Gardening is all about planning, and while container displays of spring bulbs are now in their prime, it’s time to start thinking about what will replace them. With the right conditions, attention and careful selection, a massed gathering of plants — no social distancing required — will fill the garden with colour right through summer until autumn, no matter how small your outdoor space. And with garden centres and online nurseries offering an increasingly wide selection of tender perennials and annuals, gone are the days when the only options were busy lizzies, petunias and lobelia.
The right container
Selecting the right containers can make a huge difference, not just to how the plants will look, but more importantly to how well they will grow. Watering can be a chore, particularly during prolonged hot weather when you’d rather be relaxing with a glass of something chilled than wrestling with a hosepipe or filling the umpteenth watering can, so for the summer months I forgo the small pots I use for spring bulbs and focus on larger containers with a diameter of at least 25-30cm, as these hold more compost and won’t dry out so quickly. They also give the roots room to grow — you’re aiming for summer plants to be in their pots for four to five months, so they need space to thrive.
I have an assortment of terracotta and ceramic garden-centre purchases alongside vintage tin baths and metal containers I’ve picked up from flea markets, and galvanised water troughs are my latest discovery — you can find characterful old ones online, but mine are new and from the local agricultural supplier. They’re good value for the size, are nice and deep so they’re perfect for growing dahlias, and they work just as well in cottage-style gardens as they do in more contemporary spaces.
Terracotta pots are porous, which means they’ll dry out more quickly than ceramic or metal, so it’s a good idea to line the sides (not the base) with sections of old compost bags. Whatever the material make sure the containers have plenty of drainage holes in the base, if not then add some more using a drill.
Large planters should be positioned where you want them first before you fill them with compost, otherwise they’ll be too heavy to shift. If you want to save your back then a plant trolley, a base with castors (kaiserkraft.co.uk has a good range), will come in useful for mid-sized pots, or look for containers that have their own castors. Designer Jennifer Newman has created a range of stylish planters made from powder-coated lightweight aluminium that come mounted on castors — perfect for balconies and patios where you might need to move pots regularly for access (prices from £275, jennifernewman.com).
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Bola Artstone containers are made from a crushed stone and synthetic composite, giving them the appearance of stone, but without the heaviness — a great option for balcony or roof gardens where the weight is an important consideration (from £19.99, hortology.co.uk).
Potting up
For most summer containers I use a 50:50 mix of peat-free multipurpose compost and John Innes No 2, as this will release nutrients over a longer period. Try the Sylvagrow range for peat-free composts.
The jury’s out on whether adding crocks — broken pieces of terracotta pot — to the bottom of containers actually helps with drainage or not. For temporary summer displays I don’t bother, but if I’m planting up succulents or other plants that like very good drainage, I do mix in some horticultural sand or grit with the compost and add a layer of grit to the top of the pot so that moisture doesn’t sit around the plants; it looks attractive too.
Leave an inch gap between the surface of the compost and the top of the pot so there’s space for water to sit while it’s absorbed, otherwise it’ll spill over the side. Then use a trowel to make planting holes in the compost and plant up — I find this easier than filling the pots halfway, then placing the plants and back-filling around them with compost. Check the spread of the plants and space them in the pots so they have room to grow.
Tender perennials and half-hardy annuals need protecting from frost, so don’t plant these outside until at least mid-May. If you have a greenhouse, sunny porch or conservatory, you can plant up indoors and move the pots outside when it’s warmer, or grow the young plants under cover until the danger of frost has passed before planting. It’s worth gradually acclimatising them to the outdoors for a week or so, which is known as hardening off, taking them out during the day and covering them up with horticultural fleece or moving them indoors at night.
Long-lasting colour
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Cosmos are known for their flower power, and compact cultivars such as ‘Sonata White’ and lemony-yellow ‘Xanthos’ are ideal container candidates. Salvias will keep on blooming well into autumn, there’s the pretty white daisies of Argyranthemum frutescens or Nicotiana alata, which has evening-scented flowers. Compact dahlias — ones that grow no taller than 60cm — will reward you with months of colour, and single, open-flowered cultivars such as ‘Waltzing Mathilda’ will keep bees and butterflies happy too. The small daisy flowers of brachyscomes create a fabulous froth of lavender blue or white, and diascias and nemesias come in a good range of colours that will suit your chosen planting palette. Forget blowsy frilly begonias; instead seek out those with more sophisticated single blooms — turn up the heat with the fiery orange ‘Glowing Embers’ or opt for the subtler ‘White Elegance’.
Trailers
Include at least one plant that will gently tumble over the edge of the pot. These plants help create that all-important feeling of abundance that’s key for summer containers. Look to trailing verbenas; calibrachoas are daintier than petunias, but just as floriferous; and ivy-leaved pelargoniums have attractive leaves and colourful blooms. For something more unusual, Origanum ‘Kent Beauty’ has hop-like, creamy flowers that are a magnet for bees, or there’s the exquisite pale blue blooms of Convolvulus mauritanicus.
Foliage
The calming greenery of scented-leaf pelargoniums will add a restful note among a profusion of flower colour, and they have the added bonus of smelling incredible too — I love the soft-to-touch, minty leaves of Pelargonium tomentosum. Purple leaves, such as those of Ipomoea batatas ‘Sweetheart Purple’, work particularly well with rich reds, magentas and vibrant oranges. The silver foliage of Plectranthus argentatus ‘Silver Shield’, the trailing Dichondra argentea ‘Silver Falls’ and Helichrysum petiolare combine well with pastel shades. For a shot of extra colour look to the zesty lime green, coppery orange or deep burgundy of coleus, which are making a comeback, and don’t forget perennial grasses — they might not be traditional bedding plants, but compact ones such as carex, pennisetum and anemanthele will be happy in pots and they’ll add a fabulous tactile quality to a display.
Scent
The deep purple flowers of Heliotropium ‘Midnight Sky’ smell like marzipan, the tricky-to-pronounce Zaluzianskya ovata, or night-scented phlox, opens its flowers in the evening, releasing a sweet fragrance, and dianthuses have delicious clove-like perfume — the white-flowered ‘Memories’ is especially long-flowering and strongly scented.
Container care
Deadheading
Regularly snip away any fading flowers and yellowing foliage, cutting back to just above a leaf. This will trick the plant into producing more flowers, keep the plants looking fresh and stop fungal diseases taking hold.
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Feeding
The nutrients in most composts will be used up within six weeks of planting, so feed every two weeks, increasing this to once a week from mid-July. Use a diluted liquid tomato fertiliser that is high in potassium, the nutrient that promotes flower production.
Watering
Gather pots together either in one place or in several clusters to speed up watering. Water first thing in the morning or in the evening so the water is absorbed by the plant rather than it evaporating in the heat.
To make sure the compost is thoroughly soaked, water, then go back and water again. Direct the hose or watering can nozzle on to the compost rather than watering the foliage — more water will reach the roots, avoiding moist leaves, which can attract fungal diseases.
