Do seeds need light to germinate? This is a question that many people ask themselves, but the answer is not always so cut and dry. It all depends on what type of seed you are talking about.

Some sown seeds do need light to germinate, while other seeds do not but do need oxygen. The type of seed you are working with determines how much light is necessary to get that sprout going and growing into a complete plant.

In the post, we will go over a few different types and do our best to explain why light is necessary for them to sprout. This including a list of herbs, vegetable seeds, fruits, and their light requirements for better germination.

What do seeds need to germinate best?

germination process

For seeds to germinate best indoors, three conditions must be met. Such conditions are soil moisture, oxygen, and temperature.

All fully formed seeds contain a seed embryo, and in most seeds, a store of food supplies is covered by a seed coat. For crops, seeding should usually "wake up" when conditions are suitable for growth in soil temperature and moisture. 

Every plant seed variety has a unique need, and take a minute to read some of their light requirements for germination.

Oxygen

Seeds need oxygen and proper airflow to produce enough energy to spring back from seed dormancy. This is due to glucose which assists in the aerobic respiration process. At this stage, seeds release energy from food stores, and they require oxygen to do so.

Oxygen is partially converted to carbon dioxide during growth; the carbon dioxide needs to move away from the seed through aerated soil.

Temperature

A specific range of temperature conditions is needed to sprout seeds. This is because the enzymes that do all the work within a seed can only do so at particular temperatures.

Timing is everything for some plant seeds, requiring them to be planted at the right time and in a given season. Some like it hot spring and summer, while other seeds prefer cool conditions. 

And some need to be put in cold stratification before winter, which promotes sprouting once again when placed back outside next spring.

When seedlings develop indoors, do not expose them to temperatures beyond the recommended range. In some cases, a heating mat is needed.

It's crucial to provide the appropriate amount of light, moisture, and control temperature for your seedlings during their germination process.

However, you must be careful when utilizing light as the only heat source because it can also kill shallow seedlings. It's essential to understand the needs of seed sprouting to ensure success.

Moisture

Moisture is the most important thing to provide for a seed to sprout. Watering your plant often enough will ensure that it does not suffer from a lack of nutrients or dryness, both of which can cause death in plant seeds.

If you do not have any over-watering problems, follow up with watering instructions for your specific seed, as each seed has different requirements.

Light (*)

Some seeds do not need light to germinate but do require light for solid growth.

Most commercially created seeds germinate even without light because they have been carefully selected for their viability in different conditions. However, some seeds need to be exposed to light for them to germinate. More on this later in the article.

Is light really necessary, and how much light is enough?

Most seeds germinate in light, but the amount depends on which type of seed you are growing. 

For example, some plants will do fine as long as they have a few hours per day, while others may not grow at all with less than an hour or two. It's essential to know your plant requirements before exposing them to too much (or little) light.

Why do some seeds germinate in dark conditions?

Some seeds do not need light to germinate. This is because they do not contain chlorophyll in their cells. 

Therefore, they do not use sunlight for photosynthesis like other plants do but still provide an essential role inside the ecosystem. These would include fungi or bacteria that break down organic matter, which ultimately helps decomposition and returning nutrients back into the soil.

How deep should you sow seeds, and what it has to do with light?

plants that needs light

Recommended planting depth has to do with whether light is necessary for the growth of plants.

Therefore, light from the sun is necessary for plants to grow. Light provides the energy needed by a plant to do photosynthesis and other life processes that make it possible to survive until the next day.

What happens if you plant a seed too deep?

A seed that needs light planted too deeply will not do well. This is especially true for seeds that do not germinate in the dark such as lettuce, cabbage, and dill.

Some types of seeds do well without exposure to light. These seeds need less energy for their growth process because they grow roots downward instead of seeking out more light like most plants do when growing upward.

They also do not have many leaves on them compared with other plants. Meaning, they require less water, making them perfect candidates for gardening no matter what your climate is like!

What happens if you plant a seed too shallow?

If you do not plant a seed deep enough, it will never grow roots. The top of the soil surface is mainly made up of air and water, so there is no room for the root system or seeds to grow deeper into the ground.

Which seeds need light to germinate?

seeds that needs light to germinate

There are three types of light for seed germination:

  1. Seeds that need light to germinate should be left uncovered by soil.
  2. Seeds that need a thin covering layer (a few millimeters) of soil over them to germinate
  3. Seeds that prefer darkness to germinate with soil cover (Ideally, it is best to bury the seeds at least twice their diameter in depth.)

Which vegetable seeds need light to germinate?

Some vegetables, fruits, and herbs seeds that need light to properly germinate should not be covered in soil. All the examples here are of plants with tiny seeds that have a thin seed coat. Here is a list:

  • Brussels sprouts
  • Cabbage
  • Cauliflower
  • Celery
  • Chinese cabbage
  • Collards
  • Dill
  • Leeks
  • Onion
  • Lettuce

What seeds need to germinate in the darkness?

