Defining Perennial Status for Calla Lilies
The question 'are calla lily plants perennials?' doesn't have a single, simple yes or no answer; it depends significantly on your local climate and how you manage the plant. Calla lilies, scientifically known as Zantedeschia, are native to South Africa, a region with a generally warmer climate than many parts of the UK or North America. In their native habitat and in USDA hardiness zones 8-10 (or equivalent mild climates), they are indeed perennial, returning year after year from their rhizomes.
However, in regions with colder winters, such as most of the UK, much of northern Europe, and many parts of the United States (zones 7 and below), calla lilies are typically treated as annuals. This means they are planted in spring, bloom through summer, and then die back with the first frost, with gardeners usually replanting new stock each year. This practice is often more convenient and ensures vibrant blooms without the risk of rhizome rot or insufficient warmth for survival.
- Calla lilies are perennial in warm climates (USDA zones 8-10).
- In colder regions, they are often grown as annuals.
- Overwintering in cooler climates is possible but requires specific care.
- Zantedeschia is the botanical name for calla lilies.
The term 'perennial' refers to a plant that lives for more than two years, typically regrowing from its root system each season, unlike annuals which complete their life cycle in one year or biennials which take two. For calla lilies, their rhizomatous root structure is the key to their perennial nature. If these rhizomes are protected from freezing temperatures and excessive moisture, they can lie dormant through winter and emerge with new growth come spring.
Rhizomes: The Key to Perennial Growth
The underground part of a calla lily is a rhizome, which is a modified stem that stores energy and nutrients. It's from this rhizome that new shoots and roots emerge. For calla lilies to be perennial, this rhizome must survive the dormant period. In mild climates, the soil temperature rarely drops low enough to kill the rhizome, allowing it to naturally regrow. In colder climates, however, the rhizome is vulnerable to frost and waterlogging, which can lead to rot.
This fundamental difference in survival based on climate is why you'll find differing advice and experiences regarding their perennial status. Understanding your local hardiness zone is the first step in determining whether your calla lilies can become reliable garden features or if you need to adopt overwintering strategies.
Cultivating Calla Lilies as Perennials
For gardeners in cooler climates wishing to avoid the annual expense and effort of purchasing new plants, cultivating calla lilies as perennials is achievable with careful planning and execution. The primary challenge is protecting the rhizomes from winter conditions. This typically involves either digging them up and storing them indoors or providing significant protection in situ.
Overwintering in situ (in the ground)
If you are in a marginal zone (like USDA zone 7, or parts of the UK where temperatures occasionally dip below freezing but not consistently for long periods), you might be able to leave calla lilies in the ground. This requires a substantial layer of mulch – think 4-6 inches of straw, shredded bark, or compost – applied after the foliage has died back naturally. This insulating layer helps protect the rhizomes from extreme cold. Ensure the planting location has excellent drainage; waterlogged soil is the enemy of dormant rhizomes, even in milder climates.
Digging Up and Storing Rhizomes
The most reliable method for gardeners in colder zones (USDA zones 3-6, or most of continental Europe and the UK) is to dig up the rhizomes before the first hard frost. Once dug, gently clean off excess soil, taking care not to damage the rhizome. Allow them to air dry for a few days in a frost-free, well-ventilated area. Then, store them in a cool, dry, dark place – an unheated garage, cellar, or even a shed can work, provided temperatures remain above freezing (ideally between 7-10°C). Pack them in peat moss, vermiculite, or dry sand to keep them from drying out completely. Check them periodically throughout winter for any signs of rot or excessive drying.
When replanting stored rhizomes in spring, wait until all danger of frost has passed and the soil has warmed sufficiently. You can start them off indoors in pots a few weeks prior to planting out to give them a head start.
Planting and Care for Returning Blooms
Whether you're in a warm climate where they naturally perennialize or you've successfully overwintered rhizomes, consistent care ensures repeat flowering. Calla lilies prefer well-drained, fertile soil and full sun to partial shade. In hotter climates, afternoon shade can be beneficial. Keep them consistently moist during the growing season, especially when flowering. As their growth cycle involves a dormant period, you may notice them looking less vigorous or even dying back in late summer or autumn, which is normal.
The successful perennialisation of calla lilies hinges on preventing rhizome desiccation and freezing, while ensuring adequate dormancy and spring revival conditions.
As the foliage naturally dies back after flowering, this is the signal that the plant is preparing for dormancy. For natural perennials, this might happen in autumn or winter depending on the climate. For overwintered bulbs, this period follows their spring and summer growth. Avoid cutting back the foliage until it has completely yellowed and withered, as the plant uses its leaves to store energy for the next growing season.
Alternatives and Related Perennial Bulbs
While calla lilies are unique in their specific care requirements for perennialisation in cooler zones, many other popular bulbs readily naturalise and return year after year without intervention. If your primary goal is a reliable display of spring or summer blooms from bulbs, exploring these tried-and-tested perennials can offer peace of mind and less labour.
Reliable Garden Perennials
For guaranteed returning flowers, consider the many bulbs that readily multiply and naturalise in most garden settings. Daffodils (Narcissus) are a prime example; they are famously reliable perennials that spread, and there are countless varieties suited to different conditions. Similarly, tulips, while often treated as annuals for their most spectacular display, can persist for several years if conditions are ideal and they are not disturbed, though their vigour may decline. Planting bluebell bulbs in autumn is a classic way to establish a carpet of spring colour that returns reliably.
Other excellent choices for perennial interest include alliums, which offer striking architectural flower heads and are best planted in autumn when should allium bulbs be planted for optimal spring growth. Hyacinths provide strong fragrance and colour in spring and can be grown successfully indoors or out, with outdoor bulbs often returning. Freesias are tender bulbs that are perennial in mild climates and can be lifted and stored like calla lilies in colder areas; they are also often grown as annuals.
Bulbs Requiring Specific Post-Bloom Care
Some bulbs, much like calla lilies, require a little attention after their main flowering period to ensure they perennialize effectively. For instance, irises, particularly bulbous varieties, benefit from being divided every few years to maintain vigour, and you might wonder what to do with irises after they bloom; deadheading and allowing the foliage to die back naturally helps the plant store energy. Similarly, understanding when to cut iris leaves back is important to prevent disease and support the plant’s perennial health.
Daffodils are known to multiply, forming larger clumps over time, a trait often sought after in perennial planting. While they do this naturally, ensuring they have good drainage and are not overcrowded aids their propagation. The question 'do daffodils multiply' is a common one for gardeners seeking natural expansion of their displays. Growing hyacinths inside requires specific light and temperature cycles, but outdoors, they can perform as reliable perennials in many gardens.
When considering the broader question of plant toxicity, it's worth noting that while beautiful, some popular garden plants can be harmful to pets. For example, some sources indicate that lilies, generally, can be toxic to cats, and while the direct toxicity of Zantedeschia to pets is less commonly cited as severe as true lilies (Lilium species), caution is always advised around any plant if you have curious animals.
Frequently Asked Questions about Calla Lilies
Here are some common questions gardeners ask when considering the perennial nature and care of calla lilies.