Do Weed Seeds Need Light To Germinate

Do You Need Grow Lights Before Germination? | Germination Tips Starting plants indoors from seed can be a rewarding way to get a head start before the main growing season or get started with an Why is darkness recommended for germination? Doesnt seem to make much sense to me, why would darkness be beneficial to the seed in any way? Just curious. I…

Do You Need Grow Lights Before Germination? | Germination Tips

Starting plants indoors from seed can be a rewarding way to get a head start before the main growing season or get started with an indoor garden. However, germination (the process by which a plant begins to grow from a seed) can sometimes be spotty.

Some of your seeds might not germinate, or they might take too long to germinate. This can lead to gardeners seeking other ways to increase germination success, such as trying to add fertilizer after planting seeds, adding extra water, or putting them under grow lights to get them started.

You may have heard that grow lights can improve germination. That is not necessarily the case, but as always, there are exceptions.

Do You Need Grow Lights Before Germination?

In most cases, any source of light is unnecessary before germination, and grow lights in particular are not really useful at all for germination.

As explained below, light is not important for seed germination, with a few exceptions. However, grow lights are necessary for sprouted seedlings unless they are in a sunny window or otherwise getting direct sunlight.

The only benefit of grow lights before germination is that they can provide extra warmth which helps speed up germination. Germinating seeds at room temperature or slightly warmer is sufficient for most seeds, and some gardeners use a temperature-controlled seedling heat mat if they need extra heat.

Do Seeds Germinate Better in the Dark?

For most seeds, while they will still germinate with exposure to light, they germinate better in the dark. In some cases, such as with seeds in the onion family, light can actually inhibit germination.

If you think about it from an evolutionary standpoint, in nature, seeds with the most success will be those sitting on or in the soil. A sprout sitting on a rock or otherwise away from the soil would die even if it had the moisture and warmth to start the germination process.

Do Any Seeds Need Light Before They Sprout?

There are some seeds that actually need light before they sprout. These are mainly flowers, herbs, or vegetables with very tiny seeds.

These types of seeds can still germinate without light but sprout much better with light exposure. For example, celery is recommended to be surface-sown because the seeds are so tiny and germinate best with sunlight. Even lettuce seeds, which are less picky, sprout better with sunlight.

As a rule of thumb, you should plant seeds about two or three times deep as they are wide, so even if you bury tiny celery or lettuce seeds into the soil, about 1/4 inches deep is shallow enough to allow some light through. In nature, this is advantageous because small seeds don’t have enough stored energy to grow up through deep soil.

Does that mean you need a grow light to germinate these seeds? No. Ambient light from a room or next to a window will be enough.

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If you are germinating seeds at home to grow and eat your own sprouts in a jar, it’s recommended to keep them out of indirect light.

SANSI LED grow lights over pepper and tomato plants.

When Should I Turn On My Grow Lights for Seedlings?

Seedlings should start getting light as soon as they appear. When you see the first sprouts emerge, you can turn on your grow lights.

If you leave your seedlings to grow without light, they will stretch and get leggy. This isn’t a problem for some vegetables like tomatoes, but most of the time it leads to weaker stems and more fragile seedlings when transplanting outdoors. If kept in complete darkness, seedlings will die.

The only exception is if you are growing microgreens. Often, microgreen growers will allow their sprouts to grow in the dark for a few days to become leggy on purpose. Then they will expose them to their grow lights, which perks up weak, yellow seedlings and turns them green. Leggy microgreens are much easier to harvest by cutting above the soil layer with a sharp knife or kitchen scissors.

Should Seedlings Get 24 Hours of Light?

In general, plants should not get 24 hours of light a day, and seedlings are no exception.

While it’s true that more light will lead to faster growth, and some plant species can be healthy with a 24-hour photoperiod, most plants need a period of darkness for plant metabolism.

For seedlings, you can keep them under 12 to 16 hours of light per day. Make sure to keep the lights close enough to the seedlings to keep them from getting leggy but far enough away to avoid overheating your seedlings (unless you like cooked sprouts).

What Kind of Grow Light Do I Need for Seedlings?

Unlike mature plants, seedlings can get away with much less powerful grow lights. Any kind of grow light, from LED grow lights to standard fluorescent lights.

If you already have T12 fluorescent lights, they can be used for starting seedlings, but seedlings will eventually outgrow the energy output of T12 bulbs. If you are buying a fluorescent grow light, T5 bulbs (especially T5 high-output bulbs) are brighter so they don’t have to be placed very close to the seedlings and can be used for larger seedlings.

LED grow lights are another option. The prices have gone down significantly over the years, and you can get full-spectrum white LED grow lights that are even better than the older pink/purple style of LED grow light that used to be more common. LED grow lights are energy efficient and can last for years, and you can get grow lights for under $100 that are strong enough to grow full-sized plants as well.

Germinate seeds under light?

Why is darkness recommended for germination? Doesnt seem to make much sense to me, why would darkness be beneficial to the seed in any way? Just curious. I have some seedlings already but decided to go for a few more plants, so i’ve put the seeds in the pots in the same room, threw some black garbage bags over the pots to avoid some of the light + it add more moisture..

