Glycyrrhiza glabra. Yes, it is what it claims to be: This is the plant that produces the distinctive flavour found in confectioneries and candies world wide. Liquorice is an herbacious perennial legume that is harvested for its roots. The roots contain a compound called glycyrrhizin, which is said to be 30 to 50 times sweeter than sugar. Much of the distinctive flavour or liquorice is produced by the compound anethole, which is also found in fennel, anise, and star anise, although it is botanically unrelated to those plants. Space the 1m (3') tall plants at least 60cm (24") apart in the row, and harvest in the second or third year. Reserve and replant some of the roots to keep the crop going. This plant is hardy to Zone 6.
The roots of this shrub have been harvested for centuries as a medicine and flavouring for sweets. Liquorice is easy to grow and manage once it is established, but it should probably be left to grow for three years before the first harvest. Find out more about how to grow liquorice from seed in the guide that follows.
Season & Zone
Season: Warm season
Exposure: Full sun
Zone: 7 – 10
Start seeds indoors March to May. Transplant out after any threat of frost has passed. Ideal temperature for germination: 20°C (68°F). Seeds should sprout in 7-14 days.
Sow 5mm (¼”) deep. Keep the soil moist until germination — a seedling heat mat will speed germination. Transplant at a spacing of 1m (3′).
Liquorice will grow to chest height, but it can be kept a bit smaller if grown in a large container. It has an extensive root system that primarily requires good drainage. Soil fertility is less important. Liquorice is a legume that will fix its own nitrogen in the soil around its root system. It is quite cold hardy and tough once it is established.
The roots can be harvested after the first or second year of growth. It is probably a better practice to harvest after three years be removing most of the larger roots and then re-planting each stem. Harvest in late summer.
Usual seed life: 3 years.
As a legume, liquorice will fix atmospheric nitrogen in the soil around its roots. Leafy greens like lettuce or spinach will do well planted around the base of liquorice plants. The plants have attractive blue or violet flowers that appear August to September.
More on Companion Planting.