Modern container gardening

Choosing containers

There is a wide range of containers available made from traditional terracotta, concrete and zinc in many different sizes and materials. You can also recycle items to produce a display that’s uniquely yours. Your local garden centre will have a good selection to choose from, and you’ll also find a fantastic choice online. Take the time to consider the sizes, shapes, colours and prices. Putting containers together to create a “garden” is a real opportunity to experiment with different textures and shades.

I think it’s better to buy a couple of key containers than lots of smaller ones. Don’t forget the importance of matching the style/material of the containers to your property. For example, lead-effect planters look great with older properties, modern apartments call for more up-to-date materials, such as zinc, and cottage gardens are enhanced by informal containers, such as terracotta or stone.

 My top tips for choosing containers

• The bigger the container, the better (this will ensure that watering is needed less frequently and that your plants have room to grow).
• Deeper pots are better than shallow ones.
• Ensure containers have at least one drainage hole (three is better).
• Pick containers that will create focal points.
• Include containers of different heights and sizes in a scheme.

Container materials

Natural materials, such as terracotta, stone and wood, make the best containers for plants, being more cooling for roots and ensuring plants don’t overheat. You can also buy very good imitation terracotta and stone versions that are just as appealing visually and less expensive. Look for containers made from reconstituted stone and lighter materials such as fibre glass. Lighter containers may be the best option for a balcony or roof garden where weight is a consideration. Wood is also a great choice, but bear in mind that it can rot over time.

Load-bearing considerations

If you only have a balcony or roof garden, it is essential to check with an architect or structural engineer how much weight the space can take before committing to buying containers and plants. If you are planning any major work, such as building raised beds, then also check whether planning permission is required. Make sure you find out whether the balcony is waterproof. Remember, a fully watered container is very heavy, so it’s best to place containers near load-bearing walls, or over a load-bearing beam or joist.

How to choose healthy plants

Here is a useful checklist of what to look out for: 

Plant health — check for signs of pests and diseases. The eggs of insects, for example, are often attached to the undersides of leaves, so look over the foliage carefully.

Root system — if possible, remove the plant from its plastic pot and inspect the roots. They should be firm and look healthy. A plant that is pot-bound, with a mass of tangled roots growing out of the bottom of the plastic pot, is best avoided.

Leaves and flowers — make sure these look healthy, without any discoloration or markings.

Flowering plants — choose plants that have lots of unopened buds. That way, you know you’ll get great value, particularly from annual bedding plants.

Designing container plantings

Putting together wonderful planting displays in containers is both creative and rewarding. From a single specimen in a large planter to miniature “borders” of flowers and foliage in a collection of containers, the opportunities for experimenting with colours, patterns and shapes are endless.

There is a useful phrase to remember when you are designing a container scheme: “Thriller, filler and spiller”. This can be helpful when you’re working out the design for a container and how to compose your plant combinations. For example, if you have a large container, you might want some tall plants at the back to provide height (the “thriller” or focus plant) and then some shorter plants to fill up the middle area of the container (the “filler” plants). To finish the planting, you could choose plants that trail over the sides (the “spiller” plants).

Here is a list of my favourite thrillers, fillers and spillers:

Thrillers Argyranthemum, azalea, campanula, dahlia, delphinium, euphorbia, ferns, fuchsia, grasses, hydrangeas, lavenders, lupins, phormium, pittosporum, sweet peas, tall verbena, veronica

Fillers Anemone, antirrhinum, aquilegia, aster, astrantia, coleus, cosmos, diascia, heuchera, impatiens, pot marigolds, matthiola, osteospermum, poppies, pelargonium, salvia, tiarella, vinca, zinnia

Spillers Calibrachoa, erigeron, ipomoea, lobelia, petunia, trailing ivy, trailing verbena

Putting it all together

• Planting in odd numbers is the most aesthetically pleasing to the eye, so plant one, three or five plants in a container.
• Consider restricting the colour scheme, opting for shades of one or two complementary colours. This is because too many colours can make a display look too busy and your space smaller – unless, of course, your intention is a cacophony of colour!
• Remember “Thriller, filler, spiller”: choose a focal plant and complement it with a mixture of upright bedding plants and those that will trail over the sides of the container.
• Use a focal plant such as evergreen box, lavender or bay to provide year-round interest to which you can ring in the seasonal changes by underplanting with perennials and annuals for summer and bulbs for spring and autumn.
• Combine plants that have similar growing requirements for the best results. For example, combine plants that prefer full sun or those that require partial or full shade.
• For small-scale containers, look for dwarf varieties or alpines that will be happier in more confined conditions.
• Opt for drought-resistant plants such as cacti and succulents, or perhaps sun-loving herbs, if you don’t think you can commit to a daily watering regime for them.

Planting mediums

There will be a wide selection of potting mixes on offer at your local garden centre and online. There are two main types of potting mix: soil-based potting mix and soil-less potting mix.

 Soil-based potting mixes

A soil-based potting mix is a reliable, all-purpose mix containing a combination of sterilised loam (soil), peat, sharp sand and fertilisers, making it perfect for most containers. It provides plants with a good supply of nutrients for the weeks immediately after planting and retains moisture well. It is also free-draining, which encourages roots to grow.

Soil-less potting mixes

As the name indicates, this type of potting mix doesn’t contain any loam (soil). Instead, it is usually peat- or peat-substitute-based. If you are concerned about the environmental impact of removing peat from bogs to make peat-based potting mix, then choose one made from a peat substitute such as coir or wood fibre. Soil-less potting mixes are perfectly adequate for most types of plants. They have the advantage of being lighter than soil-based potting mixes, plus they are also often cheaper and ideal for small containers. Their main drawback is that they tend to dry out very quickly and can be very difficult to rehydrate once dry. For this reason, it is a good idea to add some moisture-retaining granules to the potting mix when you plant up your containers. You will also need to feed plants grown in this type of potting mix regularly to keep nutrient levels topped up. I advise against using them for long-term container plantings.

 Taken from Modern Container Gardening: How to Create a Stylish Small-Space Garden Anywhere by Isabelle Palmer, published by Hardie Grant Books, £12.43