Oak Leaf Gardening Monthly Cuttings

Newsletter 60 - May 2016

What to do now

Ornamental plants

  • Finish off sowing hardy annuals early this month. Continue to sow biennials such as honesty, foxgloves, stocks and wallflowers.
  • Keep on top of the pricking out, pinching out and potting on of seedlings.
  • Harden off and plant bedding and tender plants (leave towards the end of the month in cooler climates) including containers and hanging baskets.
  • Plant out summer bulbs including acidanthera, cannas, eucomis, dahlias, gladioli, galtonia, calla lilies, arisaemas, liatris, oxalis and tuberous begonias.
  • Clear spring bedding to make way for summer blooms.
  • Continue to deadhead spring flowering bulbs and camellias. Cut down the foliage from spring flowered bulbs six weeks after the flowers have died down.
  • Put supports in place for tall perennials.
  • Train climbers such as clematis while the shoots are still young and pliable.
  • Prune spring flowering shrubs such as Ribes sanguineum, Clematis armandii, pyracantha, chaenomeles and forsythia after flowering.
  • Clip beech, hornbeam, box, thuja, privet, Lonicera nitida and leyland cypress hedges late this month, making sure no birds are nesting in them.
  • If you spray your roses, start to do so towards the end of this month.
Fruit and veg
  • Sow tomatoes under glass and, later in the month, sweet peppers, chillies, aubergines, melons and cucumbers.
  • Outdoors you can sow swedes, beetroot, maincrop carrots, Brussels sprouts, autumn cabbages, autumn/winter cauliflowers, calabrese broccoli, peas, Swiss chard, radishes, lettuce, mangetout, French beans, runner beans, turnips, endives, fennel, kale, kohl rabi, sweetcorn, courgettes, squashes (including butternut squash), pumpkins and spring onions.
  • Continue to earth up potatoes regularly.
  • Keep soft fruit bushes well watered.
  • Put straw or other liners under strawberries to protect the fruit from grey mould.
  • Cover or put up a barrier (of fine mesh/plastic film) 45cm high around carrots to protect them from carrot fly. Cover cabbages with a similar material to keep off the cabbage white butterflies.
  • Start harvesting your asparagus, lettuce, radishes, rocket, baby potatoes and overwintered onions.
General tasks
  • Mow your lawn weekly to around 2.5cm, longer if a drought is forecast. This is your last chance to re-seed any dead patches before the summer.
  • Use a ‘weed and feed’ product on your lawn, if you didn’t do it last month.
  • Keep on top of the weeding.
  • Apply summer shading to your greenhouse towards the end of the month to protect plants from scorching.
  • Ventilate greenhouses during warm days, but remember to close them up in the evening.
  • Scoop duckweed and blanketweed out of ponds and re-stock with aquatic plants.
  • Take photos of what your garden looks like this month so you can remember what's growing where to help you plan design changes.
Plant of the monthAlchemilla mollis

Alchemilla mollis is a deciduous, clump forming plant which is great for ground cover, particularly in dry areas as it's drought tolerant. It produces small yellow flowers in sprays above the foliage in summer and early autumn, but arguably the pleated, light green leaves are the most attractive feature of this plant. It self-seeds freely, so deadhead the flowers as soon as they start to fade unless you want it to migrate to all parts of your garden! Find out more...

Problem of the monthCuckoo spit from a froghopper

Froghopper nymphs appear on plants from May and are most recognisable by the protective white froth they cover themselves with, which is known as 'cuckoo spit'. The nymphs feed on stems, leaves and roots but generally do little damage unless they feed on the tip of a shoot, in which case distorted growth may occur. They mature into adults by late July. Find out more...

In the news

Ash tree 'Betty' shows tolerance to dieback

Government backed researchers in Norfolk have found the first UK tree, nicknamed 'Betty', which shows signs of being tolerant to the ash dieback fungal disease. The team, after comparing the genetics of trees with different levels of tolerance to the disease, have identified markers to predict how well a tree will cope with an infection. Trees like Betty could enable selective breeding to propagate plants which are not severely affected by ash dieback, replacing those which have succumbed to the disease.

Live near a green space and live longer

A study by scientists at Harvard University in the US have found a significant link between living near greenery and longevity. The 8 year study assessed more than 100,000 women by the amount of vegetation within 250m and 1,250m of their home. Once other factors were discounted the researchers discovered that there were 12% fewer deaths when comparing the women living in the greenest areas to those in the least green situations. The women living in greener surroundings also showed improved mental health, a 34% lower risk of dying from a respiratory disease and a 13% lower rate of cancer mortality.

