Marvellous May

Hawthorn blossom

Hawthorn blossom, Richard Croft, CC BY-SA

With blossoming hawthorn, May has arrived. The days are longer and warmer, growth everywhere is rapid, and wildlife fills gardens with frantic activity. Our native bluebells carpet the woods, creating a haze of violet blue, the hedgerows are laced with cow parsley and meadows are dotted with buttercups. Butterflies are emerging from hibernation, hoverflies and bumblebees flit from flower to flower seeking nectar. There is so much to see, to enjoy and to do, seed sowing, planting, cutting back, weeding and simply appreciating our green spaces and countryside.

April brought a panoply of weather: hot, cold, wet, dry, blustery, a confused variation for plants and wildlife. Much of the South East has had little heavy rain; the ground is parched and fissured despite the cold end to the month, so watering has been necessary even in this weather. Blossom has been tossed by the wind and stripped from the branches; some seedlings have struggled, growing up in the early April warmth only to be killed off by later frosts. Hopefully May will bring an end to the cold and more stable, warmer weather and steady growing will follow.

In the garden

Wisteria in bloom

Wisteria in bloom, Colin Smith, CC BY-SA

Gardens are blooming this month with the flowers of many plants on show or emerging. These include the floriferous Clematis Montana, the flowers borne on their rampant and vigorous climbing stems; the elegant, pendulous flowers of wisteria; the trumpets of columbine Aquilegia sp., reminiscent of old fashioned bonnets, the intoxicating scent of lilac flowers, Syringa sp. and Mexican orange blossom, Choisya ternata and the distinctive purple globes of the ornamental allium, Allium Hollandicum ‘Purple Sensation’. Brilliantly coloured geum cultivars are beginning to flower with euphorbias bringing a contrasting lime green to spring borders.


Azalea, Richard Croft, CC BY-SA

Gardeners with acid soils may be treated to a showy display from vividly coloured Azaleas and Rhododendrons. These create a wonderful spectacle in woodland gardens such as the Isabella Plantation in Richmond Park at this time of year. Many other woodlanders also flower in May, trying to reproduce before the tree canopy becomes too dense and restricts the light. Foam flower Tiarella cordifolia, bleeding heart Laprocapnos spectabilis, corydalis Corydalis flexuosa and Siberian bugloss Brunnera macrophylla are all putting on a good show.

With all of this growth, colour and nectar, garden wildlife is flourishing and working hard; pollinators are fluttering and buzzing away collecting nectar and pollinating plants; caterpillars are beginning to emerge and looking for a snack; the dawn chorus is rousing and throughout the day birds are foraging for food for their fledgling chicks. Pause a moment and appreciate the cycle of life that is taking place.

Spring pruning

Ribes sanguineum

Ribes sanguineum, Mark Robinson, CC BY

It’s time to prune back spring flowering shrubs when their blossoms are spent such as Bachelor Button’s, Kerria japonica, and the flowering currant, Ribes sanguineum, to tidy them up and allow them put on growth for next year’s flowers. Firstly prune out old and dead wood and crossing or congested stems. For Kerria prune back all shoots that have flowered either to ground level or to a strong side shoot, whilst aiming to maintain an even form. For Ribes, cut back ¼ of the oldest branches. These shrubs can be renovated if they are very old and congested by cutting back all stems to ground level. It seems brutal and not all shrubs respond well to such extreme treatment, which is hardly surprising as they may have reached that point when they are old and tired, but many will be revived and will reward the hard shearing with refreshed and invigorated growth.


Boxleaf honeysuckle 'Lonicera nitida'

Boxleaf honeysuckle ‘Lonicera nitida’, Vijverin, CC BY-SA

It can be an onerous job but it’s time to get box hedges, balls, cones, triangles and whatever other topiary forms there are, pruned into shape. It is often a fiddly job as hand shearing is better than a bruising mechanical trimmer but if the trim is kept close to the desired shape it should not need to be done again until mid – late autumn. Best to prune on a still day to prevent the cuttings from flying away before they can be collected.

Box blight is becoming an increasing problem. If your box has succumbed to blight, it may be better to replace it with Ilex crenata or Lonicera nitida that can also be closely clipped.

Plant supports

Delphiniums at Coleton Fishacre

Delphiniums at Coleton Fishacre, Derek Harper, CC BY-SA

Early May is a good time to stake or support tall, fleshier herbaceous perennials such as delphiniums and mullein, verbascum sp. to encourage their emergent foliage to grow through and envelope the supports and create a more natural display. Some supports such as ornamental wire frames and grids or cane and metal wigwams or cloches are positioned to become a focus of a bed, adding visual structure to the scheme as well as support to the plants within it. Either way, without them it is possible that taller plants or flowering stems may collapse or snap in wind or rain and be ruined. It can be tricky to retrospectively stake a flopping plant without making it look restrained and bedraggled. If plants have already leapt ahead and it is too late to stake them it is worth trying to strategically place canes or sticks around the plants so that they have at least a little support. If all else fails it is also possible to cut the offenders back hard to let them grow up again in a more supportive, staked environment yet with time still to flower this year, albeit a little later. Better that than a bed full of collapsed, broken or restrained flowers.

