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You always hear on gardening or allotment sites about people ‘potting on’ or ‘potting up’ different plants – have you ever wondered why they need to keep moving plants from pot to pot?

Plants need to be repotted because they grow at different rates and in different ways. So, just like a toddler growing up and needing new shoes – plants need new pots.

Most young plants need a pot swap every month or so often until they reach their mature size or can be put out directly into the garden. Mature or indoor plants only need repotting once a year – unless you are feeding them regularly.

Their new, larger pot allows for fresh nutrients to be added and gives more space for new roots to form. If you don’t upgrade plants into bigger pots – they become ‘pot-bound’ and their growth will be stunted.

The Compost

When you put in new compost – it is full of nutrients that will feed and sustain the plant. Usually, when repotting, you put in a layer of the new soil at the bottom and then sit in the whole root ball from the old pot. There is only so much energy and nutrients in compost – so each new pot only has a certain lifespan.

These nutrients are gradually used up by the plant for food – or are washed away if you water from the top and don’t have a catch-tray. Once they are all used up the plant can’t grow anymore – so needs to be repotted.

The Pot Itself

There is only so much space inside a pot – so you need the right balance. Starting young plants off in smaller pots makes sense while they are growing so you don’t have a tiny seedling in a foot-wide pot.

It also helps to control the root’s growth so it stays more dense.

When you notice the roots coming out the bottom of the pot – it is time for an upgrade.

Ideally, you do this when the plant is quite dry so you can gently prise apart the exterior of the existing root system to let in some fresh air.

This allows the roots to send out new shoots into the fresh compost of your bigger pot – encouraging new growth.

The Type Of Roots

Each plant has its own favorite way to grow – and this can sometimes affect the pots you use. Some plants, like lupins; and vegetables, like beetroot, don’t like their roots tinkered with at all – it can kill them.

Therefore, they need to be started off in a larger or at least deeper pot so they don’t need to be repotted quite so often – or at all. Other plants are so sensitive as seedlings that they should be planted in tiny pots or trays so they all have their own tiny piece of dedicated space or they can’t form a good early root system.

Yet more plants only need to be sitting on top of the soil to germinate – any deeper and they won’t get started.


Needless to say, understanding plant roots can be key to a successful garden. Plants will always need to be repotted as they grow if you want them to achieve their full size. So, take care of their roots and work with them: you won’t be disappointed.