How to Prune Leptospermum

Question from Ralph:
Happy Memorial Day….a special “thank you” for any service from your loved ones. I served from 1966-1970 and can appreciate the sacrifices of our men and women in uniform servicing our great country.

Thank you again for your quick reply, I had read in two places this would not be a good idea based on the roots be resistant to disturbance? Anyway, my lady has great talent in floral arrangements – but without any idea as to growth patterns etc…..so we cross paths often…and I can’t win. Anyway, I suppose from past trimming of these….that I can trim them back down to an acceptable height and maintain the shape. I would hate to pull them out and destroy, so will just cut back….unless you tell me that too will kill them. All the best and thank you for your input.

Answer from Pat:
Thanks for the kind wishes on Memorial Day. My brother and my husband served in World War II; my uncle was in the RAF. All three lived to tell the tale, though my other uncle was killed in World War I.

You are correct in your assessment of why leptospermums don’t transplant easily. Their fine, wiry roots, typical of many drought-resistant plants, are good at stretching out in the soil and finding water, but cannot adapt to the shock of being dug up. The feeder roots break off during transplanting and the stronger ones close to the plant cannot make new feeder roots quickly enough for the plant to survive.

In regard to cutting back, yes if you chopped of three or four feet off the top, the plant will die. The best way is to prune selectively in winter by taking of armloads of flowers when the plants are in bloom. This should, I hope, please your wife who wants to use them in flower arrangements. By cutting back in winter this way you can make the cuts quite deeply into the shrubs, allowing long stems for cut flowers. You can even cut stems deeper into the shrub than needed for arrangements and then your wife can simply trim the stems to the correct length needed for vases. Don’t cut the shrubs all at once but continue cutting the flowers during bloom throughout winter and even into spring if the plant is still in bloom until all the blooms are gone and you have lowered the whole plant. By doing the pruning this way you solve several problems: You allow the plant time to regenerate between cuts and you avoid shearing the plant. Shearing leptospermums, though often done, is a deplorable way to prune them since it destroys their natural shape and makes them develop a lot of dead growth inside the bush. Most importantly by pruning in winter you avoid destroying the following year’s bloom. Of course, if you saw through a thick branch the wood cannot regenerate, but most L. scoparium shrubs stay pretty twiggy. ‘Ruby Glow’, however can become a twisted tree.

Since it is now May and since you didn’t do the above step in winter, it would be all right to follow the rule of “Prune After Bloom” and cut some height off now by shearing. Even though I like the pruning system recommended above, shearing would be the safer way now. By pruning immediately after bloom you would still get bloom next year. On old woody shrubs like this don’t cut too deeply all over or you would indeed risk killing the plants. Follow up with fertilizer and water.