Watering your plants is complicated. Plants need different amounts of water based on their type and their environment. When considering how much water to give plants, plant doctor Maryah Greene says most people are making the same mistake.

“Watering is one of the most confusing topics out there,” says Greene. “A really common misconception about watering is how often to water your plant, as opposed to how much.”

In the latest episode of Greene Thumb by Well+Good, a series on the Well+Good YouTube channel, Greene explains what to think about when you’re deciding how much water to give plants. “The main factors are the size of the plant, the type of plant, whether or not the pot has drainage or no drainage, and how much light it’s getting,” says Greene. Once you know how much water to give your plants, a water meter ($14) can help signal when they’re ready.

4 questions to ask yourself before deciding how much water to give your plants

1. How much light is your plant getting?

“Lighting and watering go hand in hand, and how much water your plant receives will really be determined on how much light the plants receiving,” says Greene. “Your plant is going to absorb a ton of water each time you water it. But some of that water will also evaporate into the air and the light will dictate how quickly that happens. So plants that are getting more light might need water more often. However, there are a couple of things that dictate whether or not that’s exactly true: Whether or not the plant is in a pot with drainage and the type of plant that it is.”

2. What type of plant is it?

“When it comes to the type of plant, you want to do your best to recreate its original environment. And so if you have something like a tropical that likes to stay fairly moist and allow the soil to dry out every now and then, you might have to water it every seven to 10 days, whereas if you have a cacti or succulent might be watering it every two to three weeks. But again, this is based on lighting and its original environment,” says Greene. “For tropical plants, you want to keep in mind that they like to dry out in between waterings, so just because the top of the soil is dry, doesn’t mean that underneath is time for water, whereas with cacti and succulents, you might only need to water them once every three to four weeks, but again, that’s based on the lighting.”

3. Does the pot have proper drainage?

“For plants that are in pots with the drainage hole, it’s almost impossible to overwater them, because any excess moisture is draining out the bottom,” says Greene. “Now for plants that are in pots without a drainage hole, this is where you have to be extra mindful about the quantity of water that you’re giving them. You might only need to water it once every one to two weeks, but you want to be really mindful about how much you’re giving it, because any excess moisture isn’t going to be able to escape out the bottom.” Greene recommends placing rocks at the bottom of pots without drainage holes so the water isn’t just sitting in the soil causing root rot.

4. How big is the plant?

“Larger plants stay moist for a longer period of time and that’s mostly because they have more soil, and it locks in moisture for a longer period of time,” says Greene. “So a plant that’s in a 20-inch pot may only need water once every three to four weeks, whereas that same exact plan in a six-inch pot, might need water every one to two weeks. So that’s where the size of your plant and how much soil comes into play.”

Making sure your plant isn’t getting too much water

To ensure your plant isn’t getting too much water at a time, Erin Marino, director of brand marketing at The Sill, says to use a water meter. This three-in-one meter from Surenshy can check moisture, light, and soil pH levels.

Raintrip 4-in-1 Soil Test Kit — $15.00

“Water meters can be incredibly helpful! They are easy to read and save you from sticking your fingers deep into the potting mix to check for moisture,” says Marino. “I find that they are incredibly helpful for larger plants, where digging a finger into the soil isn’t as feasible. I definitely recommend it for anyone who tends to overwater their plants! You’d be surprised how long your regular potting mix can hold moisture for.”

For more tips on properly watering your plants, watch the full video above. Subscribe to the Well+Good YouTube channel for future episodes.