Plant Doctor Archive

Less than lush lavender

I have a lavender hedge of stoechas planted, which is about two years old. My concern is that all the plants are looking pretty ill and dry at the moment. Is this a dormant phase which they go through? Some of the plants have little shoots coming away again, but the tops of the plants are looking very grey and dry. I pruned the plants after they had flowered which was around Feb/March, and only pruned them to the bottom of the flowers. Another question — what should I feed them?

I have a 30 metre long lavender hedge along the road front of my property and after watching a segment on Maggie's Garden Show in autumn, about pruning lavender, decided to give it a whack as they recommended it before the colder months. This has resulted, however, in two-thirds of the hedge dying off. Is this a result of the pruning or some other dastardly deed I have unwittingly performed?

Question 1
Stoechas lavender grow best in warm climates and in soils that are well drained. Although more tolerant of humid conditions than other lavenders, they do not grow well in excessively humid regions or areas with high rainfall.

You may find that the damage you describe has been caused by pruning your lavender too late in autumn affecting new growth which has been nipped by frost. If you are going to prune your lavender, the best time to do it (in frost prone areas) is summer - late January/early February to allow the new growth to harden off before winter. Growth is rapid in summer. Prune again after flowering has finished in spring/early summer. You will find that your plants will come away, although plants may look scraggly for a while.

Lavenders that are growing in the ground do not require a lot of additional feeding. An application of Osmocote once a year in spring, or sheep manure pellets, will give a boost to plants, but generally they do best in a lean, mean soil. Mulching in spring will help enrich the soil.

Questions 2
Refer to above question. Are they stoechas type lavenders e.g., dentata, Avonview, Marshwood, Major, Helmsdale, or are they English types e.g., Munstead, Hidcote, spica, angustifolia? Do you live in an area prone to frost, high rainfall, or very humid? If so, then the answer to the top question applies. English type lavenders are more frost tolerant, but less tolerant of humid condtions.

You may find that you pruned too late in autumn and the new growth did not have time to harden off before winter. Your lavenders will come away; you may only need to lightly trim (dead head) in summer until the growth regenerates. Lavenders do respond to trimming, and stoechas types can be trimmed quite hard, but in some regions the time of year this is done can be quite crucial, as they are frost tender.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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