Growing prize-winning veg

Pumpkins

What judges want: Good weight and girth, freshly cut, no cracks or pest damage

Top variety: 'Atlantic Giant'

Medwyn's growing tip: Grow two or three pumpkin plants, ideally in a polytunnel or greenhouse, and bury each leaf joint, encouraging a huge root system to develop. Ensure the plants grow in very rich soil, and you feed them once a week.

Carrots

What judges want: Straight roots with a well-rounded stump end, no cracks or greening

Top variety: 'New Red Intermediate'

Medwyn's growing tip: Grow carrots in containers filled with sand, with holes filled with compost. Alternatively, make beds of damp sand 60cm deep, then twist out 40cm deep cores. 7.5cm in diameter. Fill each hole with compost and sow three seeds on top, thinning to the strongest. Cover with insect-proof mesh to keep out carrot fly.

Tomatoes

What judges want: Uniform size, firm texture, even colouring, blemish-free with a bright green calyx

Top varieties: 'Shirley', 'Myriade' and 'Goldstar'

Medwyn's growing tip: Grow in a cool, well-ventilated greenhouse. Water just-planted seedlings with a pint of water, then leave the plants for 10 days, to encourage the roots to grow deeply to search out water. Give them a good soak and keep them moist from then on.

Runner beans

What judges want: Deep green colour, uniform length and no strings - the judges will snap one to check

Top variety: 'Stenner'

Medwyn's growing tip: Runner beans need rich soil and strong supports. A few days before, look for straight, flat beans, 35-40cm long. Stand them in water, stalk down, then the next day go back for more, so that by show morning you have a set of identical beans.

Onions

What judges want: A uniform shape and size, with a firm texture and well-ripened, unblemished, dry skin

Top variety: 'Kelsae'

Medwyn's growing tip: Start early. Sow onion seeds into heated propagators in late winter, then move them outside in mid-May, planting through black and white polythene, laid white side up to reflect heat onto the bulbs. Lift the bulbs three weeks before show day to dry.

Marrows

What judges want: Uniformity of size, colour and shape, with no yellowing or soil splash marks

Top variety: 'Table Dainty'

Medwyn's growing tip: Even colouring can be tricky, as marrows on the ground usually turn yellow beneath. To avoid this, train them up a framework. Alternatively, put each fruit on glass raised up on two bricks, so light can reach the underside. Give marrows rich soil and lots of feeding and warmth.

Leeks

What judges want: Straight, with an equal ratio of leaves to shank. A perfect V where the leaves wrap round the barrel.

Top variety: 'Windermere'

Medwyn's growing tip: Exhibition growers raise leeks from 'pips' formed on their best plants from the previous year. In September, trim your best leek's roots and cut the top down to 15cm. When it flowers in spring, snip off every bloom. It will produce grass-like baby leeks from the seedhead - gently remove and pot up for this year's champions.

Potatoes

What judges want: Tubers of identical size and shape, with unmarked skin, shallow eyes and no signs of scab

Top variety: 'Mona Lisa'

Medwyn's growing tip: Grow the potatoes in bags. Plant just one chitted tuber per 20-litre plastic bag, using compost boosted with general-purpose fertiliser and ground, calcified seaweed. Dig a shallow trench outside, stands the bags in it and earth up around them. The plant's roots grow through the bags' drainage holes into the soil. Water and feed well for the perfect, clean crop of tubers.

Peas

What judges want: Evenly coloured pods, with an unblemished bloom, well filled with 6-15 peas.

Top variety: 'Show Perfection'

Medwyn's growing tip: Grow each plant up a sturdy cane, remove sideshoots and tie in at every leaf joint, as mature plants are top heavy. To select perfect pods, shine a torch through them to show up any missing peas. Hold by the stalk only, as the pod's delicate boom is easily damaged. Sandwich the pods between nettle leaves to keep the bloom intact.

Beetroot

What judges want: Smooth skin with no scabs or splits, and a single, intact tap root

Top variety: 'Pablo'

Medwyn's growing tip: Sow seeds in deep, well-turned soil and thin to 5cm apart. As they grow, earth them up to cover the globe so the skins don't turn corky on top. On show day, keep the skins moist by covering with damp kitchen paper until the judges come round. Damp skin has that fresh, just-pulled look and it helps soften scuff marks.

Cucumber

What judges want: Straight, fresh fruits, a short 'handle' (the thinner, stalk end) and an untarnished, natural bloom.

Top variety: 'Carmen'

Medwyn's growing tip: Keep humidity levels so high that you have to take off your glasses when you go into the greenhouse. To achieve this, lay down thick wads of straw, and soak with water so they steam on sunny days. To straighten crooked fruits, let them dry out – when almost wilting they become rubbery and are easy to shape by hand. Water again and they shoot away again, straight.