Container maintenance

Growing plants in containers is a great way to bring life and colour into otherwise dull spots in your garden. Patios, balconies and window boxes are all places where plants can be easily introduced in containers. Plants in containers do require more care than those in gardens, but by following our advice you will find this easy.

You can grow a wide range of plants in containers. Image: Neil Hepworth/RHS

Quick facts

Suitable for: All plants grown in pots, troughs and other containers
Timing: All year, but mainly from mid-spring until early autumn
Difficulty: Moderate

Plants for containers

Almost any type of plant can be grown in a container. Generally, the bigger the pot and the plant, the easier it is to care for. Soft, fleshy, leafy plants such as tomatoes and fuchsias are more demanding than ‘leathery’ plants such as pelargoniums (tender geraniums) or lavender.

For more on ideas of plants to grow in containers, see the links below;

Lilies: growing in containers
Roses: growing in containers
Trees: growing in containers
Fruit in containers
Herbs in containers
Vegetables in containers

General maintenance

Planting

Plant in early spring so that plants quickly grow roots and become established. Autumn planting may lead to losses from waterlogging and evergreens may deteriorate over winter from dryness at the roots or wind-burn of the foliage.

Watering

Watering is one of the most important jobs when growing plants in containers. Roots need a balance of air and water to grow well which is easy to provide if you have a good quality compost or soil. Plants don't grow well if their roots are in very wet compost (not enough air) and plants will often benefit if the compost is allowed to dry a little between waterings. See the advice below on summer care and winter care for information on watering plants in containers. How much you need to water is very weather dependant.

Feeding

See the advice below on summer care and winter care for information on feeding plants in containers.

Re-potting

Plant roots eventually fill containers and this often reduces growth. This is not necessarily a bad thing as slightly stressed plants are often attractive and the slower growth reduces the maintenance needed. However, eventually the plant will need to be moved to a bigger container or the compost refreshed in the same pot, as composts lose their structure over time. Shrubs and trees that stay in a pot for years are especially vulnerable unless re-potted.

These steps will ensure success when re-potting into a larger container:

  • When moving plants to a larger container (one size larger at each stage), re-pot in early spring as soon as they show signs of growth
  • Remove a little of the old compost, slide the plant out and tease out roots, cutting them if necessary
  • When it is no longer convenient to repot them every year into a bigger pot, they should be repotted in the same pot at least every other year. Replace one-third of existing compost and roots with fresh compost

In years when re-potting is not carried out, topdress by removing 5cm (2in) old compost from the top of the pot and replacing with fresh compost.

Summer care

Plants in containers need attention all year, but summer is the most critical period as plants can soon run short of water and nutrients.

Watering

  • Check for moisture daily during warm or windy weather (twice daily in hot weather). If it has rained, it is still worth checking that the soil is moist below the surface
  • Water slowly but thoroughly, filling the container to the rim and allowing it to drain into the compost, then filling it a second time to ensure that the whole of the compost is adequately moistened
  • Most plants will be fine if they are allowed to dry out a little between waterings and they will adapt to using less water if less is available to them
  • Try to avoid letting plants reach the wilting stage; although they are likely to recover, their growth may be affected
  • There is no need to water until it runs out of the bottom of the pot. You could use a saucer to capture the excess and save both water and nutrients
  • If water is not draining out freely, check the drainage holes for blockage and assess compost structure – as the organic components decay, the compost becomes soggy, dense and lacking in air spaces
  • Lining or sealing terracotta pots with waterproof materials is unlikely to significantly reduce the need to water as most water is lost though plant leaves
  • Grouping pots for mutual shade will reduce heat stress on container plants
  • Mulching pots will help reduce heating and suppress weeds, but as most water is lost through plant leaves careful watering will still be needed

Feeding

  • Check the instructions on your compost bag but from April to the end of August you may need to use a general-purpose proprietary liquid feed or, preferably, a high-nitrogen feed
  • Alternatively, add a controlled-release fertiliser at planting time
  • With soil-less composts, make sure fertiliser includes essential trace elements
  • After late summer, feeding is usually suspended until mid-spring; however bedding plants and other short-lived annuals will still benefit from feeding until early autumn
  • Feed when the compost is moist

Winter care

In winter, the main danger is compost freezing, which may kill plants.

Frost protection

  • Protect pots with bubble plastic or bring them under temporary cover
  • In very wet periods move plants under temporary cover if the compost becomes sodden, until it has dried out a little. The ‘rain shadow’ of walls can be sufficient
  • In wet weather, raise pots up off the ground on ‘feet’ or similar to keep the bottom of the pot out of the water
  • Remove saucers in winter

Watering

  • Watering may still be necessary for conifers and other evergreens, especially if you have moved them under cover, so that they receive no rain. Check evergreens and conifers at least weekly and water if needed
  • Watering is seldom necessary for deciduous or other dormant plants
  • Avoid watering if frost is forecast

Feeding

  • Feeding is not necessary during the winter months

Problems

Overwatering is the most common cause of loss of container plants; watering should aim to keep the compost moist, never soggy and avoid alternating dryness and saturation.

Plants grown in containers suffer from many of the same pests and diseases as when grown in beds and borders, such as aphids, algae, liverworts and moss and scale insects. Vine weevil and fungus gnats are particularly common pests of container-grown plants.

Overpotting is another common cause of problems.

See also...

RHS video: Potting on


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