When is the best time to cut back my New Guinea impatiens?

Question

They are looking a little ratty & have finished flowering .I am in Sydney Metro (Australia)

Answer 1

I do not hesitate to cut back any plant that is looking ratty. I figure it can't look worse than it already does. Always remove anything dead or weak looking. If the stem-ends look healthy enough, throw them in a glass of water and keep in a semi-shady windowsill--they will root at the nodes to create fine new plants to replace the ratty ones eventually.