Growth and Flowering
Basic Needs
Like all plants, orchids have a set of needs: light, water, nutrients, as well as airflow and suitable temperatures. Orchids come from a range of environments, and their native environment will give an indication of how you should care for them.
Sunlight
Most orchids are shade loving plants, as many have evolved to live under the forest canopy, competing for light and making the most of what they can get.
Like succulents, orchids use CAM photosynthesis to convert light into energy. This means that they do not transpire (or effectively, sweat) during the day, which can easily lead to overheating as most lack the fleshy structures to resist and transfer heat that succulents may have.
The general rule is, look at the colour of the leaves. Dark, glossy and sometimes larger leaves indicate too much light. Yellow or burned leaves indicate too much light. A light green, much like a granny smith apple or a green olive colour, usually indicates a good level of light. Some plants, often those with darker flowers, will get a red tinge, which usually indicates a perfect amount of light.
The second general rule is that light is linked to temperature. In colder temperatures the light can be a lot higher, whereas in warmer temperatures most plants will need higher amounts of shade. Even cool growing plants can endure a hot summer if they are kept in deep shade.
On burned leaves, they never repair, but don't fret as often they can trigger growth of new leaves so it's not always a bad thing.
Water
Most orchids don't need a lot of water. Or more accurately, most orchids need less water than their owners would expect of them, as most orchids have adapted to live in areas that receive sporadic rainfall. Many orchids feature water storage organs such as pseudobulbs, tubers, thick fleshy roots or leaves to store water and use CAM photosynthesis to reduce water loss.
The general rule with epiphytes is to "water them when they are dry", and with terrestrials it really depends where they are from - some live in swamps that are continually wet, while others live in arid forests or even deserts. But even then most will benefit from a wet/dry cycle, leaving them to dry out between waterings reduces the chances of infection from fungus and bacteria, and promotes good root growth.
Just like light, the second general rule is that watering is linked to temperature. Warmer temperatures = more water, and this goes across the board for almost all orchids whether they are terrestrial or epiphytes, come from tropical or cold climates. The only real exception is for mainly terrestrial orchids that go dormant over the hotter seasons, such as Pterostylis species.
The only other thing about water is that it is generally better to water early in the day, and it's best to avoid watering during the heat of the day as this can encourage rot to occur from water sitting on warm leaves for too long. Not many orchids enjoy being cold and soggy, especially at night, so it is best to avoid watering late in the day during cold weather.
The only other thing of note is that some plants, such as cymbidium, can benefit from the temperature drop caused by watering late in the day during warmer weather. The temperature drop often encourages flower spikes to form in the following seasons.
Nutrients
Please see the section on Fertiliser.
Getting an Orchid to Flower
Most orchid species have a certain time of the year when they flower. This means you'll either have to research the times of the year that your orchid flowers, or wait for it to flower. Many hybrids, however, will flower throughout the year as they may combine the genetics of species that flower at different times of the year.
An orchid will flower when:
- It is happy - the humidity, watering, and amount of light match optimum conditions (though not necessarily natural conditions)
- It is stressed - if an orchid is under stress, it may produce flowers to ensure it can reproduce in the event of impending doom.
Orchids that go through seasonal dormancy (e.g. lose their leaves on older growths or simply stop growing), will often need special conditions during dormancy to ensure flowering occurs. Soft cane Dendrobiums (e.g. nobile, loddigesii) benefit from being left dry during dormancy, and strong light during cold conditions to encourage flowering. Some Terrestrials will also depend on being dry during dormancy followed by heavy watering when new growths appear, in order to ensure there is enough growth and energy to produce flowers.
Some orchids, such as Cymbidiums, benefit from a 10-15C difference in day/night temperatures. A good hack to trigger spike formation in these plants is watering with cold water in late afternoons during late summer/early autumn.
There are also some orchids that need very particular trigger for flowering, such as thunderstorms and sharp and unusual changes from hot to cold weather. Some of these can be triggered by watering with chilled water, and applying sharp changes in light, e.g. moving the plant from a dark to bright location and vice-versa.
Fertiliser (unless applied to point of stress) will not trigger flowering, but will enhance it. Applying a high potassium (K) fertiliser will encourage flower cell growth, resulting in stronger stems and potentially larger flowers with more substance or a higher flower count.
