Most orchid deaths can probably be attributed to bad watering practices… and more often than not, due to too much water than too little. While watering really does not have to be as complicated as some think, it is hard to get a good feel for it until you understand a little bit about how orchids work and the specific needs of the species you grow. Even though many orchids are tropical and are often drenched by heavy rains, they also dry up quickly in between showers thanks to a constant breeze in the canopy or on the rock face where they grow. When drying the roots can take in oxygen and convert the stored sugars created during the photosynthesis into energy at the same time as it releases carbon dioxide. Orchids are also highly evolved plants and have adapted to each unique growing situation as well as potential dry seasons and wet seasons where they grow. All we need to do is to figure out just on how each species grow in nature and try to replicate those conditions as best we can to grow them successfully in cultivation. Easy as pie…
When to water orchids
A majority of the orchids in cultivation are epiphytes or lithophytes. In the wild these orchids grow attached to trees or rocks and the roots are mostly exposed rather than buried deep in the earth. Evolution has surrounded the orchid roots with a thin membrane called a velamen. This membrane not only helps the roots grab onto the surface where it is growing, but more importantly it helps to soak up the water quickly when it is available. When water filled the velamen is green or mottled and when dry it turns white or silver in color. In species with thick and fleshy roots, like Phalaenopsis for example, it is easy to see when the roots are dry. In species with pseudobulbs these are another indication. When not in rest, pseudobulbs should be firm and plump, just as fleshy leaves should be firm and thick. Some species require a dry rest and during this time the bulbs should be allowed shrivel some. A dry pot is much lighter than water filled pots. Different media take different time to dry out, some faster than others. You need to adjust your watering regimen accordingly. Learning how much the pots should weigh when it is time to water really is the very best way to go across the board. After a while this will become natural.
When not to water
Don’t water too late in the day. It is important to let the surface water dry up before the evening brings cooler temperatures. If water is left in the folds of the leaves it is an invitation to rot or fungus problems. The same goes for misting, I actually prefer not to mist my orchids at all as it does very little to raise the humidity around the plants for any meaningful length of time, it can cause problems with fungus. If you have to water late in the day, make sure you have adequate air circulation.
How to water orchids
Weather you have an automatic misting system or water by hand, water thoroughly. There is some old wife’s tale in circulation that the correct way to water an orchid is one shot glass a week. Well, let’s kill than one off right now – before more orchids are killed. It probably came about because people tend to overwater their orchids – but come on, let’s not be ridiculous. Many home growers choose to dunk their orchids, submerging them completely in a bucket of water, pot and all, for a few seconds before dunking the next plant. I used to water all my windowsill orchids as well as the warm vivarium orchids this way, but it can be a risky practice. Should you get an infected plant in the collection the problem can rapidly spread through the entire collection via community water bucket. But it is much too time consuming when you have as many plants as I do anyway. So now I water everything with the help of a 5 liter high pressure pump sprayer instead. I quarantine all new plants before placing them among general population, hoping to avoid many problems this way. Bare root species, like the vanda, I spray more often, every day the warmer part of the year when they are in active growth, but in the winter when it is colder and primarily darker and they do not grow as much I space out the watering to every other or third day. I spray with a pretty hard stream until the roots are soaked until the velamen turn nice and green and the roots are fully saturated with water each time. Vanda are heavy drinkers, but it is critical that the roots are allowed to dry off fast after each watering, why they do best grown bare root – and never ever in glass vases! The glass does not allow for good air circulation around the roots and will eventually lead to fungus or rot. Should the vase be placed in direct sun it will also easily turn into a burning glass and torch the roots with heat, that goes for all orchids. Just say no to glass pots.The cool vivarium is a bit more advanced… here I use an automated a rain system (basic misting system by Vivaria) that creates so fine water droplets they look like mist. The rain is controlled by a digital timer.
The best way to water orchids by hand
If you only have a few orchids to water I recommend you soak the pot under running tepid water for a few seconds until the media is thoroughly rinsed through every time and thoroughly soaked, then pour some fertilized water over the wet media using a watering can. Fertilizing dry roots can burn the roots. If you have a few more orchids (or a lot more, like me) a simple pump pressure sprayer really cannot be beat. Most garden centers here carry them. Just make sure the roots and growing media gets thoroughly soaked when you use it.
It is better to give a low dose fertilizer every watering instead a strong doze once a month, easier to remember when to do it too. You can use a weak fertilizing solution once a week, 1/2 of the recommended doze is good for most orchids. For more sensitive specis such as many Pleurothallids I use 1/4 of the recommended strength every week.