Some vegetables, fruits, and herbs do not need light to germinate. All the examples here are of plants with tiny seeds that have a thick seed coat. Here is a list:

  • Asparagus
  • Artichokes
  • Basil
  • Eggplant
  • Kale
  • Peppers
  • Pumpkin
  • Squash
  • Tomato
  • Watermelon

How To Provide Light For Germination

seeds that needs darkness

It may seem overwhelming when trying to provide enough light for seeds but don't worry! Many ways work wonderfully. Light conditions do not need to be perfect.

The quality of the light is essential when it comes to germinating seeds. Some do better with natural sunlight, while others do best with artificial bulbs. Artificial light is usually brighter than natural sunlight and does not change as much between day and night.

If you do not have a lot of space, it is better to find seeds that are doing well with artificial light. Some examples are tomatoes, peppers, and eggplants.

Here are some examples for light sources:

- Sunny window: Place a small container with the seeds in it on top of your sunny window sill, and do not cover. Make sure to water them every day so that they do not dry out!

- Grow lights: If you have them, place them close to the seed starting containers or directly over one side of your light table.

- Fluorescent lights: keep bulbs close to seed starting containers or directly over one side of your light table.

- Led light: Place a few of the seeds barely covered in small containers on top of your desk or table. Turn them on when it is dark outside to provide artificial light during the day

The best way is to do a mix of natural and artificial light. There are also lamps that you can purchase for the sole purpose of growing seeds indoors! These will usually give off more colors than just white light, so they are perfect if you want to grow


Keeping Seeds Moist When Exposed to Light

Most importantly, make sure that you check if there's enough water before and after exposure to sunlight so that the soil doesn't dry out during this process. Both lack of moisture and heat can stop germination from happening altogether if these things aren't taken care of.

You do not need to do anything special with the soil before exposing it to light, but make sure that you plant your seeds in a pot or seed tray (that has drainage holes) so that excess water can flow out and stay fresh.

The soil should be moist, not saturated and wet. You do not want waterlogged or flooded pots - it's vital to maintain this balance with the plants you grow in your own home garden. 

In the event of excess water on top of the soil after watering, we recommend putting a layer of mulch at the surface to help keep things moist while reducing evaporation from the plant leaves.

Getting your questions answered

Do carrot seeds need light to germinate?

carrot seeds

Tiny carrot seeds grow without light. They need to be planted in moist, well-drained soil about an inch deep when the temperature is between 60 and 75 degrees Fahrenheit. 

If they are not germinating successfully, the soil may not be moist enough, or the temperatures are too low.

The best thing to do is place a plastic cover over your container. This will help maintain moisture in the air and also keep out any weed seeds that might blow on top of your seedling containers from nearby gardens. 

Generally, carrot germination occurs after about 14-21 days, depending on temperature and humidity levels. It's essential to get them growing right away to grow big enough before winter sets in.

How many hours of light do lettuce seeds need to germinate?

Lettuce seeds germinate properly only if you expose them to light for about 12 hours a day. The ideal soil temperature for lettuce seed germination is between 65-70 degrees Fahrenheit. 

Once the soil temperature is close to that range, a lettuce seedling can germinate approximately two days after being planted into the ground. You can sprinkle them on soil or vermiculite and then cover them with a thin layer of soil or vermiculite.

How much light do onion seedlings need to germinate?

Onion seedlings need light to germinate. The amount of light most seedlings need depends on the type of onions you have planted. 

Generally, sweet or yellow onions do not require light to germinate. For dry onions, you do need to expose them to at least eight hours of sunlight a day for three weeks before the first seeds begin sprouting.

Onion seedlings do not like cold soil or direct sunlight. They do best in soil temperatures of between 60 and 75 degrees Fahrenheit. They will not develop properly and die quickly if these two conditions constantly exist in their environment.

Suppose your onion seeds do not produce any green shoots after you sow them. In that case, it is likely because of cool temperatures and/or that there wasn't enough water available. When planted into the moistened potting mix on top of a heating pad or under grow lights.

Do tomatoes plants need light?

Tomato seeds need three conditions to germinate. Those are warmth, water, and oxygen. 

They do best when they are planted in warm soil that is lightly moistened. The soil temperature should be a minimum of 75 degrees Fahrenheit for most plant species to sprout well.

Tomato seeds do not need light exposure to sprout and do better in moist soil than in dry, cracked earth. It's essential to water your tomato seeds often so that the soil doesn't dry out. If you tomato seeds are not germinating, that's probably because it lacks sufficient water or warmth.

Conclusion

So now you know which vegetables and herbs seeds that need light to germinate. Light is unnecessary for all plants to grow. Still, it can be the difference between a few wilted leaves and a healthy plant with a bountiful harvest.

If your seed is a type that doesn't need light to grow but does need oxygen, you should still provide it with plenty of water for hydration purposes. There are many varieties out there, so if you're unsure whether or not your seed needs light, then do some research on its specific type before planting!

Happy Planting 🙂