Have you ever watered your plants thoroughly, only to come back later and realize that the soil is still dry in some areas? This frustrating issue is more common than you may think. There are several causes, from compacted to hydrophobic soil that repels water rather than absorbing it. Luckily, there is a simple solution to deliver the water the roots need—bottom watering.
Bottom watering evenly saturates the soil, keeping your potted plants happy. To bottom water, start by testing the soil moisture levels. Fill a tray with water and place the pot inside, allowing the soil to draw up moisture through the bottom. Drain and return the pot back to its home.
Although the process is simple, there are a few essentials you need to know to get it right. Follow the easy steps below to become a bottom watering pro.
The Benefits of Bottom Watering
Watering from the top is the most common watering method. It’s convenient and quite self-explanatory. However, it isn’t always best for the health of your plants.
That’s where these benefits of bottom watering come in:
Keeps Leaves Dry
When watering from the top, moisture often sits on the leaves and between the stems. While this can help rinse off debris, it can also lead to disease issues when done too frequently. If the moisture does not evaporate off the leaves, it can lead to rot that spreads to the rest of the plant, potentially killing it.
African violets (Saintpaulia ionantha) are a great example. These plants have sensitive leaves that become discolored when watered overhead, especially with cold water. The fine hairs on the leaves trap water that sits on the foliage, resulting in serious damage.
Bottom watering avoids all these issues, keeping the leaves dry but the soil moist. The same applies to other plants, particularly those that are prone to rot or placed in low-light areas.
Ensures Even Saturation of Soil
When top watering, it’s tough to ensure the distribution of moisture is completely even. This problem can leave you with dry soil patches, even if the soil appears well-watered. That dryness will affect the surrounding roots, leading your plant to start showing symptoms of underwatering.
With bottom watering, this usually is not a problem. As long as you leave the container in the water for long enough and have the correct soil, water will slowly travel upwards to parts of the soil that need it. Since it’s moving under forces that attract it evenly, it distributes evenly, leaving no dry spots.
Prevents Problems With Fungus Gnats
Fungus gnats are a particularly nasty breed of insect that thrives in moist soil. Although the adults are usually seen flying around plants, the larvae reside in the soil while they develop. Wet topsoil encourages fungus gnats that settle in your pots and become incredibly difficult to remove.
Water doesn’t have to reach all the way to the top when bottom watering. As long as the bottom layers where the roots sit are moist enough, the top layer of soil can stay dry without any impact on plant health.
Therefore, bottom watering can be an excellent way to protect your plants from fungus gnats while providing them with enough moisture to live.
How to Bottom Water Step-By-Step
Now that you understand the benefits, let’s look at how to get bottom watering right:
1. Check the Soil for Moisture
Regardless of your technique, the first step you should always complete when watering is checking if your plant actually needs water.
Unless you keep your plants under an extremely controlled watch, environmental conditions can easily cause moisture changes in the soil. For example, a change in humidity can cause faster evaporation, leading to a depletion of the water content in the soil. The same thing can happen due to temperature changes.
Ignoring these factors can lead to problems with under or overwatering.
While plants love moisture and need it to stay alive, too much water will cause more harm than good. Excessive water in the soil can cause fungal problems like root rot, drown the roots, and lead to stunted growth. That’s why it’s vital to check moisture levels first before you consider watering.
The best way to check for soil moisture is using the simple ‘finger test method’. Place your index finger into the soil up to the second knuckle.
If you can’t feel any moisture, then it’s likely time to water your plants. If you can, then it’s best to wait a bit longer.
This will depend on the type of plant you’re growing though, as some plants like to dry out completely before watering again (succulents are a great example).
2. Use the Right Water
Once you’ve determined that it’s time to bottom water your plants, the next thing you’ll need to do is to choose your water supply. Like plants, not all water is created equal. Different water types have different impacts on plants, usually over time with long-term use.
These are the water types to consider and how they will influence plant growth:
Hard Water
Hard water has a high mineral content, containing an excess of calcium and magnesium salts. Over time, these salts build up in the soil, negatively impacting root growth and health.
It also impacts plants sensitive to pH changes outside their preferred range, causing leaves to brown and wilt. The impact of hard water use is also visual, leaving patches of white on the foliage.
If your tap water contains an excess of these salts, it’s best to avoid using it to water your plants. While the effects may be minor in the short term, they can become seriously damaging with long-term use.
Greywater
Greywater is water that has already been used in the house and collected for reuse. This type of water is potentially worse for your plants than hard water, depending on its source.
For example, kitchen water has a high chance of containing things like grease, which can suffocate roots over time. Additionally, if you use non-biodegradable detergents, the increased chemicals in the soil from greywater can wreak havoc if not controlled.
While recycling water is great for the environment and your water bill, make sure you consider the source of the water before using it on your plants.
Distilled or Filtered Water
Distilled water is one of the best choices for your plants. Distilled water is pure and pH neutral, so it does not alter your soil significantly outside of giving plants the moisture they need.
Understandably, few people have the time or resources to buy distilled water whenever they want to water their plants. The best alternative is filtered water. It’s much easier to get your hands on because you can simply install a filter at home and get your water straight from the tap.
