Germinating weed seeds. It’s not a difficult task as such because in almost all cases it works in one go. Sometimes, though, there are a couple that don’t want to germinate and naturally you‘d like to know why. And guess what? Very often the problem has a completely logical cause. There are lots of factors that can result in weed seeds not germinating. Are you too experiencing these problems? This blog examines the commonest problems and provides tips for helping germination in the best way.

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Germinating a seed. At first sight it seems so simple. And in most cases everything goes well. Even so, it occasionally happens that customers come back to us about a seed that wouldn’t germinate. We then try to figure out the cause and help out our customers. Apart from that, we want to properly inform everyone and prevent the same mistake from being made twice. So, read this blog carefully to make sure that you do everything correctly and don’t waste any expensive weed seeds.

Cheat Sheet for Germinating Weed Seeds

  1. Use a germination tray or coffee filter and keep away from sunlight.
  2. Make and keep weed seeds moist throughout the entire germination process.
  3. For germinating weed seeds use mineral water with the correct pH.
  4. Germination takes a maximum of one week. Usually 2-4 days.
  5. Germinated? Always plant root downwards.
  6. Storing seeds? Can be stored for a good 10 years if kept cool and airtight. Otherwise for a maximum of 6 months.

Germinating Weed Seeds in Various Ways

Weed seeds can be germinated in all kinds of ways. In a cup of water, between cotton pads, in a coffee filter or directly in the ground. Everyone has their preferred method. But it’s important to know that some methods are more effective than others. In any event, we recommend you to first germinate the weed seed before planting it in the soil. This method gives you the most chance of success. Moreover, this gives you the most influence over the germination process. This is far less the case when you put the seed directly into the soil.

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Make sure there is a root coming out of the weed seed before putting it in the soil

Why Weed Seeds Don’t Germinate

Weed seeds should germinate in 95% of cases. They are of course natural products and it can sometimes happen therefore that you get one that doesn’t want to come out of its shell. But if several weed seeds fail to germinate then there is something wrong with the conditions under which you are trying to germinate the seeds. We list all the possible causes below. Read through them carefully and see whether one of these factors might apply in your case. 

Temperature and Humidity

- Temperature and humidity are probably the key factors in the germination of weed seeds. They need warmth and a high humidity to be able to come out of their shell. Ensure a temperature of at least 20 degrees. The humidity must also be high. 

+ The ideal temperature for germinating weed seeds is around 22 to 25 degrees Celsius. To maintain high humidity we recommend you place the dampened germination tray or coffee filter in an airtight Zip Lock bag. It’s worth investing in a humidity and temperature meter to keep a close eye on everything.

Tip: do you want to be assured that the conditions are always right? If so then germinate the weed seeds in a Propagator! This container ensures the correct temperature, humidity and light.

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Seedlings from weed seeds germinated in a propagator

Water and pH Value

- Germinating weed seeds involves working with water. It’s important for the water you use to have the right pH value (acidity). The seeds are very sensitive to this. A good pH value for germinating weed seeds is 6.0. So don’t use rain water or tap water. This may have a pH value of 8.0 or higher.

+ It’s best to use mineral water for germinating weed seeds. But please note: not every brand has the same pH value. In the Netherlands, for example, you can use Spa Blauw. This has a favourable pH value of around 6.0. Check the packaging to see whether the pH value is stated.

Amount of Water

- Moisture is very important for germinating seeds but you shouldn’t overdo it. Too much moisture is not good for the seeds and can reduce their germinability. 

+ Sometimes we are sent photos of germination trays or filters that are completely filled with water. This is not the idea. Make pads, filters or trays nice and wet but never allow the seeds to be completely under water. Certainly don’t put them in a glass of water for a couple of days.

Sun and Light

- Weed seeds are averse to direct sunlight. Light is not necessary at all for germinating seeds. Just think – roots grow under the ground. In the absence of sunlight. So don’t lay the seeds uncovered on the window sill or next to the window.

+ It’s best to put your weed seeds in a warm, dark place. For example, in the cupboard next to the central heating boiler, or on your TV cabinet in the living room (out of direct sunlight).


- Are you working with older weed seeds? These are quite capable of germinating but what’s important is that they were stored in the right way. Weed seeds should be stored airtight and in the refrigerator. If you don’t do this then the seeds are viable for about 6 months. Thereafter the germinability is reduced and they might no longer sprout.

