How many hours of light does a hydroponic garden need?

How many hours of light does a hydroponic garden need?

Your garden is in a dimly lit kitchen. Should you move the device closer to a window? Leave the LED on from morning to night? Or even 24 hours a day to speed up growth?

The short answer is no.

For hydroponically grown lettuce and herbs, the University of Minnesota generally recommends 12 to 14 hours of light per day. For young seedlings, the requirements can increase to 16 to 18 hours.

But good lighting is about more than just counting hours.

The lamp's intensity, its distance from the leaves, the plant being grown, and the natural light already available also matter.

And above all: leaving a grow light on 24/7 is not a good general rule.

Why is light so important in hydroponics?

Hydroponics changes how roots receive water and nutrients.

It does not change a fundamental plant requirement: light.

Leaves use light energy to perform photosynthesis. A plant properly supplied with water and hydroponic nutrients can still grow poorly if it does not receive enough light.

This is particularly important indoors.

On a balcony or in a garden, the sun naturally provides this energy. In a kitchen, the situation is different.

A window can provide a lot of light at certain times of the year and very little at others. Its orientation, the weather, the season, neighboring buildings, and the distance between the plant and the glass greatly affect what the plant actually receives.

This is precisely the benefit of grow lighting: making light input more predictable.

How many hours should a grow light be left on?

For an indoor garden, there is no single perfect duration that applies to all plants.

The University of Minnesota Extension nevertheless provides very useful guidelines:

• young seedlings: 16 to 18 hours per day ;

• hydroponic lettuce and herbs: 12 to 14 hours per day ;

• foliage houseplants: 12 to 14 hours ;

• flowering plants: 14 to 16 hours.

These figures are rough estimates, not a universal timer.

Lettuce and tomatoes do not use light in exactly the same way. And two lamps running for 14 hours can provide very different amounts of light if one is much more powerful or much closer to the leaves.

To get started with basil, mint, or lettuce, a regular cycle of around 12 to 14 hours is therefore a simple and consistent guideline.

Can the light be left on 24 hours a day?

This is generally neither necessary nor recommended as a growing rule.

A plant does not simply need to accumulate as many hours of light as possible.

The light-dark cycle affects different physiological processes. The length of the day—called the photoperiod—influences growth and, in some species, flowering.

This is why horticultural recommendations provide periods of light and periods of darkness rather than continuous lighting.

For a home garden, there is therefore no reason to try to "maximize" the lamp by leaving it on day and night.

More is not automatically better.

You would also consume more electricity without any guarantee of improving your crop.

Is a window enough for indoor growing?

Sometimes.

But not always.

A very bright, well-exposed window can provide a significant amount of natural light. A window facing a different direction or located behind a covered balcony can offer completely different conditions.

The season also plays a big role.

A location that works perfectly in June may be insufficient in December.

This is what makes grow lighting interesting for regular indoor growing: you no longer depend solely on your home's exposure.

This does not mean you should banish the sun.

A plant can obviously benefit from available natural light. Grow lighting is primarily used to supplement or replace this light when it is not enough.

What kind of light does a grow light use?

Not all visible light is equal for growing.

Grow lights are designed to provide wavelengths that plants can use.

The University of Minnesota distinguishes blue and red lighting, as well as white or balanced spectrums.

Blue or mixed lights are particularly suitable for seedlings and leafy greens. Red components play a greater role in certain processes related to flowering, while white or balanced lighting may be suitable for many plants at different stages.

For a home user, however, it is not necessary to start by analyzing every wavelength.

Grow lighting adapted to your system simplifies this question.

How far should the lamp be placed from the plants?

This is a question almost as important as duration.

Imagine a lamp left on for 14 hours.

If it is much too far from the leaves, the plant may receive less light than it needs.

Conversely, very close and powerful lighting can cause stress or symptoms on the foliage.

The correct distance therefore depends on the lamp's power and design.

The best approach is to follow the manufacturer's recommendations and gradually adjust the height as the plants grow.

The Verdia One, for example, has a 20 W grow LED and an adjustable pole from 22 to 52 cm. The height adjustment is designed to accommodate plant growth.

