Guide to growing Prickly Rhubarb (Gunnera)
Members of the Gunnera genus are hardy perennials that can reach up to 1.8M in height, and are often wider.
They have very large leaves that are both lobed and toothed.
Though they bloom in summer and the start of autumn, it is the attractive combination of foliage and flowers that Gunnera are usually grown for.
The flowers grow to be cone shaped and may be red, yellow or green. A commonly grown member of Gunnera is Prickly Rhubarb.
How to grow Prickly Rhubarb
When growing prickly rhubarb and other Gunnera species outdoors from seed sow just after the last frost; lightly cover the prickly rhubarb seeds once sown. Gunnera are very large plants; space normal Gunnera at 1.2 to 2 metres apart; the gigantic Gunnera species available need to be grown at least 3 metres apart. Gunnera are able to grow in both sunny and partially shaded parts of the garden. Due to their massive size it is important that Prickly rhubarb and similar plants have a very deep soil in which to grow; the soil should also be rich and moist.
If starting off indoors, sow Gunnera seeds about 8 weeks in advance. Gunnera seeds should take from two to ten weeks to germinate at a temperature of 15 to 20 degrees centigrade.
Caring for Gunnera
As Gunnera plants such as Prickly Rhubarb are very large they require a lot of water and food, so water them frequently and supply regular feeds of liquid fertilizer. Once they have finished flowering in the autumn, cut off their leaves, and cover their crowns with a a mulch of leaf mold. If you require more plants then propagate Gunnera in the spring by division.