Gardeners’ World 2021 episode 7: At Longmeadow, Monty Don gives us a masterclass on growing Mediterranean herbs, plants lily bulbs for summer scent, and in the vegetable garden, he begins to sow seeds for salad root crops.
Carol Klein is in Devon, where she takes a close look at late summer planting combinations. Meanwhile, in Cumbria, there’s a gardener whose passion for exotic plants and dahlias has taken over his family garden and spilled over onto his allotment. In Milan, Arit Anderson visits an extraordinary high-rise building which has been designed as a living forest, and in Kent is a man with a collection of over 80 different varieties of wisteria.
Meanwhile, viewers give hints and tips from their own gardens.
Gardeners’ World 2021 episode 7
Rhubarb is a rhizomatous perennial whose leafstalks (technically leaf petioles but often referred to as ‘sticks’ or ‘stems’) are grown as a vegetable but used mainly as a dessert. It crops over a long period, is completely hardy and grows in any garden soil.
Any fertile garden soil can be used for rhubarb, as long as it is well drained and in full sun. Crowns (‘sets’) can be cropped for ten or more years, though division may be necessary after about five years. Although the large foliage can help smother weeds, the ground should be free from perennial weeds before planting. Dig in one to two bucketfuls of well-rotted organic matter, such as manure, before planting.
Plant crowns in November or December. If necessary, planting can continue up to the beginning of March. Buy named cultivars, or choose a division from a strong, healthy-looking plant.
Plant the crown with the growing point at, or just below, the soil surface. On wetter soils, planting with the buds just raised out of the soil may help prevent rotting. If planting more than one crown, space plants 1m (3ft) apart, with 1-2m (3-6ft) between rows. Expected yields range from 4½-13½kg (10-30lb) per 3m (10ft) row.
In hot summers, if the ground becomes dry, growth will slow down and even stop. A spring mulch of well-rotted organic matter 7cm (2½in) deep will help to retain moisture, but do not bury the crowns. Plants will also respond to watering during prolonged dry periods in summer. Apply a general fertiliser such as Growmore in spring or summer at 70g per sq m (2oz per square yard).
How to grow wisteria – Gardeners’ World 2021 episode 7
This gorgeous climber produces cascades of fragrant mauve or white flowers in late spring. It’s a vigorous plant that needs regular pruning and training to keep it in check and flowering well, but is well worth the effort. It looks amazing in full bloom clothing the front of a house, draping over a pergola or scrambling along a sunny wall.
Wisterias do best in well-drained, fertile soil, in full sun. They are native to China, Japan and eastern United States and, of the ten species, the three most commonly grown are Wisteria floribunda (Japanese wisteria), Wisteria sinensis (Chinese wisteria) and Wisteria brachybotrys (silky wisteria). All three species are strong-growing and capable of reaching around 10m (33ft) in trees or spread up to 20m (66ft) against a wall. You can also train wisteria as a free-standing standard in the border or large container.
Planting of wisteria is best done between October and April. Container grown wisterias can be planted at any time of the year, but are easier to care for in autumn or winter. Plant them in fertile, well-drained soil.
Wisterias flower best in full sun so choose a south- or west-facing wall or pergola. They will grow in slight shade but flowering will be reduced.
Wisterias are hardy, vigorous climbers reaching over 10m (33ft) height and width. You will need to provide support in the form of wires or trellis against a wall, or garden structures like pergola or arch. Wisteria can also be trained up a tree or grown up a support to form a standard. By training a wisteria into a standard it restricts its vigour and allows to you to grow a wisteria in a border or container.
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.
Ornamental grasses – Gardeners’ World 2021 episode 7
The variations in colour and texture of ornamental grasses provide structure, movement and interest in planting schemes, even in the dead of winter. Usually partnered with late summer perennials, grasses provide a long season of interest.
Ornamental grasses are adaptable, reliable plants, easily cultivated in sun or shade with some thriving in both. Although ideally well-drained soils suit these plants, some will grow happily in moist or wet soils.
Hardening off tender plants
Plants raised indoors or in a greenhouse need to be acclimatised to cooler temperatures, lower humidity and increased air movement for about two to three weeks before they are planted outdoors. This ‘toughening up’ process is known as hardening off.
Young plants bought from nurseries or grown from seed or cuttings at home for summer display outdoors when the weather improves often need to be hardened off.
Hardening off allows plants to adapt from being in a protected, stable environment to changeable, harsher outdoor conditions. If suddenly placed outside, the shock can severely check a plant’s growth. Although plants usually recover eventually, hardening off is thought to be preferable to a sudden shock.
The effect of hardening off is to thicken and alter the plant’s leaf structure and increase leaf waxiness. It ensures new growth is sturdy although growth will be much slower than in the greenhouse. But be warned: hardening off does not make frost-sensitive plants hardy.