Get your borders summer-ready

In this three-part series, I will explain some simple changes to transform your garden, suggest some great plants that provide long-lasting colour, and tell you how to keep your border looking good for longer.

May is the perfect month to assess your border and see how plants are doing. Trees and shrubs will be in leaf, summer perennials will be sending up fresh new foliage and you will see what has and has not, survived the winter.

From the beginning to the end of the month, herbaceous perennials put on a huge amount of growth, but if you get in early enough there is time to move things around and add new plants.

• Five plants for a low-maintenance border
• Six ways to get your border ready for summer
• Five plants for a border on a budget

Common border design mistakes, and how to fix them:

Narrow borders that limit growth

If you love summer colour in your border, don’t restrict it to a narrow strip along your garden fence. Plants won’t have room to grow or they will lean outwards, searching for light.

Bring the border out and make it wider. Give it a sinuous edge or curve it round to a focal point, like a tree or large pot. If there is a path in the way, make a new border on the other side to line the path with flowers. Then you can spread your plants around and give them space.

In May, they will be growing, so dig them up with plenty of soil to protect the roots, and water them well once replanted. Of course, you will also make room for new plants.

• Guide to border depths and shapes

Individual plants get lost in the mix

However beautiful it is, a plant will have far less impact on its own than in a group. When you buy a new perennial for your summer border, think about getting at least three instead of one. If you can afford nine plants, buy three each of three different varieties. Planted together they have a much greater effect.

If you already have a favourite plant, try and buy two more of the same or take cuttings to get more plants. Cuttings taken now can be ready to plant out in autumn, for more colour the following summer.

• How to take summer cuttings

Plants that are too short, or too tall

Plant height isn’t always considered and tall plants can end up dominating a border, or small perennials are dwarfed by an adjacent hedge or fence. A beautiful border will have plants of different heights, mingling together to create a sumptuous display of flower and foliage.

When moving plants around or buying new ones, check how tall they will grow and arrange them so you have a mix of sizes. You can bring taller plants forward but try not to hide smaller plants behind them.

• Top plants for the back of a border

A border lacks structure

A border of summer flowers can be very colourful, but without any structure it could look like a jumble of plants just thrown together.

Structure could come from clipped hedges, a couple of small trees or evergreen shrubs, or you could plant some tall ornamental grasses, like Miscanthus or Calamagrostis, that will make fountains of leaves all summer, with pretty seedheads in autumn.

You don’t have to replant everything, just add in two or three structural plants that are repeated along the border, to tie it all together.

Planting in the wrong place

A common mistake is to grow a sun-loving plant in shade, or a shade-loving plant in sun. Either way the plant will struggle to grow and become weak. By May, you will have a good idea of where shade is cast by surrounding trees or buildings so you can plan to move anything growing in the wrong place.

Moving plants is best done early in the month before they have grown too much, or you can make notes to move them in autumn. Match plants to the conditions they need and you will have a much healthier looking border.

• Five plants for a deep shade border
• Plants for a north-facing border
• Plants for a south-facing border
• Planting scheme for a sunny border

Thrifty tip

Don’t be tempted to buy big plants in full flower; look for the smaller pots. They won’t be flowering but will grow quickly once planted and there are often multi-buy offers.

Take cuttings instead of buying plants. This can be done throughout the summer but avoid hot, dry spells. Some plants, like penstemons and catmints, will root in a few weeks.

Swap plants with friends and neighbours. Plants that do well next door will probably do well in your garden. You can also join your local garden club for plant exchanges.

Summer border inspiration

There is no better inspiration for your own summer borders than visiting other gardens. Some of the best summer borders can be seen in these gardens, which are also all included in the 2023 2-for-1 Gardens guide, included with your May issue of BBC Gardeners' World Magazine.

Kew Gardens has the longest double herbaceous borders in the country and they are planted for summer colour. From May to September there is always something to see.

Powis Castle and Garden is in a stunning setting. Terraces full of colour descend from the imposing castle walls, with the famous cloud-like yew hedges and views over the surrounding countryside.

Sussex Prairie Gardens is planted purely for summer colour and the wide, sweeping beds are a wonderful sight.

Bressingham Gardens in Norfolk has a huge range of plants for a variety of conditions, from sunny borders to woodland

Levens Hall in Cumbria

If you want ideas for structural plants, visit Levens Hall in Cumbria, which includes the world’s oldest topiary garden. It shows that summer borders don’t have to be all about herbaceous perennials.