May Gardening Tips

April was a tough start to the growing season for us gardeners. Cold temperatures, constant rain and frequent torrential downpours have kept us in our winter gardening wear for longer than we would have liked. However, better weather is coming and you can sense that the plants are in suspense, waiting for the warmth to arrive for good (a few sunnier days will burst them all into life!). With the workload increasing in the garden, here are a few things you can be doing this month.

1. Lightly trim formal evergreen hedging – Hedging such as Box (Buxus sempervirens) can be trimmed now.  It does not take to being cut back hard, so the sooner it starts being trimmed to keep it in shape, the better. This is best done with hand shears, rather than with a mechanical hedge trimmer which can bruise the leaves and does not cut cleanly.  It may take a little longer with shears but the overall look will be much better. Remember to clean your shears before cutting to limit the chance of spreading the fungal disease ‘box blight’.
2. Start staking and tying in perennials – This applies in particular to tall stemmed varieties such as Delphiniums. Place several bamboo canes around each plant, with string tied around the canes. Alternatively, you can tie each stem to an individual cane. Metal plant supports are also available and come in various sizes and styles, depending on the shape and height of the plant you wish to support. Ask our plant centre staff to show you our selection of plant supports.
3. Sow perennials seeds outside – You can collect seeds from plants growing in the garden or from a packet, either way, there is no more cost effective, or more satisfying way to grow new perennials. Most perennials can be grown this way, including hardy geraniums and achilleas. Rake the soil to a fine tilth and create shallow drills in the soil. Water the drills if the soil is dry and spread the seeds thinly, before covering them lightly with soil. Don’t forget to label the drills so you remember what you’ve planted.
4. Continue deadheading spring flowering bulbs- We touched on what to do with daffodils in the March gardening tips and it’s the same with other spring bulbs such as tulips. Cut off the tulip heads and leave the stalks and foliage for at least 6 weeks after the last flower. If you must move them, lift the bulbs carefully with a fork and dig a shallow trench, place them in the trench with the bulb covered and the foliage above the ground. You can then lift them again when the foliage has died down.
5. Prepare the ground for summer bedding – It will now be time to clear the spring-flowering bedding plants and prepare the ground for summer bedding. Plants that are removed can be placed on the compost heap to ensure a supply of organic matter next year. Lightly fork over the soil, removing any weeds and adding a little organic fertiliser (just a light sprinkling otherwise you will get a lot of soft growth at the expense of flowers). Then plant in your summer bedding plants such as Begonias and Petunias.
6. Plant out marrows and courgettes – This is best done at the end of the month, as they are prone to frosts. Plant into soil that has been enriched with plenty of organic matter, as marrows and courgettes require a lot of water during the growing season. They need some space (around 90cm each way) and must be kept well watered during the summer. Why not grow one or two in an ornamental border? The large leaves are bold and attractive and provide a good contrast to other foliage plants in the garden.
7. Water and feed containers – Do this regularly as the weather warms up. Watering containers can become a daily or twice daily task, hanging baskets in particular can dry out quickly. A high potash feed is best for flowers and supports a prolonged display. High nitrogen fertilisers can produce a lot of leafy growth at the expense of flowers so consider which is best for your chosen plants.
8. Watch out for vine weevils – The adult vine weevils are rarely seen as they only come out at night.  Notched foliage is always a sign of their presence, however it is the grubs that do the most damage. They eat at the roots of the plants and can wreck havoc when they multiply within the closed confines of a tub or window box.  The most effective control is an organic biological nematode which kills the grubs and can be bought via mail order.  I have found this to work well in my gardens.
9. Newly sown lawns – If you have recently sown some new lawn seed and it has germinated and grown to about 2.5cm high, roll it with either a lawn roller or the roller on the back of a lawn mower. Rolling encourages the grass shoots to grow from the base of the plant ensuring a close knit sward.  Give the new lawn its first cut when its about 5cm high.  Place the mower on its highest setting at first and gradually reduce the height of each cut, each time you mow.
10. Shade the greenhouse – It is best to avoid great fluctuations of temperature under glass and the best way to reduce temperature is by using shading. There are few methods of doing this. One is to mix a whitewash for the glass made of a commercially available powder and water, which is then painted or sprayed onto the glass and can be wiped off at the end of the summer.  However, this type of shading will be there even on dull days reducing the light inside the greenhouse. Alternatives are roller blinds fitted on the outside of the greenhouse, or a fine mesh netting which can be thrown over the structure on sunny days and removed for greyer days.