Cattleyas, oncidiums, and dendrobiums should be in full bloom and/or producing new root and bulb growth.  Increase watering frequency and fertilizer as new growth is observed and repot as appropriate. 
  • Neofinetias can be repotted at this time especially if they are maintained in sphagnum moss.
  • Repot cymbidiums now if they need it after they bloom.  You should keep at least 3 growing pseudobulbs and no more than 2 back bulbs per pot.
  • Catasetums are coming out of their dry winter rest.  New roots should be 3-5 inches long before beginning to water.  Once you start to water and fertilize, do so regularly as growth will be very rapid all summer.  More details on culture can be found on Fred Clarke’s website


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!