Potting up theory - why in stages? How does a large pot stress a plant?

Hello everyone

I've been thinking about this with regards my tomatoes, but I'm also curious about it from a more general point of view... I should add that I am a newbie too, with an enquiring mind! :)

What I'm wondering is, why do plants need to be potted up in stages? Taking tomatoes as an example, why pot them up from trays, on to 7cm/9cm pots, then to 9cm/12cm pots, and then onto their final growing positions? I am presuming that potting them into too large a pot from the start will stress the plant, but how and why?

Yours curiously

Max

Posts

  • Pete.8Pete.8 Billericay, EssexPosts: 4,736

    re-potting will stress any plant to some extent due to root disturbance, but the broken roots soon recover.

    Planting a small plant in a big pot wont cause any more stress directly, but with a lot of wet compost around the small rootball, the roots don't need all the extra water and nutrients which can cause the compost to become stale before the roots actually penetrate it and make use of it.

    Fast growing plants like tomatoes are usually ok in a big pot as they grow quickly when the warm weather arrives, but something much slower growing may end up rotting due to the abundance of water that isn't being used.


    I'll be transplanting my g/house toms from their 8" pots directly into 22L pots soon as the weather allows

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Or, to put it another way, do you immediately feel more comfortable in clothes that fit you or hand me downs that you have to grow into ?image

    Sorry Pete - must be this excess of sun todayimage

  • Pete.8Pete.8 Billericay, EssexPosts: 4,736

    :) that's the quick answer

    Not much sun here today - huge clouds, a very chilly breeze and a few brief hail showers - where are those balmy days of March?

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • I think also that some plants are more liable to rock around and be unstable if they're put into a pot much larger than the rootball. It's easier to plant them firmly in a pot that's not too big.

  • WelshonionWelshonion Posts: 3,114

    Too big a pot is a waste as roots will go outwards so most of the soil will be wasted as the roots will never go in it.  In a smaller pot the roots will have to utilise all the soil.

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