Water Water Everywhere: Understanding the Art of Watering Orchids
When I give talks about orchids, one of the first questions asked by those in the audience is, “How often should I water my orchids?” I really wish this question had an easy answer, but it doesn’t. So many variables are involved in watering. In the following sections, I cover some of the factors that affect how often you should water.
The type of pot
You can grow orchids in clay or plastic pots. The potting material dries off much more slowly in plastic pots than it does in clay pots. With plastic, the potting material dries out from the top down, so even though the potting material may be dry on top, it may be damp 1 inch below the surface. With clay pots, the potting material dries out more uniformly (clay pots are porous, so they “breathe” and allow water to evaporate through the walls of the pot).
The bottom line: If you’re using a plastic pot, you’ll want to water less often than if you’re using a clay pot.
Either type of pot will grow orchids, they merely have different watering requirements. For orchids that do best when they’re always slightly damp (like miltonias, slippers, and moth orchids), I prefer to use plastic pots. For those that need to dry out more between waterings (like cattleyas and most of the dendrobiums), I recommend clay pots.
The type of potting material
Potting materials vary dramatically in terms of the amount of water they retain. For instance, sphagnum moss, a highly water-absorbent plant that is harvested from bogs to be used as a potting material, usually stays wet much longer than bark, which isn’t as water-retentive.
If you’re using a potting material that absorbs a lot of water, you’ll want to water less often than if you use a potting material that doesn’t absorb the water. To determine whether the potting material is absorbent, soak some of it in water for a few hours. Then remove the material and squeeze it. If it’s absorbent, it will release this water, under pressure, like a sponge.
The age of the potting material
Fresh potting material requires much more frequent watering for the first few weeks, until it gets properly wetted. As it gets older, it retains water longer.
Whether the orchid is pot-bound
An overgrown orchid (sometimes referred to as an orchid that is pot-bound) will dry off much more quickly than one that has plenty of space in the pot. When pot space is limited, there is less potting material to hold onto the water, so the overgrown plant quickly uses it up.
In general, most orchids need to be repotted every one to two years.
The growing environment
Are you growing your orchids in high humidity or low? Orchids and potting materials in low humidity dry off more quickly, because the drier air quickly absorbs the moisture from both the plant and the potting material.
Warmer temperatures increase water evaporation because warmer air absorbs more moisture and because the plants are growing more quickly in warmer temperatures and require more water. If you’re growing orchids in a cooler temperature, you won’t need to water as often.
The amount of ventilation
The more ventilation your orchids get — especially if air is vented to the outside, or if the air is hot and dry, as is found in most centrally heated homes — the quicker the water in the potting material evaporates. Gentle air movement is ideal. It will keep the air fresh without excessively drying out the plants or potting material.
Whether the orchids are growing or dormant
When species of certain orchids (like some of the dendrobiums and catasetums) are going through their winter rest period, they need and should only be given very little water. But when they start active growth in the spring and summer, they require copious amounts of water.
The type of orchid
Some orchids, like cattleyas, like to dry out between waterings; others, like paphiopedilums, phalaenopsis, and miltonias, prefer to always be damp. This difference has a lot to do with where the particular type of orchid grows naturally. If the orchid naturally grows in an area where it doesn’t get natural rainfall on a regular basis, it won’t need watering as often as orchids that grow in areas of frequent rainfall.
Proven Watering Techniques
When you’ve considered the factors such as potting material, environment, and type of orchid (see the preceding section), you need to make the decision as to when and how much to water.
I find the pot-weighting method of determining when to water is one of the easiest. In this method, you’re relying on feel instead of precise weights. Here’s what you do:
1. Thoroughly water the orchid in its pot.
2. “Weigh” the pot by picking it up.
Now you know how heavy it is when it’s saturated with water.
3. Wait a day or so and “weigh” it again by picking it up.
You’ll feel the difference in the weight as the potting material becomes drier.
4. Repeat Step 3 each day until you judge, by looking at the surface and sticking your finger into the top 1 inch (2.5 cm) or so of the potting material to see if it’s damp, that it’s time to water.
Keep in mind whether this type of orchid prefers to be on the damp or dry side.
5. Note what this dry “weight” is.
Now the orchid is ready to be watered thoroughly.
This entire process may sound tedious, but you’ll be amazed at how quickly you catch on. And when you do, you’ll always know the right time to water. Just lift the pot, note its weight, and you’ll have your answer.
If you’re still not quite sure about watering, keep the following watering tips in mind:
Grow orchids of the same type, media, pot type, and size in the same area. This strategy will make watering them easier, because they’ll have very similar moisture requirements.
Water with warm water. Very cold water can cause root and bud shock, which sets back the plant and slows down its growth.
