May in Your Garden

Top essential jobs 

1. Watch out for late frosts, so far this has been the coldest spring for 8 years.

2. If you planted early seed potatoes, earth up this month and cover if there is a danger of frost.

3. Towards the end of the month in sheltered locations plant out tender annuals.

4. If it is dry, consider watering newly planted perennials and annuals. Remember to water in the morning, or evening for best use of the water.

5. Keep hoeing weed seedlings as they appear.

6. The sun can be quite strong when it is out so vent greenhouses with seedlings and young plants growing in them.

7. Mow essential areas of the lawn, but consider leaving areas under orchard trees, or at the extremities of the garden longer for wildlife.

8. Clip hedges this month, only after checking no birds are nesting.

9. Now tulips and daffodils are in the green you can lift and divide, much like snowdrops.

10. Check over emerging lilies for beetles and destroy by hand.

 

 

Trees & Shrubs

• This time of year is nesting season, so always check for signs of activity before getting out the pruners. The Wildlife and Countryside Act 1981 protects bird nests, so it is an offence to damage, or destroy them. Smaller shrubs are less likely to hide a nest but be especially cautious if tackling dense or mature shrubs and trees. Only start work once you are happy you will not be disturbing wildlife and stop immediately if you have any suspicion birds may be nesting. If need be, you can complete the work after August when nesting season should be over.
   

• Cut back tender shrubs and sub-shrubs such as Penstemon, Caryopteris and Fuchsia after the danger of frost has passed. Clip evergreen hedges. If not too woody, shredded clippings can be added to the compost heap, ideally in combination with soft material such as grass clippings.
   

• Prune spring-flowering shrubs such as japonica or Japanese quince (Chaenomeles), Choisya and Ribes after flowering. Remove one stem in three from Kerria and Spiraea ‘Arguta’ and shorten the other flowered stems to a suitable side-shoot. Evergreens such as Viburnum tinus can also still be trimmed this month.
   

• Prune overcrowded, dead or diseased stems of Clematis montana once it has finished flowering. Untangling the stems can be fiddly, but once you can see where you are cutting, you need not worry about pruning this plant - it will take even hard cutting back very well. Remove any reverted green shoots on hardy variegated evergreens, to prevent reversion taking over. Prune wall-trained pyracanthas, removing any shoots coming out from the wall, and shortening other new growth to about 8cm (3in). This encourages spur formation, and increased flowering relative to green growth.
   

• Tie in climbing and rambling roses as near to horizontal as possible. This will restrict sap flow causing more side-shoots to grow along the length of stem meaning more flowers will be produced. Twining climbers (such as honeysuckle and Clematis) need regular tying in and twining around their supports.
   

• Finally, loosen any tree ties that are digging into the bark, or could do so soon as the trunk girth expands.

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Perennials

• Plant out Dahlia’s when the danger of frost has passed. Containers can be planted up with summer displays in milder areas. In colder areas further north or at high altitudes, it is advised to wait until early June, or until all risk of frost has passed.
   

• If you want to grow your own spring annuals for next year, many common choices (including wallflowers, pansies, and daisies, Bellis perennis) need to be sown between now and July in order to flower next spring, as they are biennials.
   

• Remove faded wallflowers and spring annuals from beds and containers, to make space for summer plantings.

 

Cutting back, pruning and dividing

• Divide clumps of herbaceous perennials that you want to propagate. Bamboos and clumps of bulbs or rhizomes can be divided in the same way. Cutting back clumps of spring-flowering perennials such as Pulmonaria and Doronicum can encourage a fresh flush of foliage.
   

• Divide Primula (primroses) after flowering, planting them in a nursery bed until they are ready for planting out again in the autumn, for a display the following spring.
   

• Divide hostas as they come into growth.
   

• Spreading and trailing plants such as the annual Lobularia (sweet alyssum), and the perennials Alyssum and Aubrieta, can become tatty and patchy. Trimming them back after flowering encourages fresh growth and new flowers.
   

• Lift and divide over-crowded clumps of daffodils after they have flowered.
   

Propagation

• Take softwood cuttings of tender perennials like Argyranthemum, Pelargonium and Fuchsia. They will provide new plants for display later this summer.
   

• Perennials that are showing new shoots from the crown can be propagated via basal stem cuttings.
   

General work

• Apply a liquid fertiliser such as liquid seaweed to spring bulbs after they have flowered, to encourage good flowering next year, and help prevent daffodil blindness.
   

• Allow the foliage of daffodils and other spring-flowering bulbs to die down naturally.
   

• Lift clumps of forget-me-not once the display wanes, and before too many seeds are released. They can become invasive if left unchecked.
   

• Put supports in place for herbaceous plants before they are too tall, or for those - like peonies - that produce heavy blooms.
   

• Harden off plants raised from seed and cuttings by leaving them outside for gradually increasing periods of time. Start with only the warmest part of the day, and build up to overnight exposure. Doing this for 10-14 days before planting them outdoors permanently (whenever the risk of frost has passed), will reduce any check to their growth while establishing in their final position.
   

• Thin out direct sowings of hardy annuals and vegetables such as radishes. This is best done in two or three stages at fortnightly intervals. Final spacing should be between 10-20cm (4-8in), using the upper limit for tall or spreading plants, and the lower limit for smaller plants. Prick out indoor sowings when they are large enough to handle without damage.
   

• Hoe borders to prevent annual and perennial weeds from spreading and seeding themselves.
   

• Sweet peas need training and tying to their supports to encourage them to climb and make a good display.
   

• Pinch out the leading shoots on plants such as Chrysanthemum and Helianthus to encourage bushy plants. However, if tall thin sprays are preferred, they can be left un-pinched, perhaps removing a few buds (known as ‘disbudding’) to encourage larger blooms.
   

• Liquid feed plants in containers every two to four weeks.
   

• Keep containers, hanging baskets and alpine troughs well watered. Use collected rainwater, or recycled grey water, wherever possible.
   

• Pot on plants showing signs of being root bound. You can tip out the root balls of unhappy looking contained specimens, to see if they are indeed pot bound or if they are suffering from some other problem.