There is no single month when all lupins should be cut back. For herbaceous border lupins, time deadheading to the end of a flower spike and dead-foliage cleanup to seasonal dieback. Climate, hemisphere, variety and the weather shift those stages, so look at the plant rather than applying a fixed date.
This timetable concerns border lupins. Annual species and woody tree lupins need their own guidance; check the label before using it.
During the main flowering period
Inspect spikes regularly. Remove a finished spike when you are ready to deadhead, while protecting flowers or shoots that are still developing. Do not cut down the whole green plant simply because its first flowers have faded. In a garden with several varieties, different plants may reach this stage weeks apart.
The RHS deadheading guidance bases the action on spent flowers and remaining growth. A photograph or calendar reminder can help you monitor a plant, but neither replaces that inspection.
After flowering, decide whether to keep seed
If collecting seed, retain the selected spikes until the seed is ready for collection rather than deadheading them immediately. Keep seed safely labeled and away from children and pets. If seed is not wanted, remove spent spikes as appropriate and leave healthy foliage.
Do not attach a guaranteed second bloom or improved next-year flowering to a particular cutting date. Conditions and the plant’s health still matter. Record what happens in your garden to improve next year’s timing.
At autumn or winter dieback
Wait for foliage to die back before treating it as dead seasonal material. In colder climates this may follow frost; elsewhere the timing can differ. Clear dead growth carefully where needed without damaging the crown or emerging shoots. It is not necessary to strip a plant’s healthy leaves merely because autumn has arrived.
The RHS growing guide describes border lupins as needing little pruning and discusses dead foliage after frost. Adapt the seasonal cue to your location rather than transferring a British month directly to every country.
When new growth starts
If dead material remains, distinguish it from fresh shoots before tidying. Inspect the crown and surrounding area. Do not use blanket cutting as a supposed cure for slugs, poor drainage or an unidentified disease; those require their own assessment.
A simple annual record can contain three dates: first flowering, first spent spike and substantial foliage dieback. Add the variety and unusual weather. Those observations are more useful than alternating between contradictory instructions to cut every plant in spring, early summer and autumn.
What if the plant is still green?
Identify the purpose before cutting. Healthy foliage outside your expected calendar window is not automatically a problem. Check whether the plant is an annual, herbaceous perennial or woody type, and investigate damaged growth separately. For the practical distinction between deadheading and pruning, see whether lupins need cutting back.