I’ve tried germination using a few methods, nowadays i always plant the seeds directly into the large pots. I’ve noticed that it seems to speed up the development quite a bit. I guess it’s becaue it’s much less stressful. I don’t get those methods of first germinate the seed using paper, then putting it in a cup, then moving it to larger puts etc.. that’s seems pretty stupid and is just a hassle imo, the seed and the seedling should be handled as little as possible i think.

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ilyaas123
Well-Known Member

You don’t need a black bag over them, just treat them as any old seed and stick them in dirt and wait for them to pop out. There is nothing different about germination of a cannabis seed compared to germination of any other similar seed i.e. klip dagga, catnip, fruit seeds etc.

You do not need lights to germinate cannabis seeds and if you do then it is not at all going to help speed up the process; I mean, how are lights going to help your seed absorb more moisture and root?

cat of curiosity
Well-Known Member

light kills roots. end of story.

as for germinating, you don’t wait on seeds that don’t germ to sprout. you only plant root tips. for smaller cups, it’s called root building, you get bound in a cup, then transplant larger, to utilize the maximum amount of medium. if you plant in a large container, roots grow to the outside of the pot, then coil, with virgin soil between center and perimeter. big waste, especially if you’re paying for the privilege.

NanoBrainz
Active Member

ilyaas123: I’ll leave the bags on for now, the HPS does dry out the top layer quite fast.. and no, i’m not saying the seed NEEDS light, i know it doesnt. Just wondering why total darkness is always recommended in guides.

catofcuriosity: I’ve heard that too, but a lot of times i’ve germinated seeds in clear plastic cups, the roots has been exposed to my 1200w HPS lights, no problem at all.. The pots i’m using now are of the usual kind (black) and the roots are not exposed to light, but yes it’s possible that light maybe seeks its way through the soil and therefore it could be harmful to the roots..

I usually have 100% sucess rate of germination, so it’s not an issue that some will not sprout. If they don’t no big deal since i always have 2 as back-ups in cups. And yes i’ve also read that it’s important to build a root ball, but i’ve never seen any difference to be honest (i always examine the roots of the finished plants).

ilyaas123
Well-Known Member

Well. At the end of the day it’s all up to you and I can’t force you to do whatever so good luck. Doing what you are doing will not harm your plants but is unnecessary.

NanoBrainz
Active Member

Well my argument was that it seems unnecessary and possibly harmful to go through the paper method, putting it in a cup, transplating (some seems to transplant 2-3 times – very stressful to the plant to say the least). That’s a a real hassle when handling a lot of plants.

But yes, each to his own i guess.

cat of curiosity
Well-Known Member

Well my argument was that it seems unnecessary and possibly harmful to go through the paper method, putting it in a cup, transplating (some seems to transplant 2-3 times – very stressful to the plant to say the least). That’s a a real hassle when handling a lof of plants.

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But yes, each to his own i guess.

ilyaas123
Well-Known Member

Agreed, You do it right then you get a 100% success rate and it’s not that hard so it’s almost impossible to mess up on it unless you have really shaky hands or are just purposely trying to kill them before they even get to absorb some light

NanoBrainz
Active Member

yeah never had a plant die on me because of transplant, i just mean it seems like the plant does develop a bit quicker when not under the stress of transplanting several times.. i’m quite sure a lot of the roots are harmed when transplanting, even if very careful, the roots are extremely fragile (newly developed parts)

midnitetoak
Active Member

Find what works for you & stay with it- you don’t have to copy others or do what anyone says to make up your own rules

churchhaze
Well-Known Member

I’m with you 100% on this. I’ve never understood why so many people/guides insist on putting seeds in the dark while germinating. There’s no scientific basis behind this. In fact, for many plants like lettuce, light is required for high success rate and speed.

One experiment that’s repeated a lot with lettuce seeds is having a sequence of pulses, either 660nm (R) or 730nm (FR) followed by dark, and what they determined was only the pulse at the end of the sequence mattered. If the last pulse in the sequence was red, most of the seeds would germinate, and if the last pulse was far red, most would fail to germinate.

For example, if your pulse sequence was [R, FR, R, FR, R], it would be equivalent to [R] since R was the last pulse in the sequence and all the seeds would germinate.

Light helps lettuce seeds germinate, so why would it inhibit cannabis germination?

With pot, light seems to contribute little to germination success however.

Theory aside, I’ve always germinated in the light for years and see no reason not to. I feel like the plant wants to start its life off in the day, and not have an extended period in the dark as its first experience.

Why is darkness recommended for germination? Doesnt seem to make much sense to me, why would darkness be beneficial to the seed in any way? Just curious. I have some seedlings already but decided to go for a few more plants, so i’ve put the seeds in the pots in the same room, threw some black garbage bags over the pots to avoid some of the light + it add more moisture..

I’ve tried germination using a few methods, nowadays i always plant the seeds directly into the large pots. I’ve noticed that it seems to speed up the development quite a bit. I guess it’s becaue it’s much less stressful. I don’t get those methods of first germinate the seed using paper, then putting it in a cup, then moving it to larger puts etc.. that’s seems pretty stupid and is just a hassle imo, the seed and the seedling should be handled as little as possible i think.