Plants for pollinators

A field of lavender

A field of lavender, Andy Peacock, CC BY-SA

Pollinators are on the wing; bees, ants, hoverflies, butterflies and moths all rely on the nectar of flowering plants for their food. In the process they also pollinate these plants, transferring pollen from one flower to another so fertilizing them and allowing them to reproduce and develop seeds and fruits. Without pollinators, agricultural economies, our food supply and our countryside would fail. Pollinators tend to prefer simple and wild flowers. A succession of flowering annuals, perennials and shrubs can provide nectar and pollen throughout the growing year. Think about planting some plants for pollinators; lavender Lavandula angustifolia, yarrow Achillea sp, giant hyssop Agastache sp, sage Salvia sp, catmint Nepeta x frassenii, purple coneflower Echinacea purpurea and coneflower Rudbeckia can all be planted now, kept well watered they will then provide nectar and pollen for visiting wildlife later in the year.

Pests and diseases in apple and pear trees

Apple tree with canker

Apple tree with canker, Cherubino, Public Domain

Scab, canker and powdery mildew are the most common apple diseases. Scab, canker and pear leaf blister mite the most common for pears. Well prepared soil with good drainage, good compost with chopped leaves and grasses or stable manure left on the soil to feed the trees will reduce the likelihood of problems.

Cankers are dead sunken areas in the bark often found near a wound where the fungus has entered. Completely cut out any infected small branches, spurs and as much as possible of large branches to prevent spread, all infected material should be cut back to fresh green tissue, then painted with a wound paint to prevent reinfection. Removed wood should be bagged or burnt.

Blotchy dark green spots on leaves and black spots on fruit are signs of scab, caused by a fungus. The best way to control this is to prune out blistered young shoots and dispose of infected leaves and damaged fruits to prevent spread.

Powdery mildew is a fungus that forms a white dusty coating on leaves. Good circulation, not crowding trees closely, mulching and watering regularly will reduce stress and make the trees less prone to powdery mildew. A spray made from a mix of 1 tablespoon of baking powder, 1 teaspoon of vegetable oil and 1 teaspoon of liquid soap in a gallon or 4.5 liters of water, sprayed onto the leaves may help if an outbreak occurs.

Raised pink or yellow blisters on the leaves, is a sign of pear leaf blister mite. The tree may look unhealthy but the mite does not impact on fruiting. For local infections the infected leaves can be removed. If the infection has spread widely leave, as the mite will not seriously affect the long-term health or fruitfulness of the tree.

Pond plants

Water plantain 'Alisma plantago-aquatica'

Water plantain ‘Alisma plantago-aquatica’, Peter O’Connor, CC BY-SA

With warmer weather, the water heats up rapidly and it is the best time to plants pond plants, they will quickly fill out. Try water mint Mentha aquatica, water plantain Alisma plantago, marsh marigold Caltha paulustris, flowering rush Butomus umbellatus or water forget–me-not Myosotis scorpiodes. To keep pond water clear and healthy, nutrient levels need to be kept low. Top up your pond using rainwater from a water butt or tank as this is much better balanced than tap water and use only aquatic soil, low in nutrient levels, for your pond plants. Plant native plants rather than exotics. Invasive non-native species can escape into the natural environment and cause havoc with local biodiversity.

Around 50% of the surface of a pond should be free from vegetation. Thin out areas that become overgrown, taking care to leave the thinned plants on the pond’s edge for 24 hours to allow pond creatures to make their way back into the water. Use a twirling stick to remove excess blanket weed and a net to skim unwanted duckweed from the water’s surface. Enjoy watching the watery activities, pond skaters, tadpoles, water boatmen and the local birds and bats that visit your pond.

Gardening tasks in May

Woody Plants

  • Prune back spring flowering shrubs when they have finished flowering such as Bachelor Button’s, Kerria japonica, and the flowering currant, Ribes sanguineum and Japanese quince Chaenomeles japonica to tidy them up and let them put on growth for next years flowers.
  • Prune box hedges, balls, cones and triangles into shape. It can be a fiddly job but keep the cut close to the desired shape ideally using hand shears.
  • Evergreen hedges can be pruned this month to maintain their health and form. Check first for nesting birds and use hand tools until the end of the breeding season to avoid disturbing them. If you see a nest do not attempted pruning until the fledglings have left.


