What I used to think was beetroot. Was infact the perennial herb, red sorrel.
The second photograph underneath this description shows the specimen in the London Wildlife Centre, see how it’s possible for this perennial herb to flourish and flower.
Tralamander's Red Sorrel Care Instructions
Red-veined dock normally grows to a mature height of 91.0 cm (that's 2.96 feet imperial) so ensure you have enough space in your garden for this plant.
Your garden's USDA Hardiness Zone (9a) is not within the ideal known range for Red-veined dock. The recommended range is between Zone 4 and 8. You may have to reassess this planting for suitability in your garden.
More information about Red Sorrel is available in the Folia gardener's wiki. All Red Sorrel Care Instructions have been kindly provided by our members.