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Does cannabis pot size affect plant growth? You bet it does! Container size makes all the difference for a good harvest! The right size container is the first step toward successful grows that thrive and flourish.
But how do you determine the right size? What are the advantages of one size over another? Choosing the correct sized pot isn’t as easy as it seems. In fact, it can be quite difficult and confusing.
The right choice depends on several factors. How many cannabis plants do you plan to grow in containers? Do you plan to use a grow tent? Will you grow indoors or outside? What marijuana strain will you grow? How much available space do you have for your cannabis grow containers?
Don’t worry and read on! Take advantage of this article to learn how to choose the best grow containers for your needs.
Cannabis Root Needs
First, let’s talk about what a pot is meant to protect—the roots.
During the germination of a marijuana plant, the first thing that emerges from cannabis seeds is the plant’s central tap root. As the cannabis plant grows, roots and tiny hairs branch off of the central root. A healthy marijuana plant will develop an underground structure that’s similar to the structure of the branches that are above ground.
Although you don’t see your cannabis plant’s roots, they require just as much care and consideration as the leaves and flowers. Cannabis plants breathe and absorb the nutrients they need through healthy root systems. They are fed through the plant’s roots.
So what do cannabis roots need to make plants thrive? Primarily, room for the plants to grow, proper draining, and no competition for nutrients.
Room To Grow
More than anything else, marijuana plant roots need enough space to grow properly in their environment. This is especially true in the vegetative stage of growth. Root growth in the vegetative state is directly related to the plant’s ability to manage water and nutrients in the flowering phase.
If the container doesn’t have enough room, the roots become tangled together. This is known as “root bound” (or sometimes “pot bound”). In pot bound plants, root development and growth is inhibited. If that happens, your marijuana plants won’t get the nutrients they need. This can lead to nutrient deficiencies and lower yields. Make sure they have enough room if you want big yields!
That said, there’s such a thing as too much room. If your marijuana plant is in a larger pot than it needs, your soil will stay wet. If you soak your plant, they are susceptible to root rot.
To support healthy roots, your soil should stay a little wet. It should never be soaked. Make sure your soil dries between each watering. It should retain just enough to keep moist and not be completely dry. No overwatering! Waterlogged soil, excess water, and moisture can eventually cause root disease. Cannabis pots need good draining to keep dry. Get rid of all the moisture.
Marijuana growers should avoid using the wrong containers. Avoid containers unless they’re designed specifically for growing plants. A Solo cup might seem like a cheap solution, but when your crop fails and your plants die because of runoff water, you’ll see that isn’t the case! And although a pottery bowl is pretty, it won’t look so great when it’s holding a dead shrub covered with pests!
Pots designed for growing have drainage holes in the bottom to manage water. Containers that are fabric pots or plastic pots that have holes everywhere are even better. You don’t want to waste time drilling holes in pots that weren’t designed for plants!
Place large trays or saucers under the pot to collect any excess water that drains out after watering. Some people use a matching saucer or trays that match the size of the pot. The shapes aren’t an issue as long as you ensure that you catch the water runoff!
If it’s not impossible, install a drainage system so that your plants never sit in stagnant water. If you can’t setup a drain, empty the runoff water from the saucers after each watering. You don’t want excess moisture in your garden from water runoff!
Never put more than one weed plant in the same pot, no matter what size it is. Each plant should be contained in its own pot. If more plants are in a pot, the roots compete for the nutrients you pour in the pot. With this method, none of them will reach their full potential.
There’s another good reason to set a limit of one per container. If trouble occurs in one container (for example, build-up of toxic nutrient levels), you’ll only lose one plant.
What Cannabis Pot Size Should I Use?
Now that you understand what cannabis roots need, you can see why pot size is so important! But what pot size is best? Your marijuana plant will live in two or three separate containers during its life. You’ll use different pot sizes (in gallons or litres) each time.
One thing to remember is to start small with seedlings. They need large amounts of pampering to begin the best way. During the early stages of growth, sow your seeds in a seed starter kit designed for baby plants.
Most starter kits for cannabis seeds have an insert with several small cells. Put your seeds in one cell each. The kits also have a humidity dome with an air vent and a tray at the bottom to collect excess water.