Always use a water breaker (a water diffuser that you attach to the front of your hose to soften the flow of water).
For only a few orchids, a sprinkling can with a long spout with a rose (a water diffuser placed on the end of the water-can spout) that has many small holes works well. These devices allow thorough watering without washing out the potting material.
A huge selection of watering wands is available. I really like the ones with multiple settings on the head that allow you to drench or mist without changing attachments. Regulating the flow of water is much easier with wands equipped with finger triggers than it is with those that have an on-and-off valve.
Never let the water breaker or end of the hose touch the ground or floor. This commandment was given to me by my first horticulture professor, Dr. D. C. Kiplinger, who preached that floors and soil are where the diseases and insects hang out, and a hose can be an all-too-effective way of spreading them.
When you water, water thoroughly. The water should pour out from the bottom of the pot. This method of watering ensures that the potting material is saturated and flushes out any excessive fertilizer salts.
Never let the pots of orchids sit in water for over a few hours. If the orchid pots have saucers, make sure to keep them free of water. Excess standing water will prematurely rot the media and roots and will be a source of accumulating fertilizer salts and pathogens (disease-causing organisms, like bacteria, fungi, or viruses).
Water the orchids early in the day or afternoon. That way, the foliage will have plenty of time to dry off before nightfall. Wet foliage in the evening is an invitation for disease.
Over- or Underwatering: Roots Tell the Story
Over- and underwatering show many of the same symptoms because the effect of both practices is the same — damaged or destroyed root systems, which result in the orchid becoming dehydrated. The signs of dehydration include
- Pleated leaves on orchids like miltonias (see Figure 6-1)
- Excessively shriveled pseudobulbs (thickened, swollen stems) of some orchids, like cattleyas
- Droopy, soft, and puckered leaves on cattleyas
- Yellow and wilted bottom leaves on phalaenopsis
- Bud blast (in which the buds fall off instead of opening) on all orchids
Figure 6-1: The pleated or puckered leaf of this miltonia orchid is a sign that the orchid is dehydrated.
Figuring out whether watering is the problem
In order to better evaluate whether over- or underwatering has caused these symptoms, remove the orchid from its pot. Many beginner growers are reluctant to do this, but if you’re careful, removing the orchid from its pot won’t disturb most orchids to any degree and it’s an absolutely necessary procedure to see what’s going on with the root system.
To determine if you’ve under- or overwatered your orchid, follow these steps:
1. Turn the orchid plant, in its pot, upside-down.
2. Gently rap a hard object (like the handle of a gardening tool) against the pot to loosen the potting material.
Cup your hand over the surface of the pot to hold the loosened potting material as it falls out. Doing this over a workbench or a table covered with clean newspaper to hold the potting material is a nice, neat approach.
3. If the potting material doesn’t loosen easily, use a thin knife to circle the inside of the pot to loosen the potting material from the wall of the pot.
In some situations, the potting material may be so packed into the pot that it won’t come out easily.
4. When the orchid is removed from the pot, check out the potting material.
Is it soggy? Does it have a bad (rotting) smell? Are the roots dark and mushy? These are all signs of overwatering.
If the roots are dry and shriveled, not stiff and plump, and have no or few growing root tips, the orchid probably hasn’t gotten enough water. The potting material may be too coarse, making poor contact with the roots; otherwise, you simply haven’t watered the orchid frequently enough.
5. If the roots look okay or only slightly damaged, pot up the orchid again in fresh potting material.
6. If you find that the roots are badly damaged, read the following section for more information.
Mission: Orchid rescue and resuscitation
The approach you take to remedy root damage depends on how dire the situation is.
If the orchid still has some healthy, firm roots, cut off all the soft, mushy roots with a sterile tool, like a single-edged razor, and repot the orchid in new potting material. Go light on the watering for a few weeks to encourage new root development. Using a spray bottle, mist the orchids a few times a day to prevent the leaves from drying out.
If the roots are almost all gone, emergency measures are called for and recovery is not definite. This is what I recommend:
1. Cut off all the dead or damaged roots.
2. Drench the roots with a liquid rooting hormone like Dip ‘n Grow.
3. Let this liquid hormone dry on the roots for about an hour, then repot the orchid in fresh potting material that has been predampened.
4. Don’t water for a day.
5. Water once, and then put the potted orchid in an enclosed terrarium (like a high-top propagator, a clear plastic box with vents at the top and a tray below to hold potting material) or an empty aquarium, with damp sphagnum moss or pebbles on the bottom to add humidity.
