Planting the tuber
Container size -- You may start your tuber in a pot that is about 1 quart (1 liter) to 1 gallon (4 liters) in size. The pot should have drainage holes.
Soil -- The Hercules Calla can adapt to many types of soils, but it prefers a well-draining soil that is high in organic matter. An example of this is a mix of 2 parts potting soil to 1 part perlite or pumice (or coarse horticultural sand).
Planting the tuber -- Fill your container to within 3 inches (7 cm) of the top, place the tuber sideways on it, and cover with 2 inches (5 cm) of soil. Don't compress the soil. Water just enough so that the soil is moist throughout, but not soggy.
Keep the pot at room temperature until it sprouts. Your tuber may take from 2 to 8 weeks to sprout, but allow up to 3 months, especially at cooler temperatures. Keep the soil lightly moist the entire time (don't over-water it). Once it sprouts, you may start increasing the waterings.
Light -- Give it bright light after it sprouts, but not strong sun. This Calla doesn't need as much direct sun as most Callas. It grows fine in bright shade with some filtered sunlight. If exposed to more sun, it will require more watering and feeding. Protect it from hot afternoon sun.
Watering -- This Calla likes consistently moist soil when it is not dormant. During warmer or sunnier weather, make sure the soil doesn't dry out. It reportedly can be grown in boggy conditions, but i have not tried this.
Climate -- The Hercules Calla prefers mild temperatures. In warmer climates, shade it during the warmest part of the day, and don't plant it where heat can accumulate, like near a sunny wall. The plant can go dormant during summer, and if it does, the tuber (or entire pot) may be brought indoors during this time.
The tubers are winter hardy to Zone 8 (20°F/-6°C) if planted deep. But since the plant prefers to grow throughout winter, it's best to grow it in a pot and bring it indoors before frost strikes.
Repotting -- When the roots reach the bottom of the container, it should be transplanted to a larger container, or into the ground in suitable areas. Each time you repot, bury it 1-2 inches (3-5 cm) deeper. After several years, it will need a large pot, such as 10 gallons (40 liters) or more. A mature plant with a 6 inch (15 cm) tuber may need 30-40 gallons (100-150 liters).
Winter strategies -- If you bring it indoors over the winter, try to keep some or most of the leaves intact, if possible. Removing the leaves may delay flowering.
Fertilizing -- While your plant is actively growing, feed every 2-3 months with a slow-release (pelleted or organic) fertilizer.
It's normal for an older leaf to occasionally turn yellow, but if it seems excessive, it could be from not enough nitrogen fertilizer, or overly dry soil down in the root zone.
Bugs to watch for -- Spider mites, Aphids, snails/slugs.
If any questions or problems come up, feel free to email me.
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