Growing Pot in Pots

Soft Secrets
22 Jul 2013

Growing with pots and soil is a great introduction to indoor gardening; it is also a cheap way for amateurs to get started.


Growing with pots and soil is a great introduction to indoor gardening; it is also a cheap way for amateurs to get started.

Soil growing (known as 'biological' cultivation in Europe, as opposed to hydroponic or aeroponic) is also relatively forgiving when it comes to under- or overfeeding, and there is little need to amend the pH of your feed, as the soil will buffer it for you.

Inoculate your medium with mycorrhizae at every stage of potting-up

This method is pretty straightforward and can help a new grower to anticipate the watering schedule for their plants. If the pots feel light-weight, it is time for a watering; if the pots are heavy, just leave them for a couple of days - you will get a feel for this after some practice. Plants are also pretty good at telling us when they are hungry and need feeding or, on the flip side, if we are feeding them too often and 'killing them with kindness'.

 

Knowing when and how to re-pot a plant can be confusing, but once you understand why you need to do it, then it all starts to make sense. Re-potting the plants into larger containers is known as transplanting or potting-up.

Why should you pot-up?

If you are new to growing in soil and pots, you may well be asking yourself why you don't save yourself the effort of potting-up and just plant or transplant straight into your final pots? In theory, this is possible - particularly if you only wish to grow small plants, or if you are growing auto-flowering plants, which will begin flowering after a couple weeks of growth.

Potting a small plant into a very large container will slow its growth for two reasons:

  • The plant's energy will be focused upon producing roots to fill the available space in the container, rather than being sent upwards (producing leaves and branches), so the plant will spend time growing downwards instead of up.
  • When you water a large pot with a small plant in it, the medium will stay wet for a long time. This is because there are not enough roots in the container to uptake all the water and nutrients. The saturated medium will contain less oxygen, which further slows growth.

At this stage, it is essential to avoid re-potting plants that are flowering. When a plant is in flower, it should be directing all available energy into producing buds, not roots or new leaf growth. Its root zone - its foundation - should already be established by the time you switch to flowering. The stress of re-potting will also have a detrimental effect upon the yield of the plant.

The key to fast growth in the vegetative cycle is to start with a small container and encourage the plant to fill it with roots as quickly as possible. You can then pot-up to the next size of container before the plant becomes pot-bound.

Do not let your plants become pot-bound

'Pot-bound' refers to when the roots of the plant have completely filled the pot, become incredibly tight and begun to grow into each other. The amount of available oxygen in the root zone will decrease and plant will basically stop growing. A retardation of growth is one of the first indications that it is time to pot-up.

The second warning will be yellowing leaves. Most growers understand that yellowing leaves are a signifier of nutrient overload (or, concerning certain elements, underfeeding) and increase the dosage of nutrients when they next water; in the majority of cases, this approach is correct. However, when your plant is pot-bound there is simply not enough space left in the root zone for new growth, and the root system is struggling to sustain the existing growth. This can be rectified by feeding more frequently, but it is easier to just pot-up.

After yellowing leaves, the final and most obvious 'red flag' is that leaves will start to die off. If your plants get to this stage, there is clearly something wrong and the roots are choking out nutrients.

When should you pot-up?

When re-potting a plant, the size of container you choose will be dependent upon how many times you want to re-pot throughout the growth cycle, how soon you want to flower your plants and how large you want your plants to grow.

For a regular growth cycle, around twelve weeks, you probably will not want to pot-up more than two or three times. The first pot-up involves placing the starter cube into a small (ten- to fifteen-centimeter) pot; some growers even plant seeds directly into these small pots and place a plastic bag over the top to act as a mini propagator.

Concerning the second pot-up, once the roots of the young plant have filled the starter pot, the plants can go into the next size up, anything from a three-liter to eleven-liter pot. For many growers, this will be the final pot, the one in which they flower the plant.

For gardeners who are growing bigger plants and want to finish them in a relatively large container, a third pot-up is suggested. Be sure to let them fill this final container before switching them into the flower stage.

Remember, in order to efficiently use both the soil and nutrients, the roots should fill the pot before you switch the plants to flower. Otherwise, you are just wasting growing medium.

How soon you want to flower your plants is a major consideration when deciding upon your final pot size and how many times you will need to pot-up. Obviously, every grower is aiming for maximum yield. However, you need to decide if you want to achieve that yield by growing lots of plants and switching them to flower quickly - which will keep them small - or if you are aiming for harvesting large yields from each individual plant.

If you want to do the latter, then you will need a longer vegetative period and larger pots. The vegetative period is the time to build the foundations of your grow. Once you switch to twelve hours of light to flower the plants, they will stretch and then you will want to pretty much stop root and leaf growth, diverting all their energy into producing flowers. The size of the flowers that they produce will be relative to the foundations built during the veg period.

