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Growing Agapanthus

One of the best summer plants - and one that many people struggle with - is the Agapanthus. Originating in Southern Africa, this perennial plant has the common names “African Lily” and “Lily of the Nile” and it grows best in a sunny, well-drained position, although shade for a short time during the day is not a problem. They have no soil preference in terms of acid or alkaline.

Height and spread vary according to variety and they may be evergreen or deciduous (lose their leaves in winter). The ones that lose their leaves tend to be slightly more hardy than the evergreen types, which need protection against cold winds and wet weather. In the UK, the deciduous types fare well generally, but evergreen ones need winter protection in northern areas.

The long, slender leaves vary according to variety from rich green to grey-green and there are several variegated forms. The flowers may be white or range through shades of blue from dark violet to palest mauve. Bi-colours like ‘Enigma', ‘Twister' and ‘Queen Mum' tend to have white flowers with a blue reverse to the petals or a blue flush at the base.

So what tends to go wrong? The main issue is planting too deeply, thinking you are being kind. These plants need sunshine on their rhizomes (roots) to initiate flower buds and, if the roots are covered, the result is plenty of lush, healthy leaves, but no flowers. You can cure this very easily by inserting a garden fork at a 45-degree angle into the soil under the roots and levering the whole plant upwards. To prevent the plant settling back into the same place, wash some soil down into the hole under the roots and then lower the plant into place. It should sit on the surface of the soil. You can mulch around the plant for protection over winter, but remember to pull the mulch back off the roots once the threat of cold weather has passed.

Feed your Agapanthus regularly for the best results, using a high potash fertiliser every 3-4 weeks between late spring and early autumn. Water young plants during dry weather to help them establish, but older plants can usually manage unless there is an exceptionally dry period.

There is a myth that Agapanthus growing in pots will only flower well if they are pot-bound. Not so. As long as the plant has enough water and was planted correctly into good, free-draining compost (e.g. John Innes no.2 with added grit) it will flower. This idea comes from the fact that any plant suffering stress (shortage of air, water or food) will flower profusely to ensure continuation of the species.

The main thing to avoid with a container is over-potting into a container that is much too big for the plant, for three reasons:

  • the quantity of fertiliser in the compost may scorch the roots
  • the compost may stay too wet, causing the roots to rot, and
  • the amount of space will mean the plant will grow to fill it rather than producing flowers.

Any Agapanthus growing in containers benefit from being moved to a covered or sheltered spot for the winter. If they are outdoors, wrap the pots in a double layer of bubble polythene and place next to a sheltering wall. If you have space to put them in a greenhouse or shed, make sure evergreen varieties have light throughout the winter.

Winter weather is not kind to some varieties of Agapanthus, which may struggle if it is too wet. They usually recover, but may not flower as well as usual the following summer.

For more information, Steve, Elaine & Colin of Agapanthus specialists Hoyland Plant Centre, will be happy to help. www.somethingforthegarden.co.uk

RHS Garden, Wisley, Woking Surrey are currently running a trial of Agapanthus varieties if you wish to see the different colours and sizes before you choose which one to buy for your own garden. www.rhs.org.uk

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This story was published on: 04/08/2018

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