This is the best time to cut agapanthus back for big blooms next year, according to its type

I’ve noticed a lot of gardeners wondering when to cut back agapanthus in recent weeks, and if you’re gearing up to trim the plants pretty soon, you’re bang on the money.

Knowing when to deadhead agapanthus is one thing, but it’s best to cut the plants right back for the final time in late autumn, when they’ve finished flowering. There’s an art to timing it just right, though, and you mustn’t jump the gun.

Plus, it depends on the type of agapanthus you’re growing: deciduous or evergreen. One will benefit from being cut back, while the other is best left alone. To find out which is which, I spoke to the experts.

What you'll need

• An agapanthus plant, like Agapanthus ‘Midnight Star’, from £13.99 at Crocus
• A pair of secateurs, like Spear & Jackson Razorsharp Advantage Bypass Secateurs, £9.99 at Amazon
• Garden tool cleaner, like Agralan Citrox Natural Disinfectant Spray, £11.99 at Amazon
• A garden trug, like the Draper Garden Caddy, £34.11 at Amazon

When to cut back deciduous agapanthus

If your agapanthus loses its leaves over the colder months, it’s deciduous. Cutting it back is actually one of the best things you can do with agapanthus after it's finished flowering, but for the plant to grow back strong next year, you’ll need to wait until the foliage has died right down.

‘If there are still green leaves, you need to leave these in place, as they will be feeding energy back to the roots, ready to start growing again the following year,’ explains Lucie Bradley, gardening and greenhouse expert from Easy Garden Irrigation.

Once the leaves have completely yellowed, they’re no longer of use to the rest of the plant, and they, along with the stems, can be cut to the base. Just remember to clean your garden tools between pruning sessions, and use a pair of reliable secateurs to make the job easier.

October and November are the target months for cutting back agapanthus, but don't just go by the calendar; yellow leaves are the best indicator.

When to cut back evergreen agapanthus

If you’re wondering when to cut back evergreen agapanthus (like Agapanthus ‘Fireworks’ from Thompson & Morgan), the short answer is that you, well, shouldn’t.

‘These varieties keep their leaves all year, and cutting them right back can do more harm than good,’ warns Elise Harlock, flower expert at Prestige Flowers.

‘Instead, wait until early spring and remove only the tatty or damaged leaves, leaving the rest in place to keep the crown protected through winter.’

So, it’s best to leave evergreen agapanthus alone at this point in the year, until the spring, when you can give the some light TLC.

A little extra winter protection can go a long way, though. Lucie recommends protecting the plants from frost with mulch by adding a layer of compost, bark or straw around the base.

RocketGro Magic Mulch from Amazon, is a brilliant peat-free choice. You could even protect them with a layer of horticultural fleece, like these plant jackets from B&Q, to be on the safe side.

The rules around cutting back agapanthus depend on the type. If it's deciduous, wait until later in the autumn, when all of the foliage has yellowed. If you're growing evergreen agapanthus, though, keep the secateurs well away this year.