Glad to see the return of gladioli He starts planting in mid-March, with the first crop going in under plastic, but recommends most gardeners wait until the second week of April. The semi-tender bulbs will then need no extra protection. His gladioli are given no extra feeding, as here they're treated as a one-year crop, but in our gardens, a potash-rich feed such as organic comfrey pellets is worthwhile. When harvesting, glads are best cut with a sharp knife and that's how they do it here, with every stem hand-picked. If you want to store the bulbs to plant again the following year, you must leave at least a third of the height of the flower spike below the cut, to allow the bulb to continue to photosynthesise and store food to enable reliable flowering in the following season. Clean water Once picked, gladioli - as a bulb - do not need flower food. Sugar in the water will not extend their vase life, but keeping the water clean and bacteria-free is important. Change it every two to three days (you can extend that to four or five if you add a drop of bleach) and keep your vases away from direct sun. As the flower column opens from bottom to top, remove the basal florets as they go over. Try arranging the large-spired varieties in a glass vase and they look wrong. You need the weight and solidity of something ceramic or metal. White varieties of gladiolus - such as 'White Star' or 'Bangladesh' can look funereal, but arranged on their own in a container of a contrasting colour they look classy and calm, more Chanel than coffin. The searingly strong reds such as 'Magma' or 'Cardinal' are almost impossible to mix with other flowers and any other colour. In the garden I plant these with acid-green euphorbias and dill, and in the vase they're best in metal. I like cramming them into a sheeny, stainless-steel champagne bucket as a centrepiece for a party, a full-on, 6in (12cm), sparkly heel of an arrangement. Best of all and easiest to place in the garden and in an arrangement are the classy, rich dark colours, the deep purple 'Purple Flora', deep burgundy 'Espresso', rich magenta 'Plum Tart', or purple magenta 'Black Star'. These are the velvet queens of the family. You can contrast them to the acid-green 'Green Star', the only green I've come across which does not fade out to a nasty yellow as the individual flowers go over. Both in the garden and a vase, I love these erupting through a frothy dome of grass such as Stipa gigantea, or even better, Panicum 'Frosted Explosion'. All gladioli are phototropic: that is, the tips of their spires, if laid flat in a box, quickly turn up and angle themselves towards the light. This is one of their saving graces. Without this they can look rigid and formal, perfectly straight and regimental. They look much prettier with a twist and turn in the top few inches of their stem, so encourage this by leaving them flat in a box for a few hours before arranging. At Winchester Growers they chop up the bulbs after flowering, treating them as an annual crop, but we don't have to do this in our gardens. To lessen the chance of pests and diseases, it's safest to lift the corms in the autumn and split the baby satellites away from the central mother bulb; you can keep these and replant separately, but they won't flower for a couple of years. Store bulbs dry, cool and frost-free, in an onion bag - or something similar - through the winter, for replanting the following spring. I don't always follow this advice, but mulch them deeply as I would a dahlia, in 4-5in (10cm) of green waste compost. Most seem to come back reliably the following year. My favourite combination in the garden for glads is with dahlias. I love 'Green Star' erupting through the skirts of dark dahlias such as 'Rip City' and 'Chat Noir', with 'Purple Flora' mixed up with orange dahlias like 'Jescot Julie', 'Raffles' and the long and brilliant flowering, 'Happy Halloween'. Gladioli give you the all-important verticals in contrast to the rounded, bosominess of the dahlias and they both thrive in identical positions. They make a perfect garden duo. For a range of gladioli corms, visit Sarah Raven Pests and diseases Rust and botrytis can affect gladiolus. In both cases, ensuring wide spacing on planting is key to prevention. Thrips are another common problem - this tiny (less than 1mm) insect lodges itself in between the new leaves and flower buds and feeds on the developing flowers as they emerge. Petals become discoloured with paler stripes, speckling and flecking, making them look as if they're going over as soon as they come out. Sadly, thrips are attracted to the nicest dark-coloured varieties, particularly the dark purple. Replanting year on year in the same place is not a good idea, which is why commercial growers rotate them. At Winchester Growers, they don't replant glads in the same field for 10 years. Lacewings and ladybirds feed on glads, but owing to their tiny size and high rates of reproduction, biological controls are not very effective. The only guaranteed treatment is a spot spray with a systemic insecticide and to avoid damage, you must start treatment before the buds emerge, concentrating on the underside of the leaves. Cold storage of the bulbs through winter - just above freezing - will also help eliminate them. £e_STnSDwarf Gladiolus nanus mixed are ideal for naturalising and the vibrant colours look stunning at the front of a border. Height 30in (60cm). Buy 25 for only £6.99 or buy 50 for £13.98 and receive a further 25 free. Orders to Telegraph Garden Service, Gladiolus nanus mixed, Dept. TL236, 14 Hadfield St, Old Trafford M16 9FG. Cheques/Postal orders payable to Telegraph Garden Service. For debit/credit card orders, call 0161 848 1106 or visit gardenshop.telegraph.co.uk/offers. Quote ref. Allow 28 days for delivery. Supplied as winter hardy 3-4in (7-8cm) corms. Competition Waitrose is offering 10 Telegraph Gardening readers the chance to win a gorgeous gladioli bouquet. During August, through to September, Waitrose is celebrating the best of British flowers by stocking some of this country's best loved blooms. Ten lucky winners will receive a delightful "Super Blue Summer Garden" bouquet, worth £42, which includes heavily scented oriental lilies, white antirrhinums, blue agapanthus and British purple gladioli - simply stunning! This bouquet is part of a wide range of bouquets and plants guaranteed to look gorgeous for seven days, available at waitrose.com/flowers. Simply answer this question: What percentage of British flowers does Waitrose sell all year round? Enter online only at waitrose.com/telegraph. Please provide a contact phone number and an email address. Closing date Sunday 25 August 2013, by 23.59. Prizes: 10 x Waitrose "Super Blue Summer Garden Bouquets," each worth £42, delivered. For full terms and conditions, please see waitrose.com/telegraph.