Plants growing in pots from the very small (50mm diameter) to very large (half wine barrels or planter boxes) have a finite quantity of potting mix around their roots.
This mix is made from composted bark. The composting process doesn't stop when the mix is bagged for sale - it is a continuing process which results in the mix eventually breaking down completely
The symptoms of a potting mix being past its useful life include:
The frequency of repotting will be influenced by the quality of the potting mix that:
Over time, the level of the mix in the pot will drop ('slump') because the mix has broken down to such an extent that it has washed out the drainage holes or has compacted to become a solid mass.
If you use a premium mix that meets the Australian Standard, this may take two or three years due to the high quality of the raw ingredients it's made from.
However, if you've used a cheap mix made from un-composted bark or sawdust, you're likely to find that it has slumped badly in just a couple of months.
We recommend repotting or topping up* at least every two years with a superior or premium potting mix to ensure your plants have the best growing conditions and nutrition you can provide.
* Large containers and barrels that are physically too large and heavy for a complete repot may be topped up with fresh mix every year or so, to bring the mix back to its original level and replenish the nutrients in older mix.
If you don't repot when plants need it, you run the very real risk of plants becoming pot bound - they outgrow their existing pots. Their roots may completely fill pots, displacing the potting mix and depriving them of water and nutrients. Pot bound plants will struggle to survive.
Some plants are very vigorous and may outgrow their pots in just a few months. These fast growers may be moved into pots one or two sizes larger than you would normally use, to cater for their rapid growth and reduce the number of times you have to disturb their roots over a growing season (Spring to Autumn).
Plants may also become pot bound because you've forgotten about them for a few years, noticing them only when they are showing signs of decline. They are likely to have exhausted all of the available mix and nutrients and their roots will completely fill the pot, may be even growing out through the drain holes around the base.
You have a reasonable chance of saving them by repotting into larger pots and fresh mix, and then lavishing them with some TLC for a few weeks!
After repotting, make sure to water plants thoroughly to 'settle' the mix, removing air pockets and ensuring it is thoroughly wet. To help plants overcome the trauma of being disturbed, add Scotts Pure Organic Premium Seaweed Plant Food to the water (30mL to a 9L bucket).
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A premium potting and planting mix that nurtures plant growth and health above and below the soil, it contains a blend of composted organic materials enriched with Scotts Osmocote® plant food
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