How to Water Plants in Pots

Proper watering of the plants in your containers is crucial to having them perform their best. Once you get a little bit of experience, understanding when and how much to water becomes almost second nature.  However, when you are first starting out, figuring out how to make those plants happy can be pure frustration. The most common cause of early plant death is generally considered to be over-watering. Luckily for us, ninety percent of the plants out there will be happy if you follow these simple guidelines.

If you are planting in a pot, make sure there is at least one drainage hole in the bottom of the pot. Proper drainage is essential to happy roots, and happy roots are essential for happy plants. Pots that do not have proper drainage are very easy to over-water.

Rather than watering on a set schedule, check first to see if your plants need water. If your plant is in a pot, check the surface of the soil in the pot either by looking at it or touching it with your finger. Wet soil will be dark in color while dry soil will be lighter in color. For peat based soil mixes (the most common type), this means dark brown to black is wet, while ‘paper bag’ brown is dry.  If the surface of the soil is dry to the touch (or looks dry) water your plants. You may need to check your plants twice a day to see if they need water. Remember just because one pot needs water that doesn’t mean they all do. Differences in pot and plant sizes will impact how quickly a pot dries out.

When you water be sure to moisten the entire root zone. In other words, water until water comes out of the drainage hole in the bottom of the pot.  It may take as much as ¾ or a gallon of water to thoroughly water a 10 to 12 inch container. More plants are killed with a ‘cup of kindness’ rather than a good long drink of water. Plants that frequently receive a cup of water, seldom develop roots in the bottom 2/3’s of the container. When that daily cup of water is not available, the plant wilts and could easily be lost due to dehydration. 

Making sure the whole root zone is watered is important for two reasons. First it will encourage roots to grow all the way to the bottom of the pot, which means happier plants. Second, you won’t have to water as often if you water thoroughly.

Do not allow the pot to sit in water. Pots sitting in water will keep the soil in the pot too wet, allow excess water to drain away.

It is best not to water at night. If you water your plants too late in the day the foliage will tend to stay wet all night. Wet foliage at night makes a great breeding ground for disease. If your plant isn’t wilting and it’s after 6:30 at night you should be able to wait until morning to water. If the plant has wilted, go ahead and water that evening, its need for water outweighs the chances of catching a disease.

Here is your crib sheet: 

1. Be sure your pot has drainage holes
2. Water only when the top of the soil is dry
3. Water until water comes out of the drainage holes
4. Don’t allow your pot to sit in standing water

A few more tips on containers. Early in spring when your plants are smaller and the temperatures are lower you may only have to water every 3 or 4 days. As the plants get larger and the mercury creeps higher be prepared to water every day, with small pots or water “pigs” you might even have to water twice a day. You will also need to water more quickly if it is a windy day. Wind will cause pots to dry out more quickly, especially hanging baskets.

If you want to water less often use larger pots. Larger pots hold more soil volume. More soil volume means more water held in the pot. More water in the pot means watering less often. 

There are additives that can be added to the soil to help it retain more moisture. These can be helpful in long dry summers. If you do incorporate these additives be careful that you don’t over-water in spring when the pots are drying out less quickly, something I learned the hard way.

If you have dried your pot down to the point that the plant is wilting it may take more than standard watering practices to get the plant hydrated again. Commercial potting mixes can become almost water repellent if they get too dry. If you water your plant and it seems like all of the water is running down between the sides of the pot and soil ball, you may need to take steps to re-hydrate the soil. Fill a tub with water and soak your pot in the water until the soil has expanded and is no longer pulled away from the edge of the pot. Resume normal watering practices. 

If soaking your pot or basket in a tub of water is impractical you can also rehydrate by watering repeatedly. To do this water the plant liberally, it will probably seem like most of the water is running around the soil rather than soaking into the soil. Wait 30 minutes to an hour and then water again, it should seem like more water is soaking into the soil. Wait another 30 minutes to an hour and water one last time, by the third watering the soil should be hydrated and taking up water like normal again. This method works because the first watering starts to moisten the soil surface even though not much water soaks in. The following waterings then get the water to penetrate the soil ball and moisten the entire basket. Waiting between each watering allows the water you have already added time to soak into the soil and helps to make the soil less water repellent.

Most plants will do best when fertilized using a water soluble fertilizer every 7 to 10 days or a controlled-release fertilizer once a season.

For most plants the watering guidelines described above are perfect. There will always be those plants that prefer to be kept drier than this (cacti, some succulents, etc…) or wetter than this (Juncus (Rushes), Papyrus, Acorus, Elephant Ears (Alocasia, Colocasia) etc…) but for the most part these guidelines will fit the bill.

Container Gardening Guide

For more information on general watering practices read "Watering Container Plants."

For information on what to do if you have overwatered your plant read "Wait That Plant is Drowning!"