Growing plants in pots and containers

Pots in autumn

There are many reasons to have plants in pots. You may not have a garden, but a balcony or roof terrace instead. Or you may need to bring greenery and colour to a part of the garden where you can’t plant into the ground such as beside the front door or on the patio. You may want to grow a type of plant that doesn’t want to grow in the conditions that your garden provides: in a container you can manipulate the soil type and the drainage far more easily that you can with open ground.  Another good reason for gardening in pots is that you may be renting your house or apartment. If you plan on moving at some point, you can have a mobile garden that you take with you when you move, eventually planting things into the ground when you have your own garden.

Pretty well all plants can grow in pots. In a garden centre, people often ask “What plant should I put in my containers?’” My response is normally to ask where the container will be going (ie sunny or shady, exposed or sheltered) and how big the plants should end up. It’s worth bearing in mind that most pots end up in more exposed parts of the garden, and many of them are for apartments where there is more wind and exposure to the elements than at ground level. The other big consideration is if the plants are going to be in an extreme of either sun or shade. You need very different plants for an essentially shady north-facing aspect than you do for a sunny south-facing area. (See my listing of top plants for containers below).

If you want a plant to grow big and stay healthy, then you need a big pot. You can grow trees and large shrubs, provided that the pot can sustain them. Taller plants such as trees and bamboos should be in lower, squatter pots as this makes them more stable. If you have a plant with a large surface area – ie a lot of leaves – that makes it act like a sail and catch the wind.  Square pots with the proportions of a cube can be good for taller plants as they have a relatively low centre of gravity. Always chose a pot size that will be able to sustain a plant into the future and has room for more growth. If the pot is too small it will stop the plant from developing properly and also mean that it needs constant watering. The larger the pot the slower it will dry out and the healthier the plants will be.

If you are growing something that you intend to have for a long time – say a tree or shrub – you should choose a pot that doesn’t narrow towards the top. If you plant, say, a gorgeous Camellia or Japanese maple that after five years needs to be transplanted, you will need to be able to get it out of the original pot. If that pot doesn’t widen towards the top it cannot be got out and either the pot has to be smashed or the plant has to stay put and suffer.

On the other hand, if you want to grow smaller plants such as bedding or bulbs, you should select smaller pots. Again, if the pots are too small then they blow over easily. When the plants develop a lot of foliage the compost can dry out quickly and the pots are less steady. Generally, a mixture of shapes and sizes is best: small pots for flowers, herbs and bulbs and larger pots for trees, shrubs or topiary.

It’s important to choose good quality compost. Using pure topsoil from the garden rarely works as it is too heavy. The best medium is to mix a multi-purpose, low peat compost mixed with John Innes compost (a soil-based compost) and some soil enricher – we use Gee-Up which is the best soil improver we know. If you are planting Rhododendron, Camellia or any plant that requires acidic soil, be sure to choose Ericaceous compost which has the correct pH (acidity level) for these plants. If you use regular compost they will look unhealthy and possibly die.

Plants in pots require special care. They don’t have access to the moisture and nutrients of open ground, so you need to provide these. Regular watering is essential. Evergreen plants such as Box, Laurel and Skimmia need watering all year round: every second week in the winter and every week during spring, summer and autumn. Plants with a lot of foliage – such as Bamboos – need a lot of water if they are in pots. In an exposed place such as a balcony they really shouldn’t be planted: they don’t much like the wind, and they don’t like drying out.

Plants in pots also require regular feeding, and the easiest for is to use a liquid feed when watering. A couple of capfuls of feed (liquid seaweed fertiliser is best) approximately once per month should keep the plants healthy. Every year the top layer of compost should be discarded and a new layer applied. We use Gee-up for top-dressing as it feeds the plants slowly and also helps maintain moisture levels in the pot.

Top plants for containers:

Agapanthus: tall blue or white fowers. Best in sun.

Bay laurel (Laurus nobilis): excellent specimen plant or topiary.

Box (Buxus sempervirens): excellent for topiary and evergreen structure.

Bulbs: Tulips and Daffodils thrive in pots.

Camellia: a glossy evergreen shrub. For a sheltered spot out of full sun.

Herbs: Oregano, Mint and Rosemary (preferably the prostrate form). Best in sun.

Hosta: away from the slugs, Hosta grow well in pots. Best in light shade.

Japanese maple (Acer): excellent tree for a container. Needs a sheltered spot.

Olive: in a sunny sheltered spot an olive can thrive in a pot. Milder areas only.

Pine: dwarf pines such as Pinus mugo make excellent container plants.

Rhododendron: often better in pots than in the ground. Use ericaceous compost.

Skimmia: a fragrant evergreen shrub. Best in shelter and light shade.

Stipa: (grass) the best ones for pots are ‘Pony Tails’ and Stipa arundinacea.