How Often Should You Water Seedlings in a Greenhouse?

It is a big task to take care of seedlings, especially if you’ve never done it before—there’s a lot to learn and figure out. Greenhouses come with their own rules that you have to follow. And since watering is such a big part of plant care, it’s important to know exactly how often you should water your seedlings.

You should water seedlings at least twice a day in a greenhouse. The soil for your seedlings should almost always be moist to the touch. Watering in the morning and at night, will usually keep your soil within these conditions. 

Along with moist soil, there are many other things that you need to keep within optimal conditions. Keep reading to learn all about caring for your seedlings.

Why Should You Water Seedlings in a Greenhouse Frequently

The general rule of thumb is to water plants frequently enough for the soil to be constantly moist. This can sometimes involve a large amount of work, but it’s something you definitely shouldn’t skip.

Watering seedlings frequently will allow them to grow properly. Water provides moisture and makes available many essential nutrients that plants need for growth. Also, seedlings are fragile when compared to mature plants and are less resistant to low moisture environments.

Along with the regular requirements of plants, environmental conditions like temperature, humidity, and light intensity can alter the amount of water your seedlings will need. You’ll need to adjust accordingly.

Keeping up with a watering schedule is something you get into once you know the type of system you’re running. Everyone prefers their greenhouse a certain way, so there are different things to account for depending on your setup. 

This uniqueness means that there is no one size fits all solution to all the potential problems that could come up. However, it also means that since your setup is unique to you, you’ll eventually become familiar enough with it that you can manage it efficiently.

That said, this won’t come immediately, especially if you’re a new gardener. You’ll have to learn how to water properly and how environmental conditions outside your control and the greenhouse conditions interact.

How to Water Seedlings In a Greenhouse

Now that you know the timing and the reason for watering your seedlings, it’s important to know how to properly water them for optimal growth. There’s quite a bit involved, as watering is far more than just pouring water. Regulating moisture content is crucial for all your plants, and many factors play a role in it.

Wet Your Plants Lightly

The first thing most people learn when they want to start growing seedlings in a greenhouse is that plants love water. While there is some truth to this, it’s more precise to say plants love moisture. 

Although both sentences sound similar, there is a subtle difference. As nice as water is, plants, and seedlings especially, do not need an overwhelming amount of it. Rather, they need enough for the soil to be damp to the touch but not so much water that they’re drowning in it. 

Because of this, the best rule to follow when it comes to watering your plants is to use enough water to wet the soil but stop once it’s there. Once you go past this point, you open up your plants to pathogens, root rot, and a variety of other problems. 

Frequency is as important as amount here. You will rarely ever need to water your plants more than a couple of times a day. Doing this will most likely bring more harm than good, even if you water lightly. 

One light watering session in the morning before the sun comes out and another in the evening after it sets will be enough to last the plants through the night.

Keep the Light Intensity at Optimal Levels

Light intensity in your greenhouse affects how well your plants grow. Plants use different wavelengths of light for photosynthesis, so it’s not always very straightforward.

It is also extremely important to factor in how light intensity affects watering and what you should do to account for it. 

Light intensity affects plants in a similar way to the popular magnifying glass test. Although the sun can and will heat your greenhouse, its effects are usually more positive than negative. 

However, once you water your plants and leave water on the leaves, this water can act as a magnifying glass, focusing and increasing the light intensity on the leaves. If the heat gets bad enough, the leaves can burn. 

Of course, they won’t catch fire randomly. Rather, this burn comes in the form of white discoloration on the leaves. Think of it this way: there’s a reason you don’t go out in the burning sun without sunscreen, and you definitely wouldn’t go out without clothes either.

It’s much the same for plants. Seedlings are still very early in their development cycle and are even more susceptible to this damage. 

On the bright side, plants won’t just up and die once they show the telltale signs of discoloration. While you can’t cure the damage outright, careful attention, proper watering, and a good amount of shade should get them back on the right track.

Although this problem can happen under grow lights, it’s a lot more common with direct sunlight.

Regulate Water Temperature 

The temperature of the water you’re feeding your plants is almost as important to regulate. Most people share the same water source for their homes and their greenhouses.

However, during particularly hot or cold weather, the water temperature running through your home can rise or drop considerably. Although plants will almost always use the water regardless of the temperature, how well they use it will change depending on the temperature.

Ideally, the temperature around the roots should be about 64-75℉ (18-24℃). If it’s too hot, there is a lot less dissolved oxygen in it, and if it’s too cold, the amount of uptake at the roots is reduced.

A good workaround for this is to invest in a water heater. This way, you won’t have to depend so strongly on ambient temperature.

Adapt to the Weather

One of the best parts about owning a greenhouse is that with the right steps, you can grow whatever plants you want year-round, regardless of the weather outside of it.

While this is true, the weather can still affect your seedlings and how you water them.

During winter, for example, cold temperatures can cause any watering you do to be counterproductive and sometimes even fatal. Reduced sunlight can make your seedlings start to photosynthesize less than they normally would.

This, combined with the naturally low temperatures during winter, can reduce the total amount of water the plant can hold. During these periods, you’ll likely need to water your seedlings a lot less frequently. 

One risk that comes with colder weather is edemas. With transpiration lowered and evaporation from the soil reduced, the water stays in plant cells for longer than it should, which can eventually cause them to rupture.

Similarly, during summer, increased temperature and humidity can cause the opposite effect. You might need to water your seedlings more than you normally would.

Use the Right Soil

When it comes to watering your seedlings, it can’t be overstated how important the type of soil you use is. Different types of soil hold different amounts of water because of their retention capacity

Here’s a good rule of thumb: the tighter the soil, the more water it holds. On the other hand, in looser soils, the water just drains through, which means they hold significantly less water.

Neither of these things is good or bad on its own. However, since water retention means some soils hold more water than others, it follows that you should change the amount of water you use depending on the type of soil you have. 

If you water all soils the same way without accounting for their water retention, you’re bound to run into problems eventually.

Invest in Overhead Systems

Overhead watering systems are expensive. There’s no workaround for that. However, if you can afford one, it will pay for itself in the amount of time and energy you’ll save doing your daily watering, and before long, you’ll be wondering how you ever got around without one. 

Alternatively, you can go for a good drip irrigation system, making your watering even easier. This system uses pipes called “driplines” with small units called “drippers.” These pipes are inlaid into the soil, delivering your plants both water and fertilizer in the most efficient way possible.

Key Takeaways

Plants are delicate and seedlings even more so. Because of this, it’s important to water your seedlings frequently and make sure the soil is always moist. 

However, more is not always better. Try not to overwater and always keep in mind factors like water temperature, seasonal changes, and sunlight. Paying attention to all these details will give your seedlings the best chance of growing into healthy plants.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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