Best of the bunch - gunnera

The spectacular leaves of the gunnera, or giant rhubarb, are among the sights to behold in the garden at this time of year, providing a show-stopping architectural spectacle as a stand-alone feature or a canopy for smaller, shade-loving specimens.

All gunnera like bog gardens and plenty of food and water but not all of these perennials are as huge as the G. manicata, which reaches some 2.5m (8ft) or more within a season.

For smaller spaces, there are some small, mat-forming gunneras growing to no more than 15cm (6in) tall, or for a medium-sized type look to G. tinctoria, whose pleated leaves make a bold impact, although it needs other large plants to keep it company.

The large-leaved varieties make fantastic architectural plants alongside streams or ponds - but are only really suitable for large gardens. They make good plant partners with astilbes and other moisture lovers.

Gunneras thrive in moist soil in the sun or partial shade in a sheltered position. Their crowns will need protecting in winter with a covering of the old leaves.

Three ways to... deal with seasonal pests

1. Bright red lily beetles may be munching their way through your emerging lilies now. To control them, move the beetles and grubs (which are reddish brown) by hand or, as a last resort, spray plants with a contact insecticide and repeat if they reappear.

2. Aphids start multiplying in mid and late spring. Disperse them with a jet of water from a hose or pick them off, and encourage their natural predators such as ladybirds, lacewings and hoverflies by planting nectar-producing and pollen-rich plants such as the poached egg plant (Limnanthes douglasii).

3. Check under leaves for egg clusters left by moths and butterflies, which can be crushed with finger and thumb. Remove caterpillars when you notice them.

Good enough to eat... sweetcorn

Sweetcorn plants should be almost hardened off and ready to plant outside, unless you live in a frost pocket, in which case leave them another week or two. Sweetcorn is usually grown in blocks of at least nine plants (three by three), which should ensure that pollen from the male flowers at the top of the plant reaches the female tassels which make the kernels.

Put the plants 35cm apart to give you around two cobs per plant, although you may only get one. To save time on weeding, plant through a sheet mulch, which allows rain through.

In July, when they start to flower, they will need a really good soaking regularly and later in the summer you will need to heap earth around the stems to stop windrock damage, as the cobs start to ripen. They can be harvested when the tassels on the cobs start to shrivel.

What to do this week

:: Start to harden off aubergines, courgettes, marrows, peppers and tomatoes grown from seed, but keep them under cover if late frost threatens.

:: Ensure fruit trees and bushes have enough water while the fruit is setting or the trees may shed fruitlets.

:: Hoe regularly on dry days to prevent weed seedlings becoming established.

:: Feed seedlings and young plants which are growing poorly or have pale, yellowing foliage.

:: In the greenhouse, pinch out the tips of side shoots of cucumbers two leaves beyond developing fruits.

:: Apply lawn feed. Liquid feeds can be applied with a watering can, or slow-release granular feeds with a wheeled lawn spreader.

:: Cover gooseberries, currants, strawberries and soft fruits with netting to keep birds at bay.

:: Complete planting out of tender bedding plants.

:: Plant out chrysanthemums and dahlias raised from cuttings.

:: Prune late-spring and early summer-flowering shrubs such as philadelphus, weigela, ceanothus, escallonia and kerria immediately after flowering.

:: Lift and divide water lilies.