Pruning rosemary plants (Rosemarinus officialis)
Rosemary is an evergreen shrub (herb) that is often used in cooking recipes. It is often mistaken for Lavender as it looks very similar to the untrained eye. Unlike Lavender, it is not essential to prune Rosemary but it does benefit from a yearly pruning to keep it looking healthy and to stop it getting overgrown.
They can reach heights of 5ft (150cm) if left un-pruned and can quickly outgrow their desired area and become very woody. They are often planted as formal or informal hedges but do grow well in pots as well as a border shrub against walls and fences. They are also now commonly grown as a topiary plant due to their evergreen characteristics. There are many varieties, from dwarf bushy ones to trailing spreading varieties that are ideal for trailing over pots.
When to prune Rosemary
If you have a rosemary hedge, single plants in pots or bushes planted in the ground they are all best pruned in the same way every year.
Rosemary is best pruned with secateurs after it has finished flowering which is usually in spring / summer.
How to prune Rosemary
Simply cutting around 2-3 inches of green growth away will keep the plants looking compact and healthy. They will then have time to grow new soft fresh growth that will have time to mature before winter when the first frost can damage younger growth. Pruning too late will risk the new growth being damaged by the frost. Although it usually does not kill plants it can make them look unsightly.
Did you know Rosemary is generally disease and pest free?
Sometimes you may have a plant that has become overgrown and too big, or is starting to look leggy and woody. Ideally you want to avoid this by pruning yearly as described above. Should you need to prune it back hard, they do usually respond well and will come back looking better than ever.
Ideally you want to do hard pruning in intervals to reduce the amount of shock to the plants. In spring when the frost has finished, usually May cut back the whole plant by around one third. Once this is done leave the plant to grow again.
Once there is substantial new growth, prune again by another third which is usually around August. This second prune will give the plant time to recover before winter.
If you need to cut back harder because pruning back by one third is simply not enough then pruning back by 50% is usually okay. Pruning back any harder will be risky and could kill the plant although lots of gardeners have done this successfully.
Rosemary are very easy to grow and thrive in poor soils and are drought resistant once established. They prefer moist but well-drained soils in full sun. They grow well in exposed or sheltered locations and are suited for coastal gardens, wall borders and cottage and rock gardens.