Anne Swithinbank’s Masterclass

Q

A few years ago, I planted a few bulbs of a tall, purple-flowered allium. At first they did well, but now all I’m getting is leaves but no flowers. Everything has yellowed and died back now. How can I get them to bloom again?

A

There are 700 species of allium, mainly from dry, hilly regions of the northern hemisphere. The lovely durable

Allium christophii, for instance, comes from Turkey and central Asia.

A number of species and many cultivars make popular garden plants, especially those with spherical heads of purple or white flowers sitting atop tall, sturdy stems. Now is a great time to order bulbs for planting in autumn and flowering next May and June. They are especially effective threaded through borders in waves.

Although described as easy to grow as long as they have sun and well-drained soil, alliums do need some good earth beneath their roots if they are to thrive. Foliage grows in spring and has only a short window for taking up water and nutrients to fuel bulbs for the following year’s blooms. A general-purpose liquid fertiliser is going to help things along. By flowering time, leaves have often turned yellow and died back.

A failure to bloom is usually caused by bulbs rotting in waterlogged soil, or poor growth in dry springs. Bulbs propagate naturally by offsets and might form a congested mass of small bulbs, unable to reach flowering size. I suggest some detective work by excavating carefully under the dead foliage.

We’ve had no flowers on our ‘Pinball Wizard’ for a couple of years, so I took a trowel to the spot where the last vestiges of leaves were withering. The soil of this slightly raised bed was dust-dry and it does have a hard, stony base. I found the bulbs had also been invaded by the roots of a nearby dwarf pine.

Moved to a better position, the leaves that appear next spring should boost the bulbs ready for a show of 4in (10cm)-wide flowerheads on stems 2ft (60cm) high in 2022. Site alliums in areas of the garden where the bulbs can settle undisturbed by regular forking or digging.

I remember buying three bulbs of ‘Pinball Wizard’ from a garden show several years ago. One was dug out and eaten, probably by a badger. My digging has revealed 22 medium-sized bulbs Spectacular ‘Pinball Wizard’ in full bloom, reaching to 8in (20cm) across and 24in (60cm) tall Novelty ‘Green Drops’, with flowerheads that sprout mini florets, will grow happily in pots