A filter will remove the majority of the impurities in the water that can cause problems for your plants. Unfortunately, it won’t cure hardness, but a healthy top-watering session every couple of weeks should flush accumulated compounds away.
Rainwater
Rain is nature’s gift to plants and is still the best source of hydration. During the rainy season, you can collect rainwater as it falls directly from the sky into a barrel. Avoid collecting rainwater from the gutter, as it may be contaminated with rust or bird waste.
You can use this freshly collected rainwater to bottom water your indoor plants. It will give them a taste of nature with highly dissolved oxygen and nutrients.
However, watch out for weather forecasts regarding potential issues with acid rain in your area. Also, if you live near coastal areas, it’s possible that rainwater may contain salts that can be bad for your indoor plants.
3. Prepare a Planter and Tray
Once you’ve picked the water type of choice, you can gather your tools.
The most important things you’ll need are a planter and a bowl or tray:
Planter
To properly bottom water your plants, you’ll need a planter with a drainage hole at the bottom. For the soil to transfer water from the bowl or tray into the pot, there has to be somewhere for the water to pass through. Drainage holes are also essential in preventing root rot, so this is a step that shouldn’t be skipped.
You can opt for a ready-made planter that comes with a drainage hole or drill holes in your planter yourself. Be careful not to make the hole too wide or crack your planter.
Tray
The second essential component of bottom watering is a tray. It should be larger than your container and able to hold enough water to saturate the soil. If you don’t have a tray, you can also place your pots in a slightly filled sink or bath instead.
Your bowl or tray should hold at least half a gallon of water (just under 2 liters), potentially more for larger containers. Depth is also essential here as once you put the pot into the bowl, it will displace some of the water. If your bowl is too full, the water will simply spill out and leave a mess rather than absorb into the pot.
4. Mix in Fertilizer
One of the best things about bottom watering is how easy it makes applying fertilizers to your soil. Simply mix in the amount of fertilizer you want with the water and proceed as you usually would. As long as you mix evenly, the fertilizer will distribute evenly throughout the soil as the water is taken up.
One disadvantage is that some nutrients will be left in the basin after taking the pot out of the water. Still, it’s important to be sparing when it comes to fertilizer. Although the soil needs nutrients to keep the plants healthy, overfeeding can lead to several growth problems.
Fertilizing too often can lead to a nutrient imbalance, as well as salt build-up in the soil. These issues impact root health, limiting moisture uptake and leading to wilting and scorched leaves.
I like to apply fertilizer at half strength first, especially when bottom watering as the excess doesn’t get flushed out of the container as easily.
5. Place the Pot in the Tray
When you’re prepared, simply place the pot in the bowl or tray and watch the magic happen. The soil will slowly start to absorb moisture from the bottom, traveling upwards until the soil is completely saturated.
Different soil types absorb water at different rates. Bigger pots will also require more time to take up as much water as required. For this reason, the amount of time it will take your plant to get all the water it needs may differ.
How Bottom Watering Works
Ideally, you’ll want to stop before the water soaks the top of the soil completely. After ten minutes, dig your finger into the soil. If the layer down to your first knuckle is moist, you can take the pot out. Otherwise, leave the pot for longer.
This process typically takes about 10-30 minutes, depending on the soil dryness, pot size, and soil type.
6. Drain the Excess
Once you’ve checked that the soil is sufficiently moist, lift the pot to start draining the excess water. Simply take the pot out of the bowl and put it in an empty bowl or sink for a few minutes to let any excess moisture drip out the bottom.
It’s crucial not to leave your plant in the water bowl for too long and allow it to drain properly after. Skipping this step can lead to waterlogging, potentially root rot, and other issues.
7. Top Water Frequently
Bottom watering is an excellent technique, but you shouldn’t rely on it alone. Top watering is still important because it’s the best way to flush the soil periodically.
A good top watering session will take away most of the excess minerals and salts from frequent watering and fertilizing, keeping the roots happy.
It’s best to water the plant from the top every four or five times you bottom water it.
Here’s how to do it:
- Place the planter (with a drainage hole) in a sink or tub.
- Run water through the soil in the planter using a bowl or tap, focusing the stream on the soil only. Rotate the pot to ensure all parts of the soil are flushed.
- Allow the pot to drain thoroughly after watering.
- Afterward, place the pot in a saucer or tray to catch any runoff still dripping from the bottom of the plant before moving the plant back to its original home.
Is Bottom Watering Worth It?
Considering all the steps involved, especially compared to top watering, you might be wondering if bottom watering is worth it. After all, top watering your plants seems a lot more straightforward.
However, top watering can leave parts of your soil dry, negatively impacting root health. Bottom watering is worth it as it distributes water evenly throughout the soil. It’s also a great choice for plants like African violets that do not like water on their leaves.
Even though bottom watering is extremely beneficial, it needs to be done right by following the steps I’ve talked about. While it can provide a wide range of benefits, bottom watering the wrong way will leave you with waterlogged soil and weak roots.
Conclusion
Bottom watering could be a great approach if you constantly get dry, unevenly watered soil. Although it’s less straightforward than top watering, it only requires following a few quick steps that are easy to repeat once you get the hang of it.
If you decide to try your hand at bottom watering, always remember to flush out the soil a few times a month to prevent nutrient buildup.
Written by Alexander Picot, Reviewed by Madison Moulton
