Thujas, the useful evergreen conifers are conical in shape, with flat, scaly foliage and decorative cones. You can buy a dwarf variety for the rockery or a larger type to use as a specimen tree in the border or lawn.

In fact thujas are invaluable for structure and colour and most of them are aromatic. If you want a tall specimen look out for T. occidentalis (White Cedar) ‘Holmstrup’, while dwarves worth looking out for including T orientalis ‘Aurea Nana’, which has golden yellow leaves, and ‘Hetz Midget’, a dark green globe reaching only 23cm in 10 years. Thujas like moist but not waterlogged, well-drained, fertile soil in sun or light shade.

Kitchen garden: Sowing greenhouse peppers

This month is a good time to sow peppers in a heated propagator or on a windowsill indoors at a temperature of 21-27C (70-80F), to give them a head start for summer.

When large enough to handle, the seedlings can be pricked out and potted on to individual small pots to grow at 16-19C (60-65F). Harden them off carefully as peppers are extremely frost sensitive.

They can be planted in an unheated greenhouse from late May to early June, or outside, preferably in a sheltered spot, in mid-June.

Water them in well after planting and then sparingly until they are starting to flower. Support them with canes and apply a liquid tomato feed once a week once the first flowers open.

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What to do in the garden this week

:: Sow under glass quick-growing perennials to flower this year

:: Begin to feed plants in established borders using a controlled-release slow-acting fertiliser, taking care not to get the liquid on to new foliage

:: Spray nectarine and peach trees to prevent or eradicate peach leaf curl disease

:: Cut back hedges before birds start to nest in them

:: Prune large-flowering clematis (group 3) including C. viticella and hybrids such as C. ‘Jackmannii’, taking stems back down to 25-45cm (10-18in) above ground level

:: Check if rain-sheltered trees, shrubs and climbers in containers are dry and, if so, water containers from time to time

:: Check seedlings growing indoors have plenty of natural light so they don’t become leggy

:: Cut back deciduous buddleias, lavatera, hary fuchsias and ceanothus, which produce their best show of flowers on wood made from spring onwards

:: If it’s not too wet or frosty, brush over lawn surface that has become covered in worm casts, using a besom or brush

:: Scoop out leaves, twigs and other debris from guttering on conservatories, greenhouses and garages