Make sure you find a spot outside that drains well. If the soil still has puddles in it 5-6 hours after a downpour, find somewhere that doesn’t. Everything else about planting amaryllis outdoors is the same as planting indoors.
Depending on the bulb size, pots need to be from 10 to 16 inches (25 to 41 cm) in diameter to have 2 bulbs in each pot. If you are having trouble weighing down the pot, put a little bit of gravel at the bottom.
Once the flowers have bloomed, which will occur in 7-10 weeks, store the plant in a slightly cooler location to help prolong the life of the flowers[4] X Research source
You should plant the bulb so the stringy roots are in the soil. Avoid damaging the roots when you plant your amaryllis. If you are planting your amaryllis outside, be careful to avoid planting in a clay-based soil as this drains more slowly than sand-based soil. If the roots sit in water for too long, they will get waterlogged and may begin to rot. Add compost to your potting soil to make it nutrient-rich.
Packing the soil down also helps to ensure that the plant has a strong foundation once it begins to flower. [6] X Research source
If you planted the bulbs in a pot, make sure you have a dish underneath it to prevent water leaking out onto whatever surface you have below. Be sure to empty the dish after watering rather than letting the plant sit in the water. [7] X Research source
Once the plant has started to flower, water more frequently, such as twice per week. The watering needs of a plant do vary slightly depending on the heat and humidity of where the plant is growing, but these measures should be a good estimate. [9] X Research source
Staking up the plant is a very easy way to make sure that the stem doesn’t fall over and cause harm to your plant. [10] X Research source Stake a plant up by hammering a long, thin piece of wood into the soil with a mallet, to about 12 inches (30 cm) higher than the plant. After this, tie the stem to the stake at 3-4 different points using pieces of string.
Trim the stems once the flowers fade, but let the leaves grow until they start to wilt and turn yellow. Cut them down to 2 to 3 in (5. 1 to 7. 6 cm) above the bulb. Leave the bulb in the ground if you live in an area that doesn’t have frost. Otherwise, store the bulb in a cool, dry place for at least 6 weeks before replanting it in the spring. [11] X Research source
