If we had to name the biggest concern among our customers, it would certainly be watering their treasured plants properly. And to be fair, watering issues are likely the most common cause of problems in indoor gardening, so we've created a simple, easy-to-follow guide for our customers.
In order to create a proper watering schedule for your plants, you'll need to take several factors into account:
Consideration #1: Environment
It might seem self-evident, but beginning gardeners, especially, often fail to consider that their homes often present very different conditions from those plants were grown in prior to purchase. Cooler temperatures, more (or less) sunlight, and the method of watering may impact your plants' water requirements.
At Specialty Tropicals, we generally grow our tropical plants under the following parameters:
Temperature | Daytime Maximum: 90 F / 32 C Nighttime Minimum: 65 F / 18 C |
Light Intensity | 1,000-1,300 lumens ("Bright shade", provided by 70% shade cloth overhead) |
Photoperiod | 10-11 hours per day fall-winter / 13-15 hours per day summer |
Humidity | 70% |
Watering | Aroids, Begonias, Foliage Plants: 1-2x daily bottom watering via capillary mat Cacti & Succulents: 1-2x per week bottom watering Native American Carnivores: Constant standing in one inch of water Nepenthes: 1-2x daily flush until pots drain freely |
In short, know your own conditions.
Consideration #2: Proper Potting
The size and material of your plant's container has a big impact on its water needs! Plastic nursery pots don't allow moisture to evaporate from their walls, while unglazed ceramic materials like terra cotta, do. A small plant in a large pot has a greater reserve of moisture available in its surrounding medium than a larger plant in a smaller container. Because of this, we often advise against over-potting (for instance, moving a plant from a 4-inch to a 10-inch container), because it greatly increases the risk for overwatering, unless the schedule is adjusted to take into account the moisture-holding capacity of the soil. Likewise, if a plant has mostly filled its container and tends to wilt between waterings, the simplest way to cure this is by moving it up to a pot a couple of inches larger.
Just as important as pot material and size is soil composition. Actually, we often use the term "medium", because strictly-speaking, few of our plants are grown in actual soil. For the majority of tropicals, we use a medium containing either milled sphagnum peat moss or coco coir as a base, with the addition of perlite, vermiculite, fir bark, or other materials that provide air flow and prevent compaction of the medium arounds the plants' root systems. The proportions of these ingredients vary, depending on the class of plants. Aroids, for instance, typically get peat, fir bark and large, chunky perlite (a volcanic mineral "popped" under high pressure to produce a very lightweight soil amendment, sometimes confused with styrofoam.) Begonias get lots of perlite and peat, but no bark. Some species need a finer medium as seedlings or explants from tissue culture, moving up to a "chunkier", more open medium as they mature. Soil that lacks coarse materials holds more moisture, has less opportunity for drainage and airflow around the roots, and is more prone to compaction than media composed of mostly peat and vermiculite (perlite's much finer, flakier cousin.) All of these variables need to be taken into consideration, in order to ensure that plants are neither starved for water, nor sitting in wet, stagnant soil which quickly leads to root rot.
Consideration #3: Frequency
In general, our rule of thumb is this: heavier watering with less frequency is safer than frequent, light watering.
When plants are watered sparingly (even if it's every day), only the upper half or so of the soil gets truly saturated. And while peat is an important component of most potting mixes for lots of great reasons, it does have a drawback: when it gets thoroughly dry, it's surprisings resistant to water! If you take a handful of fully dried peat and apply water, particularly at less than room-temperature, you'll find that the water initially sheds off the peat like water off a duck's back. Because sphagnum peat is a once-living plant itself, its cells need time to rehydrate in order to capture and hold moisture. When you have a plant in a peat-based medium and water only enough to partially soak the pot, the remainder of the medium becomes hydrophobic, and it takes a good deal of water exposure to bring it back to a state capable of holding water reserves for your plants. A common sign of this happening is that the pot seems lighter than you'd intuitively expect, with tall plants often becoming top-heavy and falling over easily. When this happens, you need to set the entire pot into a bucket or other container of water for at least an hour, until it has gained weight, then allow it to drain well, and increase the amount of water given each time your care for your plants.
