Gardeners and garden magazines often refer to the need to 're pot a plant' but how do you know when to do this?
Re pot too soon and you risk a small plant loosing itself in an overly large pot, too late and the roots are a tangled mess and the plant is pot bound.
The first thing is to look at the underneath of the pot, carefully holding the plant in place. Can you see roots and plenty of them?
If so slide the plant out of the pot and look. Illustrated left is a cucumber plant and you can see that there are lots of roots, filling the space and most of the compost, but not jammed in. This plant has filled up its pot, it is ready for potting on, just at the right stage before it becomes too congested.
Given that I want to make sure the cucumber has lots of growing space I potted it on into a pot around 10cms (in total) larger than the existing pot so it has about 5cms depth and on each side to grow into. This is a bit generous, but cucumber are vigorous and growing strongly at this time of year. It will expand nicely into the space and hopefully soon some juicy home grown cucumbers to enjoy.
Take care not to pot a plant into too large a pot, especially in the early stages when the plant is small. Often in a too large pot the plant will sulk, it can die back. Compost is differently constructed to soil and the compost and be too wet for the small plant, it takes longer to dry out than soil causing the plant to become stressed and fail to thrive. It is essential to plant health in containers to pot up size by size, just a few centimeters up each time not a leap into a large pot.
If you think the pot is a little too large hold back on the watering until the plant gets further establised.