6. Close the top of the terrarium and put it in a location with diffused light.
In a greenhouse, this would be a shady spot with no direct sunlight. Under florescent lights, put the terrarium at the ends of the tubes where there is less illumination. If the terrarium is in the cool part of the greenhouse or growing area, put the entire terrarium on water-resistant soil or seedling heating mats, available at most garden centers. Get one that has a built-in thermostat set for about 70°F (21°C) to provide bottom heat to stimulate rooting.
7. If you’re concerned about disease, spray the orchid leaves with a disinfectant solution.
A good disinfectant is Physan, a commonly used hospital disinfectant available from mail-order orchid-supply companies or at garden centers.
In this environment of 100 percent humidity, the leaves won’t dehydrate, so there will be no stress on the orchid while it reroots itself. Water the potting material only when it gets dry, keep the gravel or moss in the bottom of the terrarium damp, and leave the orchid enclosed until new root growth is very apparent. This may take a few months.
This method has no guarantees, but following this procedure has saved orchids for me that were in the “hopeless” category.
Figure 6-2 shows my orchid rescue, the place where I put orchids that have suffered a loss of roots. It’s like a miniature greenhouse with high humidity, which encourages the orchids to form new roots.
Figure 6-2: My orchid rescue, the place where I put orchids that have suffered a loss of roots.
Fertilizers: Not Magic Potions
Many people place much too much faith in fertilizers. They think fertilizer is some type of elixir that will save the day. Actually, if the orchid is in poor health, fertilizers are rarely the answer.
In fact, if the roots are damaged (a frequent problem), applying fertilizers will make the problem worse. If roots aren’t functioning well, they can’t absorb the fertilizer, and if the fertilizer isn’t used by the orchid, it can accumulate in the orchid potting material. This buildup of fertilizer salts can further dehydrate and damage the remaining roots.
Fertilizers are most useful as a boost to help an already healthy orchid grow better.
Many people mistakenly think of fertilizer as food — which it isn’t. Plants produce their own food from sunlight, carbon dioxide, and water. That’s the miracle called photosynthesis. By fertilizing, you’re merely providing minerals that your orchids can use to make photosynthesis more efficient.
The number and types of fertilizers on the market can make your head spin! You’ll hear a lot of mumbo-jumbo about why one fertilizer is better than another. Fortunately, the choice is not nearly as complicated as some manufacturers seem to make it.
What to look for in orchid fertilizers
From my experience and after listening to other veteran orchid growers, I’ve come to some conclusions about fertilizers. The following suggestions apply to most orchid-growing situations:
Look at the label and choose a fertilizer that has the words nitrate nitrogen or ammoniacal nitrogen, not urea.
Although all forms can be used by plants, recent research shows that the nitrate and ammoniacal forms, not urea, are most beneficial to orchids. These chemical terms may sound like Greek to you, but it’s not really important for you to know any more than to look for these types of nitrogen in your fertilizer. It will be spelled out on the label.
Look for a fertilizer with 20 percent or less nitrogen (this is listed on the label). High amounts of nitrogen, much more than 20 percent, are not necessary to grow the best orchids no matter what media they are grown in. Too much of any nutrient cannot be used by the orchid plant and, as a result, merely ends up as a pollutant.
Don’t worry about the amount of phosphorus in the fertilizer. It was earlier thought that a high-phosphorus fertilizer was necessary for better orchid bloom. This has now been found not to be the case.
In most cases, a fertilizer with supplementary calcium (up to 15 percent) and magnesium (up to 8 percent) is a real plus.
For most water sources, adding trace elements (chemicals in very small amounts), including sodium, manganese, copper, zinc, boron, iron, and molybdenum, has been found to be beneficial to orchid growth. Don’t worry about the exact amounts; just check the fertilizer container or label to see if they appear in small amounts.
Any fertilizer that meets these requirements will do. To find out if your chosen fertilizer does, carefully look at the fertilizer container. By law, the manufacturer is required to list what chemicals are included in the fertilizer. Figure 6-3 is an example of a label so you can see what to look for.
Figure 6-3: The label on an orchid fertilizer reveals what the product contains. Read it closely.
Do not use water that has passed through water-softening units on your orchids. Such water may contain high amounts of sodium that can be harmful to orchids.
Types of fertilizers and how to use them
Fertilizers come in many forms — granule (which looks like small pieces of gravel), slow-release, and water soluble being the most commonly available. Table 6-1 lists the pros and cons of each of these types.
Most granule fertilizers are best suited for agricultural or lawn application. Slow-release fertilizers are chemicals that have been encapsulated in a shell that slowly releases nutrients. Although some orchid growers use this type, I’ve found, especially with some of the very porous potting materials that are frequently used with orchids, that the fertilizer can wash out and not be effective. Also, some orchid roots are very sensitive to fertilizer salts, so these fertilizer capsules can damage or “burn” their roots.
