Compiled by Dixie McCulloch, a longtime KOS member who joined in 1988.
| Temperature Range (˚F) | Days | Nights |
|---|---|---|
| Cool house | 55-65 | 50-54 or lower |
| Intermediate house | 65-70 | 61-65 |
| Warm house | 70-73 | 70 |
The main vegetative growth begins in March. New growth is controlled by increased moisture and humidity, increased temperature, and longer daylight hours. From now on the days will become longer as the sun moves closer to us. The resting period is extended to some extent by keeping temperature lower and withholding water. You should not interfere too much with nature’s growth cycle.
With increased sun intensity the temperature does not vary as much in the greenhouse. Night temperature can still drop, so be on guard. Gradually add more shading if needed. Plants that are in the dark all winter should gradually be adapted to the abundant sun to prevent burning. The plants need good light for best growth, so do not shade too heavily.
Gradually increase water. Too much water suddenly will hinder root growth. Spraying of foliage could be done part of the time instead of pot watering. However, be aware that cold water sprayed on a leaf that is very warm may cause cell rupture, which results in rotten spots on the leaf (this is especially true in Phalaenopsis and Cattleya). To prevent this, spray plants early in the day before heat builds up in greenhouse.
Now that the plants are starting into active growth you should start fertilizing with high nitrogen fertilizer. This should continue during the summer active growth period. The more light the more the plant can use fertilizer every time you water with an occasional watering of plain water to flush out salts in the pot.
The warmer types of plants, and ones not in a rest period, can be repotted now. After repotting keep slightly damp (not soggy), and spray the plant frequently until new root action starts (about three weeks or so). Start planning your spring repotting schedule.
Plants potted properly just before roots emerge will establish quickly with little, if any, set-back.
Repotting is the time to give each plant a little TLC. Check for bugs, fungus or other problems. Take a good look at the roots, they tell you a lot about your growing practices.
If one of your new years resolutions is to give your orchids better care, this is the time of the year that you will see the most benefit from improved culture. Remember that orchids are a hobby so enjoy giving them good care as well as enjoying the blooms.
Cattleya and Laelia: Because of large leaf area, leaves can burn easily. If leaves feel warm to your hand, increase ventilation and shading, to decrease leaf temperature. You can start repotting now.
Paphiopedilum: They like high humidity and good shading which will stimulate new root growth. Summer blooming paphs, such as Maudiae will begin to show their buds. You can still continue to repot if necessary. But keep in mind that well-established plants in good condition always produce the best flowers. At the same time, carefully check for signs of basal decay. There is nothing that perks up a paph more than fresh mix.
Phalaenopsis: Will be in full bloom. When the last flowers have faded on the primary spike, cut it at the base, and grow the plant this summer and autumn for best performance in next winter’s flowering season.
Dendrobium: nobile types could start blooming now. Phalaenopsis types can be repotted. Keep water off new growth or rot will occur. When they finish blooming give them high light for the production of strong plump canes. Spindly canes indicate inadequate light.
March is the peak of flowering for the Australian types. Most deciduous Dendrobiums will be blooming now. Do not neglect watering because dryness can cause bud drop in all of your Dendrobium species and hybrids.
Odontoglossum and Oncidium: They continue to need frequent watering along with cool, moist growing conditions. Sufficient shade goes a long way toward keeping them healthy and growing well. Keep Odontoglossums medium green. These should be repotted now, if not in bloom. You should avoid excessive moisture and heat after repotting, but plants want as much light as possible. Do not overpot. Allow for one year’s growth when choosing the size of container. If a plant is suffering, relocate it to where it will receive more shade.
Oncidium: Repot now. Avoid extreme heat and moisture. They need lots of light. Remember Onc. papilio is a perpetual bloomer; do not cut off the inflorescence because it will continue to bloom year after year from the same inflorescence.
Masdevallia: Keep cool (down to 45 degrees) with lots of water and air circulation. Never let them dry out. You want to repot these before the warm weather, so they are well established before the heat hits.
Catasetum, Cycnoches, and Mormodes, which many people thought were dead for months, began to grow again. Once the roots emerge from the new growth, repot or divide. Use a well-drained mix and make sure the plants have abundant water and food throughout their growing season. Watch for spider mites on the leaves later and treat. These orchids can use heavier doses of fertilizer during their growing period than most other orchids.
P.S. If growing under lights, you should start to lengthen the number of hours you leave your lights on. It should correspond to the natural daylight hours. You should go from around 12 hours to up around 16 hours or longer, depending on genera, but do it gradually
Information for these culture calendars is 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 