Hertfordshire gardening experts share their top tips for June

PUBLISHED: 00:00 18 June 2020

'Olivia Rose Austin'

'Olivia Rose Austin'


This month is a peak time in our gardens, which got Philippa Pearson wondering what plants fellow gardeners love most on their plots.

Phlox paniculata 'Utopia' in Roger Trigg's Rickmansworth gardenPhlox paniculata 'Utopia' in Roger Trigg's Rickmansworth garden

June is seen as the pinnacle of the season by most gardeners, a time when many plants are putting on a fabulous display and all the hard work getting the garden ready and prepared in spring pays off handsomely.

We all have our favourite plants, and I’m a huge fan of perennials and grow many from seed when I can. I also like lots of annuals for summer borders packed with colour, and I grow lots of cosmos in many shades, putting young plants sown in February and March outside in the garden in June. Some of my favourites include Cosmos bipinnatus Purity, which has elegant pure white flowers, and Cosmos b. Seashells, which has unusual fluted rolled petals, just like its namesake. Last year I discovered Cosmos b. Double Click Cranberries and was stunned by the gorgeous burgundy ruffles of double flowers. I’ve grown at least double the amount this year as it’s my favourite must-have of the moment.

All Cosmos flower from June to the first frosts in November, and the trick to keeping the display going for these and many other plants is to deadhead regularly. Try and spend 15-20 minutes or so pottering around the garden at least once a week and snip off the spent flowers before they go to seed to encourage plants to produce new flowers. Garden Divas, an online gardening shop based in Hitchin with lots of tools and lovely gifts, has a good range of little deadheading snips which are perfect for the job.

Interested to know what plants other gardeners are favouring this season I asked Kevin Hilditch, head gardener at Knebworth House, what plants are catching his eye in the stately home’s gardens.

Coronillia in Heather Osborne's garden in St AlbansCoronillia in Heather Osborne's garden in St Albans

‘Choosing a favourite plant from a 28-acre all year round garden is not easy!’ he laughs. Luckily, with the help of his gardening team, a selection of favourites were chosen.

The mature Cornus kousa chinensis, Chinese dogwood, in the garden’s wilderness area is spectacular this month – covered in what look like large creamy white flowers.

‘These are mainly bracts,’ Kevin explains, ‘modified leaves, which enhance the small flower at the centre of each cluster. And there’s also good autumn colour when the leaves turn pink and orange’.

Another favourite of the team is mistletoe. The old bramley apple trees have plenty of mature mistletoe and Kevin says visitors love to see it growing wild.

Colourful CosmosColourful Cosmos

‘It needs no maintenance and we harvest a little each December for Christmas decorations.’

Elsewhere at Knebworth, the impressive snowdrop tree, Halesia carolina, is covered in scented creamy white snowdrop-shaped flowers in late spring, while the old cherry trees in blossom, and primroses are favourites too.

The nation’s favourite flower, roses, are at their peak in June, and Heather Osborne, who opens her St Albans garden for the National Garden Society, has several favourites.

Cornus kousa chinensis at Knebworth House GardensCornus kousa chinensis at Knebworth House Gardens

‘I grow lots of roses. Favourites among them are Albertine, Alberic Barbier in our apple tree, Munstead Wood, Rose de Rescht and Rambling Rector, which as well as having small creamy flowers has lovely hips in autumn.

‘Rosa Desdemona has gorgeous chalice shaped blooms, white with a hint of pink and an intense myrrh fragrance. It’s a repeat flowering David Austin English rose. Rosa Olivia Rose Austin, with a strong fruity perfume, has cupped pink flowers and is repeat flowering. They are both shrub roses which I grow in mixed borders.’

Heather uses a general rose feed, mulches with homemade compost and sprays with Uncle Tom’s Rose Tonic, a specialist foliar feed.

Other favourites of Heather’s include Coronillas. ‘Fabulous shrubs, in flower for up to nine months of the year and wonderfully scented. I also have the paler form with more lemon coloured flowers, var. Citrina, but I’m told Brockhill Blue is hardier, and its leaves have a bluer tinge.’

'William Lobb' rose on the right in a border at Heather Osborne's garden'William Lobb' rose on the right in a border at Heather Osborne's garden

Her Iris lazika hides itself away unobtrusively for most of the year but then she spots a sudden burst of violet colour in early spring with ‘fabulously detailed flowers which continue popping up for weeks.’

Heather is also a fan of epimediums recently introduced by plant hunters in the Sichuan and Yunnan provinces of China. ‘I love the way the pixie hat flowers hover above the new bronze foliage. I have over 20 different epimediums in the garden, my favourite which is yet to flower is E. fargesii. Epimediums – a real bomb-proof plant. The ordinary bright yellow E. x pulcherrimum is great in dry shade, even under evergreen shrubs, and makes good ground cover. The only thing you have to remember is to cut off the old foliage in February before the delicate new leaves and flowers emerge. They seem immune to pest damage.’

Hostas are at the top of her list, too. ‘I keep the mini, small and medium sized ones in pots so I can move them around to different places.’ She also has a good selection of larger hostas planted throughout the gardens.

One of the most frequently asked questions at Heather’s garden openings is how to deal with slugs and snails on hostas.

‘I’ve found that the bluer more glaucous leaved hostas are more resistant to slug and snail damage, so I’ve planted Halcyon and Krossa Regal,’ she says. ‘My other tip to deal with pests is to mulch around plants with horticultural grit, use Grazers spray and organic slug pellets.’

A final word goes to Roger Trigg who opens his garden on the Loudwater estate near Rickmansworth for the NGS. He highly recommends Phlox paniculata Utopia.

‘For me, this is one of the best phloxes for the garden and grows taller than most, at around 150 cm, and has interesting dark foliage,’ he says. ‘It’s fairly mildew-resistant and seems to do well both in sun and shade.’

Whatever plants you love best, our gardens have been a haven during lockdown and, with the displays of early summer, they just keep giving.

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