Gunnera manicata is one of the biggest and most spectacular architectural herbaceous plants, commonly known as 'giant rhubarb'. However, a study conducted by the Royal Horticultural Society has found that Gunnera manicata was actually lost to cultivation soon after it was introduced and that plants thought to be Gunnera manicata are actually a hybrid of Gunnera manicata and the invasive Gunneratinctoria. This hybrid has now been named Gunnera × cryptica.
Sales of Gunnera manicata / Gunnera × cryptica have since been banned and gardeners with existing giant gunneras must ensure they don't let them spread beyond their gardens. Small gunneras, such as Gunnera magellanica and Gunnera perpensa, are not banned and are still legal to buy and grow in gardens.
If you have a gunnera in your garden and would like to remove it, the best thing to do is cut it back completely and then dig it out. Alternatively, to stop it spreading, simply cut flowerheads in summer before they set seed, and burn them on site or take them to an authorised landfill site or other suitable disposal site.