This leaves the most common form of fertilizer used with orchids — the water-soluble type. Water-soluble fertilizers are packaged as a concentrated liquid or in dry forms.
Here are some of the advantages of these types of fertilizers:
- They’re readily available in a wide range of formulations.
- Because they’re soluble in water, they’re easily and quickly absorbed by roots and even leaves of orchids.
- They’re very simple to use. You just dissolve them in water and apply them with a sprayer or sprinkling can. If the orchids are mounted on slabs or in baskets, you can dunk them in the fertilizer solution.
When too much fertilizer has been applied, if it has been applied when the media is dry, or if the roots of the particular orchid are hypersensitive to the salts in fertilizer, the roots can become dehydrated by these moisture-robbing salts, resulting in fertilizer burn. This damage shows up as brown or black root tips and/or leaf tips. It looks as though the root tips or leaves have been burned (thus, the name). To prevent it, don’t apply more fertilizer than is recommended and fertilize only when the potting material is damp.
The disadvantages of water-soluble fertilizers include the following:
- The nutrients don’t last long in the potting material, so the fertilizer needs to be applied once every two to three weeks (or constantly if you’re using a very low dosage).
- These fertilizers, in their original containers, are very concentrated and can damage the orchids if you don’t dilute them correctly.
- The application rate or dosage of all fertilizers depends on the concentrations that are used. The safest procedure is to always check the fertilizer container for their recommended application rates. Never apply more than recommended or plant damage can result.
Table 6-1 The Pros and Cons of Different Fertilizers and How to Use Them
Type of Fertilizer
How It Is Applied
Easy to use
Short-term (lasts a few to several weeks)
Can easily burn orchid roots
Often doesn’t include valuable trace elements
In dry form
On top of or incorporated into the potting material
Easy to use
Lasts a long time
(three to nine
on the formulation)
Can sometimes burn sensitive orchid roots
In coarse potting material, can be washed out when watered
In dry form
On top of or incorporated into medium
Readily available in a wide range of formulations
Easy to apply
Nutrients are instantly available for plants
Must be applied frequently — every few weeks when plants are actively growing
Diluted in water and applied by watering can
Here are some pointers to help you know when it’s time to fertilize your orchid:
Fertilizing frequently at a more dilute rate is better than fertilizing less often at a higher concentration. Some orchid growers, including me, find that feeding their orchids every time they water with a diluted amount of fertilizer works great. It’s the most natural way (as opposed to the feast-or-famine routine of fertilizing at a higher concentration every two or three weeks).
Never apply more fertilizer than is recommended by the manufacturer. When in doubt apply less, not more, fertilizer. Remember that fertilizers are a form of salt and salts were some of the earliest weed killers, so they’ll damage orchids at high concentrations.
Drench the potting material, several times in a row, every few weeks or so with fresh water that contains no nutrients to wash out any excess fertilizer salts. This process is called leaching.
- Look at the orchid’s leaves and flowers. Very dark green leaves that are succulent and floppy can be a sign of over fertilizing. If orchids are over fertilized, they also produce poor-quality flowers.
- When the orchids are actively growing, fertilize them. When they aren’t, don’t.
- If the orchids are diseased and in poor condition, stop fertilizing.
Fertilizer deposits on pots
As water evaporates from the potting material in the pots, it leaves behind any solid minerals or salts that were dissolved in the water, including fertilizer salts. These salts can accumulate on the edges of the pots. When this salt crusting is noticed, remove it with a damp cloth. If you don’t, these deposits can burn the leaves of the orchids when they touch it.
Because clay pots are porous, they tend to accumulate more salt deposits on the edges than plastic pots do. One way to prevent this is to dip the tops of the clay pots into about >2 inch of melted paraffin (wax used to make candles) before potting your orchids in them.
Watering and Fertilizing Orchids on what-when-how, In Depth Tutorials and Information
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By Steven A. Frowine
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Other works by Steven A. Frowine
Miniature Orchids (www.members.authorsguild.net/stevefrow/miniature_orchids_77055.htm)
Fragrant Orchids: A Guide To Selecting, Growing, And Enjoying (www.members.authorsguild.net/stevefrow/fragrant_orchids__a_guide_to_selecting__growing__and_enjoying_38984.htm)
Orchids for Dummies (www.members.authorsguild.net/stevefrow/orchids_for_dummies_38975.htm)
Moth Orchids - The Complete Guide to Phalaenopsis (www.members.authorsguild.net/stevefrow/moth_orchids__the_complete_guide_to_phalaenopsis_65954.htm)
Growing Tropical Slipper Orchids Under Lights (.pdf file free to download)(www.members.authorsguild.net/stevefrow/growing_tropical_slipper_orchids_under_lights_121823.htm)
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