White asparagus - Protected from the sun, etiolated and blanched under a constant blanket of soil, so that no chlorophyll is produced, white asparagus is meltingly tender and has a milder, nuttier flavour. Grown on light soil, and using wider row spacing with a deeper ridge, burying the crowns 35cm (14in) below the surface (as opposed to 15cm/6in depth for the green) is best. In Australia, growers are experimenting with black plastic igloos to keep spears in the dark.
Purple asparagus hails from the Albenga region of Italy, though nowadays the more productive varieties come from New Zealand, with 'Pacific Purple’ and 'Stewarts Purple’ as pick of the crop. More challenging to grow – it’s a separate species – the ferns fall over easily, making them more susceptible to disease. The plant is not as prolific as the green varieties, is shorter lived and doesn’t thrive in wet weather. It’s sweet and tender, though, and delicious raw because the spears contain less fibre. The purple colour contains higher levels of antioxidants. Cooking dulls the colour, and lemon juice dressings enhance it.
White asparagus stems need to be peeled with care. Place them gently on a flat surface and remove the outer layer with a vegetable peeler, leaving the top 2-5cm untouched. I prefer steamed asparagus, but to boil, stand upright in a saucepan in bundles of 10 and cover with water halfway. This method cooks the thickest part of the stem and steams the more delicate tops. Favourite recipes this season include rolling spears in Parma ham and grilling briefly; steaming and serving with a pared lemon peel, melted butter and parsley dressing, and dipping in soft boiled eggs.
When storing asparagus, trim the ends, then stand your tied bunch upright in an inch of cold water, then cover with a plastic bag, but eat as soon as possible – after harvest, the sugar in the stems converts to starch and they soon turn dull and limp. All the more reason to grow your own.
Plant crowns in a raised bed full of weed-free, well-drained soil, mixing in plenty of compost and fertiliser. Dig a straight trench 30cm (12in) wide and 20cm (8in) deep, making a ridge along the middle. Spread your crown roots over the ridge, about 30cm apart, and cover with soil, earthing up as the plants grow.
Water well and resist the temptation to harvest for two seasons. Just let the ferny foliage grow on until it yellows, then cut it down. Hand-weed beds to avoid damaging the spears, and at the beginning of year three, your patience will be rewarded. Cut with a Sheffield-made knife from cook Silvana de Soissons’ online shop: thefoodiebugleshop.com.
Asparagus is food of the gods; pictured in Egyptian friezes in 3000BC, it features in Roman recipe book the Apicius. Sales have risen in this country over the past decade. Strangely, although until now white and purple spears are almost exclusively eaten on the Continent, the dernier cri for foodies over there nowadays are the green spears we know and love.
Paolo Arrigo from seedsofitaly.co.uk sells white asparagus crowns 'Superiore’ from the Cesena; a historic purple variety from Albenga; and a wild asparagus 'Scaber Montina’ with tasty thin spears as well as white asparagus from the Veneto region.