When to Put a Light on Germinated Seeds

It’s seed-starting season (or at least at the time of writing it) and it’s absolutely thrilling to see those little seeds turn into plants that turn into veggies, herbs, and flowers.

Some of you may be growing plants indoors for the first time. You may have a lot of questions such as when to start seeds indoors, what are heirloom seeds, or where to buy the best heirloom seeds.

Another common question about starting seeds is when to put a light on germinated seeds.

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What is Germination?

Before we talk about when to put a light on germinated seeds, let’s take a step back and discuss what germination is.

Germination is the sprouting of a seed usually after a period of dormancy. When a seed is germinated, it triggers the plant inside that it’s time to begin growing.

A seed has all the things that are necessary to the life of a future plant including:

• A protective coat
• Food
• Embryo (or beginning of the new plant)

Different seeds require different conditions to sprout (or germinate).

Things that might help trigger germination include:

• Moisture
• Temperature (While most seeds respond well to warm temperatures, there are some that work better after they have been through a cold period. This is called Stratification.)
• Oxygen
• Some seeds require direct light or sunlight to germinate but it is rare
• Other seeds may require smoke or fire to germinate

In a more technical explanation, Britannica writes, “In the process of seed germination, water is absorbed by the embryo, which results in the rehydration and expansion of the cells. Shortly after the beginning of water uptake, or imbibition, the rate of respiration increases, and various metabolic processes, suspended or much reduced during dormancy, resume.”

Now that we have a clear understanding of what germination is, let’s go on to the question of the day.

When to Put a Light on Germinated Seeds

There are a few seeds that require light before they germinate. These seeds include:

• Begonias
• Geraniums
• Petunias
• Columbine
• Impatiens
• Lettuce
• Poppies
• Snapdragons

If you are starting these seeds indoors, don’t cover them deeply with dirt, and turn on your grow lights as soon as they are planted.

For other seeds, it isn’t necessary to put on a light until after they have sprouted. Some gardeners prefer to put the lights on as soon as they plant a seed so they don’t miss an opportunity for the newly sprouted plants to get light. Personally, I’d rather save on the electricity and wait until they’ve germinated.

So my answer to when to put a light on a germinated seed? As soon as your seed has germinated it’s time to turn the light on.

What Kind of Light Do You Need for Seedlings?

When your seed germinates it enters the next stage of its life: seedling.

Seedlings need a lot of light to help them grow. Some seeds can be sown directly in the soil outside, but many of your seeds will need to be started inside to give you enough time to grow them to maturity and collect fruit.

Some people have luck setting seedlings in front of a sunny window or on a sun porch, but where we live we don’t get enough sunlight to successfully grow healthy seedlings. Plants that don’t get enough sunlight will be long, leggy, and leany.

You can grow seedlings indoors with the help of grow lights.

What Are The Best Grow Lights For Your Seeds?

There are many opinions about the best grow lights for your seedlings. We bought low-end ones at our local box store because it’s what could fit in the budget.

They were like these from Amazon.

These have been working well for us, but because we haven’t used any other options I am sure there are many other wonderful options for grow lights.

Other lights that have been recommended to me include:

People who plan on keeping their plants inside through maturity may want to use more expensive lights, but I think the less expensive lights will work for seed starting indoors.

LED lights are probably the most popular today, although some people still use fluorescent. Fluorescent lights are no longer or will soon no longer be available for sale in certain states such as Colorado and California.

Although many people don’t like the government dictating what type of products they can use, there are some benefits to using LED lights. LED lights tend to be more efficient and last longer than fluorescent lights. They are more expensive to buy upfront, but will cost less for your utility bill over time.

Frequently Asked Questions About Grow Lights

There are a lot of questions about grow lights so I thought I would make a quick list of them for easy reference.

1. How High Should I Place My Grow Lights?

How high you should place your lights depends on a number of factors. If you place your lights too low. you can burn your plants, and if you place them too high your plants will become leggy and weak trying to stretch for the light.

A lot of gardeners recommend putting your grow lights about three inches above your plants. Then continue raising them as they grow. For more intense LED lights, some people recommend placing them about 12-14 inches above the plants.

The grow lights you purchase may tell you how high to place your grow lights above your seedlings (mine did not). I have been using my lights about 3-6 inches above my plants and they seem to be doing well. In the beginning, I had one light that was too close to my cilantro and it did suffer a little “sunburn.”

2. How Do You Know if Grow Lights Are Too Close or Too Far Away From Seedlings?

It’s really easy to tell if your grow lights are too far away. Your seedlings will have this wispy long tall look if they are too far away from the grow lights. They’ll look like they’re stretching to reach the light — because they are!

If your seedlings are too close, they’ll get a burnt look. They may have browning around the edges or the leaves may take on a sort of whiteish color from too much intense lighting. They may also crinkle up or curl over from too much light.

3. Can Plants Recover From Sunburn?

The leaves that are affected by the sunburn will not return to normal afterward, but the plant can recover once it’s safely away from intense light.

4. Can Leggy Plants Recover?

You can help a leggy plant become fuller and less leggy, but it will require a little extra work. The first step is to move the plants into bigger pots and to bury the long stem under in soil (this is an especially good practice for tomato plants).

After that, you can move the lights closer to your plants to they can start benefitting from the correct amount of light they require.

Some people also run a fan inside their house to replicate the wind and nature that they would experience outside. This can make the plants heartier when it comes time to transplant them outside.

5. Do Seeds Germinate Faster With Light?

The only seeds that will germinate faster with light are the ones mentioned above in this article (or other seeds that require sunlight to germinate). Most seeds do not need grow lights until after they germinate.

Most seeds germinate faster if they are warm. I suppose a grow light could help speed up the process if it’s providing warmth, but a better solution would be a heat mat.

This is the one that I use:

6. How Long Do You Leave Grow Lights On?

You may think that the more light the better for seedlings, but that’s not entirely true. While they do require a great deal of light, they still need a period of rest at night time.

Most seed growers recommend 14-16 hours of light for young seedlings. I manually turn my lights on in the morning when I wake up and turn them off at night when I go to bed. For a more consistent schedule, and to ensure that they get the full 14-16 hours, you can use a timer.

6. Can You Take Your Seedlings Outside?

When the weather is nice you can take your seedlings outside, but only for short periods of time. This process is called hardening off.

If you take your fragile seedlings outside all day they will likely suffer from sunburn or they may be blown over by the wind. Instead, take them out for short periods of time to build them up to be ready for the harsher conditions outside.

When to Put a Light on Germinated Seeds (A Wrap-Up)

Growing seeds and growing a garden is always a bit of an experiment. I am constantly learning new things and I love being able to share my experiences with all of you.

Bottom line: Most seeds do not need to be placed under a light until after they have germinated. There are a few exceptions that do require light to germinate, but most of the things you are planting will not.

Did I answer all of your questions? Do you have anything else to add to this post? Let me know in the comments below.

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