Horticulture Magazine

Common Agapanthus Growing Problems

yellow leaves of an agapanthus failing to bloom

Agapanthus are popular flowers.

While native to South Africa, these plants can cope with British conditions as long as you take care of them, especially over the winter.

But while they can often do very well in our gardens, there are certain problems to look out for.

My Agapanthus Won’t Flower

agapanthus plants with very few flowers

The most common issues gardeners experience when growing agapanthus relate to flowering.

Agapanthus can flower fairly reliably when cared for correctly. However, they can flower poorly, or fail to flower at all.

A problem with flowering is usually due to one of the following issues:

  1. Too much shade
  2. Too little water or too much
  3. The wrong size of container
  4. Low fertility (especially when grown in pots)
  5. Incorrect winter care and protection
  6. Agapanthus gall midge
  7. Plant diseases

Of course, in addition to causing poor or non-flowering, these issues can also cause other symptoms in Agapanthus plants.

Read on to explore each one of these issues in a little more depth –

Sunlight Issues

a large, round agapanthus plant in part shade and part sun

Most issues with Agapanthus non-flowering relate to some problem with the environmental conditions.

One such common issue is a lack of sunlight.

Remember, Agapanthus need a spot that is as sunny as possible.

Too much shade is one reason why your plant may not be flowering as well as it should.

Watering Issues

watering a potted agapanthus plant

If the weather has been very dry, and especially when growing in containers, a lack of watering over the previous spring, summer and early autumn may be to blame for poor flowering.

Once established, these plants can be relatively drought tolerant.

But still have to be watered frequently when growing in pots, and certainly until they are well settled in.

However, Agapanthus also needs well-drained conditions.

Waterlogging, and excessive watering, can also cause issues.

Roots may rot (and fungal diseases, see below, may be more likely to set in) when conditions are too damp.

Problems When Growing Agapanthus in Pots

a pot bound agapanthus plant with brown and yellow foliage

Another reason for poor or non-flowering in Agapanthus is being in too commodious a container.

Agapanthus will flower better when it is fairly snug in its pot.

However, being hugely constricted can also cause a plant that previously flowered well to stop flowering.

So a lack of flowering could be a sign that you need to move your Agapanthus to a larger container, or, where this is no longer practicable, to divide it and repot each section.

Agapanthus Fertility Issues

hand pouring liquid fertiliser into a measuring cup

Agapanthus, especially when grown in containers, can also suffer from a lack of fertility.

Low potassium, for example, may reduce flowering, or even mean that a plant does not flower altogether.

It is a good idea to feed your plant with a potassium-rich liquid feed from spring through to early autumn.

Fertility issues may also cause other symptoms, such as yellowing leaves, in certain cases.

Issues With Agapanthus Winter Care

potted agapanthus plant overwintering inside a home

Another common issue with Agapanthus is incorrect winter care.

Hardier Agapanthus can often overwinter outdoors, but usually need some protection – such as a mulch of straw or autumn leaves piled over the crown.

In more northerly gardens, and for more tender cultivars, it will usually be necessary to move plants to an unheated greenhouse or other protected frost-free location over the winter months.

Where this is not done, plants will be damaged, and can die.

Exposure to cold can also reduce flowering the following year, even when plants do survive the winter.

However, poor quality flowering can also be due to being kept in too warm a location over the winter months.

Agapanthus spaced in heated conditions over winter may flower earlier, but the flowers will usually be inferior in this case.

Gall Midge

gall midge up close on a leaf

If the flower buds on an Agapanthus become discoloured and deformed, and don’t open, this can be due to Agapanthus gall midge.

This is caused by the larvae of a small fly, Enigmadiplosis agapathi, first observed in the UK in 2014.

When the deformed buds are opened, little maggots can be seen inside. The affected flower heads should be carefully removed and destroyed.

Plant Diseases

foliage of an agapanthus plant affected by fungal disease

While Agapanthus are not usually troubled by disease, there are several fungal issues that can occur – such as Anthracnose, powdery mildew, grey mould, and root rot, for example.

Ensuring that you have provided the right environmental conditions for your Agapanthus, and are not causing problems through your watering, can help reduce the chances of such problems taking hold.

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