Late May marks the time when the growing season truly accelerates. The soil has warmed sufficiently, daylight hours are at their maximum, and crucially, the risk of late spring frost has generally subsided across most of the country.
Direct Sowing and Transplanting
Fast-growing seeds can now be sown directly into the ground, while tender plants started indoors can be moved outdoors. If temperatures drop, protect them with horticultural fleece, cloches, or even a cardboard box. It is also the ideal moment to plan for a stunning summer and autumn display, whether by planting for immediate impact or sowing seeds that will bloom later.
Expert Advice from Chris Bonnet
Chris Bonnet, founder of Gardening Express, says: "There are so many options when it comes to planting in May. The garden really starts to come to life at this time of year." He has shared five summer crops and flowers to sow and plant now.
Tomatoes
"The last frost really is crucial for a lot of plants, so make sure temperatures near you are consistently over around 10C before planting tender summer crops like tomatoes," says Bonnet. Tomatoes thrive in full sun, a sheltered spot, and well-drained soil. He adds: "Ideally, plant them deep into the soil so they can establish a strong root system."
Courgettes
Courgettes develop quickly once temperatures rise. They are hungry and thirsty plants requiring about 90cm of space to spread out. Bonnet explains: "Courgettes need regular, generous watering at the base, and they should be harvested regularly to encourage more growth. Plant courgettes in a warm and sunny location in moisture-retentive soil."
Lavender
Lavender is a hardy aromatic perennial loved by pollinators. "The warm soil in May helps lavender establish well. Be sure to plant it in a full-sun area and avoid overwatering, as they generally prefer dry conditions. When planting, keep space around the roots for airflow and continue to lightly trim the plant after flowering to keep it compact," advises Bonnet.
Dahlias
Dahlia tubers started in pots or bought in leaf can now go into the ground, but must be hardened off first if they have been under glass. Place them outside in a sheltered spot during the day and bring them back inside at night for about a week. Bonnet adds: "Slugs also love dahlias, so consider creating barriers around young plants and use things like empty egg shells and coffee grounds to deter them."
Sunflowers
For those wanting to encourage wildlife, sunflowers are ideal. The giant central disc consists of thousands of tiny flowers providing nectar and pollen for bees. In autumn, the flowerhead becomes a natural bird feeder packed with oil-rich seeds. Bonnet says: "Sow directly outdoors around 2cm deep in a sunny location and be sure to support any taller varieties with sturdy stakes."