What types of pots are most commonly used for growing and transplanting Cannabis?

Unlike your local garden center, your local grow shop is unlikely to stock ceramic or metal containers. That is because these containers can leach substances when they become wet and this can upset the balance of nutrients in the growing medium. They also tend to have pretty poor drainage - particularly ceramic containers - and this can leave your plants water-logged and slow their growth. For the best results, it is safer to use non-leaching plastic containers.

Plastic containers are fairly low-cost and come in a variety of different colors, with the least expensive usually being black. Dark-colored or opaque plastic is best, as it protects the root systems from damaging light. It can be tempting to head down to your local garden center and pick up some really inexpensive, circular terra cotta pots; these will certainly do the job, but they crack easily and cannot be used again. Many growers prefer the more heavy-duty black plastic pots that can be used for a good few grows - as long as you can be bothered to clean them! And, as a side note, it is nice to support your local grow shop by purchasing your pots from them.

When you visit your local grow shop, you will be faced with a wide range of containers of varying sizes and shapes. Whether you select square or circular pots is really down to personal preference, and what they have in stock at the time. Square pots are more space efficient as they can be placed next to each other, leaving no wasted areas. If you prefer a very large container - over eighteen liters - these are usually only available in circular sizes.

A fairly recent addition to the market is 'air-pruning' pots, which are designed to increase the root mass of the plant, resulting in faster vegetative growth and, consequently, higher-yielding plants. Air-pruning pots have perforated sides that expose the root tips to the air, once they reach the sides of the pot. In a regular pot, the root would simply circle around the inside circumference; however, in a pruning pot, its progress is halted. This causes the root to put out secondary shoots, which in turn reach the side of the pot, are air-pruned and put out their own secondary roots. Thus a larger root mass is created, which means greater nutrient uptake and faster growth.

Air-pruners are available in a few different variations, each with their own pros and cons. The air-pots come flat-packed and are easy to transport - and conceal - but need to be assembled before you use them. Some air-pruning pots are made out of soft fabric material, which are easy to conceal in a bag when you are exiting the grow shop; unfortunately, though, they can really only be used once the roots grow into the fabric, and need to be scraped out once the plant has been harvested.

Root-pruning pots provide a larger root mass than regular pots

A good compromise is the root-pruners that are shaped like a circular pot, with slits cut out of their sides. These can be stacked like regular, circular pots and certainly work as well as the other air-pruning pots out there. Again, the choice is all down to personal preference and experimentation.

Bear in mind that, with all air-pruning pots, the medium in the pot will tend to dry out faster than it would in a regular, 'solid-sided' pot, due to the additional exposure to the air. Couple this with the fact that - if the air pruning pot is doing its job - there will be an abundance of roots in the pot, increasing uptake, and you will find yourself watering your plants more often.

What is the best way to transplant or pot-up?

The first thing to do when re-potting a plant is to ensure that there is adequate drainage in the container. Poor drainage will cause the medium to become water-logged or saturated; this reduces the amount of available oxygen in the root zone, which slows growth. The water needs an escape route; most pots available from grow shops come with several drainage hole in the bottom.

It is a good idea to put a small layer of (clean) clay pebbles into the bottom of the (clean) pot before you add your soil. This will provide an extra level of drainage and will prevent the soil at the bottom of the pot from sitting in the runoff after each watering and becoming saturated.

Next, remove the current pot from the plant by gently squeezing the sides and/or tapping the bottom and sliding it off, taking care not to damage the roots. Soil that has not been recently watered will slide out more easily; too-dry dirt will fall away and potentially leave the roots exposed to damage while transplanting.

A healthy white root-ball, ready for potting-up

If you have left the plant in the pot for a little too long, or if you are re-potting a mother plant that has been in the pot long-term, you definitely need to gingerly loosen some of the roots with your fingertips. If the roots are not freed they may continue to circle, instead of reaching out to the new soil, and will slow down the growth of the plant.

Fresh soil should be placed into the new container on top of the layer of clay pebbles. Keep filling and then use your hand or a scoop to make a hole for the plant. If you are using an inoculant in the soil, such as mycorrhizal granules, then sprinkle a good layer into the hole before adding the plant.

The plant goes in and soil is added around, until the container is full to the brim. You can then lightly pat down the soil to secure it in place. The top of the medium should be about half an inch lower than the top of the container.

Give the plant a light watering and then let her settle into her new home. Re-potting will cause some stress, so it is a good idea to give a small dose of stress relief, like a vitamin booster or nitrogen booster, applied as a foliar or watered in.

 

S
Soft Secrets