7 reasons your agapanthus isn't flowering and what you can do about it to ensure beautiful blooms next year

As we approach mid-August, you might find yourself asking, 'Why is my agapanthus not flowering?'

This cottage-garden staple is loved for its impressive height and eye-catching blue hue. Typically, growing agapanthus is easy; they are low-maintenance and drought-tolerant, reliably producing beautiful blooms year after year. However, if yours isn't flowering, there could be a few reasons why. To help solve the problem, we've consulted the experts for their tips and tricks.

1. Plants are too young

'Newly planted agapanthus needs a couple of years to establish before they start flowering, so if yours is new, you may need to be more patient,' explains Chris Bonnett, founder of Gardening Express.

This is particularly the case for bulbs – like these from Crocus.

If you want guaranteed blooms this year, planting established plants in summer, rather than planting bulbs in February , may be the way to go. Gardening Express has a wide selection of agapanthus, guaranteed to be in bud or bloom – we love this Agapanthus Poppin Star from Gardening Express.

2. An established clump was recently divided or repotted

Just like new bulbs need time to settle, if you recently divided an established clump of agapanthus, you may need to wait a few years before you see flowers again.

'The plant can look completely healthy and still not flower,' says Julian Palphramand, head of plants at British Garden Centres. 'Dividing and repotting an established clump can often set agapanthus back a year or two before they settle in again. To solve this, leave established clumps alone as much as possible; give them full sun, and feed with a potash-rich tomato food through summer.'

Tomato food, like this Levington Tomorite Concentrate from Amazon, is often recommended for plants that are struggling to bloom – including gladioli that are not flowering.

'Resist the temptation to divide agapanthus too often because they do still flower well when their roots are slightly congested, meaning they don’t need to be moved too often,' adds Morris Hankinson, managing director of Hopes Grove Nurseries.

3. Not deadheading

Deadheading is one of the best things you can do with agapanthus after it's finished flowering and can help encourage flowers the following year. So if you're questioning whether or not you should deadhead agapanthus, the answer is yes.

‘Make sure you deadhead the faded flowers by snipping off any spent areas above the next set of healthy leaves,’ advises Elise Harlock, flower expert at Prestige Flowers. ‘This not only tidies up the plant but also prevents it from putting energy into seed production, which can result in fewer flowers appearing in the future.’

While there are some plants you should never prune in autumn, the best time to deadhead agapanthus is autumn.

4. Heatwaves and drought

If your agapanthus normally flowers reliably, but hasn't flowered this year, it could be due to the May heatwave.

'Severe drought when the plant is actively growing and forming buds can stunt or stop the development of flower spikes. Potted plants are especially vulnerable to this, as they dry out much faster,' says Richard Barker, horticultural expert and commercial director of LBS Horticulture.

During prolonged dry spells, water deeply and occasionally – a couple of times a week should be enough. For potted agapanthus, water more frequently but make sure your pot has good drainage to prevent overwatering.

5. Overwatering

The opposite of drought, overwatering might also cause your agapanthus not to flower.

'Plants sitting in wet soil over winter can weaken plants and reduce flowering. Make sure the soil is well drained and if the plant is growing in pots or containers, ensure there are drainage holes,' explains Morris Hankinson, managing director of Hopes Grove Nurseries.'You could also place pots onto pot feet or bricks over winter to allow rainwater to drain out of the bottom easily.'

These invisible pot feet from Amazon are compatible with all pots and a must for the garden.

6. The buds were killed off by frost

Frost is one of the leading causes of agapanthus not flowering. 'The flower buds form deep in the crown the autumn before, and these can be killed off by frost over winter,' explains Julian Palphramand, head of plants at British Garden Centres. 'To prevent this from happening, protect the crown from frost with mulch, or move pots somewhere frost-free over winter. Get that last bit right, and they'll reliably flower most years .'

There are lots of different types of mulch that can help protect plants from frost – Suregreen Melcourt SylvaBark on Amazon is RHS-approved – or you could use a horticultural fleece, like this sustainable wool fleece from Amazon.

7. Wrong sized pot

Agapanthus are great container plants – in fact, they are some of the best drought-tolerant plants for pots.

However, they perform best in smaller pots. 'Agapanthus prefer to be slightly root-bound. Putting a young plant into a pot that is too big can cause it to use its energy producing roots and excess foliage instead of flowering,' explains Richard Barker, horticultural expert and commercial director of LBS Horticulture.

'However, severe overcrowding can begin to restrict the water and nutrient uptake of plants, starving them of water and nutrients, which will eventually shut down flowering completely.'

Crocus stocks a specifically designed Terracotta Agapanthus pot. This pot has a slender shape to keep roots constricted but is less prone to waterlogging.

8. Not enough sunlight

Like sunflowers, agapanthus need at least six hours of sunlight to flower. So it's no surprise that a lack of sunlight is one of the main causes of agapanthus not flowering.

'If they are planted in the shade, the flower stems can grow leggy as the plant searches for light. As the plant forms the following year's buds inside the plant in late summer, shade during this time can ruin the display produced the next year,' says Richard Barker, horticultural expert and commercial director of LBS Horticulture.

If you're looking for cottage garden plants for shade, consider foxgloves and hellebores instead.

For potted plants, this is easy to rectify; relocate the pot to a brighter spot. However, for agapanthus planted in the ground, you will need to lift the plant and relocate it to a full-sun aspect. It's important to note that relocating your plant could also cause your agapanthus not to flower for a few years.