Time to re-pot? Look for these signs
Potted plants make a great show, writes Gerry Daly, and a little care will help them flourish all summer
WHATEVER the size of your garden — and many of us now have just a balcony or backyard — potted plants are more and more popular. They add greatly to the decorative value of the garden, paved area, conservatory or indoor space, partly because of the plants in the pots and partly because of the decorative value of the pots themselves — their colour, shape and the materials of which they are made. While the pots are pretty much unchanging through the years, perhaps acquiring an attractive patina of age, the same cannot be said of plants in pots.
Invariably, because pot-grown plants have limited root space, they begin to decline after a couple of years unless efforts are made to maintain their vigour and health. The roots continue to grow round and round the inside of the pot when they reach that barrier. Year after year, new roots are produced from the start of the growing season and a fair proportion of these die off at the end of the year.
The build-up of old dead roots makes a kind of dense thatch of withered material just inside the pot surface. This can seal the root ball and make it more difficult for new roots to thrive, and for air and water to penetrate. In fact, some plants even force themselves out of their pots, layer upon layer of dead and living roots building on top of each other.
The pot’s compost is limited too and capable of carrying only a certain amount of nutrients and water, which the plant is completely dependent upon. If the plant isn’t watered and fed regularly during the growing season, it will grow poorly and might even die.
Even with regular watering and feeding, there comes a point, after a few years, when the volume of compost is simply not adequate to the plant’s needs. Its top will have outgrown the root system and try as it might, the root system is only capable of barely keeping the plant going and is not sufficient for growth.
Plants in pots need to be re-potted every few years. Whether that is two years, five or even 10 years depends mainly on the size of the pot, the size of the plant, its rate of growth and how well it has been looked after. Ironically, if a plant has been well fed and watered regularly, it is likely to outgrow its pot more quickly than one that has been neglected.
These few weeks, as potted plants start into growth again, is the time to look at each one and make an assessment of whether it needs to be re-potted. If you re-pot a few each year, the stock of plants will remain in good condition and many more years can be got out of them.
If they are left to struggle, some will die and others will look miserable. Some may need to be planted out into the open ground, or given away to people with more space for them.
During the summer, make a note of which plants will need to be repotted next spring. If a plant needs nearly constant watering and tends to fall over or blow over easily, re-pot it now, even though growth is well advanced, because it is not going to get any better during the drier months of the year. This advice applies both to outdoor potted plants, such as rhododendron, Japanese maple and pieris, and to indoor plants that may have become tired and shabby in recent years.
When potting up any plant, mix half compost with garden soil as this keeps vine weevil, that common pest of pot plants, at bay, and use only a slightly bigger pot.
Remember that plants in pots are completely dependent on their owners for water and feeding. Water enough to keep them just moist — so keep a close eye during sunny spells — and feed them every two to three weeks with a liquid fertiliser until the end of August.