Euphorbia milii, or the crown of thorns plant, blooms abundantly through the spring and summer. Oddly, it's also known to bloom throughout the rest of the year--an unusual trait for a succulent plant. This handsome Madagascar native is so undemanding and drought tolerant that even the greenest novice with the blackest thumb can proudly grow it successfully.
Set your crown of thorns plant in the brightest spot in your home out of direct light. A warm windowsill with southern exposure is an ideal location. The area should be well-ventilated with good air circulation. The ideal temperature range for a happy crown of thorns is between 60 and 85 degrees F throughout the growing season.
Water the crown of thorns deeply and thoroughly. Allow the soil to dry out about 1/2 inch deep before watering again throughout the growing season. Water even less during the winter, only when the top 1 inch of soil is completely dry. This succulent plant stores water in its stems much the same as cacti do, so it requires less watering than many other houseplants. If leaves begin turning yellow and dropping from the plant, you're watering it too much.
Feed the crown of thorns a balanced liquid fertilizer once in mid-May and again in early to mid-October. Follow the packaging instructions carefully.
Move the plant to a cooler location during the winter months, if at all possible. A temperature range between 50 and 55 degrees F is perfect. Don't allow crown of thorns to be exposed to temperatures below 40 F.
Prune your the slow-growing crown of thorns plant back to half its size in the spring of its second or third year. This will encourage branching and fullness. New growth will emerge from just below the cuts.