We tend to water our plants from the top as that is a common practice. But you can also water plants from the bottom which could be beneficial to some of them.
It is better to water plants from the top because it flushes excess salts and minerals that build up in the potting soil over time. Watering plants from the top helps you get better control over the watering so you don’t overwater.
There are some benefits of watering plants from the bottom that I will show you below. You can then decide if using a combination of both watering methods is beneficial for your plants.
I conducted a survey with my fellow gardeners and experts whether it’s better to water plants from the top or bottom. You can see the results below where 67.2% preferred to water from the top while 32.8% are watering from the bottom.
Benefits of watering plants from the top
Better control over the watering
It’s much easier to control the watering when using a watering can. You can water just near the base of the plant and avoid splashing water on the foliage.
You will know how to give your plants a deep watering because you see the water draining out from the holes at the bottom of the pot. This means that the potting soil has received plenty of water for the plant roots.
You can get even better control of the watering if you use drip irrigation or a soaker hose. You can set up a timer to ensure the right amount of water is given to the plants at the right time.
Removes salt and minerals from the soil
You will add organic fertilizer to your potting soil. This could be a slow-release fertilizer or a liquid fertilizer. As the nutrients get used, there will be some salts and minerals deposited into the potting soil.
These materials will build up over time and can be toxic to the plants. When you water the plants from the top, it will flush out these salts and minerals.
You should avoid using hard water to water the potted plants because the water itself would contain salts and minerals that would deposit into the potting soil.
Easy method to water the plants
It’s very easy to water plants from the top with a watering can. You can target the water at the plant base and ensure the potting soil is watered well.
You could also use drip irrigation or a soaker hose if you have many plants in your garden. With the help of a timer you can provide a precise amount of water to the plants and at the right time.
Drawbacks of watering plants from the top
Can attract pests and diseases
One of the biggest problems with watering from the top is spraying water on the plant foliage. This can create a humid environment that attracts pests and fungal diseases.
You need to be very careful to only water at the base of the plant. It also helps if you water in the morning so the excess water evaporates once the sun comes out.
The problem can be solved by using methods like drip irrigation or soaker hose that ensures watering only happens for the soil rather than the foliage.
Leaches nutrients from the soil
The potting soil contains nutrients from the compost and organic fertilizer you add to it. When you water from the top, the slow-release fertilizer will also release nutrients into the soil.
But the watering will also leach the nutrients out of the soil through the drainage holes. The potting soil will keep losing nutrients with each watering.
So you need to replenish the nutrients by adding compost and organic fertilizer every few weeks to the potting soil.
Can compact the soil
The potting soil you use for container gardening will be light and fluffy because of the materials like perlite, vermiculite, and peat moss.
But the more you water the potting soil, the more compact it will get. So after some weeks of watering, the soil will become a bit hard.
This means the water will not flow as well as it did when you started with the potting soil. It may also reduce the airflow through the soil.
Can displace the seeds
If you start growing plants from seeds you will use a seed-starting tray. If you water from the top, there is a risk that you displace the seeds from their original position in the soil.
This can especially be a problem for tiny seeds as you will find it difficult to notice they have been displaced.
Benefits of watering plants from the bottom
Lower risk of pests and diseases
Since the water does not splash on the foliage, there is less risk of pests and diseases. There is no moist environment that these pests and diseases are attracted to.
You do need to be careful not to overwater the potting soil as that can cause moist conditions in the soil itself and attract fungal diseases.
Does not compact the soil
Since the water is not falling on the soil’s surface, it does not add pressure on top of it. This helps to avoid the compaction of the soil.
The soil will be fluffy and help with good circulation of moisture, nutrients, and air to the plant roots.
Will help start seeds without displacing them
You may start seeds in the potting soil and need to water them. If you water from the top it can displace the seeds especially small ones.
Watering from the bottom can help avoid this problem as it will not cause the seeds to move around.
Does not leach nutrients from the soil
When you water the potting soil from the bottom it will not leach out the nutrients. They will tend to stay in the potting soil and be available longer for the roots.
So you will need to spend less time and money adding slow-release fertilizer and compost to the potting soil.
Drawbacks of watering plants from the bottom
Difficult to water the plants
It can be difficult to water plants from the bottom because you need to place the container on a saucer or take it to the kitchen sink or tub.
You also need to know exactly how long to keep the container soaking the water. You need to check the potting soil every 10-20 minutes if it’s absorbed the required moisture.
Can cause build-up of salts and minerals
You will apply a slow-release fertilizer or liquid fertilizer to the potting soil. The plant roots will absorb the nutrients, but some salts and minerals will be left in the soil.
These will build up over time and can cause harm to the plants because they will start to dehydrate with excess salt.
Can lead to overwatering if not careful
You need to be careful how much time you leave the potting soil to absorb the moisture from the bottom. If you leave it for too long, the roots will remain in moist soil.
This can lead to fungal issues like root rot that will damage the roots and cause the plant to die.
Can be a time-consuming process
You will need to monitor the plants every 10-20 minutes when watering from the bottom. You need to check whether the potting soil has absorbed the required moisture.
