What are the benefits of regularly repotting plants?September 4th, 2015
It is often easy to forget that container planting requires much more attention than plants that are in the earth. Containers do not have their own ecosystems, a constant supply of nutrients or moisture retention and even when planted in the best media, its structure will not last longer than one season.
If a container plant is failing the first action should be to repot it. If possible taking care to do this after the plants flowering period, but if the option is ‘kill or cure’ then repot straight away
Compost in pots quickly becomes spent and will lose its structure and ability to retain moisture. You will notice this easily when watering your containerised plants as you will find that the water instantly drains through. This is a good indication that the plant needs repotting.
Once stale peat based compost will dry out and you will not be able to rehydrate it. Loam based composts like John Innes will form a ‘panned’ crust on the surface that won’t allow water to penetrate and you may find fungi or algae growing on the surface.
When repotting a failing plant all dead material should be cut off and where possible remove 1/3 of the foliage, this prevents water loss through the leaves whilst the plant is recovering. Always cut down to a shoot or node, and cut at an angle away from the node. Any dead or diseased foliage will only cause problems at a later date, if part of a stem is black/brown then remove it until you see green fresh material.
At home a repot my shrubby Salvias, Pelargoniums and any containerised shrubs every year. Within two weeks of doing so you can easily see fresh new green growth even without feeding. Always remember that certain plants do not require heavy feeding, Salvias and Pelargoniums prefer a low nitrogen compost, therefore repotting them will rejuvenate them without the need for additional fertilisers. Hungry plants like Dahlias and Chrysanthemums require more feed and moisture.
Appropriate feeds can be added to containers through either slow release fertiliser granules added to the compost. Top dressing with bonemeal or liquid feeds such as seaweed or ‘Tomorite’. I use organic all round feeds like comfrey and nettle made at home.
Pictured is an example of a container planted Pittosporum that sadly received a few months of neglect before I noticed its dire state. (yes, it happens even to experienced gardeners!) The shrub was severely dehydrated and brown throughout, my only indication of life was a slight amount of green cambium at the base after I had removed the bark with a sharp knife. I instantly repotted the plant into the same container, rubbed off the stale compost and cut back the dead growth, I barely had six inches of stem left but I had a large amount of hope.
Three weeks later the shrub as fully recovered with fresh new growth. It is not often I give up on a plant and this experience shows me I’m right not to do so.