Is bottom-watering better than top watering? Sometimes, but it is not always practical. I bottom-water pots and containers when it is practical.
Because there are several advantages to bottom watering.:
- Your pots will never flood
- The soil will not compress and go hard and compact
- It makes it easier to reach even soil moisture
Your seeds, seedlings, and plants do not ask for much: light, nutrition, a growing medium, air, and water.
Today, we will look at how bottom-watering plants can help you better care for your plants and herbs.
Bottom-watering is a technique that has been used for decades.
We will look at bottom-watering seeds, seedlings, and more mature plants. Because plants have different needs, you also need to factor in the age and stage of development.
TL;DR: Bottom-watering helps the soil reach the correct moisture level throughout the pot and prevents over watering as the soil only absorbs what it can hold. Also, bottom-watering will help prevent pests like fungus gnats as the top layer of the soil does not flood and dries quicker.
What is bottom watering?
Everyone is familiar with top watering, where watering cans are used to water the pots from above. Bottom watering is a form of reverse watering.
With the bottom-watering method, you put pots with drainage holes in a partially filled container for the soil to absorb the water it needs.
Bottom-watering is quite common for houseplants, but it is less used for outdoor pots with herbs and vegetables.
And I have never understood why houseplant care would differ from looking after pots with, for example, herbs or tomatoes.
How to bottom water pots
Bottom watering is a simple method perfect for smaller plants and pots. Larger plants are more difficult to water as they are heavier to lift and require a larger container.
Follow the four steps below to master bottom-watering like a professional.
1. Partially fill a container with water
Fill the container with a minimum of 3 cm (at least an inch) of water. You will need to add more water (up to 10cm or a few inches) for larger pots.
If the tap water in your location is rich in chlorine, you should consider using distilled or filtered water. Signs of chlorinated water are cloudy or hazy water, any discoloration of the water, or a strong smell.
2. Place the pots in the container
Make sure to provide proper support. You do not want the plant to fall over. Now step away and let the plant sit and soak in the water.
3. Check moisture level every 5 minutes
Remove pots from the container when the soil’s surface is moist or changes color. From my experience, medium-sized plants need about ten minutes to soak up enough water.
4. Remove the pots from the container
Place plants in a sink or an empty container to allow any excess water to run off.
Using a sink is more straightforward. If you are using a container, I recommend putting a layer of LECA pebbles on the bottom and then placing the pots on top. Place pots back on their saucers after a few minutes.
3 Advantages Bottom watering plants
1. Prevent flooding of seeds and seedlings
Most people use a regular watering can when top watering pots and plants. You may or may not have a rose (like a shower head) on your watering can to gently spread the water.
Still, you may find that if you pour too fast, even what may seem like the smallest amount of water can overfill smaller pots. The potting mix will soak up water but not fast enough, and water spills over the edge.
And when this happens to seeds and seedlings, you risk displacing seeds and the young developing roots of seedlings.
The water you add risks shifting the soil as seeds and roots get flooded and start floating around.
When you instead water pots from the bottom, the soil’s surface is left moist but intact and undisturbed.
2. Bottom watering helps find the correct level of moisture
Top watering is easy and convenient, but it is not very exact.
When we water using a watering can, it isn’t easy to know when the potting soil reaches the correct moisture level throughout the pot.
And we don’t want to water too much. Or equally bad, not enough.
When you water pots from the bottom, the soil will soak up as much water as it can absorb. And any excess will run off as you remove the pot from the container.
You will know that you have reached the correct moisture level throughout the pots when you see the soil’s surface changing color.
Still, you should check on your pots every 5 minutes to avoid overwatering. Any excess will run off but overwatering is never healthy for a seed, seedling, or plant.
Overwatering soil can also lead to problems with pests and diseases like for example fungus gnats and leaf miners.
3. Bottom watering pots will not compress the soil of the potted plant
Root systems need water to develop. This is true for seeds, seedlings as well as established plants. But they also need air or oxygen.
Have you ever noticed that fresh soil shrinks in volume as you water the pot? Watering pushes the air out and makes it more compact.
- Over time, top-watering seeds, seedlings, and plants will compact the soil, making it harder for the plant’s roots to develop.
- On the other hand, bottom-watering plants will never create this downward pressure as the soil soaks up the water.
You are not adding water to the pot. You are making water available to be absorbed.
When bottom watering is better than top watering
Top watering is the most commonly used method for watering pots and plants.
The general principle is to water from the top. And watering at the base minimizes the risk of wet leaves that can invite pests and fungal diseases.
The plants are considered watered when the water runs through the pots and out the drainage hole. And it is easy to assume that the soil must be saturated as the water runs through the pots.
But this is rarely the case.
The water runs through too fast, and the soil does not have enough time to fully absorb what it can hold.
This is also why we may need to top water our pots several times and empty the excess after each watering. And this is one of the main reasons bottom watering is a superior method.
Bottom watering allows the plant to soak up water at its own pace. And depending on the quality of the potting mix and the size of the pots, the time needed can range from a few to well above ten minutes.
