Carol Klein visits Trebah Garden in Cornwall, where she finds plants which can add early summer pazazz to our borders. Nick Bailey is at RHS Wisley to look at a variety of shrubs that can be used as alternatives to traditional box hedging.
We travel to the seaside in Kent to meet a group of gardeners who have transformed an unloved public space, and in Wales, we find a garden packed with unusual and prehistoric plants.
Gardeners’ World 2021 episode 14
How to grow dahlias
Dahlias put on a show in summer and autumn. They come in a wide range of colours from pastels to brights. Very floriferous, they’re also good for cutting.
You can buy dahlia plants in summer that are potted up and in full growth. Alternatively, buy dormant tubers in bags in the garden centre in spring or pre-order dormant tubers and rooted cuttings from specialist nurseries for spring delivery. To grow on tubers and cuttings, you’ll need a frost-free place like a greenhouse with heating or at least insulating fleece, depending on where you live in the country and how cold it is in spring. Bedding dahlias are often seed-raised and will flower that same season. They usually come in a mix of colours or a single colour strain that’s not as uniform as plants-raised from cuttings.
Plant dahlias on free-draining, lighter soils, where they are more likely to survive the winter. While they will grow on heavy soils, you are more likely to need to lift the tender tubers at the end of autumn as they would otherwise suffer when heavy ground gets colder and soggier in winter.
All dahlias like a sunny site, ideally with space between them and their neighbours.
Box blight – Gardeners’ World 2021 episode 14
Box blight is a fungal disease of box resulting in bare patches and die-back, especially in topiary and parterres.
Hold any commercially sourced plants in isolation for at least four weeks to confirm they are free of infection before planting out. Commercial nurseries may use fungicides which suppress but do not kill the fungus, and this isolation technique will allow time for suppressed disease to become visible. Taking cuttings from healthy box in your garden will reduce the risk of introducing the disease.
Inspect plants for early symptoms as box blight spreads very rapidly in warm and humid conditions and is difficult to manage. Reduce the frequency of clipping to create more ventilation throughout the plants (regular pruning creates dense foliage and less air movement). Prune a hedge with a convex top rather than flat and prune only in dry conditions. Clean pruning tools with a garden disinfectant or mild bleach solution between different areas of the garden and between gardens to minimise unwitting spread of the disease.
Avoid overhead watering as box blight thrives in humid conditions. Use mulch under plants to reduce rain splash. Feed plants moderately.
How to grow hostas – Gardeners’ World 2021 episode 14
These shade-loving plants are primarily grown for their beautiful foliage. There’s a vast range of cultivars to choose from, with leaves in all shades of green, as well as dusky blues and acid yellows, sometimes variegated or flashed with cream or gold, ruffled, smooth or distinctively ribbed. Many also produce small trumpet-shaped mauve or white flowers in summer. Hostas are notoriously irresistible to slugs and snails, but are also much loved by gardeners, who often amass large collections.
Hostas are one of the best foliage plants. They are easy to-grow-plants and long-lived.
There is a wide range of hostas, which vary in leaf shape, size and colour. With a such huge range of leaf shapes, sizes and colours, choosing a hosta is mainly a matter of personal taste. However, it’s also wise to match the plants to the conditions you have in your garden. In general, most thrive in moist soil in light to medium shade. However, blue-leaved hostas flourish in light shade, while yellow-leaved ones prefer some sun.
Miniature types such as ‘Blue Mouse Ears’ or ‘Pandoras Box’ are a good choice if space is tight or for containers. Most also produce clusters of flowers in shades of white, lavender and purple on tall stems.
How to grow tree ferns
Tree ferns are slow-growing architectural plants with spreading fronds above a thick trunk. They make striking plants for a sheltered, shady garden. Tree ferns thrive in a sheltered, humid and shaded position, with plenty of room so that the top of the plant can spread without crowding. Fronds on mature specimens may reach 2m (6ft) or more in length. They should be planted in humus-rich, neutral to slightly acid soil.
Extremely slow-growing, these desirable plants only increase by about 2.5cm (1in) a year. Therefore, if you want a plant for immediate effect, you should choose a fern with a length of trunk that suits your planting scheme. If you buy containerised ferns in leaf, plant at the same level as they were in the container.
Frondless lengths of trunk are also available. Soak the base, and plant just enough of the trunk to ensure that the plant remains stable. After planting frondless tree ferns, water every day until the foliage starts to emerge. To encourage rooting, don’t feed the plant during its first year.