As the earth warms and frosts are fewer, Benjamin Pope throws off the woollens and brings out young plants from under glass, ready to brighten beds, borders and containers
With the arrival of May comes a reassurance that I love; a time when sub-zero temperatures are banished from the garden and woolly jumpers are packed away. Windowsills and greenhouses heave with tender plants that seem desperate to get outside, stretch and enjoy the passage into summer.
In a sun-drenched border, bearded iris begin to flower, differing greatly in size, colour and scent. From the intoxicating ‘Blue Shimmer’ and the vibrant ‘Mer du Sud’, to the charming ‘Benton Lorna’ and mysterious ‘Hocus Pocus’, there really is an iris to suit all. These flower alongside the many bulbous perennials appearing now, including the reliable Allium hollandicum ‘Purple Sensation’ and its attractive progeny A. ‘Purple Rain’. For an alternative colour, try Allium obliquum with its neat chartreuse drumsticks. Gladiolus tristis, Muscari latifolium and Narcissus ‘W.P. Milner’ complete the picture, alongside bold clumps of Euphorbia characias subsp. wulfenii and the filigree foliage of Ferula communis, with its tall, acid-yellow flowers reaching for the sky. Not to be outdone, the shadier corners can be fun too, whether in a border or collection of pots. Here I love to emphasise shape and texture, combining the fine foliage of Adiantum pedatum, Aruncus ‘Kneiffii’ and Hakonechloa macra, with the bolder shapes of Arisaema ringens and hostas such as ‘Devon Green’ and ‘Royal Standard’. Adding further interest, I add detail with choice woodlanders, including Disporum longistylum ‘Night Heron’, Erythronium ‘Joanna’ and Podophyllum versipelle ‘Spotty Dotty’.
With the borders expanding and grass growing, May is a good time to redefine lawn edges using a half-moon edging tool to create a sharp line that can easily be trimmed in summer. Tackle any weeds now to prevent spread and water anything newly planted if there is a dry spell. May is about final preparations and the establishment of new additions to the garden, ensuring they prove a success as the year goes on.
What to sow and plant
Seed sowing in the greenhouse has started to slow down, as now many crops can be sown direct into the soil outside. I repeat sowings of salads and roots, such as carrots and radish, to continue the supply, while sowing or planting out tender beans including borlotti, edamame and French.
Summer-loving crops, such as celariac, tomatoes and sweet potatoes, leave the greenhouse and are planted into beds or containers. I like to plant our squashes and pumpkins among sweetcorn, incorporating Amaranthus ‘Autumn Palette’, Persicaria orientalis, Tagetes ‘Cinnabar’ and Tropaeolum majus. By summer the patch is full of foliage and colour that gets better as harvest approaches.
If space is at a premium, try a tumbling tomato mixed with Tropaeolum minus ‘Ladybird Rose’ and Thai basil. All suited to container growing, they’ll look good all summer while providing something to taste. In the borders, seed-grown antirrhinums, cosmos and scabious are planted to fill gaps, while containers hold nemesias, salvias and verbenas. For foliage fillers, I love to use scented pelargoniums such as ‘Pink Capricorn’ or the silvery Helichrysum microphyllum ‘Silver Mist’ and Plectranthus argentatus. Experimentation is key and this year I’m including the cascading Dichondra ‘Silver Falls’, with floriferous perennials such as Verbena ‘Bampton’.
What to harvest and pick
If they were sown under glass or fleece this spring, fresh salad leaves, pea shoots and rocket will be ready now. Perennial vegetables, such as asparagus, garlic cress and forced sea kale, can be harvested, taking advantage of the soft new growth.
To get super-early potatoes, I like to grow ‘Swift’ in tubs or sacks, somewhere sheltered and warm (an unheated greenhouse is ideal) where an early March planting can see you harvesting in the latter days of May. Outside of the vegetable garden I’ll forage for wild garlic. Its leaves and flowers make tasty pesto while its seeds can be preserved as delicious ‘capers’.
May brings with it many options when cutting for the house. Classics include lilac, peonies and Viburnum opulus ‘Roseum’. Along with lily of the valley, they can all be grown and cut straight from the borders. Use early perennials alongside bulbs for great combinations – favourites of mine include Geum ‘Mai Tai’ with Camassia quamash. But don’t forget the mighty tulip.
Garden jobs for April
Tie in the new growth of climbers
As summer approaches, tie in young climbing plants such as clematis and sweet peas, along with crops such as tomatoes, climbing squash and beans.
Earth up potatoes and oca
As the top growth of potatoes and the potato-like tubers of oca emerge, gather soil or apply compost to make a mound around the young stems to encourage more tubers and protect from late frosts.
Chelsea chop perennials
Now is the perfect time to ‘Chelsea chop’ perennials such as Althaea cannabina, hylotelephium, nepeta, phlox and symphyotrichum. Cut back new growth by about a third to encourage stouter, sturdier plants.
Plant tender additions
Harden off your tender plants and get them into the garden. Traditional summer bedding, along with cannas, dahlias and hedychiums, can be planted, as too can the unusual Amicia zygomeris and Eupatorium capillifolium.
Take cuttings of perennials
Bulk up numbers of summer perennials such as anthemis, penstemons and salvias by taking stem-and soft-tip cuttings. Initially keep in a humid environment, so they root quickly and can be grown on to plant out in summer.
GARDENS ILLUSTRATED MASTERCLASS
Don’t miss Benjamin’s Masterclass at 6pm on 12 May. See here for details.