Water related problems
Over watering can cause the leaves to turn yellow and shrivel due to starvation because sugars aren’t being converted to energy. Novices often panic and water more, but a quick root inspection will reveal mushy black or brown roots incapable of using the water. Saving an overwatered plant usually start with repotting it into fresh well drained media and trimming off the dead roots, then keeping it evenly moist but not wet until new root growth is detected.Under watered roots shrivel and become gray and brittle with little or no capacity to soak up water. This can be caused either by not watering often enough, or not giving it enough water when watering (the shot glass method for example). In case of the latter the plant will not seek to grow deep well developed root systems and since the water never penetrates very deep into teh media, and since pot is never flushed though properly salt and minerals and fertilizer will cling to the mix eventually rendering it toxic.In either case, if the roots are in really bad shape, placing it in sphagnum moss on high humidity environment then carefully water so the medium is never soaking wet, only constantly damp. This can stimulate new root growth and save the plant. When you see signs of new root growth you can slowly begin to water like normal again.
What to do with poor root systems
If the roots have been damaged, either by too much water or too little, they will not be able to soak up a whole lot of water. So if you water too much then the rest of the roots will simply rot and the plant will die.
The most common first aid method is planting the struggling orchid in lightly damp sphagnum moss in a high humidity environment. Some people use a bag (sphag-n-bag method) but I think it is hard to provide enough air circulation this way. A plastic tupperware with a small air gap left by the lid might be a better solution.
Some orchids are particularly sensitive to the mineral content of the water. Regular tap water can have rather high salt and mineral content. You can actually see white deposits forming on your plants, the media or on the pots. Too much buildup can harm the roots which of course is not good. You can help minimize this buildup by thoroughly running each pot under running water without any fertilization once every 4-6 weeks. This is also recommended to flush out any buildup from the fertilizer in the pots.In softened water the calcium and magnesium is often replaced by sodium, which can build up to toxic levels very quickly in the orchid. Some claim that leaving the water standing in an open container overnight or boiling it will help. Sure, any chlorine present will dissipate in the open container overnight but if your water contains chloramine you’re going to need a charcoal filter to remove it. Boiling the water will not remove minerals either since minerals are not volatile, you are more likely concentrating the minerals instead since a lot of good pure water evaporates in the boiling process.Or you can do what many growers do, including me, use RO water or collect rain water. Since I live in the city and cannot collect rain water I installed a reverse osmosis filter on the water main leading to my washing machine. It is an AquaLight system from Germany and it is rated for up to 285 liter per day. It fills my 25 liter jug in about 5 hours. It is recommended you replace thecarbonfilter and demineralisation filters regularly so the expensive membrane last longer. I draw 50 liters of RO water per week and replace mine once a year.I use 90% RO water mixed with about 10% tap water to buffer it back up a little bit and stabilize the pH. I do this even when I fertilize, even though I really do not need to since the MSU fertilizer I use is specifically developed for RO water and has stabilizers in it already. Orchids do best with slightly acidic water with a pH of about 6.5, but most species can be grown successfully in alkaline water too with a pH up to 7.5. With optimum pH the orchid can metabolize more beneficial nutrients and less harmful elements are absorbed.
Although some people swear by the use of special bloom formulas in order to bring their orchids to flower I believe it is best to just use a balanced fertilizer throughout the year. Some people have very good results using a 20-20-20 mix. These 3 numbers you see on most nutrient labels represent the percentages of nitrogen, phosphorus and potassium (N-P-K) in the product.Orchids need nine macronutrients and seven micronutrients to be healthy. The macronutrients are: Hydrogen (H), Carbon (C) and Oxygen (O) = food production, Nitrogen (N) = growth, Phosphorus (P) = flower production, Potassium (K) = health and tissue building, Calcium (Ca) = cell building, Sulfur (S) = combine to produce proteins, Magnesium (Mg) = producing food. Micronutrients are: Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo) and Chlorine (Cl).Since I use RO water I use a fertilizer specially developed for the use in combination with rain- and RO water. That means that they have put back some of the macro- and micronutrients absent in this kind of water. A solution developed for tap water will not be sufficient in this area as most of them only include nitrogen, phosphorus, potassium, calcium, sulfur and magnesium. The N-P-K for the MSU (Michigan State University) fertilizer I use is 13-3-15 – 8Ca, but they also make one mixed for tapwater at 19-4-23- 2Ca.