You can’t go wrong by purchasing a pack of 5 or 10 trays at the Amazon market place website. It won’t cost much money. Put it in your cart for less than $10.
Don’t forget the importance of the right media for your cannabis seedlings. To avoid stressing your marijuana plants, always decide and start with the media you’ll use during your plant’s life. If you choose to cultivate in rockwool, start with rockwool. If you choose to cultivate in soil, start with soil. You can use any form of media in a seed starter kit.
Seedlings are ready to transplant to a larger container when several white roots come out. If there are only one or two, the seedling needs more root development first.
Transplanting success is closely tied with how quickly you deliver them into the containers. Work quickly! A good process is key. The tiny, exposed hairs will desiccate if they are exposed for more than two minutes.
Transfer the young plants to fresh soil in clean containers. Sprinkle some mycorrhizae fungi on the fresh soil before you transplant. The overlooked task of adding microorganisms will really help!
The first time you transplant, move your cannabis plant into a 2 to 5 gallon pot. How do you decide the right pot size? Which pot sizes are correct? Here are some things to consider:
- Will you grow indoors or outdoors? If you’re growing inside, use a small container. If you’re growing outdoors, the sky (literally) is the limit! You won’t be limited in any way. That means you can use large pots when growing outside.
- If you’re growing marijuana inside, how big is your grow space? A full-grown adult cannabis plant takes around four square feet of space. That’s a lot of space—especially if you’re growing marijuana in a small space like an indoor grow tent. It’s vital to have easy access to your garden. Don’t let large pots get in your way. A grow tent pot size should be around 3 gallons (11 liters). You can reduce the size of your weed by limiting how long you keep it in the vegetative stage of growth. If you want to do that, go with a small pot or small pots. If you have more room, use large pots or a large container.
- What strains will you cultivate? Sativas tend to spread out a lot more than indicas. Since the cannabis plant root structure is similar to its branch structure, a sativa strain needs a bigger pot than an indica plant. Smaller plants need smaller pots.
- Do you want to maximize yields? If you want to produce as much weed as possible, you’ll need bigger containers to hold your massive plants!
- How much can you lift? If you’re not strong, use a small container. It needs to be light enough to pick up and move. You can’t do that with a heavy weight.
You may wonder about the vegetative cycle for 1 gallon pot vs 3 gallon pot. How long to veg in 3 gallon pots? 30 to 35 days (5 weeks). How long to veg in 1 gallon pot? 2 or 3 weeks (14 to 21 days).
Can you flower in 1 gallon pots? You can, but it’s not a good idea. The smaller the pot, the faster growth cycle you should have. Note that when flowering in 1 gallon pots, the Screen of Green method is recommended. With big pots, you can veg as slow as you want.
Outdoor growing gives you the freedom to do what you want. If you’re growing outdoors or in a huge indoor grow space, you aren’t limited at all! You can let your cannabis plants grow as huge as you want (at least to the extent you can handle).
In this case, you may need to repot your weed more than once. As a general rule of thumb, pot size should double each time a plant is transplanted for good balance. The bigger the plant, the bigger pot you need.
So what is the best pot size based on the plant size? Growing larger plants requires larger pots. Check out this plant pot sizes chart. It shows plant height to pot size ratio!
As a rule of thumb, you should add around 5 gallons (19 liters) of plant container space for every 12 inches of growth. So if you’re growing cannabis in 3 gallon pots, induce flowering or transplant when the plant is 2 feet tall. However, that idea might lead to a really big pot grow. Sativas can grow as high as 25 feet!
Keep in mind that moving to new containers is stressful. Your cannabis plants will do better if you move them directly to the container they’ll need until harvest. They can stay in that container for the rest of the grow cycle.
Best Grow Pots for Weed Plants
So many different cannabis pots are available for growing weed! The best pot material for growing weed depends on the grow system and soil that you’re using. That said, don’t opt for materials like metal, clay, or terracotta. You’re better off with fabric pots that have more airflow.
Here are some of the best pots we recommend for growing marijuana. These different types of containers will work in your budget!
If your plants grow in soil (or in a soil-like growing medium like peat moss with perlite), your set up is well suited for Smart Pots.
