What you should do in your garden this month - Now that the warm weather is finally here, it's time to start thinking about your garden! Here's a guide to what you should be doing at this time of year.

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Be careful of frost damage - Keep an eye out for late frosts and protect young and vulnerable plants. The last overnight frost generally comes in late May in the south of England, and June elsewhere in the UK.

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Earth-up potatoes - Earth-up young potato plants by pushing soil around the stems to form a ridge. The final height of the ridges should be 20 to 30 cm. This prevents light from reaching the tubers, which stops them turning green. Green tubers are potentially toxic. 

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Plant out bedding plants - Plant out bedding plants in late May/June and September/October.

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Open greenhouse vents - Greenhouses can overheat in sunny weather, so if the forecast is good, open up some vents or a door.

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Divide crowded bulbs - Lift and divide overcrowded clumps of daffodils, crocuses, and other spring-flowering bulbs this month.

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Mow lawns - During spring, mow your lawn once a week for optimal condition.

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Sow new lawn - Sowing new lawns or over-seeding dead patches can still be carried out in May.

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Harden off plants - Harden off young plants raised from seed or cuttings by leaving them outside for gradually increasing periods of time. 

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Harden off plants - Start at the warmest part of the day, and build up to overnight exposure. Doing this for a couple of weeks before planting them outdoors will increase their chances of survival.

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Cut back shrubs - Cut back tender shrubs after the danger of frost has passed and clip evergreen hedges. Shredded clippings can be added to the compost heap, ideally in combination with soft material such as mown grass. Prune spring-flowering shrubs after flowering.

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Check for nests - But don't forget to check for nesting birds before clipping hedges.

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Thin out aquatic plants - Thin out, cut back or divide excessive new growth on established aquatic plants. You can still plant new aquatic plants this month.

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Stock ponds with fish - Begin stocking ponds with fish after plants are established. Avoid introducing goldfish to wildlife ponds, where they will disrupt the existing foodchain.

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Divide clumps of perennials - Divide any herbaceous perennials that you want to propagate. Bamboos, bulbs, and rhizomes can be divided in the same way.

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Trim trailing plants - The RHS states that spreading and trailing plants such as sweet alyssum can become tatty and patchy. Trimming them back after flowering encourages fresh growth and new flowers.

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Pinch shoots on chrysanthemum - Pinch out shoots on chrysanthemum and helianthus to encourage bushy plants, or leave them as-is for a taller growth.

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Look out for pests - Inspect lilies for red lily beetles and keep an eye out for vine weevil larvae, which become active this month.

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Look out for pests - Aphids can multiply rapidly during mild spells. Remove early infestations to prevent the problem getting out of hand. Protect sweet pea plants in particular, as they can get sweet pea viruses.

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Spring cleaning - May is a great month for cleaning up after winter. Pressure-wash or scrub algae from patios and planters.

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Paint fences - Use the good weather as an opportunity to paint or stain fences and fix up any furniture that was damaged in winter. 

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