For the Best Blooming of your Cymbidiums, keep them outdoors or in a place which is cool at night (40-55F is ideal and they are tolerant down to freezing) until the first flower opens. In temperatures that are too warm, buds may drop. If the location has bright filtered light, the flower color will be brighter. As the flowers begin to open, you can display the plant where you like.
While cymbidiums may be considered temperature tolerant - withstanding limits of 27 to 100°F - most require periods of cooling in order to bloom. With the exception of some heat-tolerant miniatures, flower-spikes are initiated in autumn when the differential between day and night temperatures plays a key role. Indoor conditions or climates that stay persistently warm without cooling off at night (below 55°F in winter) are not suited for blooming standard cymbidiums. The ideal temperature range for cymbidiums is 40 to 90°F. During heat spells, it is essential to boost the humidity by watering and misting more frequently. During cold spells, cymbidiums can take 32°F but should be given some protection in case the temperature drops further. Damage to spikes will occur at 27°F and to the plant at 25°F. To guard against effects of the cold, plants should be moved up against the house or under a tree. If plants must be brought indoors, they should be brought into a bright location with night temperatures below 55°F. Warmer night temperatures for any prolonged period can cause developing buds to turn yellow and drop off; however, once flowers have opened, they no longer require the cool and may be brought indoors for show.
Light is the most important factor in attaining good cymbidium culture. Mature cymbidiums need bright filtered light (55% shade) all day or full morning sun. Without proper light you will see weak growth and no flowers. Good light also brings out the best in cymbidium colors; shady conditions result in greener, muddier-colored blooms. Watch the color of the leaves; foliage should be yellowish-green in color, but too much light will result in a pale yellow color. Burning will cause a black spot at the arch of the leaf, or if severely burned, the leaf will be bleached white. If too shady, plants will be dark, lush green but will bloom less or not at all.
When watering a cymbidium, water thoroughly, and then allow the mix to almost dry out before watering again. We recommend running copious amounts of water through; first to wet the mix and then again for the roots to drink up. Thorough watering also helps prevent salt build-up, which can result in tip-burn (browning on the tips of the leaves). Plants should be grown in a well-draining medium and should never be left sitting in water, which can lead to root or bulb-rot. One way to tell when to water is to judge by the weight of the pot; the pot will be heavy as long as there is plenty of moisture; light when it is dry. This may be an average of once a week depending on climate, plant size, and the condition of the mix; water more frequently in periods of dry heat and winds and less in cold, wet weather; finer mediums will hold more moisture and need less watering than courser mediums, which tend to dry out faster; large, overgrown plants will take more watering than younger disivions or seedlings.
Fertilizer should be provided throughout the year since the potting medium provides none. The most convenient method is to apply a timerelease fertilizer such as Osmocote 18-6-12 once a year, at one tablespoon per gallon of pot size. Alternatively, a water soluble fertilizer such as 7-9-5 DynaGro or Peter’s 20-20-20 at 1/2 strength can be used along with regular watering.
The ideal time to repot is after flowers have finished blooming and the new growth is just starting (late spring for most varieties), if and when the potting medium has broken down or the plant has grown over the sides of the pot. Typically this is every 3 to 4 years. If the plant has room to grow (even if crowded) and the mix is in good condition, leave it. Plants may either be divided (to make more, smaller plants) or kept together and potted up into larger tubs (to make a multi-spike specimen). First, take the plant out of the pot and remove the old bark. Cut away any dead or compacted roots from the bottom of the root-ball. Always sterilize cutting tools between plants. If you decide to divide the plant, look for natural divisions which allow three to five-bulb groupings. If the dormant bulbs (back bulbs) can be removed without destroying the strength of the division, remove them. These can be potted separately to resprout and bloom in two to four years. Select a pot size which will allow the plant to grow unrestrained for three to four years. Usually, two inches between the plant and the side of the pot is sufficient. When placing the plant in the pot, position the bulbs so they sit just a little into the surface of the medium and so that the newest growth is in the center of the pot, with room to grow. Plants should be potted firmly by pouring the medium around the roots while tapping the sides of the pot and pushing down on the top with thumbs or a potting stick. We use fir bark or coconut chips (1/8 to 1/4 inch size) as a potting medium - not soil or potting mixes that hold too much water and don’t allow good air movement around the roots. If you are in the area, come see us for a potting demonstration!