Watering Challenges

Your pot has no drainage holes:

If you plant directly into an enclosed container, you need to adjust your watering strategy. First, do not put a layer of gravel at the bottom of the container. When water ends up in this layer of gravel, it has nowhere to go. Stale water in a space that gets no fresh air is a recipe for growing bacteria that causes root rot. So skip the drainage layer and ensure that your plant is getting enough light to grow actively and use up soil moisture. As for watering, take care that you do not pour in a volume of water greater than a third of the volume of the soil—think of the soil like a sponge that can only hold so much water; any more and the plant would be swimming in a muddy soup. You can reduce the volume to a quarter or even a fifth of the total soil volume for succulents and cacti. Let the soil soak it all in, and the roots will use up that water before rot has a chance to set in.

The Watering Algorithm: Determining When to Water

Knowing when to water means knowing the amount of moisture a particular plant likes:

• Plant prefers evenly moist soil: The soil should be kept evenly moist at all times. The moment you see even the surface of the soil become dry, it’s time to water. Plants such as maidenhair fern, Fittonia (nerve plant), and peace lily enjoy evenly moist soil—mostly these are thin-leaved plants.
• Plant prefers partially dry soil: The soil should be allowed to dry down to an inch or two from the surface. Most foliage house plants are in this category.
• Plant prefers completely dry soil: The soil should be allowed to dry out completely before the next watering. All cacti, succulents, and thick-leaved house plants enjoy completely dry soil, because they store the water needed for photosynthesis in their bodies.

Remember: All watering techniques should be performed on plants that are actively growing. In daily light intensities below 100 foot-candles, even the most resilient “low light” plants will succumb to root rot!

The Pothos Test

You want to water a house plant “whenever the plant needs it.” The obvious question then becomes, how do you know when the plant needs it? Try this with a perky pothos (see overleaf): Put the plant in a place where it is getting bright indirect light—say, more than 200 foot-candles at the daytime high. Note how bouncy the foliage is—this is a properly hydrated pothos. Use a chopstick and gently poke around the soil to get a feeling for this evenly moist soil. Now, let the plant grow there, and notice how the leaves will be less bouncy after several days. Feel the soil again with the chopstick—now the soil probably has some dry pockets. This is the point at which you should water, but for the sake of this experiment, don’t do it yet. In a day or two more, the leaves will show visible signs of wilting—they are droopy. Now probe the soil with the chop-stick: It’s probably rocky, stiff, and compacted. What happened over these few days? The soil moisture was continually being absorbed by the roots and transported to the leaves, where some of the water was combined with carbon dioxide to produce sugar. While this happened, the soil particles were being pulled toward the roots. As these soil particles were literally sucked dry, they clumped together into rocky masses. At this point, just pouring some water into the soil won’t saturate all the dry pockets that have formed. In the future, for this pothos, you will watch for that first sign of droopiness to know when to water. While this experimental method works well with pothos because of its hardiness, some plants are so sensitive to wilting that they will suffer permanent foliar damage if their soil is left dry for even a day—maidenhair fern, for example. In those cases, instead of observing the plant for signs of dry soil, you should just directly check the soil. On the other hand, many house plants—snake plants and ZZ plants are examples—will not wilt in completely dry soil, and if you really waited until they did, they would be half dead! For these plants, do not aim to keep the soil evenly moist. Give them a thorough watering (and aerating) when the soil becomes bone dry.

The Well-adjusted Plant

Now that we’ve looked at both light and water, we can begin to understand how they affect plant growth. The following illustrations will help you understand light, watering, and, most important, plant adjustment.

LESSON

Managing the soil means understanding how water flows through the soil as you pour it. Understand that plants receiving a greater intensity of light will require soil remoistening more frequently. Compacted soil should be aerated before watering to facilitate a more even moisture distribution.

Many new plant parents mistake the effects of adjustment to a new home as the plant’s dying. A plant needs to let go of older foliage in favor of producing new foliage. Given enough time, the plant will reach an equilibrium point where foliage growth equals foliage loss—the plant is well adjusted—but this doesn’t mean it will stay looking the same forever. This is especially true of most tropical foliage plants, as they do not go into a true dormancy period, when all foliage dies back so that new foliage can grow in the next season from tubers or bulbs.

At this point, I hope you can understand why “don’t overwater” is not helpful advice. All it does is instill a fear of watering and an intolerance for the circle of life. If you ensure that your plant is getting the right kind of light, water it according to its moisture preferences, and manage its soil structure by occasionally aerating it to prevent soil compaction, it will be happy.

Add a healthy dose of acceptance that nature is about survival and not your aesthetic standards, and you will be on your way to an enjoyable plant parenthood journey.