May heralds the end of spring and the beginning of summer with the warmer days triggering many plants into flower. Gardens often look at their best in early summer, as they appear fresh and vibrant and, because plants are growing rapidly, the garden appears to change daily.
Allium cristophii – alliums are the quintessential plant of May when their sturdy, ribbed stems bear huge stately heads of small pinkish-purple flowers. Each flower head is made up of 50 or more individual, star-shaped flowers creating a dramatic effect. As the flowers fade the seed heads have a fantastic architectural form to them and they will gradually naturalise and spread. Alliums prefer to be grown in a warm, sunny border in well-drained soil and look fantastic in an informal planting such as a cottage garden.
Thermopsis lupinoides is a gem, producing spikes of dazzling yellow, pea-shaped flowers in late spring. This trouble free perennial is easy to grow and not invasive. It enjoys growing in a sunny position in moisture retentive, well drained soil but resents disturbance and division.
Chaerophyllum hirsutum ‘Roseum’ produces bright green, ferny foliage followed by round, flat heads of soft pink flowers. Chaerophyllum prefers to be grown in a moist but well drained soil in sun or part shade. Combine it with other late spring flowering perennials such as Tellima and Brunnera to make a great naturalistic combination.
Tellima grandiflora is useful for difficult situations such as dry shade, where it will flourish and spread to form a naturalistic drift. Its heart shaped leaves are bright green and it bears thin, airy flowering stems with small, lime green, bell shaped flowers for several weeks through late spring.
Nepeta ‘Six Hills Giant’ enjoys a sunny situation in the garden in well drained soil, where it will thrive and produce clusters of small lavender-blue flowers. This cultivar is taller and stronger growing than other varieties and benefits from being cut back after its first flush of flowers.
Iris is a large and diverse group of plants ranging from small alpines to aquatic species. Iris pallida subsp. pallida likes a warm, sunny situation, in well-drained soil that doesn’t remain wet in winter. It bears broad strapped shaped, grey-green leaves and in late spring stout stems emerge from the base of the plant bearing up to six large, pale blue flowers with yellow centres with an attractive fragrance.