A good watering for most non-succulent tropicals will cause water to pour freely from the pot's drain hole(s). If you can water your plant in its place and find no need for a saucer, you're likely watering too little, too often. Consider putting plants into saucers or drip trays, or moving them to the sink or bathtub to drain after watering. And if using saucers, be sure to drain any standing water an hour or so after watering.
The exceptions to these guidelines are plants like orchids and Nepenthes, air plants and other bromeliads (which all need either soaking or thorough, long drenches with water outdoors or over a sink or tub) and succulents (which need thorough watering, but far less often than most other indoor plants, often only once every week or two.)
Consideration #4: Method
Overall, bottom-watering is great for most plants in the commercial production nursery, because it provides uniform watering without wetting leaves, which can often lead to water-spotting or fungal disease in a situation where plants are grown close together with less air circulation that you'd have in your home. It also allows us to uniformly water thousands of plants every day, to ensure that every customer receives a high-quality, well-grown specimen. Unfortunately, it's not always practical at home, especially for those who have a large collection to tend. For some species, like the tropical Nepenthes and most of our orchids and bromeliads, overhead flooding provides more natural water patterns, as well as helping flush out mineral salts that can be particularly toxic to these plants.
Consideration #5: Water Quality
All of our plants receive pure rainwater captured from the roof of our main retail greenhouse and pumped onto capillary matting on their benches, or else reverse-osmosis filtered water as a backup. Both are <40 ppm (parts-per-million) of dissolved solids, meaning they carry very little mineral content that certain plants are sensitive to. Even our public water supply here in rural NC is below 40ppm, and suitable for most plants, but some home growers will need to consider a filter or store bought distilled water to keep their plants healthy. The right watering pattern with the wrong water still won't result in healthy plants. Many people make the mistake of assuming that well water is always plant-safe but depending on your region of the country, well water or public water supply may be either perfectly fine or potentially deadly to your leafy friends. The only way to know is a water test, which is often available for little or no cost via your local agricultural extension agent, college or university lab. In our area, we receive semi-annual reports of water analysis for the municipal water supply, and our own tests confirm those values are reliable. If you're serious about more sensitive species, an electronic TDS (Total Dissolved Solids) meter is a great investment, and a good one can be purchased online for well under $50.
Plants receiving top-watering typically require less frequency than those grown on capillary mats. Also, temperature and humidity have a big impact on plants rate of transpiration, which is the rate at which plants lose moisture to their environment. While humidity in the home is almost always lower than in our greenhouses, so is average temperature, which means that on average, plants will require less water, less-frequently in your home than in our facility.
Consideration #5: Observation
Watch your plants' condition, and they will "tell" you when they need water. Just as blood pressure is an important vital sign in animals, plants require what we call turgor pressure--that's the fluid (hydraulic) pressure that keeps their cells plump and stiff and allows them to stand up straight. Too high, and your plant will become soft, mushy, and quickly rot if no action is taken. Too low, and your plant will wilt like Aunt Myrtle's corsage at an outdoor church supper in the South! If you see one or two dead leaves at the base of your plants on occasion, that's perfectly natural--older leaves of all plants due as the plant produces new ones, and no concern is needed. But, if you see dead leaves constantly, that's usually a sign of watering trouble. See Consideration #3 (Frequency) above for more details on creating a good watering plan.
Conclusions
Much as we might hope, there is no "one-size-fits-all" watering plan for healthy plants. Lots of environmental conditions impact their need for water, just like field crops on a farm. The advantage of indoor gardening, however, is that you can more closely control those conditions, and you can adjust your watering schedule in response to changes. Know your plants' condition by observing them often. Respond to changes in their condition by considering their water needs, and adjust your schedule and amount of watering based on your individual plants' requirements, their potting medium and container, and environmental factors like temperature, light, and humidity. Choose an appropriate potting medium that works well with your growing routine, and when in doubt, water more, less often for healthier plants!
A Final Note
We're always happy to help our customers with advice before and after your purchase!
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