Lottery grant to help promote London's mulberries

The Morus Londinium campaign (Morus being the genus name for mulberries), an initiative by the Conservation Foundation, has been given a £69,000 Heritage Lottery Fund grant to plant and raise awareness of mulberries in London. Mulberry trees have been planted in the city since the 17th century and some of these trees are still alive today. They were originally planted to support the silk industry and the national collection grows in the grounds of Buckingham Palace.


Plants for a difficult spot – chalky/limestone soil

Gardening on chalky soils can be a challenge. The soil itself tends to be shallow due to ongoing erosion and the porous nature of chalk makes it very well draining – so drought tolerant plants will cope best. Added to that, chalk has a high lime content so the soil tends to be alkaline, but on flat ground with deeper topsoil the porosity of the chalk can actually leach out all the lime, leading to acidic conditions. The leaching effect can also wash out nutrients from the soil.

So if you have chalky soil it’s likely to be shallow, dry, alkaline (or acidic) and nutrient poor! But don’t despair, there are plenty of plants that are up to the challenge.

Trees and shrubs
Chamaecyparis lawsonianaChamaecyparis lawsoniana 'Erecta Aurea'

This conifer will tolerate most conditions, although it prefers a sunny spot. It’s a good choice for hedging in a chalky garden or, if you want an architectural shrub, try Chamaecyparis lawsoniana ‘Erecta Aurea’ (shown here) which grows to only 2 metres tall. It has a compact, conical shape and bright yellow/green foliage.

Cornus mas

Growing up to 4 metres tall, the ‘Cornelian cherry’ is actually a species of dogwood and some varieties have the brightly coloured young stems typical of this genus of plants. It can be grown as a shrub or small tree and is prized for the bright yellow blossom which appears on bare stems in late winter.

Berberis darwinii

This dense, evergreen shrub will grow to 2.5 metres height and spread and is happy in any soil so long as it isn’t waterlogged – so chalk is ideal. Bright orange flowers appear in the spring followed by blue/black fruit in the summer. It requires little maintenance, which is good because the stems are covered in very sharp thorns!

Against a wall

These climbers prefer a slightly alkaline soil and are happy on growing on chalk. If you want to cover a wall or shed then Clematis montana var. rubens ‘Tetrarose’ is a great choice. It will climb up to 8m metres and bears violet coloured flowers with yellow centres throughout the summer. Keep its roots cool by mulching well.

Jasminum nudiflorum

The winter jasmine is an excellent partner plant for clematis as it provides winter interest with small yellow flowers appearing in winter and early spring. It doesn’t ‘climb’ like the clematis does, so its gracefully long stems will need to be tied into a support.

Herbaceous plants

Peonies often work well on chalk soils. Paeonia lactiflora ‘Sarah Bernhardt’ is a popular choice. It grows to about 1 metre height and spread and has large, pink double flowers in the summer. Peonies prefer a sheltered spot and will require support as they grow.


Pinks are happiest in well drained and neutral to alkaline soils, so are an ideal choice on chalk. Try Dianthus ‘Doris’ for pale pink flowers over a compact mound of grey/green foliage. It looks great at the front of a bed or border.

Helenium 'Moerheim Beauty'Helenium

Perennial ‘sneezeweeds’ such as Helenium ‘Moerheim Beauty’ (shown here) are happy in any soil and cope well with chalk. Their daisy-like flowers appear in summer and are a perfect selection for hot borders. Taller varieties will require support.


Preferring well drained soil, crocuses are a good plant for spring colour on chalk soil. Crocus chrysanthus ‘Cream Beauty’ will work well and reward you with creamy flowers that are deep yellow in the centre, from early spring.

Use our plant selector to search for more ideas for chalky soils.


What's on this month

Put a 'spring' in your step by visiting one of the many garden events to be enjoyed this month:

  • 5th to 8th May - RHS Malvern Spring Festival, Three Counties Showground, Malvern, Worcestershire.
  • 8th May - Late Spring Guided Walk, Mount Stewart, Newtownards, County Down.
  • 8th May - Wildlife Workshop, The Plantation Garden, Norwich, Norfolk.
  • 11th May - National Garden Scheme Open Day, Tatton Park, Knutsford, Cheshire.
  • 14th May - Kitchen Garden Study Day, Woburn Abbey and Gardens, Woburn, Bedfordshire.
  • 14th & 15th May - Open Garden, Redcroft, Edinburgh.
  • 19th May - 'Down To Earth' Radio Programme Recording, University of Leicester Botanic Garden, Leicester.
  • 21st May - 'All About Propagation' Course, The Beth Chatto Gardens, Colchester, Essex.
  • 21st May to 12th June - Chelsea Fringe Festival, various locations in London and the rest of the UK.
  • 24th to 28th May - RHS Chelsea Flower Show, Royal Hospital, Chelsea, London.