Pre-growing weed? "No, just take it outside!" Some parents would prefer to put their children in third grade right away. But the proverbial kindergarten is also extremely important for weed plants. Very young weed plants can't handle much yet. That is why it is important to prepare them safely for the big bad world. You can do this by pre-growing the weed.

Pre-growing weed

Pre-growing a weed plant is nothing more than giving your newly germinated weed the opportunity to grow strong in controlled conditions. In practice this means that you germinate and sow indoors, but also let the seedling phase and first weeks of the growth phase be indoors. This way you cultivate a healthy root system so that your plants can stand a rough time once they go outside. Pre-growing weed is therefore especially important when growing weed in the garden. Pre-grown weed plants are not only more resistant to excess rainwater thanks to well-developed roots, but they also have the potential to grow bigger.

Bigger Weed plant with a higher yield by pre-growing

One of the advantages of pre-growing is that your weed plants can grow bigger, fuller and taller. This has everything to do with the development of the root system. If your young weed plant has the opportunity to stretch its legs, then it will. To grow big weed plants you do need a type (strain) that can actually grow big. Look for the maximum height in our weed seed filters. For example, set the lower limit at 1.5 metres for the largest varieties in our collection.

Weed topping, fimming, scrogging and mainlining

Another advantage of raising or pre-growing your weed plant is that that controlled environment can't do much damage above ground either. For example, the number of fungi swirling by is considerably lower than when you put your weed plant outside from a young age. Temperature fluctuations are also less extreme. All advantages that help with advanced growing techniques. 

To top a weed plant is to gently prune back the main stem to form more side branches. Pruning back also makes the plant's stem stronger. This is why topping is often combined with pre-growing. Fimming is a similar technique, only the difference between topping and fimming is where you prune exactly. The result with topping is the formation of 2 strong side branches and with fimming 3 or 4 side branches that are somewhat less sturdy. With scrogging and LST (Low Stress Training) you guide the branches past obstacles to increase the surface area. This gives the branches more light and room to grow. In ScrOG (Screen of Green) the obstacle is a fence or large mesh netting, and in LST you carefully bend the branches in a direction where no other branches are nearby. Mainlining is a combination of repeatedly topping and guiding the new branches. This gives your weed plant a very regular structure.

» You can read about these and more growing techniques in our article on advanced growing techniques!

Especially when you start this kind of technique already during pre-growth, your weed plant has a head start to give you an even higher yield. But be careful not to start too early. Do not top or fim before your weed plant has at least 4 nodes (branches), otherwise it will not be strong enough to survive the stress.

Pre-growing your weed plant yourself: 4 Tips

These practical tips are meant to get you started. If you want to start growing your own weed, but have no idea where to begin. 

When can your weed plant go outside?

Frost is the weed plant killer. The ladies simply cannot stand it. Weed plants can therefore be put outside from the moment the nights are frost-free. A popular wisdom that we know here in the Netherlands is that you can put your weed plants outside after Ice Saints. Ice Saints are 4 to 5 days in May that are named after Christian saints. May 15 is the day that, according to tradition, you can put your weed plants outside.

Of course, if we look at it a little more scientifically, that particular date is just a guess. Because the more north or south you are relative to the equator, the later in the season there is still a chance of frost. We must also take the climate into account. At sea, winters are milder than inland because seawater retains a lot of heat from the summer months and releases it to coastal areas. In meteorology, one speaks of land and sea climate because of this phenomenon. Finally, human climate change also plays a role, so that night frosts often do not occur earlier in the year. 

The result is that your weed plants can go outside earlier in the year, but that depends entirely on the weather conditions. What the ladies do need is sufficient sunlight. Sativa-dominant weed plants, in particular, which have somewhat finer leaves than the broad-leaved Indicas, only thrive in bright light. So don't think in February, "Oh there will be no more night frosts, so that Blue Dream can go outside." This kind of reasoning will cause your weed plant to remain small from the very beginning due to lack of sufficient sunlight.

How long does pre-growing weed take?

Let's get back to what pre-growing is. Your weed plant is in the growth phase during pre-growth. The growth phase or, with a fancier word, vegetative phase begins when the leaves have 5 to 7 leaf fingers. This is when they are allowed to go to "elementary school". Before your ladies reach this stage, they will first go through these phases:

  • 5 days of germinating
  • 1 week for the cotyledons to come up
  • 1 - 3 weeks in the seedling phase
  • 1 - 3 weeks in the growth phase (the pre-growing)

How long you should pre-grow weed is therefore not an exact science. First of all, it depends on how you want to pre-grow. The rule of thumb here is the longer you pre-grow your weed, the stronger it can become and the higher the yield will eventually be. At its soonest, your weed plant may go outside as soon as it enters the growth phase. But you can also keep your weed plant indoors for 3 weeks during the growth phase. From the moment of germination it takes at least 5 weeks before you can put your plants outside, but how long you want to keep them inside is up to you. You can also make it 10 weeks.

When should you start pre-growing weed?

The short answer is: you can safely germinate at least as of April 25. For the full answer, we will take a little more effort.

For auto flowers: for the sake of convenience, take May 15 as the date that your weed plant can go outside. If you calculate back from that date, you will need at least 20 days from the time of germination before your weed plant can go outside. You can also germinate later in the year without a drop in yield, as long as it is light enough. 

For photoperiod weed plants: August 25 is pretty much the date that outdoor weed starts flowering in temperate regions like the Netherlands, Belgium, France, Germany and the United Kingdom. That has to do with the amount of darkness time at night. As soon as it is dark for more than 10 hours, weed plants get the signal to reproduce. This is a gradual process, so it may be slightly earlier or later. So the length of the growth phase depends on how much time you take between germination and flowering around August 25. Weed plants give a fine yield with about 15 weeks between germination and the start of flowering. A shorter growth period and therefore germinating later in the year will result in a lower yield.

What lighting do you need to pre-grow weed?

After germination, your plants first develop two lobed leaves. The purpose of these leaves is to push the seed open. Then within a week you will see the first finger-shaped leaves emerge. But this does not yet look like the characteristic weed leaf. We only speak of pre-growth when you see 5-7 fingers on a leaf. Until then you call the toddler weed a seedling.

Seedlings don't need that much light, but for the strongest weed plants, it's best to put the seedlings under blue spectrum. CFL lights for two weeks. These are special low-energy lamps for young plants. Leave the lights on for 16 hours and give them 8 hours of darkness. As soon as they get at least 2 to 3 nodes or branches, you can put them under stronger lighting such as LED- or HID lights with a metal-halide bulb. Leave them under these lights for about 2 weeks for optimal pre-growth.

Pre-growing weed on the windowsill is not a good idea. Seedlings stretch to reach for the light. This stretching in the seedling phase leads to weak, lanky weed plants with lots of space between the leaves. You can prevent this by placing the CFL lamps 5 centimeters above your plants in the seedling phase. Never put seedlings in the dark for 24 hours. They will stretch a lot, making your plants weak and possibly unable to bear the buds later on. This is exactly what you want to prevent by pre-growing your weed plants. 

Is pre-growing weed natural?

Not really, no. But nature is tough. That's why experienced hobby growers, professionals and scientists have spent years figuring out how to give you the best chance of a high yield. It may be an elaborate article, but pre-growing weed is one of the simplest things you can do to give nature a helping hand. By doing so, you reduce the chance of disease and increase both your weed plant's chances of survival and its potential yield. And that is what it is eventually all about.

Looking for more ways to increase the yield of your weed plants? Take a look at our advanced growing techniques.