Planting in May unlocks many opportunities: from setting out tomatoes to sowing sunflowers, learn practical tips for soil, sun and watering
Late spring brings a clear message to gardeners: it is time to move from waiting to planting. After the chill of early spring fades, many gardeners use May to begin sowing and setting out a wide range of crops and ornamentals that will fill the garden later in the season.
According to Chris Bonnett, founder of GardeningExpress, this month typically presents the best window to plant species that prefer warmer conditions. Pay attention to the last frost in your area and make sure night temperatures are consistently above around 10C before placing sensitive plants outdoors.
Why timing matters in May
Understanding the role of the last frost is central to successful planting. The term last frost refers to the final date in spring when temperatures drop low enough to damage tender shoots; waiting until that threat has passed reduces the risk of losing young plants.
In practical terms, once conditions are steady and soil has warmed, you can introduce sun-loving and heat-forming crops. Also keep in mind basic site factors: choose a full sun spot for warmth, prefer well-drained soil for many vegetables, and protect new transplants from harsh winds to give roots a chance to establish.
Vegetables to plant in May
Tomatoes: placement and support
Tomatoes are one of the most rewarding summer crops to set out in May, provided you have passed the last frost threshold. Plant them in a full sun location that offers some shelter from prevailing winds and in soil that drains well. For robust development, sink the stem deeper than it stood in the pot to encourage a strong root system. Water consistently as the fruit forms and use stakes or canes to support growth; this prevents fruit damage and improves airflow around foliage, lowering disease risk.
Courgettes: fast growers that need regular water
Courgettes respond quickly to warm soil and higher temperatures, making May a sensible time to sow or transplant. Plant them in a warm, sunny bed with soil that retains moisture but is not waterlogged. Focus watering at the base of the plant to keep foliage drier and reduce disease pressure. Harvest regularly once fruits appear—frequent picking encourages more production and keeps plants productive throughout the season.
Flowers and ornamentals that benefit from May planting
Lavender: sun, air and careful watering
Lavender is a fragrant, pollinator-friendly shrub that establishes most reliably when soil has warmed. Place lavender in a full-sun site and avoid heavy, water-retentive soils; these plants prefer drier conditions and good airflow around the roots. When planting, give each specimen enough space so air can circulate; light pruning after the main bloom helps the plant keep a tidy shape and promotes stronger growth in the following season.
Dahlias and sunflowers: big impact for summer
Dahlias are chosen for their range of colours and dramatic summer blooms—plant tubers about 10cm deep in fertile, sunny and sheltered positions with shoots pointing upward. Young shoots can be vulnerable to slugs, so consider simple barriers or natural deterrents to protect them. Sunflowers are an excellent choice for beginners: sow seeds directly into the ground at about 2cm deep in a sunny spot. Taller varieties will need stout stakes for support to prevent stem breakage in wind or under heavy flower heads.
Practical tips for a successful May planting
Across all these plants, a few core practices make a big difference. Check soil temperature and only plant tender crops when nights stay reliably warm—remember the around 10C guideline. Aim for consistent, appropriate watering—deep at the root zone rather than frequent surface sprinkling—and choose soil that matches each species’ needs, whether that is well-drained or moisture-retentive. Use stakes and supports early, protect vulnerable seedlings from pests and slugs, and space plants to allow good airflow. With these basics in place, May planting will set you up for a productive and colourful late summer garden.