You don’t want to leave the plant for too long in water because the excess moisture can cause overwatering.
How to water plants from the top
This is the most common way people water their plants whether in containers, raised beds, or in-ground gardening.
You can use a watering can if you have a few container plants. Water the potting soil near the base of the plant and avoid splashing it on the foliage.
If you have many plants it can get tedious using a watering can. You can use drip irrigation or soaker hose for this. Avoid using a garden hose as you will drench the plants with water and we want to avoid that.
If you use a timer you could set it up with the drip irrigation or soaker hose. The watering will start at the preset time and for the required time.
How to water plants from the bottom
To water plants from the bottom, you could use a tray, saucer, kitchen sink, or bathtub. You place the container in any of these making sure that the pot is submerged in at least 1-inch water.
If you have rocks at the bottom of the pot you want to ensure the pot is submerged so the layer of rocks is lower than the layer of water.
How long you need to keep the pot soaking the water depends on the size of the pot and the plant. You can check the potting soil every 10-20 minutes to see how much water is absorbed.
You may see that the surface of the potting soil has started to appear moist. Or you can stick your finger 1-2 inches inside the soil. If the soil sticks to the tip of your finger it means the potting soil is moist.
Once sufficient moisture has reached inside the potting soil you can remove the pot from the tray, kitchen sink or tub.
Place the pot on dry ground for a few minutes to drain out any excess water from the soil that it does not need.
Even if you use bottom watering for the plants, it’s good to water from the top once every 3-4 weeks. This will help leach out the salt and minerals built up in the potting soil during that period.
How often to bottom water plants?
You need to bottom water plants when the potting soil has dried out. You can check this by sticking your finger 1-2 inches into the soil. If the finger comes out dry, it’s time to water the plant.
It’s the same whether you top water or bottom water the plants. You need to know the water needs of the plant before doing this.
Some plants prefer that the potting soil becomes completely dry before you water it again. Some plants prefer that the soil is kept a bit moist at all times.
Can all plants be bottom watered?
All plants can be bottom watered as long as you can lift the pot and place it in a tray, saucer, kitchen sink, or bathtub.
Some plants such as African violets lose leaves if water is splashed on the foliage. Such plants are very suitable to be bottom watered. Some other plants that prefer bottom watering include succulents and ferns.
Some people prefer to bottom water their indoor potted plants and top water their outdoor potted plants.
How to fertilize when bottom watering
One of the problems when using bottom watering is you can’t use a slow-release fertilizer on top of the potting soil. The potting soil needs to be watered from the top to release the nutrients into the soil.
One solution is to dig a little into the potting soil and add the slow-release fertilizer but you risk damaging the roots.
Another solution is to use a liquid fertilizer instead. You can spray this fertilizer on the foliage and add it to the water used for bottom watering.
You could also water from the top after adding a slow-release fertilizer on top of the potting soil. An occasional watering from the top will help get the nutrients into the soil. It will also leach out the salt and minerals built up in the soil.
Can you overwater plants by bottom watering?
You can overwater plants by bottom watering if you keep the pot in the water for more time than necessary. The potting soil will keep absorbing the moisture the longer you keep it.
You want to check the potting soil every 10-20 minutes depending on the size of the pot. Once you see that the top of the potting soil is moist, you need to remove the pot from the water.
You can stick your finger 1-2 inches into the potting soil to check for the moisture. If the tip of your finger feels moist, the potting soil has received plenty of moisture and time to take the pot out of the water.
How long does bottom watering take?
Bottom watering can take 10 to 40 minutes depending on the amount and texture of the potting soil. A large pot with more potting soil will take more time than a smaller one. Potting soil with good absorbing texture will take less time than one with poor absorbing texture.
Once you start bottom watering, you need to check the moisture in the potting soil every 10-20 minutes. You want to stop the bottom watering once the top or the layer just under the surface of the potting soil is moist.
You can put your finger 1-2 inches inside the potting soil to check if the layer under the surface has turned moist enough to stop the watering.
What size plants can I bottom water?
You can bottom water small and medium-sized plants. It’s easy to lift these plants and place a tray underneath. Or move these plants to the kitchen sink or bathtub to bottom water. I don’t recommend bottom watering large plants as it’s difficult and takes longer.
What are the different ways to use bottom watering?
The simplest way to use bottom watering is to take your pot and place it on a tray, saucer, kitchen sink or bathtub. The pot should have drainage holes and should sit in at least 1-inch of water.
You have another option of using a self-watering container for your small and medium plants. This container has a reservoir at the bottom that is connected to the pot via a wick.
You put potting soil and growth the plant in the top compartment. You fill the bottom compartment or reservoir with water. The potting soil absorbs the moisture from the reservoir using the wick.
Using an Olla is another method to water plants from the bottom. An Olla is a narrow container that is made of porous material like terracotta.
You insert the Olla in the center of the potting soil so only the top is exposed. You then fill the Olla with water. The porous nature of the Olla causes it to release moisture that the potting soil will absorb.