Garden tasks for May

This monthly guide is geared to London gardens and their unique conditions. Compiled by the RHS Wisley Plant Centre team
Sweet pea
© RHS
Sow some Scented Stock (Mattholia bicornis) or some Matucana Sweet Pea seed near the area you like to sit on warm August evenings and enjoy the heady fragrance of these easy annual plants

Must do in your garden this month


* Tie in climbing rose shoots as they lengthen, preferably on the horizontal because this encourages more flowers. Use a tie material such as “soft tie” which won’t cut into the stems.

* Deadhead tulips as they fade and give a dusting around the plants with a high potash feed to build the bulbs up for flowering next year.

* Start to harden off bedding plants and tender vegetables by leaving them out during the day to get them used to being outside in changeable conditions. Invest in some horticultural fleece and cover over at night if frost is not forecast, but bring inside if it is.

* Prune hard-back Pulmonarias when they have finished flowering to get fresh foliage which makes a great ground cover and foil for later flowering herbaceous plants and shrubs.

* Put out slug traps to capture the small slugs that do most of the damage to herbaceous tender shoots and Hosta leaves. Use one that uses beer as bait so that it is safe for wildlife and empty the traps onto the bird table so the birds still get this valuable food source.

* Sow peas and beans directly into prepared ground or planters. Make sure if you are using a vegetable patch that you are rotating the crop so that soil pests are deterred.

* In the greenhouse start to feed plants to increase their crop potential as fruiting plants such as tomatoes and peppers use a high potash feed.

* On warm, airy days get out with a hoe and agitate the soil between your plants to dislodge and kill weed seedlings as they emerge.

* With the increase in vegetable and plant waste, check your compost heap for 'residents' - such as grass snakes or toads - and if there are no incumbents, turn your heap and add some compost activator to every six inch layer as you add more waste.

* Remember to keep your bird feeders and bird baths replenished to give young fledglings much needed resources.

Chard
© RHS
Sow some Swiss Chard seed in the flower border or veg patch for a colourful show in the garden and later a tasty accompaniment to autumn hearty meals

Nice to do in your garden this month


* Sow some Scented Stock (Mattholia bicornis) or some Matucana Sweet Pea seed near the area you like to sit on warm August evenings and enjoy the heady fragrance of these easy annual plants.

* Sow some Swiss Chard seed in the flower border or veg patch for a colourful show in the garden and later a tasty accompaniment to autumn hearty meals, the variety “Bright Lights” come in a rainbow of colours. The young leaves can be picked for summer salad or leave the plants to mature and steam like spinach.

* If you have lots of planted containers now is the time to water them with a solution containing “nematodes” that will eradicate vine weevil grubs eating the roots of your precious plants. These useful natural predators are available either in garden centres or online.

* If space is limited you could make a pond in a half barrel, plant a dwarf water lily such as Nymphaea pygmaea, Helvola or Alba. Water lilies like still, calm water so don’t be tempted to put in a little fountain because they won’t flower. (With all water please be aware of the dangers to small children and keep them safe).

* Make a small wildflower patch using the more decorative varieties such as Ragged Robin, Knapweed, Birdsfoot Trefoil, Sneezewort and Small scabious. All of these will self-seed and can be weeded out if they decide to come up in the wrong place next year.

* Clip topiary and box hedges with sharp shears or clippers, remove the clippings from around the plants to take away any disease or pests, feed with a granular slow release fertilizer if in pots or planters.

* Set up a watering system for your containers and hanging baskets and try to include a timer so that you can go away and not have to leave your precious garden to neighbours or friends, because with the best will in the world nobody can look after your plot’s idiosyncrasies’ better than you can.

* Start to spray for pests and diseases, all these lovely juicy new shoots are like a six course banquet to aphids, leaf hoppers and whitefly. Use a spray that is safe for beetles and ladybirds such as “Vitax organic 2-in-1 pest and disease control”.

* Check water butts for mosquito larvae and if present pour on the surface some vegetable oil that will float and form a barrier film that their breathing spiracles cannot penetrate.

All images provided courtesy of the Royal Horticultural Society. Visit the online print shop at www.rhsprints.co.uk.

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