Comfrey

The unsung hero of the organic garden. Comfrey is a vigorous, deep-rooted perennial that functions as a potassium pump — drawing up minerals from deep in the soil and making them available to the whole garden through its leaves, which can be cut and composted or steeped in water to make a free, high-potassium liquid fertiliser that rivals any bought product.

Above ground, it produces tall, arching stems of nodding purple-blue bells from May through to August that are among the most important nectar sources for long-tongued bumblebees in the British garden. A plant that earns its place twice over.

• Symphytum officinale — Hardy Perennial (H7)
• Height: 60–120cm | Flowers: May–August
• Sow indoors February–April or direct spring; cold stratification may aid germination
• Full sun to partial shade; any soil — extremely vigorous once established
• Cut leaves 2–3 times per season for liquid feed — do not let it set seed freely
• Outstanding long-tongued bumblebee plant

Plant it in a productive corner where it can be harvested regularly — and let the bumblebees do the rest.