How to grow Agapanthus
Agapanthus are great garden flowers, tall stems with exotic looking flowers in striking blue, mauve, white and pink, and coming to their peak in July & August.
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. There are about 10 species of Agapanthus both deciduous and evergreen, but most importantly, Agapanthus vary in hardiness. As a rule of thumb, the deciduous varieties are more hardy than the evergreen, and all varieties benefit from a winter mulch and frost protection.
When growing Agapanthus outside, if your garden is not sheltered, you will need to select a fully hardy variety, *** hardy, such as Blue giant, Midnight blue, Lilliput (as you may expect a short variety up to 10cms) Snowy Owl with white flowers. Check when you buy, the label or website will state clearly if the variety is fully frost hardy. Selecting a hardy variety is essential unless your garden is sheltered and for an explanation of what is meant by hardy follow this link
If your garden is exposed, wet, and/or prone to a lot of frost, or you wish to grow a more tender variety, Agapanthus are best grown in pots and then they can be easily moved into a unheated conservatory or greenhouse for the winter. If you live in Cornwall, or the Scilly Isle you are lucky and can ignore this advise as Agapanthus grow abundantly, flowering freely in the milder conditions.
Received advice is that Agapanthus flower best when their roots are constricted. Currently all the Agapanthus I have are growing in containers and are producing flowers. Previously I had Agapanthus growing the borders but it was clear they were struggling because the garden aspect is too exposed and wet.
Even though Agapanthus like moisture retentive soil, perversely they will establish well in containers, and if growing in containers it's advisable to divide and re plant in fresh compost every few years. All Agapanthus like sun, as they originate from warm climates in South Africa. Agapanthus do well in coastal gardens, being tolerant of salty winds, and positively thrive in Cornwall and Scillies, where they seem to grow wild. For more ideas about coastal gardens follow this link. Agapanthus are very rewarding with their striking flowers and foliage, and easier to grow in milder areas of the country where they can be left undisturbed in the garden and will reward with many flowers year after year. Even in more exposed areas, by chosing a hardier variety and either mulching or growing in a container, Agapanthus can be grown all over the UK.
Still in some areas growing Agapanthus is more of a challenge, and tricky to get them to flower each year. The Agapanthus I had growing in the ground just sulked and added very little to the border. 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 worth also looking at the advice of Quentin Stark from Hole Park gardens, who knows a thing about growing Agapanthus, and he suggests if Agapanthus are not flowering in pots to replant in the ground, and visa versa. It seems to work, Stark also suggests not to molly coddle or overfeed which is the sort of gardening advice I always like; least is best.
So if your Agapanthus will not flower in the ground dig them up and put into pots. Agapanthus do look very effective in containers. If 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. I have seen this done with both Agapanthus and Dahlias to good effect, and grown this way the Agapanthus are easier to lift to store/overwinter elsewhere.
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. Many Agapanthus are described as hardy but in more northern or exposed gardens Agapanthus will benefit from some protection in winter. 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 take into account other aspects of hardiness apart from a simple temperature reading, as aspect is also important; some plants maybe described as hardy but if the ground is wet, (and cold) may not survive the winter.
Apart from mild areas a winter mulch of around 15-20 cms of straw is ideal and I find strulch very good. As the evergreen varieties are more tender they may need a fleece during the worst of the winter cold. If your garden is exposed it is best to move Agapanthus to a more sheltered spot or into the greenhouse for the winter which means growing in containers unless you like digging and can face digging them up at the end of the season to overwinter in the greenhouse. In all sheltered areas the more hardy varieties of Agapanthus will be fine with a mulch. In more exposed gardens, and the evergreen more tender varieties, Agapanthus will need a fleece or to be in an unheated greenhouse. The Agapanthus in the image above spends winter in the greenhouse and flowers very well. The main causes of Agapanthus failing to flower are too much shade, Agapanthus are sun loving, and dislike cold temperatures and lack of winter protection .