The Verdia Mini also features full-spectrum LED lighting and adjustable height.

The Verdia Plus, however, works differently: it does not have integrated grow lighting. Its location must therefore be chosen based on available light or supplemented with suitable lighting if necessary.

How can you tell if a plant lacks light?

Plants give clues.

A plant lacking light may, in particular, produce elongated and weak growth as it tries to reach a light source. The spacing between the leaves may increase, and the plant may lose its compact shape.

But be careful not to diagnose all growth problems as a lack of light.

Slow growth can also be caused by:

• a nutrient problem;

• temperature;

• root health;

• pH;

• a plant crowded by its neighbors;

• or simply the variety being grown.

So look at the whole plant before changing your lighting.

If all your young plants are stretching in the same direction toward a window or toward the lamp, the light clearly deserves a closer look.

What if the leaves are too close to the lamp?

Excess also exists.

Leaves located very close to a light source can receive an intensity higher than they need and, depending on the equipment, also be exposed to more heat.

The problem is especially noticeable when the plant grows but the lamp remains at the same height.

This is easy to forget.

A small lettuce located ten centimeters below a lamp today will obviously not maintain that distance as it grows.

So make it a habit to regularly check the tops of your plants and adjust the height of the lamp when your device allows it.

Can all plants share the same lighting?

In theory, many crops can grow under the same lamp.

In practice, their size often ends up complicating things.

Imagine basil, two lettuces, and a compact tomato.

At the beginning, all the seedlings are a few centimeters tall.

A few weeks later, the tomato may easily tower over the lettuces.

If you raise the lamp to make room for the tomato, the small plants end up further from the light source.

This is one of the reasons why the choice of plants and space management matter as much as the number of available spots.

A garden with 14 spots does not necessarily need to accommodate 14 adult plants.

Sometimes it is better to leave a few spots empty so that each plant can properly benefit from the light.

→ Read our guide on vegetables suited for hydroponics

Should you change the lighting depending on the plants?

Yes, when your system allows it and when the requirements become different.

Leafy greens and herbs are precisely interesting to start with because they remain relatively simple to manage under grow lighting.

Fruiting plants such as tomatoes or peppers generally require more attention: they grow larger, stay in the system longer, and must go through flowering and then fruiting.

They may also require manual pollination indoors.

The best setting is therefore not just the one that germinates the seed.

It is the one that remains consistent with the adult plant you are trying to achieve.

Can you program the lamp to turn on at night?

Yes.

From the plant's perspective, the most important thing is above all to maintain a regular, suitable cycle.

You can therefore program part of the lighting during the night if it better suits your organization or setup.

But you must think about your own comfort.

A grow light installed in a bedroom and left on while you sleep is probably not a very good idea.

In a kitchen, for example, you can program the lighting to run mainly during the day and turn off in the evening.

The Verdia One currently allows you to manage its light cycles from its Wi-Fi app. For another system, a timer or the device's built-in programming can serve the same function.

→ Discover Belverdia hydroponic gardens

How many hours of light should you remember when you are starting out?

If you are starting with lettuce or herbs, simply remember this:

around 12 to 14 hours of light per day is a good starting point.

For young seedlings, horticultural references often recommend a longer duration, around 16 to 18 hours.

Then, observe.

Are your plants staying compact, green, and progressing normally?

Do not change the settings simply because a forum recommends one more hour.

Are they stretching strongly toward the light?

Look at the intensity, the duration, and above all, the distance between the lamp and the leaves.

Are they almost touching the LED?

Raise the lamp if your system allows it.

Indoor growing becomes much simpler when you stop looking for a universal setting and start looking at what the plants are actually doing.

What to remember

Light is one of the pillars of indoor hydroponic growing.

For lettuce and herbs, 12 to 14 hours daily is a solid guideline to start with. Seedlings may require more time under lighting.

But counting the hours is not enough.

The lamp's power, its distance, the species being grown, the size of the plant, and the available natural light also matter.

And no: your garden does not need to look like Las Vegas 24 hours a day.

A regular schedule, a properly positioned lamp, and a few observations are enough to start on the right foot.