Whether you are buying plants or have your own potted, it is best to check they are not becoming pot-bound. This short guide to repotting plants will help you to pick a satisfactory pot and the correct compost to house the roots. Plus we’ll have a few to ensure that the plant will settle down successfully in its new home.
Repotting plants – questions you need to answer
- Is the plant pot bound? If no return the pot to its growing quarters. If yes see below.
- Is the pot less than 10in across? If yes, see below.
- Do I want the plants to grow bigger? If yes, then you’ll be repotting plants. If no, Choose a pot that is the same size as the one the plant is already in or clean the same one. Then remove about a quarter of the compost around the root ball together with the outer dead roots. then re pot with some fresh compost and trim back some of the top growth of the plant.
Choosing the growing medium
Soil taken straight from the garden is totally unsuitable for filling pots. It may well contain pests and disease organisms which would flourish under warmer conditions indoors, and its restrictions within a pot which is then regularly watered is almost bound to lead to a complete loss of structure. For this reason indoor plants are grown in a special medium known as compost. In nearly every case multipurpose composts are used, but you can buy special mixtures.
The basis is loam, made from stacked grass-downwards until well rotted. Shortage of supply has meant that good quality topsoil has been substituted in most cases. Poorer-quality soil will always produce a unsatisfactory compost. Other organic ingredients are added, and all are sterilised before being blending with fertiliser, lime and sand. The introduction of the John Innes type composts has removed the need for a wide array of mixtures.
Because loam is difficult to obtain and its quality is variable, modern composts are based on peat, or peat and sand. These soilless composts have many advantages over soil-based composts. Their quality does not vary and they are lighter and cleaner to handle. Perhaps the most important advantage is that the plant that is to be re-potted was almost certainly been raised in a peat based compost, and plants do not like a change in growing medium.
Most manufacturers of soilless compost, produce a single grade which provides the plant with enough food for a few months. This fertiliser content makes the potting compost too rich for sowing seeds or taking cuttings.
Soilless composts have one or two drawbacks. All-peat composts tend to be difficult to water, once they have been allowed to dry out, and lightness can be a disadvantage when a large plant is to be potted. Use a multi-compost which contains soil and sand as well as peat if extra weight is required.
Aggregates in hydroculture
Porous clay aggregates replace compost as anchorage for the roots, and both roots and aggregates are bathed in a dilute fertiliser solution.
The solution is usually housed in a special container – the hydropot. These hydropots first appeared in the 1970s but have not become popular and are difficult to obtain. They are expensive but have the advantage that they only need watering every few weeks.
The plants grown in hydroculture develop thick, fleshy roots in place of the thin fibrous ones which grow in soil. Some plants succeed better than others. Cacti do surprisingly well, so do Aglaonema, Philodendron, Scindapsus and Spathiphyllum.
Recognising a pot-bound plant
Most house plants thrive best in pots which appear to the beginner to be too small for the amount of leaf and stem present. It is a mistake to re-pot into a larger receptacle unless the plant is definitely pot-bound.
Some plants will only flower when in this condition and there are others, such as Bromeliads, which should never need re-potting. Stem and leaf growth very slow even when the plant has been fed regularly through the spring and summer. Soil dries out quickly so frequent watering is required. Roots growing through the drainage hole.
Final Check: Remove from the pot, holding the plant upside down with your fingers firmly supporting the stem of the plant. If the plant is pot-bound there will be a matted mass of roots on the outside, and not much soil will be visible. If it is not pot-bound, simply replace the soil ball back into the pot: no harm will have been done.
The best time for repotting plants in the spring, so that the roots have plenty of time to become established before the onset of the resting season, Choose a pot which is only slightly larger than the previous one. To large a difference will result in a severe check to growth. Have everything ready before you start, pots, compost,, watering can etc.
- If pot has been used before, it must be thoroughly scrubbed out. A new clay pot should be soaked in water overnight before use.
- If a clay pot is used, cover the drainage hole with “crocks” ( broken pieces of pot or brick). Place a shallow layer of potting compost over the crock layer.
- Water the plant, one hour later remove it from the pot by spreading the fingers of one hand over the soil surface. Invert and gently knock the rim on a table. Run a knife around the edge if it is necessary. remove the pot with the other hand.
- Take away the old crock, carefully tease out some of the matted outside roots. Remove any rotten roots but avoid causing extensive root damage.
- Place the plant on top of the compost layer in the new pot and gradually fill around the root ball with potting compost which should be slightly damp.
- Firm the compost down with your thumbs, adding more until level with the base of the stem. Finally tap the pot gently on the table several times to settle the compost.
- Water carefully and place in the shade for a week. misting the leaves daily to avoid wilting. Then place the plant in its growing quarters and treat normally.
If you found Repotting plants – top tips for healthy growth helpful, you’ll find more gardening tips and advice for all levels on our Gardening Channel.Last modified: July 18, 2023