Calla lilies (Zantedeschia) are popular ornamental plants prized for their elegant, trumpet-shaped flowers and lush foliage. These striking plants grow from thickened underground stems known as rhizomes, which are often mistakenly called bulbs. Successful growth and abundant flowering depend on the correct initial planting technique, with proper depth being a primary factor. Correct placement allows for efficient root development, helping the plant draw up necessary water and nutrients from the surrounding soil. The planting depth directly impacts the rhizome’s ability to establish itself.
Determining the Exact Planting Depth
The recommended planting depth for calla lily rhizomes generally falls between two and four inches beneath the soil surface. This range balances the need for the rhizome to be insulated from temperature fluctuations and the requirement for shoots to easily emerge. Deeper planting, closer to four inches, is beneficial in sandy or lighter soils, providing better moisture retention and stability. Conversely, planting closer to two inches is preferable in heavier clay soils, allowing new growth to push through the denser material more easily.
Orientation is as important as depth; the rhizome must be placed with its “eyes,” or growth points, facing directly upward. These knobby points are where the new shoots emerge, and incorrect placement forces the plant to expend unnecessary energy curving its growth path. After confirming the correct depth and orientation, cover the rhizome with soil and gently firm it into place. When planting multiple rhizomes, space them 12 to 18 inches apart in garden beds for air circulation, or four to six inches apart in containers for a fuller display.
Preparing the Planting Site
Before placing the rhizomes, the planting site must be prepared for root establishment and growth. Calla lilies thrive in full sun or partial shade, with afternoon shade being helpful in climates that experience intense heat. Adequate sunlight is necessary for robust flowering, but protection from the harshest midday sun prevents the foliage from scorching.
Excellent drainage is required because calla lilies need consistently moist conditions but are highly susceptible to rot in waterlogged environments. If the existing soil is heavy clay, it must be amended with organic matter, such as compost or aged manure, to improve porosity and aeration. Ideal soil composition is rich and loose, allowing for both good water retention and quick drainage. Calla lilies prefer a soil pH that is neutral to slightly acidic, typically 6.0 to 6.5, which helps optimize nutrient availability.
Initial Care for Establishment
The first steps taken immediately after planting are instrumental in successful establishment. The newly planted area should be soaked thoroughly to ensure the soil settles around the rhizome and eliminates air pockets. Following this initial deep watering, water sparingly until new leaf growth becomes visible above the soil surface. Watering too frequently before the root system develops can quickly lead to the rhizome rotting.
Once the shoots appear, adopt a regular watering schedule to keep the soil evenly moist, but never saturated. Applying a balanced, slow-release granular fertilizer at planting provides sustained nourishment during the initial growth phase. Select a formula that is not high in nitrogen, as excessive nitrogen promotes foliage development at the expense of flower production.
Applying a layer of organic mulch, such as shredded bark or straw, around the planting area helps regulate soil temperature and conserve moisture. The mulch should be kept a small distance away from the emerging growth point to prevent moisture from accumulating directly against the new stem.