Top gardening tips for May

Spring reaches its crescendo in May, as spectacular blooms of rhododendron, clematis, wisteria and iris steal the show. With light evenings and warm temperatures finally here, the experts at Robert Dyas share their top tips to make the most of this wonderful month…


Plant a herb garden

We’re all eagerly awaiting that first barbecue of the season and the aroma of sausages sizzling in the great outdoors (hopefully the reality isn’t cremated burgers and bangers!) Growing herbs by your al-fresco dining area will lead to a ready supply of fresh ingredients to infuse favourite barbecue dishes with flavour. We’re talking basil, coriander, chives, oregano, parsley and thyme, all of which will grow happily in pots of multi-purpose compost. To take your outdoor kitchen to the next level, try the VegTrug Home Farm Kit or a tiered herb planter or hinged planter which combines practicality with rustic charm, creating a stand-out feature. For a mini greenhouse feel, a home farm kit planter ticks all of the right boxes. If you only have a balcony, a small raised planter makes an ideal home for a mini herb garden.


Keep greenhouses cool

With the sun strengthening day-by-day, greenhouses packed with plants can quickly become hotter than an oven. To protect plants from roasting, open vents, louvres and doors first thing in the morning to boost air circulation. Damping down the greenhouse floor helps to lower temperatures and raise humidity – consider replacing your hosepipe if it’s plagued by leaks and kinks or struggles to reach your greenhouse. Plants can scorch under glass on sunny days, so paint greenhouse shading onto the exterior of glass or – depending on your make of greenhouse – line the interior with a UV-protected shading kit that will shield flowers and foliage from harmful rays.


Pot up flowers and veg

Whether you’ve nurtured flower and veg plants from seed or bought young plug plants, they’ll need potting on (transplanting into bigger pots) to bolster root systems ahead of planting out in June. A potting table can help to speed up the process while enhancing the appearance of outdoor spaces. Fibre pots help gardeners to boost their green credentials when repotting – not only do they do away with the need for plastic pots, but they’re peat-free and don’t have to be removed when plants go into their final growing positions, as roots will grow through the biodegradable material.


Harden-off tender plants

If you grab tender flowers and veg from a warm window sill or greenhouse and plunge them straight into the garden, chilly temperatures, lower humidity and wind can cause a shock to their system that may stunt growth or even result in plants keeling over. That’s why delicate plants need hardening off – a process of gradual acclimatisation to cooler conditions outdoors before they’re finally planted out. Cold frames, available with a rustic appearance or assembled from contemporary timber, help plants to grow used to conditions outdoors. Open roof vents by day and close at night for a couple of weeks, then leave the vents open 24 hours a day in the final week before planting out – as long as frost isn’t forecast.


Get composting!

From May onwards, garden waste starts piling up. Why pay for a council bin when composting can work its magic and transform garden rubbish into nutrient-rich, crumbly soil improver? The days of eyesore compost heaps are long gone, with ornamental composters making stylish garden features that help waste to rot down quickly by keeping material warm and moist. For best results, fill with a 50:50 mix of green and brown waste. Green waste can comprise grass clippings, vegetable peelings, annual weeds and soft, leafy prunings, while brown waste includes materials such as hedge clippings, plant stems, shredded paper and ripped-up cardboard. Mix it together and keep compost heaps damp.


Sow beans and sweet corn

Runner beans are a cinch to grow, looking just as ornamental scrambling up wigwams in flower beds as they do on veg plots. While beans can be directly sown outdoors in June, we recommend starting seeds off under cover this month, as it gives plants a head start and protects tender shoots from slugs and snails. Choose a winning variety: ‘Scarlet Emperor’ is a red-flowering, early-cropping favourite while ‘Polestar’ yields plenty of tender, stringless pods. ‘Enorma’ is the one to go for if you’re up for a challenge to see who can grow the longest bean: pods can span an enormous 50cm (20in) long! Sow seeds individually into pots of seed and cutting compost and, once shoots are growing, support using plant sticks until they’re ready to go outside after the last frosts. If you’re a fan of tender cobs of sweet corn served with a knob of butter, sow one seed per pot of ‘Swift’ – a hybrid variety that’ll reward you with an abundance of juicy cobs in late summer.


Do the Chelsea chop!

If left to grow skyward, certain herbaceous perennials (non-woody plants that die down in autumn and reappear the following spring) can become tall and leggy, resulting in plants flopping over unless provided with support. Cutting their height down by half in May, a procedure known as the Chelsea chop (because it usually coincides with the famous RHS Chelsea Flower Show), results in side shoots spreading out and compact plants that will bear further flowers. Use sharp, clean secateurs to make healthy cuts and compost the waste material. Plants that respond well to the Chelsea chop include helenium, aster, echinacea, phlox and achillea.