  • Stake or support tall, fleshier herbaceous perennials such as delphiniums and mullein Verbascum to encourage their emergent foliage to grow through and envelope the supports. This creates a more natural display. Use ornamental wire frames, grids, canes or metal wigwams depending on the plant and the desired effect.
  • Later flowering perennials can be encouraged to have a longer flowering period by giving them the ‘Chelsea chop’. Prune around one third of the stems by a third and another third by two thirds.
  • Tie in fast growing climbers such as clematis.
  • Thin out annual plants such as sunflowers, Helianthus annuus, Cosmos bipinnatus, and night-scented stock, Mattiola incana, that have been sown in situ to prevent them getting crowded and leggy. Thin out to one healthy seedling per 10-15 cm depending on anticipated growth. If done carefully enough the rejects could be transplanted elsewhere.
  • Harden off any seedlings for 10-14 days before planting outside. This means gradually introducing them to cooler and more erratic weather conditions, first leaving them without cover during warmer days and eventually all night till they have acclimatized.
  • Continue to deadhead spring flowering bulbs such as daffodil, Narcissis and grape hyacinth. This directs energy to the bulbs for next year’s growth rather than to creating new bulblets from seed. Also feed them with a liquid fertilizer to maintain and improve flowering the following year. Congested clumps can be lifted, divided and replanted.
  • Cut back dying allium foliage to keep beds looking spruce.
  • After the danger of frosts has passed, sow half-hardy annuals and plant out tender plants such as Dahlias and Cannas and any summer bedding.


  • Plant alpine strawberries for fruiting this year.
  • Lay a bed of straw around strawberries to deter slugs and net to deter birds but check for any trapped wildlife regularly.
  • Transplant indoor seed grown rhubarb to it’s final growing place.
  • Weed and mulch fruit bushes, net to deter birds.
  • Thin large gooseberries varieties removing every other one and use for cooking, the remaining fruits will grow larger and sweeter.
  • Remove unwanted raspberry canes.
  • Prune trained cherry and plum trees.
  • Cut back leaders and side shoots on mature trained apple and pear trees.
  • Hang pheromone traps in apple trees to catch male coddling moths and prevent eggs being fertilized.
  • Check apple trees for canker, powdery mildew and scab.
  • Check pears for pear leaf blister mite, canker and scab.
  • Use a fertilizer such as liquid seaweed on vines.


  • Try sowing an area with annual meadow seed, also a boost for pollinators.
  • Put out mealworms for blackbirds and robins trying to feed their young.
  • Create a deadwood habitat for small invertebrates with mini piles of twigs and stones in beds, great places to hide.
  • Fill a hanging basket or open container with sheep’s wool and dried grass for nesting birds to pick from.

Sustainable Practices

  • Keep newly planted shrubs and perennials irrigated. Watering in the early morning or evening will reduce water evaporation and therefore the amount of water used. If you haven’t got one, consider installing a water butt to save water.
  • Hanging baskets and container grown plants will need increasing irrigation. Do not be fooled into thinking that rain will help. Rainwater is likely to wash away from leaves and over the edge of the container leaving the soil dry.
  • Feed container plants every 2 – 4 weeks with a balanced liquid fertilizer such as liquid seaweed to keep them healthy.
  • Keep an eye out for any late frost forecasts and protect tender plants with a covering. Bring in or shelter any plants that are hardening off outside.
  • Continue to hoe weeds regularly, warm days are best when the weeds quickly dry out and die. Remember that weeds can provide food and habitat for wildlife too, so don’t be too tidy and leave some if you have the space.
  • Check for pest and diseases. Viburnum beetle and Lily beetle will start to appear, vine weevils may damage container plants, aphids proliferate and roses may show signs of blackspot. Try to treat with manual or biological methods rather than using pesticides or fungicides that may damage the garden wildlife. Slugs and snails may also be a problem, try nemaslug or wool pellets as oppose to slug pellets.
  • Mow lawns weekly. If you would like to try a more wildlife friendly lawn leave a patch to grow longer, clover, daisies and buttercups are likely to appear and support pollinators in you garden.

Relaxing reading

Climate Change and British Wildlife

Trevor Beebee

Britain has a long history of wildlife and weather recording. This book looks at how nature is managing with the changes in the climate, the movement of population ranges, earlier flowering, new arrivals and declines.

Buy >

A Buzz in the Meadow

Dave Goulson

A look at the natural world around a derelict farmhouse surrounded by meadows deep in rural France.

Buy >

Things to see, places to go

The RHS Chelsea Flower Show

The big gardening event of the year.


21 - 25 May 2019


Royal Chelsea Hospital, Chelsea, London SW3 4SR

Learn more >

Chelsea Fringe

If the RHS Chelsea Flower Show is not for you, why not try the Chelsea Fringe instead? Its an alternative mix of public spectacles, horticultural happenings and community celebrations.


18 - 26 May 2019


Various, London

Learn more >

Wildlife Gardener's Day

The Wildlife Gardening Forum is holding its second Wildlife Gardener's Day in partnership with the Wildfowl and Wetland Trust - its a full day of plenary talks, a great choice of workshops and breakout sessions covering many aspects of wildlife gardening.


18 May 2019


The London Wetland Centre, Queen Elizabeth’s Walk, London SW13 9WT

Learn more >

Catriona Andrews


Catriona is a landscape designer and environmental educator. Her work combines naturalistic planting and sustainable practices to create spaces that are sensitive to the environment and welcoming to wildlife. She designs private gardens, community gardens and public spaces and leads courses and workshops on garden and planting design and the environment.