How should I care for my brugmansia plant please?
Wait until after it’s flowered and prune with secateurs, taking care not to remove too much at once – you might kill the plant through shock or loss of sap if the cuts bleed. I’d get it back indoors around now – before the frosts. and water sparingly (when it’s dry or once a week) during the winter. Be careful when pruning / handling the plant material as it’s a memeber of the Solanaceae (deadly nightshade / potato) family and can be poisonous.
