A cottage garden favourite, lupins have a fantastic ability to bring structure and vibrant colour to borders. But it’s important not to leave them untouched once the striking blooms begin to fade. Spending time doing a few easy jobs after flowering can help encourage a second display, as well as preventing them from putting all their energy into producing seed.
Here's what to do with lupins once they've finished flowering.
1. Cut back spent flower spikes
The most important job is removing faded flower spikes. ‘Cut the spent spike right down to the base once it goes over,’ says Mirela Bajic, senior garden designer at House Designer. ‘You'll often get a second flush – smaller but worth having.’
Deadheading encourages the plant to redirect its energy into producing fresh flowers instead of seed, giving you the best chance of enjoying another display before the end of summer.
Use a clean pair of secateurs and cut the entire flower stem back to the base, taking care not to damage any new shoots emerging from the crown.
2. Don't let plants go to seed
While leaving seed heads can be useful for some flowering plants, it's generally not the best approach if you want your lupins to keep blooming.
‘Leave the spike on and the plant just makes seed,’ explains Mirela. Once seed production begins, the plant naturally slows down flower production, as it focuses its energy on reproduction instead.
If you do want to collect seed for growing new plants, simply leave one or two of the healthiest flower spikes to mature while deadheading the rest.
3. Check for aphids
While you're cutting back faded flowers, take a few moments to inspect the plant for pests.
‘Have a look for aphids while you're at it,’ says Mirela. ‘Lupins get a big aphid that clusters on the spikes and it can flatten a plant fast.’
Lupin aphids are larger than common greenfly and often gather in dense colonies on flower stems and young shoots, where they feed on sap and quickly weaken plants.
If you spot them early, they can often be removed by hand, blasted off with a strong jet of water, or treated with an appropriate insecticidal soap if the infestation is severe.
Read more: 6 plants that attract ladybirds to your garden – and keep aphids under control
4. Help them grow strongly
After deadheading, continue watering lupins during prolonged dry spells – particularly newly planted ones – and remove any yellowing leaves to keep plants looking their best.
‘After cutting the plant back, provide lupins with a liquid fertiliser high in potassium, such as tomato feed, as this helps to stimulate new growth,’ says Richard Barker, horticultural expert and commercial director of LBS Horticulture.
Keep the plant's soil moist during dry, warm weather, as this will ensure that the plant recovers quickly from being cut back.
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