Growing plants in containers is a great way to bring life and colour into otherwise dull spots in your garden. Plants living permanently in containers need to be repotted every few years to maintain healthy growth. If a plant has been in the same pot for some time you may find the roots have become congested and all the nutrients in the compost have been used. A pot-bound plant also dries out more quickly after watering. It’s normal to have a few visible root stragglers, but a profusion of roots erupting from the top level of soil and drain holes may signal a problem.
The signs of a pot-bound plant whose roots have run out of space in its container can include yellowing foliage and stunted growth with smaller new leaves, stems, and flowers. The plant may stop growing altogether and older leaves may drop off. The best way to check is to pop the plant out of its pot and inspect the roots. If the roots are quite congested and showing on the edge of the root ball the plant will certainly benefit from being repotted
The ideal time to repot permanent container plants is in the spring or early summer so the plant will have an entire growing season to recover, but up to late summer is also fine as the plant is still actively growing although it may be slow to bounce back.
Repotting can be into a larger pot or the same-sized container with trimmed roots and fresh soil. If you intend to use a larger container, only go up one size, from 2.5cm-5cm wider in diameter. Overpotting is a problem because the roots won’t have enough penetration to absorb water from the entire soil area, which can lead to overwatering and root rot. Also make sure the pot has ample drainage. This can be either several modest holes or a large single one.
If your plant is in such a large pot that it is impossible to pot on, it can be top dressed. The top layer of old compost should be carefully removed with a hand fork or clawed cultivator and replaced with fresh compost. This method can also be used on plants that resent root disturbance or like to have restricted, pot bound roots.
To repot a pot-bound, long-term container plant, just follow these simple steps and you will soon have a plant that will be rejuvenated and happily live again in its pot for a few years.
You will need:
- New container (optional)
- Small hand fork or cultivator
- Secateurs
- Sharp knife
- Piece of polythene to line pot
- Potting mix
METHOD
- First, remove the plant from its pot and examine the roots. Watering about 24 hours before repotting can make it easier to ease the plant out of the pot with minimal root damage. Don’t just pull the plant out of its pot. Tip the pot over on its side and gently try to jiggle the root ball out. You may have to run a long knife around the perimeter of the pot to separate the roots and soil from the inside of the pot.
- Sometimes plants left in containers for too long become congested and pot bound with a tangle of roots circling the root ball. If a plant is pot bound, use a sharp knife to first cut away the bottom 2.5cm or so of the old roots to help regenerate healthy growth.
- Next cut away some of the mat of roots from the sides, removing up to 2.5cm of roots and soil from the perimeter of the root ball, but no more than one-third of the total root ball in the root pruning process. This stimulates the growth of new feeder roots.
- Using your fingers, gently tease apart and loosen the root ball. If it's seriously entangled, take a pronged cultivator, or a small hand fork and loosen the soil and roots around the surface of the root ball, teasing out tangles and spreading the roots. This encourages the roots to expand into the fresh new soil around the ball rather than continuing to grow in circles and strangle the plant.
- Prepare the pot by placing some pieces of broken pot, polystyrene pieces or gravel in the bottom to aid drainage and prevent the compost draining out through the hole. If using a porous terracotta pot, line the sides of the pot on the inside, but not along the bottom, with a piece of polythene, cut perhaps from an old bag, to help reduce evaporation through the porous sides.
- Add potting mix to the bottom of the container. Make sure there is enough soil so that the now-smaller root ball will sit on the soil at about 2.5cm inch below the rim of the pot. A soil-based compost is ideal for a long-term container plant because the soil retains moisture and nutrients and does not break down as quickly as a multi-purpose compost. You can make your own using a mix of two parts garden soil to one part garden compost plus some slow-release fertiliser at the rate recommended on the packet to provide a steady supply of nutrients.
- Place the plant into the pot and add the fresh potting mix around the newly trimmed root ball, firming down as you go. Make sure soil gets into all the cracks and crannies between the root ball and sides of the container. If you have used a sleeve of polythene within a terracotta pot, make sure to keep the soil inside the sleeve. You may need a stick or trowel to move around the sides of the pot and make sure you have filled all the voids.
- Water generously when the repotting is done and add additional soil if needed to bring the soil level to within 2.5cm of the top of the pot which will leave space for watering. The top growth of the plant can be lightly trimmed to restore balance with the reduced root ball if necessary. Put your plant back in its familiar location but shield it from hot sun for a few days or weeks depending on weather conditions. Make sure to keep your plant well hydrated for a few weeks so it can recover and thrive. Plants vary in how long they take to recover, depending on their resiliency and how much trimming you needed to do, as well as the time of year.