People often think dry soil means they should water their plants as soon as possible. But this is not usually the best immediate course of action. So how dry should your soil get before you water your plants?
As a general rule, 1-3 inches of dried soil is the standard indicator when most potted plants need watering. But drought-tolerant plants only need watering after the entire soil dries out. Additionally, established trees and shrubs require watering once the top 6 to 9 inches of soil is dry.
Below, I discuss this further with tips on how to gauge the soil’s dryness & the causes:
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Table of contents
Do I Immediately Water My Plants if The Soil is Dry?
This entirely depends on your plant type because not all have similar watering needs or are resilient to dry periods. Knowing the general category of plants like the following will give you a basic idea:
- Urgent watering is needed for moisture-loving plants and newly planted/young trees & shrubs. Some may tolerate further drying, but most require a constantly damp soil environment to thrive. This is why it’s best to water them when 1-2 inches of the soil’s surface is dry. If the leaves are drooping and developing crispy brown edges, the plant may be severely dehydrated and needs water asap.
- Drought-tolerant plants don’t need immediate watering once their soil dries out. They have adaptive traits that allow them to store water when there’s a lack of it. But if the plant shows signs of wilt, it needs water soon.
- Established trees and shrubs need watering when 6 to 9 inches of the topsoil is dry. Frequent watering will only encourage shallow roots to grow. So, letting the ground dry out a bit longer lets the roots go deeper in search of more water.
This is a general soil dryness guide to follow for watering your plants. When in doubt, check the soil and do a quick Google search on the plant you have to determine its watering needs.
How Can I Tell if My Plant’s Soil is Dry?
There are several common ways to check for soil dryness:
A. For in-ground plants:
- Insert a moisture meter or sturdy soil probe into the ground. They come with an easy-to-read dial that will tell you whether the soil is dry, moist, or wet. The only caveat is that they work best if the soil is loose and loamy. Hard and dense soil like clay will damage the equipment. You can also use this for potted plants!
- Dig a hole about 6 inches deep to feel the soil.
- If it’s damp to the touch, you can hold off on watering for 3 or so days before checking again.
- If it’s dry, it’s time to water your plants.
B. For potted plants:
- Push your finger 1-2 inches below the soil, about knuckle deep. This finger or knuckle test is one of the easiest ways to quickly check if it’s time to water your plant. But if you don’t like to dirty your hands, using a moisture meter is a good and reliable alternative.
- Insert a pale, wooden chopstick or skewer about 1-3 inches deep into the soil for 1 minute.
- If the chopstick/skewer comes out with a darkened stain with bits of soil sticking to it, you don’t have to water your plant just yet.
- If the chopstick/skewer comes out clean, the soil is dry and needs watering.
- Lift the pot to see how light or heavy it is.
- A heavy pot means the soil is still holding onto some water, meaning you should not water it anytime soon.
- A light pot means that most, if not all, of the water, has already evaporated, leaving the soil dry.
- Note: This test only applies to small and medium-sized pots.
Another way to check is to observe the surface color of the ground/potting mix. Usually, if it still has water, it looks darker. But when it’s dried out, it will look paler. But I find this simple method does not tell the whole story below the soil level. Checking the moisture level underneath is way more accurate and tells if the plant needs watering or not. At the end of the day, it’s down to your preference and best judgment.
What Causes Soil to Dry Out?
Numerous factors may affect a plant’s soil to dry out:
- Potting mix/soil type. Clay, loamy, and sandy soil have distinct water-holding capabilities, ranging from most to least retentive. Depending on the composition, this influences how fast the soil can dry out. The same applies to potting mix since it often contains aerating materials to improve drainage.
- A plant’s growth stage. Soil for young plants often dries out faster because they need more water to develop compared to mature ones.
- In-ground or potted plant. Potted plants have a limited soil environment, so they tend to dry out faster than their in-ground counterparts. They don’t have the benefit of extracting water from the surrounding elements, relying solely on us humans for their watering needs.
- Pot type. Certain pots like terracotta and grow bags/fabric pots can contribute to rapid water evaporation due to the material’s porosity. It’s not necessarily a bad thing because specific plants benefit from them. If you want to know more, this article discusses the advantages of growing a Monstera in a terracotta pot. As for grow bags/fabric pots, this article will tell you how valuable they are in your garden.
- Current weather and season. Intense heat during summer is one of the many factors causing the soil to dry out. Windy weather can also contribute to high evaporation. Add in a drought period with no rain in sight, then you’ll have to deal with keeping your plants hydrated throughout the season.
- Local climate and humidity. Obviously, if you live somewhere warmer, the sun will do its best to evaporate water from the soil faster than you can turn on the faucet. And if your area has low humidity, the air will suck the moisture out of the ground, leaving your plants gasping for water. Dramatic as that image may be, these are viable reasons your plant’s soil can dry out quickly.
With all these factors in mind, it can be a bit of a headache to keep track of. This is why creating a set watering schedule for your plants is not advisable, especially when starting out as a gardener or a casual plant owner. Knowing your plant’s water needs and checking the soil is the best way to go about it. After a while, you become intuitive enough to know exactly when your plant needs water best.
Frequently Asked Questions About Soil Before & After Watering
The soil should feel moist but not soggy after watering. As long as it drains out excess water afterward, then it’s adequate enough. But remember, sandy soil won’t feel wet for too long because it has low water-holding capabilities.
Push a moisture meter at least 3/4 into the pot to gauge the soil’s dryness. However, most plants except cacti & succulents won’t do well if the potting mix has almost dried out, but they will bounce back once watered. You can also try lifting the pot. If it is light, this usually indicates that the soil is not holding enough water and may need watering soon. Remember that this test can only be done with small and medium-sized pots.
As a whole, damp soil on the surface and underneath indicates that it is adequately saturated. However, the soil may be too compacted if it feels dry underground despite recently watering. Tilling or raking it and adding compost can break it up and improve the structure to retain water better.
Place the soil on an open and flat surface or in a terracotta pot with sun exposure and good airflow to encourage rapid evaporation. This is useful if you’re trying to recover an overwatered plant by drying out the soil quickly. However, remember that not all plants are resilient enough to bounce back.
Final Words
All in all, there’s a general guideline you’ll need to follow when using soil dryness as an indicator before watering your plants. Not all plants are the same, but by simplifying things, getting to know their specific needs, and checking the soil, it becomes relatively manageable to handle. Happy planting!
References:
- Michaels, T., Clark, M., Hoover, E., Irish, L., Smith, A., & Tepe, E. (n.d.). 12.1 Soils, fertility, and plant growth. Open.lib.umn.edu. https://open.lib.umn.edu/horticulture/chapter/12-1-soils-fertility-and-plant-growth/
- The University of Maine. (2017). Soil and Plant Nutrition: a Gardener’s Perspective – Cooperative Extension: Garden & Yard – University of Maine Cooperative Extension. Cooperative Extension: Garden & Yard; The University of Maine. https://extension.umaine.edu/gardening/manual/soils/soil-and-plant-nutrition/
- Trees, Shrubs, and Groundcovers Tolerant of Wet Sites. (2022). Psu.edu. https://extension.psu.edu/trees-shrubs-and-groundcovers-tolerant-of-wet-sites
- Watering established trees and shrubs. (2018). Umn.edu. https://extension.umn.edu/planting-and-growing-guides/watering-established-trees-and-shrubs