Should I bottom water seeds and seedlings?
There are exceptions to the rule, but established plants generally tell us when we are not watering them enough.
Plants get that limp look, leaves start to turn yellow, and the plant begins to lose its overall vigor. But most of the time, the plants forgive us and spring back when we give them water.
But what about young delicate seedlings or seeds about to germinate? That is another story. Seedlings and seeds are susceptible to dry outs as well as overwatering.
The seeds need the moisture level to be constant to germinate and sprout. Germination will fail if the top of the soil is dry.
Seedlings are also very sensitive as they develop. They have no reserves and need water to grow and establish strong roots.
Finding the correct watering level is essential to give the plant enough water to grow and thrive but not risk waterlogging the root system.
We want the soil to stay moist but not wet. And if the soil feels dry, we need to water it.
But if we are overwatering pots, we risk root rot and other problems as the plant’s roots are constantly wet.
You need to find a balance. You need to get it just right.
And the best method I have found to accomplish this is to always:
- start seeds in pre-moistened soil mix and mist with spray bottle
- bottom water seedlings.
Bottom watering starter pots with drainage holes
It is pretty simple to water pots from the bottom: at least starter pots and smaller pots and containers.
You fill a container with 3 centimeters (just over an inch) of water and place the pots in the bath.
The soil will absorb the water through the drain holes.
When the soil’s surface turns dark in color, and you can “see the wet”, you remove the pots.
Place them on a surface to allow any excess to run off through the drain holes, and then place them back on their drainage plate or saucer.
It is that simple.
Pros & Cons Bottom watering established plants
I recommend bottom watering all seeds and seedlings.
For bottom-watering to be effective you need well-draining soil to avoid creating a dense water-logged growing environment susceptible to root rot and fungal diseases.
But it does get a bit more complicated with larger-sized established plants. Here are four factors to take into account when bottom watering established plants.
Hard work bottom watering large pots
You could, of course, water all pots with drain holes from the bottom. But it is not very practical with larger-sized pots.
It is easy and convenient to bottom water small to medium-sized plants and pots.
It is, however, not practical to bottom water a 20-gallon container. It will be hard work, and it will also take a long time for the soil to absorb enough moisture.
Bottom watering leads to salt buildups
If you decide to bottom water your pots and containers, you should still water your plants from the top once every two weeks.
Watering plants from the bottom will lead to a build-up of salt in the soil over time. This is also true when you water pots on saucers from the top. This is, however, not an issue for seeds or seedlings during the short time they need to develop.
The trick to manage salt levels in your potting mix is to every now and then use top watering to let the excess drain out of the drainage hole in the bottom of the pot. You simply flush the salt build-ups from your soil.
For mature and established plants, it is important to not only bottom water the pots. You should alternate between the two methods.
Watering root-bound plants from the bottom
Root-bound plants cannot soak up water effectively when watered from the bottom.
These plants need to be re-potted as they are “all roots”.
It is, however, easy to miss that a plant needs to be re-potted when bottom watering, as pots often get the same amount of time to soak up the water.
Bottom-watering plants with hard and compact soil
Compact soil will not absorb water effectively. Your plant will sit in the water, and when you remove it, you will see water runoff from the drainage holes.
But it will only be the very bottom of the plant that has absorbed water leaving the rest dry.
Bottom-watering in our herb gardens
As far as I am concerned, there are no real disadvantages to bottom watering.
There are things to be aware of, but I believe the advantages far outweigh the potential risks.
And when we are dealing with seeds or seedlings in starter pots, where we need to be extra careful, it is easier, and bottom watering does save you time.
Simply place all your small to medium-sized plants in a tray with an upright edge and add water. Now the pots will absorb water, and you can remove them as they have had enough water.
But as soon as the seedlings turn into young plants, I start watering using a watering can with a rose.
Why?
It is simply a matter of convenience. It is hard work to place larger pots in water baths. I also use a moisture meter that helps me check the water level and moisture when unsure.
And it takes a lot longer for the soil of the larger pots to absorb enough water to turn color and be ready.
I do, however, have some larger pots that I water from the bottom mainly because the plant spreads to cover the entire area of the pots (thyme) or prefers to dry out between watering and then to be watered thoroughly (oregano).
But I have to admit that I rarely use the bottom watering method for pots larger than 15 centimeters (6 inches) in diameter.
Frequently asked questions
Can bottom watering be bad for my plants?
When you water pots from the bottom, you still need to ensure that the pot does not sit in water for too long.
Generally speaking, a bit dry is preferable to soaking wet. It is also important to flush the soil with large quantities of water now and then to get rid of salt buildup in your soil.
Can you overwater with bottom watering?
Yes, remove the pot from the water bath when the soil’s surface changes color.
Check every 5 minutes or so to make sure you do not overwater.
To protect against overwatering, allow the excess water to run off before you place the pot back on its saucer.
Can you bottom water terracotta pots?
You can bottom water terracotta pots, but it takes longer as terracotta is a porous material that absorbs water.
It is more efficient to bottom water plastic and composite pots.
