Arguably, the most important part of plant care is watering. Done incorrectly, your plant can deteriorate rapidly if its needs are unmet. There are unfortunately no hard and fast rules for watering for all plants, other than the fact that water is essential for life, and plant life varies a great deal globally. Fortunately, for the beginner, most houseplants are resistant to improper watering, and with a little practice it takes almost no thought to recognize a plant in need of a drink.
What is proper watering?
In almost every case, watering a plant should evenly saturate the soil until any excess water drains from the bottom. Underwatering and overwatering usually describe patterns in watering habits, not the quantity of water needed when watering. If you don’t fully, evenly moisten the soil in your plant’s pot, the plant’s roots may grow unevenly (leading to an unstable, unhealthy plant) or the water may evaporate away before the plant has a chance to absorb enough water with its roots.
For many tropical plants (with some exceptions), it is recommended to let a plant’s soil dry between waterings. If you keep a plant’s soil moist all the time, microbial growth will establish in your potted plant, some of which may cause root rot or other infections that could harm your plant.
Letting your plant dry out excessively also may harm the plant. Without water, a plant may show visible signs of stress, like wilting, dried or yellow leaves, and the roots may begin to die, too. So, it’s necessary to practice watering habits that are consistent, without doing so too regularly or infrequently.
Knowing when to water
Many plants will change in appearance as they run low on water. You may notice wilting or limpness in a plant that is usually fairly upright. Some plants become noticeably dull, losing a little bit of shine that’s typically there. For very fleshy, succulent plants, you may be able to observe shrively leaves or stems. The best way to learn to recognize these signs is to observe your plant every day, acquainting yourself with your plant’s change in appearance as it becomes thirsty.
Most times, the soil of your potted plant should be dry before you water your plant. You can use your finger to feel the soil at the surface and a couple inches below. You could also use a wooden chopstick to probe the soil and see how dry it is deeper down. I would recommend using a moisture sensor to learn about how dry your plant typically becomes before it shows signs of stress. Once you’re sure your plant is thirsty, you should give it a drink.
Water evenly, until the soil in the pot is saturated, and excess water comes out of the drainage holes.
Soil and drainage
Just as different plant species have different water needs, different pots and potting mixes influence water retention and your watering habits. Because of the nuances in pot composition, soil mix, and drainage, my advice for beginners is to experiment and observe how plants behave in different kinds of pots and soil types. At the beginning, try to use well-draining soil mixes, pots with drainage holes, and water when the plant is dry (or according to its specific needs).
Drainage holes. At the bottom of a planter, you may notice one or more holes to let excess water drain away from the plant while watering. By preventing water buildup, and by allowing air flow to reach the bottom of the plant’s soil, drainage holes help prevent overwatering and root rot in plants. Planters without drainage holes are tricky, because accidental overwatering just one time can be enough to kill a plant. You may choose to use a pot without a drainage hole as a decorative cover pot for a plant, by placing a plant with a different pot (with a hole!) inside it.
Types of pots. The most common types of material for planters are plastic, ceramic, or terracotta. Plastic pots are affordable, light and easy to carry (even with a heavy plant), and resistant to breakage. Ceramic pots are more expensive, heavier, and prone to breakage. Plastic and glazed ceramic pots retain moisture very well, while porous terracotta wicks moisture away from potting soil, drying relatively fast. It is easier to overwater plants in plastic or glazed pots, and easier to underwater plants in fast-drying terracotta.
Pot size. Usually, bigger pots dry out more slowly than small ones.
Soil composition. Any general purpose potting mix should be fine for beginner gardeners, but, again, we come back to this theme that it’s not possible to generalize about all houseplants. Dry-tolerant plants often do best in fast draining soil, and moisture-loving plants do better with soil that retains more water. Chunky, light soil (with bark chips, perlite, pumice, gravel, grit, sand, etc) drains faster than small-particle, dense soil (with ground peat moss, compost, coco coir, vermiculite, etc), which retains water. If you want to avoid overwatering, you can choose to pot your plant in a well-draining mix (such as cacti/succulent mix, or orchid mix). If you want to avoid underwatering, you may want to stick to a general purpose mix.
Sunlight and temperature
Generally, water evaporates faster from a plant’s soil and tissues in sunny, hot conditions; even in the same room, two identical plants may dry out at different speeds with one on the windowsill and the other opposite the window. Placement of your plants may affect your watering habits, as will different seasons, or different weather.
Watering schedules might seem tempting, reminding you to check up on plants regularly, but it’s better to observe signs of water stress in your plant, feel the soil, and consider the weather before you water.
Being able to consider (and manipulate) factors like sun, temperature, pot types, and soil mixes takes practice and some trial and error, but you can learn to personalize your plants’ care to suit your needs and preferences.
Examples of mindful watering
Imagine picking out a new plant from your local garden center. You really want a big floor plant to bring home, and you choose an aglaonema in an 8-inch plastic pot. The plant was grown in a greenhouse with lots of good sun and high temperatures, and grew in a peat potting mix. The location you chose for the plant gets moderate sun, and your house is cooler and less humid than the greenhouse. When you bring the plant home, the soil is still moist below the surface so you leave it alone for a few days to be sure not to overwater. A week goes by, and the plant still looks happy, and the soil is still slightly damp a couple inches down. After another week, you notice the aglaonema starts drooping, and the soil feels really dry. A few hours after you water it, it perks back up and you don’t notice it start to droop for another couple of weeks.
In a very different scenario, your friend gives you an orchid she propagated as a gift, planted in a terra cotta orchid pot in orchid bark. She tells you that she keeps the plant on a table because it dries out too quickly in the windowsill. She also says that the leaves start to flop down when it’s really thirsty. A couple of days go by and you notice the orchid is wilting. You water it thoroughly, and the next day it seems okay. After a few more days, you notice it wilt again, and the bark mix seems very dry. The roots look healthy, so you water it again. The next day, it’s back to normal.
Of course, it may not always be obvious when it’s necessary to water your plant. Pests, changes in temperature, moving, or other stress can complicate things. It may be helpful to keep a log of when you water your plant, and it might be fun to take note of other things happening with your plants, too (like a plant diary!). In addition to watering, plants have other needs, like light, fertilizer, and pruning, which take practice to get right, too. With good watering habits, you can begin to learn more nuanced parts of plant culture, and introduce more challenging plants to your collection!