Compiled by Dixie McCulloch, a longtime KOS member who joined in 1988.
|Temperature Range (˚F)||Days||Nights|
During February, rapid temperature changes in the greenhouse can take place during the day due to increased sun intensity as it moves north, but nighttime temperature can still drop sharply. (This is true for windowsill growers also.) The foliage is still soft after the dull days and the increase in sunlight should help to strengthen it. If you cannot keep the temperature up to the indicated level at night, decrease the humidity by cutting down on watering a little, or only water part of the greenhouse at a time.
During the middle or end of the month, as soon as sunny days prevail, begin applying shading. Plants hardest hit by too much sun are thin or soft-leaf plants like: Miltonia, Phalaenopsis, Paphiopedilum, Lycaste, and others. Keep plenty of air circulation in the greenhouse at all times; ventilate the growing area when the weather permits during these cold months. Fresh air is important to plants. This will stop Botrytis to some extent and you will not have as much trouble with rot. A good fungicide and bactericide applied regularly will keep Botrytis and other rot problems in check. Some good ones are: Captan WP l tbs/gal; Banrot WP 1 tsp/gal; Physan 1 tsp/gal.
Cattleya and Laelia: Watch the root tips and new roots, and if tips are green increase the water. They are starting active growth and new shoots (growths) should be starting to appear. As daylight hours increase, towards the end of the month, more water will be needed. An occasional fertilizer treatment is appropriate for these robust orchids, even though temperature and light conditions are not ideal. Watch for signs of buds rising in the sealed sheaths; sometimes it is necessary to slit open a sheath to reduce pressure on the emerging buds or to allow accumulated condensation (possible result when temperatures are fluctuating) to dissipate. Use a sterile blade to slit open a sheath.
Paphiopedilum: If plants are not in bud or bloom this would be the ideal time to repot. After they have been repotted, they should be shaded a little more until new growth starts. They can be repotted at other times without harm to the plant, but because of less root activity at the time it would be more ideal. Plants should have sufficient water to keep moist. Water all plants in the morning so they have time to dry before night.
Phalaenopsis: Add a weak fertilizer solution to the watering schedule this month; be careful not to splatter the flowers or they will stain. As with any orchid, do not fertilize a dry pot.
Dendrobiums: The deciduous types, which have been resting, will now begin to show their flower nodes. Therefore, they will now need more water and fresh air. Watch for flower buds on Den. aggregatum, Den. nobile hybrids, Den superbum (now Den anosum), and other deciduous Dendrobium species and hybrids. These all seem to have longer lasting flowers when exposed to cooler night temperature as the blooms open and mature. For example, the modern Dendrobium nobile hybrids from Japan tolerate nighttime temperatures in the low 60’s with the result that the flowers remain in perfect condition for a month or more. Continue to protect evergreen-type Dendrobiums from low temperatures that may cause leaf loss.
Odontoglossum and Miltonia: Crispum type Odonts and Miltonias are in growth or spike now, so they need more water. Stake the spikes to achieve the ideal presentation of the developing flowers. Apply a week liquid fertilizer treatment just before the flowers begin to appear.
Oncidiums: If your plants are in growth with active root action, or in spike, keep watered.
Vanda and Ascocenda: They require plenty of light, moderately warm temperature, day and night, and keep them well watered. You could place them high up and on the south side of the greenhouse to accomplish this.
Masdevallia: You can still repot your plants this month, as long as the weather stays cool. Keep them cool, around 45 degrees both day and night, with plenty of air circulation and water.
Species: As a general rule, if they are in growth, keep them watered. You can tell this if you check the roots. Those on slabs need more water because they tend to dry out faster.
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, The Great Lakes Judging Center Newsletter, The Score Sheet and some of my own experiences.