There is some discrepancy in the cold hardiness of Agapanthus. While most gardeners agree the plants cannot withstand sustained frozen temperatures, northern gardeners are often surprised to find their Lily of the Nile has come back in spring in spite of a round of freezing temperatures. Is this an anomaly only rarely to occur, or is Agapanthus winter hardy? A U.K. gardening magazine undertook a trial in southern and northern climates to determine the cold hardiness of Agapanthus and the results were surprising.
Is Agapanthus Winter Hardy?
There are two main types of Agapanthuses: deciduous and evergreen. Deciduous species appear to be hardier than evergreen, but both can survive surprisingly well in cooler climates in spite of their origin as South African natives. Agapanthus lily cold tolerance is listed as being hardy in USDA zone 8 but some can withstand cooler regions with a little preparation and protection.
Agapanthus is moderately frost tolerant. By moderate, I mean they can withstand light, short frosts that do not sustainably freeze the ground hard. The top of the plant will die back in a light frost, but the thick, fleshy roots will retain vitality and re-sprout in spring.
There are some hybrids, notably the Headbourne hybrids, which are hardy to USDA zone 6. That being said, they will need special care to withstand the winter, or the roots may die in the cold. The rest of the species are only hardy to USDA 8 to 11, and even those grown in the lower category will need some assistance to re-sprout.
Does Agapanthus need winter protection? In the lower zones, it may be necessary to offer fortification to shield the tender roots.
Agapanthus Care Over Winter in Zones 8
Zone 8 is the coolest region recommended for the majority of Agapanthus species. Once the greenery dies back, cut the plant to a couple of inches (5 cm.) from the ground. Surround the root zone and even crown of the plant with at least 3 inches (8 cm.) of mulch. The key here is to remember to remove the mulch in early spring, so the new growth doesn’t have to struggle.
Some gardeners actually plant their Lily of the Nile in containers and move the pots to a sheltered location where freezing won’t be a problem, such as a garage. Agapanthus lily cold tolerance in the Headbourne hybrids may be much higher, but you should still put a blanket of mulch over the root zone to protect them from extreme cold.
Choosing Agapanthus varieties with higher cold tolerance will make it easier for those in cooler climes to enjoy these plants. According to the U.K. magazine that performed the cold hardiness trial, four varieties of Agapanthus came through with flying colors.
- Northern Star is a cultivar that is deciduous and has classic deep blue flowers.
- Midnight Cascade is also deciduous and deeply purple.
- Peter Pan is a compact evergreen species.
- The previously mentioned Headbourne hybrids are deciduous and performed the best in the northernmost regions of the test. Blue Yonder and Cold Hardy White are both deciduous but purportedly hardy to USDA zone 5.
Of course, you might be taking a chance if the plant is in soil that doesn’t drain well or a funny little microclimate in your garden that gets even colder. It is always wise to simply apply some organic mulch and add that extra layer of protection so you can enjoy these statuesque beauties year after year.