Watering your plants properly is one of the most critical elements of plant care. Ask any gardener! It’s a skill to recognise when your plant is thirsty and how best to satisfy its needs.
In this guide, we’ll start by explaining why plants need water, then uncover the best way to water your plants and how often. Lastly, we’ll end off with some FAQs. If you want to skip ahead, use the table of contents below.
Why do plants need water?
Okay, this may sound self-explanatory. All living things, plants need water. No surprises there!
But the reasons why are not as obvious. According to the University of West Virginia, water comprises up to 95% of a plant’s tissue. It is also essential to several vital functions within the plant.
These functions include:
- Transpiration: this is the process of moving water through the plant. Water evaporates from the leaf surfaces, creating a pull to draw water up from the roots. Transpiration acts as a cooling mechanism for your plant.
- Photosynthesis: most of us are familiar that this is how plants convert light energy to chemical energy. Necessary inputs into photosynthesis are water, carbon dioxide and sunlight.
- Providing a medium for nutrients to be dissolved and transported. Dissolved nutrients move from regions of a higher concentration, like the roots, to areas of lower concentration, such as the stems and leaves.
- Providing cell structure and turgor (firmness). Without water, your plant’s foliage will appear wilted as cell walls become flaccid.
So you can see — water is undoubtedly an important component of many essential plant processes. Watering your plant too much or too little impacts your plant’s ability to carry out these functions. If you ever needed proof about how water can dramatically change the appearance of your plant, just check out the Rose of Jericho.
How should I water my plants?
The best time to water your plants is in the morning before the sun is at its hottest. The cooler air slows evaporation rates, giving your plant time to absorb the water it needs.
Here’s an easy three-step method to water your plants correctly:
Step 1: Use tepid, filtered water
Fill up your watering can with room-temperature water. Just like how many of us shrivel at the thought of an icy-cold bath, your plant prefers tepid water!
Some plants (i.e. Calathea Ornata, Hoya Linearis and Anthurium Clarinervium) are sensitive to mineral salts in tap water. For plant with sensitive roots, use filtered water or rainwater. Alternatively, let the tap water sit overnight, allowing harsh salts to dissipate.
Step 2: Water evenly and deeply
Water the potting soil evenly without getting foliage wet. According to Mississippi State University, “water droplets on leaves and stems plays a major part in plant diseases”. Fungal spores and bacterial cells that cause pathogens are often not released until they are wet for a certain period.
Interestingly, some leaves have adapted to be thick and waxy so that excess water forms into droplets and quickly runs off leaf surfaces. This adaptation prevents foliage from becoming a “petri dish” for pathogens.
When watering, soak your plant until excess water drains from the drainage hole. This method is called “deep watering”, which encourages roots to grow healthy and deep.
A common mistake is shallow watering for fear of overwatering your plants. Unfortunately, this results in water penetrating only the top layer of soil and quickly drying out. The idea is to water deeply less frequently rather than water shallowly often.
Step 3: Discard excess water
After watering deeply, you can let the excess water sit in the plant’s saucer for about 15 minutes. This gives your plant (especially deeper roots at the bottom) a little more time to absorb the water. After that, discard any water in its saucer.
Leaving the saucer filled for an extended period encourages waterlogged roots. This is detrimental to your plant as it invited root rot. (For more information, you can read this guide on overwatered plants.)
How often should I water my plants?
Ah, we wish there were a simple answer to this question! The problem, of course, is that how often your plant needs watering depends on several factors. These include:
- Climate, temperature, wind, and time of day. These factors affect the evaporation rate.
- Seasons and growth stage. These factors affect how much water your plant requires.
- What kind of plant (obviously some plants need more water than others).
- The volume of your container and how big your plant is.
- Type of soil.
So there is no straightforward answer. While it would be nice to say, water every seven days, exactly 20ml of water, this is just not realistic given the number of variables present. For this reason, watering on a fixed schedule is not a good idea.
Of course, this is also why it’s essential to develop the skill of noticing when your plant needs watering. Here are four guiding principles we use to help us develop these skills.
Four Guiding Principles on how often to water your plant:
- Know your plant’s native habitat. This is the golden rule for most plant care. For example, plants like Mother of Thousands and Mother of Millions have natural habitats in arid land. Therefore, they tend to be drought-tolerant and can wait until their soil is almost completely dry before watering. On the other hand, most rainforest epiphytes want to be watered once their top 1-2 inches of soil is dry. Some examples are Rhaphidophora Decursiva and Monstera Pinnatipartita. A good place to start understanding your plant’s natural environment is our plant guides.
- Always check the soil’s moisture level before watering. For example, if you are growing a Rhaphidophora Decursiva, check that the topsoil is dry before watering. For more drought-tolerant plants, you can wait until the soil is almost completely dry before watering. When checking the moisture level, either use:
- Your finger. If the soil is wet, you will see tiny soil particles stick to your fingertips.
- An ice cream stick. Place the ice cream stick into the soil and wait a few minutes. A darker colour indicates the stick is wet.
- Underwatering is more easily rectified than overwatering. So if in doubt, err on the side of underwatering!
- Monitor your plant to check for signs of under or overwatering. Then, adjust accordingly.
Unfortunately, many of the symptoms of underwatering are similar to that of overwatering. Common symptoms include yellow, browning or wilted leaves. To differentiate, check if the leaves appear crispy (underwatered) or if they are soft and mushy (overwatered).
At the same time, check the soil’s moisture level over 1-2 days.
Moist soil and yellowed leaves that are soft and mushy indicate overwatering. On the other hand, dry soil with crispy leaves means an underwatered plant.
Watering your plant is a critical component of care, but it doesn’t have to be complicated. Water deeply and evenly in the mornings for best results. Checking your plant’s moisture levels before watering is a far better method than watering on a fixed schedule.
Lastly, the golden rule of understanding your plant’s native habitat is critical. It helps you recognise when your plant is ready to be watered. If you are new to gardening, use our plant guides to help you get to know your plant’s needs.
Frequently Asked Questions
Why doesn’t watering on a schedule work?
It doesn’t work because it does not adjust for the many factors that change your plant’s watering requirements. These factors include climate and seasons, which affect the evaporation rate and your plant’s water needs.
For example, if you are in a hot climate with higher evaporation rates, you will need to water your plant more frequently than someone else in cooler weather. Another example is if your plant is dormant in winter, it requires much less water than in the growing months.
Nevertheless, watering schedules can be helpful as a rule of thumb. But always be flexible!
What causes a plant to become overwatered?
Overwatered plants are usually due to:
- watering too frequently, or
- using a soil that is too heavy which retains too much water.
The impact is that roots’ air supply is cut off, causing roots to decay or rot. For more information on overwatered plants and how to save them, read our guide here.
Deborah is a plant enthusiast and founder of Gardening Collective.