Compiled by Dixie McCulloch, a longtime KOS member who joined in 1988.
| Temperature Range (˚F) | Days | Nights |
|---|---|---|
| Cool house | 61-65 | 55 |
| Intermediate house | 65-70 | 61-65 |
| Warm house | 70-73 | 70 |
During this month growth and root formation becomes very vigorous. As the sun moves farther north, light intensity and temperature will increase accordingly. You should keep a close watch on shading and add more as needed. To determine if you have enough shading, hold your hand approximately one foot above the plant. If you see a well-defined shadow of your hand, there is too much light. A more diffused shadow would indicate the proper amount of shading.
Pot moisture should also be increased to keep up with more light and higher temperature. Remember, with the vigorous growth and root action you have to keep up fertilizing while watering. The best for this time of the year is high nitrogen type like 30-10-10 at a rate of 1/2 tsp./gal. Once a week would not be too much, just flush pots with plain water occasionally.
Also remember to keep a lookout for orchid pests. As it warms up outside, the natural populations start to hatch and multiply and can invade the greenhouse through ventilators and doors. If they are spotted, treatment should be immediate, because with higher temperatures they multiply quite rapidly. For insect control some good insecticides are: Malathion – WP 1 tbs/gal; diazinon – WP l tsp/gal; Orthene – WP (only) 1 tsp/gal; plus several others can be used. For spider mites you can use: Kelthane — EC 1 1/2/tsp/gal – WP (35%) l l/2 tsp/gal; or Pentac – WP 1 tsp/gal. Slugs and snails are another problem at this time of year. You can use: QUE Slug and Snail granules, or Slug-Spray 50 WP l tbs/gal. Treatment should be continued until they are gone REMEMBER, follow directions on labels. Editors Note: If you do not have too many (I don’t know what that means) orchids, most of the pest problems can be taken care of with alcohol on a cotton swab. Just remember this will probably take several applications, over a period of time.
Cattleya: You can continue repotting, but try to be finished by the end of the month to allow for healthy new growth before blooming time. For any Cattleya, the best repotting time is just as new roots start. If the plant turns yellow, you have too much light and need to add more shading.
Some of the Laelias, such as cinnabarina, flava, harpophylla and milleri will flower this month. All of the rupicolous laelias need to have cool medium. Try using clay pots for the evaporative cooling effect that results when they are drying after a thorough watering.
Dendrobium: Same as for March. If any need repotting, do it now. Repotted plants should be kept somewhat dry until new roots appear, then kept well watered. Shade only during the hottest part of the day.
Paphiopedilums: Growing conditions for these should remain as nearly constant as possible throughout the year. Keep them moist but not soggy, never allowing them to dry out. Grow in semi-shade with filtered sunlight.
Phalaenopsis: They like high temperature and high humidity. Caution must be taken that the shading is heavy enough to prevent burning the tender leaves. You don’t want to spray chemicals on your blooms but you do want to keep a close look for signs of pest, scale or mite infestations. Be sure to check the underside of the leaves. When old flower spikes are cut off, a new spike often develops from one of the remaining nodes on the stems.
After this second spike flowers, however, the plant should not be allowed to develop a third. Too much flowering weakens the plants. Instead, concentrate upon building the plants’ strength for the next flowering season. Phalaenopsis need a short rest after flowering. Repotting should be delayed until new growths develop.
Masdevallia: Try to keep them as cool as you can during warm days. An evaporative cooler can be used to keep the temperature down, They like to be kept moist at all times and need good air movement.
Oncidium alliance: Repotting should be done in April or May, when new growth is starting to appear.
Species and Botanicals: All such plants should be checked over carefully. If any need repotting, get it done before the warm weather arrives, for they, too, like a long period in which to grow and store up energy for the winter.
Some of the reasons why we water are:
- To lubricate the roots through the mix,
- To transport the fertilizer to the roots throughout the pot,
- To leach accumulated salts,
- To replace transpiration,
- To lower the temperature,
- To raise humidity,
- To wash away pathogens that may be present,
- To increase photosynthesis
- It Pays to Groom Plants
Plants that are well groomed are likely to be healthy. Grooming consist of keeping foliage clean; removing infected foliage, removing faded flowers and trailing stems, and making sure that plants are growing upright rather than leaning.
Occasionally wash leaves with a damp cloth. Do not use leaf-shining preparations – these can clog pores. A little soap on a cloth does the job nicely. Actually I like baby wipes to clean a plant. Flush away the soap with a water spray.
Remove and discard all old flowers before they fall off. Decayed flowers are invitations for fungus disease.
With Phalaenopsis, cut the stem above another node to encourage a second flowering. Cut Cattleyas just above the leaf junction, removing the dead sheath and flower spike.
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 