“Keep it wet and give it light” leaves too much unexplained. Wetness depends on the container, medium and water level. Light depends on intensity as well as duration. Temperature varies through the day and across a growing area. Understanding those variables makes a species-specific care guide much easier to use.
Water quality and water level are separate decisions
Low-mineral water is a sensible starting point for many cultivated carnivorous plants; the United States Botanic Garden identifies rainwater and distilled water among the suitable sources in its general guidance. It also emphasises that growing requirements vary. That broad advice does not establish one chemical recipe for every aquatic Utricularia. US Botanic Garden cultivation guidance.
Record the source of your water, then separately record how it is used. A shallow reservoir beneath a pot, water covering the substrate and a freely drained basket describe different physical conditions, even when filled from the same bottle.
What an EC or TDS reading tells you
Electrical conductivity reflects the dissolved ions that allow water to conduct electricity. Its relationship with dissolved-solids concentration depends on the composition of the water, so conversion is approximate. A reading is useful for comparison, but it is not a complete chemical analysis. USGS explanation of specific conductance.
Keep the units with every measurement. A number expressed in microsiemens per centimetre is not the same quantity as an estimated parts-per-million display. Follow the meter's calibration and cleaning instructions, use the same method for repeated checks and record whether temperature compensation is involved. USGS measurement guidance treats equipment maintenance, calibration and reporting as essential parts of obtaining useful results. USGS: Specific Conductance.
In practice, compare your source water with the reservoir over time. An unexpected change warrants checking the water source, recent additions and the container. Do not turn one reading into a diagnosis of a particular nutrient excess or disease.
Light has intensity, duration and distribution
Lamp wattage describes energy use, not the amount of light reaching a leaf. Distance affects intensity, and a plant at the edge of a shelf can receive a different exposure from one directly beneath the fitting. PPFD describes the photosynthetic photon flux reaching a surface; photoperiod describes the hours of light. These are different measurements. University of Minnesota Extension: Lighting for Indoor Plants.
Record the lamp, distance to the foliage and timer setting. Where measured light data are available, include the measurement position. Avoid copying a lamp distance from an old article as though it guarantees the same exposure under a different fixture. A cultivation report is most useful when its growing conditions are considered together.
For natural light, note direct sun and shade through the day rather than relying only on a window direction. Buildings, trees and the season can change what reaches the plant. Introduce a new exposure progressively and assess subsequent growth rather than judging by the brightness perceived by your eyes alone.
Measure temperature where the plant grows
For a potted plant, measure near the foliage and consider the conditions around the container. For an aquatic, include the water temperature. Record maximum and minimum values instead of a single comfortable midday reading. This helps distinguish a brief peak from sustained warmth and reveals whether the plant experiences a cooler night.
Species-specific evidence is essential. A temperature recorded in one successful collection is a demonstrated example, not a proven optimum or survival boundary. Likewise, an unsuccessful trial may involve water, media and light as well as temperature. Keep those possible explanations separate in the record.
Judge the medium by its behaviour
Growing media provide a physical environment. Ask how readily water enters and drains, whether the material compacts and how much of the pot remains saturated at the chosen reservoir height. Ingredient names alone do not answer those questions.
Wyman's orchid-flowered bladderwort account describes changing media as he observed compaction and drainage problems, eventually favouring living sphagnum for many of the plants he grew. The lesson is to evaluate the medium within the watering system, while retaining the account's species-specific exceptions. Wyman, 2008.
Record ingredient proportions, the pot dimensions and the date of preparation. Distinguish living sphagnum from dried long-fibre sphagnum and from peat. When comparing recipes, check whether proportions are given by volume or weight; if the source does not say, preserve that uncertainty.
Change one understandable thing at a time
Start with the best documented method for the species and the accession's previous conditions. If growth declines, check the actual water level, temperature and light arrangement before adding products or changing every variable. Write down what changed and photograph the next new growth. A useful care record explains both the conditions and the plant's response.
Reviewed 22 September 2026. Numerical limits should come from the relevant species evidence; this guide does not impose a genus-wide pH, light, temperature or conductivity target.