Smart Pots are made of a porous fabric material. Fabric pots have better gas exchange than plastic cannabis containers. When the plant’s roots get to the edges of a Smart Pot, they stop elongating and grow fine lateral roots that enhance gas exchange. This prevents your plants from becoming root bound.
Other factors make Smart Pots a good choice. A Smart Pot provides great aeration, which enhances the health of the rhizosphere. Smart Pots dry quickly and are light weight.
Smart pots are the most commonly used pots for cannabis. Their only disadvantage is that they do not have rigid sides. Take care when moving Smart Pots!
What size smart pot for indoor grow? A 3 to 5 gallon Smart Pot will be perfect! What about a Smart Pot outdoor grow? Outdoor growers can use very large Smart Pots.
Don’t want a fabric pot? Super Roots Air Pots are excellent plastic containers. They’re good for hydroponic systems that aren’t constantly filled with water.
Air-Pots encourage the roots to follow the nutrient solution to the edges of the plastic container. This allows beneficial bacteria to release all the nutrients. When the tips reach oxygen, they dehydrate and split, creating new tips. This is known as air pruning. Greater nutrient absorption happens at these points. This encourages the plants to grow. Air Pots are also very sturdy.
Grodan Rockwool Blocks
Grodan grow cubes are rockwool, an inorganic grow medium made from basalt and chalk. The pores in rockwool facilitate the roots getting oxygen. Its massive capillary action makes it a great growing medium for hydroponic and aeroponic systems.
Grodan’s rockwool cubes have advantages over other rockwool products. They can be planted into each other. This makes transplanting very easy. Simply place the Grodan cube in a larger-sized cube and the transplant is finished!
Container Construction Material
Containers and pots intended for plants are constructed out a variety of materials, including terracotta, coir (coconut husk), plastic, ceramic, metal, wood, concrete, and rubber. The most economical, sturdy, and damage-resistant of these would be rubber or coir.
Rubber and plastic are probably the most widely used in nurseries and plants purchased for re-potting. A rubber plant container of the appropriate size makes a lot for sense for cannabis use. Many containers will shatter or chip with rough handling, but rubber bounces back and keeps performing for multiple grows.
Since nurseries rely on them so often, rubber pots almost always have adequate drainage and are able to retain moisture well.
Many cannabis growers have their personal favorite when it comes to cultivating cannabis, and compelling arguments can be made for each container medium, but there is much to be said for rubber or durable plastic, and these are the materials used most often.
Growing cannabis plants in pots requires growing media. Straight potting soil is the simplest, most widely available choice. If you have access to compost, this is an excellent way to grow organically by adding it to soil for a nutrient-rich growing medium.
A variety of premixed soils with fertilizers already added are widely available as well. Some of these are organic, while others contain synthetic additives. The vast majority of cannabis growers prefer organic media.
Other materials sometimes added to soil include sand, perlite, and coco fiber. These substances provide a less-dense soil mixture than straight soil.
This type of mixture promotes rapid root development, which is always good for a cannabis plant’s overall health. Avoid soils that contain clay or other dense matter. They will clog root development and retain too much water, neither of which is good for cannabis.
Specialized Marijuana Pots
If you read cannabis industry business publications, you’ve most likely have seen the advertisements for “air pots” and “smart pots.” These specialized pots can provide benefits for the ambitious cannabis cultivator. One of the main benefits of these types of pots is that they both provide increased oxygenation to plant root systems.
Because these pots have so much exposure from the sides, the plants never get “root bound due to the pots’ unique “air pruning” from the sides. Because the soil or other growing medium dries out from the sides when using these pots, it’s difficult to over water them. Extra healthy root systems are the end result when using them.
Unfortunately, while smart pots and air pots provide some advantages over conventional pots, they also share the same shortcomings.
Because of the dramatic increase in air exposure from the sides, these pots will require an increased amount of watering. Because of this, they will also require a decent-sized saucer to collect the excess water. This will be a minor inconvenience for some but not others. There is much to be said for the advantages these progressive pots provide.
Regardless of which pots you choose for your cannabis cultivation, be sure to follow best practices and monitor your grow carefully. With attentive care, you can produce excellent flower with most pots. Use quality genetics, provide good care, and you will enjoy the rewards of your harvest on a relatively short amount of time!
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