Best time to water plants (and how you can know)

If you are looking for a short answer, the best time to water plants is early morning between 5am and 9am before the day gets hot. Watering early allows leaves and foliage to dry before being exposed to direct sunlight and the water can be absorbed deep into the soil without risk of evaporation.

And if you cannot water in the morning, you should instead water late afternoon or early evening. The message to take to heart is that plants do need water and sunlight. But not at the same time.

How to know if you need to water

Thyme and Thai basil plants with watering can and spray bottle
Thyme and Thai basil plants have different watering needs

Watering pots and plants early in the morning is always good advice. And during the height of summer we pretty much need to water all pots and plants every morning.

And some days will not even once a day be enough for thirsty herbs and vegetables like tomatoes. 

But what about early spring or late summer? Times of the year when the temperatures are warm as in mild rather than hot. 

Do you still need to water your plants every morning?

The answer is that it depends. And here are our top 6 tips of how you can learn to tell when it is time to water your plants.

6 ways to know when it is time to water plants

Using our tips will help you to water your pots and plants with confidence. Some tips are general and work for all plants and all situations. Others are more specific and are best suited for plants in raised garden beds, vegetable and herb gardens or pots, containers and grow bags.

1. Water by weight of pot, container or grow bag

Simply pick up the pot, container or grow bag and feel the weight. 

Herbs but also vegetables like tomatoes, beans, peppers and chillies grow well in pots, containers and grow bags.

And when the container or grow bag holds a lot of soil it is not always obvious if you need to water the plant. A mere inspection of the surface of the soil may not be enough.

This method involves a five step process and the use of your muscle memory. 

  • Pick up the container before watering
  • Make a mental note of how heavy the container feels
  • Water the plant
  • Pick up the container again
  • Feel the difference and make a mental note of the weight

This is of course not an exact method as it relies on a feeling. But you will be surprised how useful the method can be when you start using it.

From my experience the method will work best when you do not try to be too exact when registering the weight in your mind. Try to create a “feeling” of what the weight is rather than attempting to label the sensation in words. 

If someone throws you a tennis ball you do not think about how you will try to catch it. You simply try to catch it using hand eye coordination and a feeling of what you need to do. That is the state of mind you want. 

The pot should not feel light when you pick it up. It should feel like it needs water. I do not mean to sound vague and I do hope you understand what I mean.

2. Stick in the soil method

Use a bamboo stick or any other stick or preferably untreated wood. Now insert the stick into the soil and leave it for 5 seconds before pulling it out.

Inspect the stick. If wet or damp you do not need to water. Should the stick however be dry you need to water your plants.

The stick in the soil method is great for plants with large root systems and where we need to ensure that the soil is draining well deep down.

No herbs, vegetables or plants like it when the root ball sits in constant wet. And with Mediterranean herbs like oregano, thyme, tarragon and rosemary it will definitely kill your plants if the roots are soaking wet.

Here inserting a stick deep into the soil will give you an idea of what is going on 30 centimetres (10 inches) or more deep into the soil.

And face it, if you are unable to insert the stick into the soil you need to look into improving your soil for more successful gardening.

3. Finger in the soil method

The finger in the soil method works really well for medium sized pots and containers.

Simply inserting a finger two knuckles deep into the soil will tell you what you need to know.

This method does however not work well for larger sized containers or grow bags as it only gives a superficial check. Also not ideal for smaller pots like stater pots where we risk hurting root systems. 

4. Overall look and vigor of plant 

You should of course not wait for your plants to suffer or dry out. You do not want your seedlings and plants to suffer dry outs. 

But there are times when a visual inspection can be what helps you save a plant. A common example is when a plant that did well this morning all of a sudden is suffering later that same day. This scenario is especially true for

  • summer and the hotter times of the year
  • plants placed in locations that get very hot like a south facing window sill
  • plants in pots that do not breath (plastic, metal)
  • pots that conduct heat (metal)
  • young seedlings and plants that are not established
  • smaller pots and grow bags that heat up more quickly

And this is why it is important to look at your plants several times every day. No need for close inspection but that casual look and observation can be what catches a plant that is starting to look stressed and tired. 

5. A garden journal to tell you when to water

Keeping a garden journal will help you remember what you did not only yesterday but also last week and in time last year.

And this knowledge and perspective is invaluable when deciding when and what to water. 

Your garden journal is a surefire way to create a deeper understanding of what works for any individual plant given specific external factors.

A garden journal is also extremely helpful if you are more than one person looking after your plants. A quick look in the journal will show when each plant was last watered preventing the risk of both over and under watering.  

6. Moisture meters telling you when to water

Moisture meters are by some hailed as miracle workers where others claim they are pretty much useless. For us moisture meters fall somewhere in the middle of this range. We do use them and yes, we do find them useful. 

Most moisture meters for home gardening come with one or two probes and cost less than USD 20. To use, push the probe(s) into the soil at an angle to reach near the roots and observe the reading. It is wise to take several readings at different depths to get a better picture of the overall level of moisture.

But as with many things gardening it is not all or nothing. We use moisture meters and find that they help us identify whether a plant needs to be watered. But only if your soil is healthy and balanced. 

Using a moisture meter will over time give you an understanding of what different readings mean for different plants. And sometimes, the actual reading will be the most useful when interpreted in context of other earlier readings. Yes, another shameless plug for having a gardening journal.

To really understand how moisture meters work and the pros and cons with different models I recommend this excellent article published by Virginia State University.

Summary: best time to water plants

You have most likely heard the expression “common sense is not a coming thing”.

And to be honest, common sense is not always easy to apply when it comes to top or bottom watering plants.

Our favorite methods include a combination of all the 6 methods listed above for different plants and depending on the time of year.

Here are 3 specific examples of how we decide the best time to water plants.

Best time to water thyme in pot

We have large thyme plants growing in large pots and here we use the water by weight and the stick in the soil methods. 

Thyme is one of the Mediterranean aromatic herbs and we have learnt that all our thyme plants like a mild dry out between waterings.

We use styrofoam type pots that are lightweight and easy to lift. The stick is used to ensure good drainage and that the soil structure is good. 

We would have used a moisture meter but the pot is simply too deep and to inspect the plant is difficult as thyme is hardy and will look healthy until it is past the point of rescue.

Best time to water basil grown in pots

We grow common basil, Thai basil and cinnamon basil year round. And basil is one of those herbs that do not like to dry out.

This is of course not a problem growing basil hydroponically indoors. When we sow seeds in soil we do however need to keep the growing environment moist but not wet. And as all our basil, including our Thai basil plants, are transplanted into medium sized pots we use moisture meters to know when it is the best time to water our plants.

Using a finger could work but it is easier with a moisture meter as basil plants tend to grow quite bushy. Also, a moisture meter will measure deeper to ensure good drainage and avoid yellowing basil leaves and other potential problems.

Best time to water tomato plants in grow bags

Tomato plants are started indoors from seed in January and February every year.

When ready tomato seedlings are planted in grow bags in a sunny location in our back garden. 

Tomato plants want a lot of sun and are thirsty. They do not like to dry out. During the height of summer our tomato plants are therefore moved around in our garden to get 4 hours of morning sun and then 4+ hours of afternoon and evening sun.

With tomato plants we use the finger in the soil method. The objective is simple, do not let the tomato plants dry out. If it is too hot midday, we simply move the grow bags to a less exposed location for an hour or two.

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants, and garden vegetables. For the past two years, he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.