How to Grow Agapanthus

Agapanthus is a summer flowering plant, with exotic looking flowers in striking shades of blue, mauve, and white. Agapanthus are perennial and of the popular varieties offered for sale are some are evergreen and others deciduous. 

Although the taller varieties are popular to grow, Agapanthus range in height from 10 to 150cm.  Growing Agapanthus is easy. Getting them to flower is more tricky. The ideal growing conditions are full sun with fertile, moist but well-drained soil and in a sheltered garden. Agapanthus belongs to that select group of plants which are in flower for a long time,  providing colour in the border for weeks, see images below. 

Agapanthus are an amber wheelbarrow plant as they can be tricky to get them to flower and some varieties are not fully hardy and need winter protection

How hardy are Agapanthus?

 Different varieties of Agapanthus vary to the extent they will tolerate frost and cold.  For best results, it is important to select the most suitable variety for your garden and to select the right planting place. Like so many of our garden favourites, when growing Agapanthus, the trick is to get the "right plant in the right place" and this is very much the case with Agapanthus.  As a rule of thumb, the deciduous varieties are more hardy than the evergreen varieties, and the less hardy types will need a winter mulch and frost protection.

In more exposed gardens a fully hardy variety,  H4 which is hardy down to a range of -5-10 would be the better option and this group includes readily available varieties such as A. Blue giant, A. Midnight blue, A. Lilliput A,  Silver Moon, (as you may expect a short variety up to 10cms) A. Snowy Owl with white flowers. Check when you buy, either the label or website will state if the variety is fully frost hardy. Selecting a hardy variety is essential unless your garden is sheltered, or you can bring the plants under glass protection for the winter. More about frost hardy.

If your garden is exposed,subject to winter wet, and/or prone to lots of frost, or you prefer to grow a more tender variety, grow Agapanthus in pots and move into an unheated conservatory or greenhouse for the winter.  There is a view that Agapanthus flowers better in containers, and you will notice visiting open gardens, noticeably further north. Agapanthus are frequently grown in containers. In colder but not too exposed areas, Agapanthus will survive a winter if covered in a good mulch. In colder areas, Agapanthus will need shelter and winter protection. 

My garden is exposed, and wet, and I grow Agapanthus in containers. Usually I bring them into the greenhouse over winter, more than once I have left outside with a thick mulch, but that is a risk if the roots freeze, the plant will die.

It can take a little time to get Agapanthus to flower, although once established, they will often flower for some years with little trouble.  If you live in Cornwall, or the Scilly Isles, you are lucky, and no doubt laughing up your sleeve at this advice, which you can ignore. In these areas, Agapanthus grows and flowers abundantly in the milder conditions. ( Which may explain why in New Zealand it's status is of an invasive weed)

How to plant Agapanthus and best soil conditions for Agapanthus

You can plant Agapanthus any time during the growing season, ideally in spring. Plant reasonably deep to protect the plant from frost. If planting Agapanthus in a container, leave room for a winter mulch to protect the plant. All Agapanthus, both deciduous and evergreen varieties, will survive a winter best if planted in soil which is not too wet. Whether in the ground or containers, Agapanthus does best in well-drained soil with plenty of organic matter.

Agapanthus will not thrive on poor, thin, dry soils. Neither do they enjoy waterlogged soils. For this reason, if your garden is on the wet side, plant Agapanthus in containers. Agapanthus originates from South Africa so you can be sure they like plenty of sun. To flower well and thrive, Agapanthus needs to be planted in a sunny spot, part of the garden which enjoys sun for at least 2/3rds of the day. Insufficient sun is a common reason Agapanthus does not flower.

The taller varieties of Agapanthus look good in containers adding style to a patio or entrance and are an ideal balcony plant.  Agapanthus will flower well without feeding. It is more about the right growing conditions. That said, in many areas of the UK, growing conditions are not always ideal and a feed (high potash to aid flowering, such as tomato feed,) can only help things along. This is especially the case for container-grown plants.

Agapanthus growing Wild on Tresco Scilly Isles

Agapanthus growing wild on Tresco Scilly Isles

Agapanthus does well in coastal gardens, being tolerant of salty winds, and positively thrives in Cornwall and Scilly Isles, where they seem to grow almost wild.

I took the image on the left at Tresco in the Scilly Isles, on route to Tresco Abbey Garden. This shows Agapanthus growing abundantly and very well all along the shoreline. They are growing wild in ideal conditions, namely, well-drained soil, a mild climate and plenty of sun. Agapanthus grow everywhere on the Scilly Isles, as in Cornwall.  It is all about "right plant in the right place" and this shows that when planted in the right place Agapanthus does not any attention.

When selecting an Agapanthus for the garden, a good starting point is to check out those with the RHS AGM is a good starting point.

Good Varieties of Agapanthus to grow

In 2014, the RHS ran a 4 year trial of Agapanthus to assess the best assessed on length of flowering, colour, balance of flowers, quality of foliage and stems. 

The most hardy evergreens (H4) awarded the RHS garden merit are A. 'Blue Ice' as the name suggests a pale blue variety 85 cm, 'Megan's Mauve' a lavender variety110cm, 'Snow Cloud' a beautiful white variety. Many more deciduous plants were awarded the AGM including 'Alan Street' described as one of the best in the trial a dark purple blue 115cm, 'Silver Moon' as the name suggests a white variety 60cm and one I really love, 'Twister' illustrated above centre. A semi-deciduous variety with bicoloured blue and white flowers it is very striking 65cm.

