Our article, How to Grow Vegetables Indoors, mentioned some supplies needed to achieve this goal. Light is chief among them. It is the most unique and essential factor to consider when growing vegetables indoors.
Firstly, light is crucial to plant growth. Without it, there is no photosynthesis. Therefore, plants can’t develop and bear fruits.
Secondly, the sun is the primary light source for plants and indoor vegetables have less access to it. Even if you grow an indoor plant near a large window, it may still get less sunlight than another plant grown in an outdoor garden.
Thirdly, vegetables are generally more light-hungry than non-edibles, like the average indoor ornamental plant.
All three of these bring us to one conclusion- if you want to grow vegetables indoors, you need to get an additional light source to compensate for the limited access to sunlight.
In fact, you shouldn’t even use any run-of-the-mill light if you want the best possible result. You need to get dedicated grow lights and learn to meet the specific light requirements of your particular indoor vegetable.
Fortunately, that is what this article will discuss. So, whether you are a newbie or a veteran of indoor gardening, read on. Join us as we discuss how to grow vegetables indoors using grow lights.
Why you need lights to grow vegetables indoors
We have already established that indoor vegetables need an additional light source besides the available natural light. We have also mentioned that it is better if that additional light is a dedicated grow light. However, we didn’t say why. Here it is.
Plants prefer sunlight. That is the kind of light they have evolved to respond to. Without sunlight or a similar kind of light, they cannot grow healthily and fruitfully. In simple terms, this is because of two light spectrums in sunlight. These two are blue light and red light.
- Blue light: It encourages plants to develop foliage and chlorophyll.
- Red light: It encourages plants to develop flowers and fruits.
Both light spectrums are crucial to plant development and health. However, blue light is more important for young plants or plants grown for their foliage. Meanwhile, blue light is more important for matured flowering and fruiting plants.
Professional grow lights can provide these two essential spectrums. Most regular lights may not. However, there is a caveat. Not all professional grow lights can also provide a good balance of both red and blue lights. Those that do are called full- or broad-spectrum lights. Those that can’t provide either red or blue light alone.
Now that we have covered the technicalities, here is the answer to the big question. Professional grow lights ensure that your indoor vegetables get the light they need to develop into healthy plants and provide a good harvest. Additionally, grow lights generally have a more powerful output than regular house lights.
Types of grow lights
There are three main types.
High-Intensity Discharge (HID) lights
HID lights are the most powerful option on this list. As a result, they are the go-to option for big professional grow houses and plant nurseries. However, HID Lights are expensive and energy intensive. They also generate too much heat and rarely have both light spectrums in one unit.
Fluorescents are a good option for hobbyists and small-scale growers. This is because they are cheap, powerful and often compatible with the electric systems in most homes. If you decide to go with fluorescent grow lights, we recommend the T5 fluorescent types.
Light-Emitting Diode (LED) lights
LED lights are fast becoming a favourite of indoor gardeners. They are also what we recommend. LED lights are highly durable and energy efficient. They also barely produce any heat and are usually full-spectrum lights. The only con is that fluorescent lights are cheaper.
How much light do indoor vegetables need?
Or how many hours per day should you use grow light on indoor vegetables? The answer to this question depends on two factors, the light requirement of that vegetable and the amount of natural light already available.
The light requirement of the vegetable
When it comes to light requirements, all vegetables generally fall into three categories. However, most of them fall into more than one category.
- Low-light vegetables: These can grow in full or partial shade. Generally, they need at least 8 hours of light per day. Examples include leafy greens (like kale, spinach, radishes, rocket and mustard greens) and herbs (like chives, coriander and parsley).
- Moderate-light vegetables: These can grow in partial shade or moderate sunlight. They need at least 12 hours of light per day. Examples include the vegetables mentioned in the low light category and others like cilantro, basil, thyme, lettuce etc.
- Full/high-light vegetables: These vegetables have the highest light requirement. They need high light levels, no less than 12 hours and as high as 18 hours per day. Examples include fruiting and flowering plants like tomatoes, peppers, basil, cucumbers, beans, peas etc.
Seedlings generally need high light levels regardless of the plant’s light requirement. All seedlings need lots of light to germinate and develop. Then, you can reduce the light supply to a more appropriate level after.
The amount of light already available
This mainly depends on where you position the plant. For example, a plant by a window will get some supply of natural light. This is why you should place your indoor vegetables near windows and doorways or on a windowsill. The natural light in such locations may even be enough to grow some low-light indoor vegetables without using grow lights.
However, this will depend on factors like:
- The size or number of windows available
- The direction of the window. In the UK, south-facing windows get the most sunlight. North-facing windows get the least.
- Obstructions from nearby trees, buildings etc
- Weather and season. Summer has the most sunlight, while winter has the least.
All of this combine to determine the amount of natural light your indoor vegetable will get daily. Then that and the plant’s light requirement determine how long you should use a grow light daily.
How to use lights to grow vegetables indoor
The following tips will always be helpful.
Get enough light
This depends on the total number of plants that you are dealing with. Whether they are few or many, ensure you get enough lights to meet their needs. Depending on the situation, you can choose a couple of powerful lights or multiple small ones.
Keep the grow light close to your indoor vegetables
This is more efficient. You won’t believe how rapidly light output reduces with distance. However, only do this with lights that don’t produce too much heat. You can use light requirements to decide whether to position your indoor vegetables closer to or farther from the grow light.
Position the grow light above the indoor vegetable
It is also a good idea to make the light adjustable. As a result, you’d be able to move it closer or farther away from the plant when necessary. However, here are some general tips for positioning the three main types of grow lights.
- HID grow lights: Place 24-60 inches above the indoor vegetable.
- Fluorescent grow lights: Place 3-12 inches above the indoor vegetable.
- LED grow lights: Place 12-24 inches above the plant.
Space your indoor vegetables properly
Do this to ensure good circulation of air and light.
Use Reflectors to make your grow lights more efficient
You can use paint, foil paper or any other form of reflective materials. Reflectors take all lighting systems to the next level. They can also help with lighting systems for indoor vegetables.
Let your indoor vegetables have some hours of darkness too
It is not just about light but the cycle of light/day and darkness/night. Plants need both aspects of this cycle to grow and develop healthily. Here is a simple explanation.
- Plants need light for photosynthesis, which involves producing chemical energy.
- Plants need darkness for respiration, which involves breaking down chemical energy into elements required to live and grow.
So your indoor vegetables need darkness almost as much as they need light. They need between 6-8 hours of darkness daily. Do note that it depends on the age and light requirement of the vegetable.
Potential problems with using lights to grow indoor vegetables
There are two possible problems.
- Not enough light: When this happens, your indoor vegetables will grow tall and weak. Their foliage will also be too dark. The affected vegetables may remedy this by growing towards a light source.
- Too much light: When this happens, your indoor vegetables will be stunted and short. Their foliage will also develop a bleached yellow-green colour.
In both situations, you will have unhealthy vegetables and poor harvests. Fortunately, you can fix both problems by increasing or reducing the light supply appropriately. There are two ways to do this.
- Add or remove light
- Increase or reduce the distance between plant and light.
By now, we hope you have realised that the key is to provide your indoor vegetables with the right type and quantity of light. Of course, this will vary depending on each plant and the circumstances of the environment. But that is the principle behind growing indoor vegetables with light—no more, no less.