+ Store weed seeds in the refrigerator at a temperature of between 3 and 7 degrees Celsius. Ensure that no moisture is present as otherwise germinability can be reduced. Fortunately, airtight often means watertight as well. Kept in this way the seeds can remain viable for up to 10 years!

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Wrong Medium

- Are you germinating your weed seeds by placing them directly into the medium? If so then it’s very important to use the right medium and for it to be in optimum condition. Use soil for cuttings instead of soil with additives. It shouldn’t contain too many nutrients. In addition, the humidity needs to be right with not too low a temperature. Mould and pests are also dangerous and increase the chances of failure. Besides all that, you cannot determine in advance that the root will be pointing downwards when the seed does sprout. Briefly put, there is plenty that can go wrong if you plant directly into the soil or another growing medium.

+ Are you nevertheless still planning to plant the seed directly into the soil? If so then ensure mould-free soil for cuttings, temperatures above 20 degrees, lots of sunlight on the medium, high humidity and the right pH value (6.0 - 6.5). But please note: as stated earlier, the germination percentage is usually lower with this method. You can’t see what is happening and once you’ve placed the seed in the soil you have no further influence over it. We therefore strongly recommend you don’t use this method.

Wrong Way Up in the Soil

- Have you got the weed seed to germinate and are now looking to put it in the soil? It’s important then for the root to be the pointing the right way. Some people think that this little thing has to grow upwards. But this is not the case. That little thing is the root which always germinates first. Point this tiny root downwards when you plant the seed in the soil.


With the root downwards in the soil

Don’t place the seed directly into the soil for germination. Although purely natural, the chance of your plant emerging is considerably less than when you follow our instructions.

Patience is a Virtue

- We often get messages from people who have given up hope after a few days. Be patient! Generally speaking, weed seeds take 2 to 4 days to germinate. But it can happen that seeds take a week for this. Are you still putting them directly into the soil, despite our warnings? If so then it can take a good 2 weeks for your seedling to emerge above ground.

+ Therefore it’s important to have patience. With the coffee filter or propagation tray methods wait a maximum of 7 days. If there’s still no sign then check whether the environment meets the above-mentioned factors, otherwise get in touch with our customer service.

Tip: don’t open the filter or the container every day to take a peek. Leave the seed alone to do its stuff. Too much messing around will reduce the germinability or damage the tiny root.

No additional nutrition for Seedlings

Germination is not the end of the matter. The seedling you end up with is very vulnerable for the first 2 weeks. It’s vital in this phase that you don’t give it any extra nutrition. That could be fatal during this vulnerable phase. So just let nature do its work and wait patiently!

Tools for Germinating Weed Seeds

We understand perfectly that it can be difficult at times to create the ideal conditions for the seeds. For that reason, we have several tools for you in our range, such as the Propagator. These things make the germination of weed seeds a good deal easier and give you the best chance of success. An overview:

  • Spongepot: this is an ideal medium for germinating and rooting your seeds and cuttings. It is 100% organic, simple to use and facilitates a high percentage of healthy seedlings. The spongepot medium is ideal for beginners and a must for serious gardeners. So, are you experiencing difficulty with getting your seedlings to come up? The spongepot will help you!

  • Seed Germination Kit: you’ll find everything you need to turn a seed into a small plant (seedling) in our seed germination kit. The germination kit includes several germination trays, cotton pads, cutting labels and clear instructions. Tip: are you buying house-brand weed seeds from Dutch Headshop? If so, you get a free germination tray with cotton pads, instructions and cutting labels as a gift with your purchase.

  • Seedbooster Plus (Plagron): the Seedbooster Plus from Plagron is a convenient and effective tool. This is a germination accelerator that speeds up the germination cycle and provides new weed seeds with extra germinability. The uniquely applied enzyme technology can speed up the entire process by up to 40%. Moreover, it can restore germinability back to older weed seeds.

  • Seedbox Germination Kit (Plagron): the most complete tool by far for the germination of weed seeds. This box literally contains everything you need: a germination tray, plugs (pieces of medium), seed booster and a user guide. Do you want to give your weed plants the best possible start? In that case, the Seedbox Germination Kit is what you’re looking for.

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Further Instruction for Germinating Weed Seeds

We’ve written previous blogs about germinating weed seeds. Looking for clear instructions? Then check out the following blogs: