During this hot weather period, our trees have been under stress. We ask you not to sit under our trees or enter roped off areas due to the risk of sudden limb drop. Areas including the Lower Woodland Walk, Learning Centre wildlife and picnic areas, and Copper Shelter are closed at this time.

Gunnera hunker down for the winter

The impressive giant rhubarb plants at RHS Garden Rosemoor receive some timely winter care

One of the most dramatic plants at Rosemoor is Gunnera manicata (commonly known as giant rhubarb), found growing along the stream and around the lake. Its huge leaves can grow more than 2m (6½ft) across and the prickly stalks sometimes grow to 2.5m (8ft) long. That a plant can produce such a huge amount of growth in the UK in the space of only a few months never ceases to amaze me.

Native to an area of South America stretching from Colombia to Brazil, Gunnera manicata is not reliably hardy in this country and the buds in the crown are prone to frost damage. As Rosemoor is situated in a frost pocket it’s important that we take steps at this time of the year to protect the crowns of the plants.  

Removing the leaves from the Gunnera plantSo, one day recently, Alex Davies, Charles Ives and I worked our way down the stream and around the lake, building protective tepees over the Gunnera (left). Using pruning saws we removed the leaves from each plant and then cut the stalk off each leaf before placing them, inverted, over the crown of the plant. Finally, we used the stalks to weigh down the leaves. The leaves and stalks will gradually break down, but should provide sufficient protection to the crowns of the plants throughout the winter. In colder areas it would be a good idea to provide the plants with extra protection by placing some dry straw, fern or bracken, over the crowns before covering them with the leaves.

We can now rest easy, knowing that the Gunnera are well protected for the winter and look forward to next spring when the first new leaves will start to appear.

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The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.