 Other varieties of relatively hardy Agapanthus include A.'Ben Hope' dark blue flowers height up to 1.2m; A. 'Blue Giant' rich blue flowers similar height;  and A. ' Blue Moon' light blue flowers growing up to 60cms. There is a hardier form of white Agapanthus ' Bressingham White' which has pure white flowers growing up to 90cms. 

What to do if Agapanthus will not flower.

In some areas of the UK, growing Agapanthus is more of a challenge, because can be tricky to get them to flower. There is plenty of garden advice to suggest that Agapanthus flower best when their roots are constricted, but also advise to the contrary.  All the Agapanthus I have are growing are in containers and producing flowers. This is because my garden conditions are not ideal.  

I have grown Agapanthus in the ground, but they just sulked and added very little to the border. As I was reluctant to throw away such expensive plants, I dug them up and potted into large containers and two years later, the flowers finally put in an appearance.  

It is less about constraining the roots and more about growing conditions. The ideal growing condition for Agapanthus is a sheltered spot in full sun with good soil, which is not too dry and drains well. Even though Agapanthus like moisture retentive soil, perversely they will establish well in containers. If grown permanently in containers, it is advisable to divide and replant in fresh compost regularly and how often is governed by the plant's flowering. If the plant is flowering, all is well best to leave alone, if it fails to flower re pot.  

A major cause of Agapanthus failing to flower is too much shade, Agapanthus are sun loving.

Agapanthus look effective in containers.  If your growing conditions are not ideal but you want Agapanthus flowers in the border, you can always place the pots in the borders by digging out a space and sinking the container into the bed. This works well for both Agapanthus and Dahlias if the garden conditions are not ideal. Grown this way, they are also easier to lift and store/overwinter elsewhere.

Agapanthus is one of our showiest summer flowering plants, but perhaps not the easiest to grow. There are some green wheelbarrow plants, i.e easy to grow plants, check out summer flowering plants and ideas for summer planting.

Repotting Agapanthus

If your container grown Agapanthus are ceasing to flower, it may be time to repot them.

To do this, turn the Agapanthus out of the container and the image left shows a pot bound Agapanthus, with its tough, very compact roots. This is a deciduous variety early in the year, not yet in leaf.

Once out of the pot, cut it into 2/3/4 pieces (depending on its size) and you may need to do this with a sharp spade to cut into the bits. Don't worry that you are butchering the plant, it will come back with foliage the same year, and it may also flower, although sometimes not until the next year.

The best time to repot Agapanthus is spring . You can do it later, but the later you do it, the less chance of flowers that year. I had 5 large Agapanthus in containers and it took time to get round them all dividing and repotting. The plants I repotted first, which were done earlier by about a month, flowered the same year, the others did not.

 

deciduous Agapanthus out of container for repotting

New Varieties of Agapanthus to grow

Each year, new varieties of Agapanthus are being produced and in 2020 Agapanthus Poppin Purple emerged. This is a semi-evergreen variety, growing up to 60cms with a long flowering season. It is described as hardy but it will benefit from a winter mulch.

Agapanthus Poppin Purple is available from Crocus along with 20 other varieties.

Available from Crocus.

Agapanthus Poppin Purple

How to look after Agapanthus in the winter

Looking after Agapanthus in the winter depends on both the variety you are growing, and your garden aspect.

Some Agapanthus described as hardy, in more northern or exposed gardens, may will still require winter protection. It is necessary to check the precise variety you are growing; as a general rule, the deciduous varieties are more hardy than the evergreen types. The RHS new hardy ratings takes into account other aspects of hardiness apart from a simple temperature reading, as the aspect is also important.  Plants may be described as hardy but if the ground is wet, (and cold)  they may not survive the winter.

In cold areas Agapanthus can spend winter in the greenhouse.

Agapanthus with winter mulch
Evergreen Agapanthus with winter mulch

If a greenhouse is not available, a winter mulch of around 15-20 cm is ideal and I find strulch very good. If it is very cold, a prolong period of subzero temperatures the more tender, evergreen varieties may also need a fleece during the worst of the winter cold. One advantage of growing in containers is if your garden is exposed Agapanthus can  be moved to a sheltered spot or into the greenhouse.  

In most areas, the more hardy varieties of Agapanthus will over winter fine with a mulch. 

Images of Agapanthus

Agapanthus growing in containers

Agapanthus growing in containers

Agapanthus grow well in containers and here in the garden at Alnwick gardens numerous Agapanthus are displayed in pots.

Agapanthus 'firework'

Agapanthus 'firework'

Another blue and white variety A. fireworks is described as hardy to -10, and grows up to 60cm it is an evergreen variety

Agapanthus with butterfly

Agapanthus with butterfly

Agapanthus do attract their fair share of butterflies over a long period because of their long flowering nature.

Agapanthus growing in a border

Agapanthus in a border

In the right conditions, Agapanthus will grow well in a border and add colour and flowers for a long period.

Evergreen Agapanthus are long flowering I took these images of Agapanthus showing the blooms looking good. They were flowering unusually late because of the summer conditions, none the less the flowers looked good for many weeks.

Agapanthus 11th September just coming into bloom

Agapanthus 11th September coming into bloom

Agapanthus 17th September flowering well

Agapanthus 17th September flowering well

Agapanthus  3rd October

Agapanthus 3rd October

Agapanthus 8th October

Agapanthus 8th October fading

updated 14.10.2021