Chelsea Chop: extend the flowering season in your borders by the pruning or selectively cutting back of flowering perennials – often referred to as the Chelsea Chop as you do it at the time of the Chelsea Flower Show at the end of May.  The technique can prolong and/or delay flowering and also produce stockier more branched and floriferous plants that are less likely to flop or need staking. Not all plants are suited to this technique but for those that are all or some of the stems are cut back by about a third. Suitable plants include later flowerers such as Sedums, Rudbeckias, Solidago, Heleniums and Asters and those that reliably give a second flush of flowers such as Phlox and Achilleas.

May is a busy month in the garden and other jobs include: 

  • Keep weeding.       And mulching – it will help plants if the summer is dry.
  • Keep a look out for pests and diseases especially as it is very likely there will be more pests around this year following the mild winter. I was spraying aphids on a clients roses in mid-April and suspect it will be advisable to keep an eye out for scarlet lily beetle on my emerging container grown lillies.
  • Protect apples from coddling moth by using pheromone traps.
  • Prune spring flowering shrubs immediately after flowering. When pruning deciduous shrubs work from the inside base of the plant and take out up to a third of the older stems – these will be the thickest ones – to allow room for new stems to grow. Also remove crossing branches to open up the centre of the plant and then lightly trim any remaining long stems to maintain the natural shape of the shrub in its allotted space.
  • Once it has flowered, Clematis Montana which has outgrown its allotted space can be cut back hard and will grow away all summer and flower again next spring.
  • Lift and divide primroses for more plants and flowers next spring.
  • Sow spring flowering biennials such as Sweet Williams and wall flowers. Sow outdoors and thin out the plants so that they can make good growth before flowering next spring.
  • Divide, if necessary, warm season grasses which include the increasingly popular Miscanthus sinensis cultivars.
  • Shade the greenhouse and open doors and vents during the day.
  • Sow seeds of courgettes, cucumbers and squashes and harden off other seedlings grown indoors before planting out.
  • Succession sow peas, broad beans and salad crops to ensure a continual supply rather than a glut.
  • Plant out sweetpeas.
  • Plant out Dahlias and other tender plants at the end of the month after the last frosts.
  • Water newly planted trees, roses, hedging and shrubs and mulch well to conserve water so roots can get established in this first year of growth.
  • Plant up containers and hanging baskets with summer flowering bedding for a splash of colour.