I have had a night-blooming Cereus for several years and it has yet to bloom. A friend has one and it blooms no problem. This plant is indoors and keeps growing, but no blooms.
What can I do to make it bloom?
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I used to have one of these, and they sometimes are tricky to coax into bloom. My plant I got at about three feet tall, and it took off from there, blooming at 5 1/2 feet and on to eight feet tall. I didn't have space, eventually, and gave it away.
I found that they tend to bloom most in July. Here's what I did, for conditions:
Light. In the summer, they stayed out-of-doors. I had it in mostly shade, with some dappled sun in the mornings. In the winter, it got 14 hours of fluorescent grow lights per day.
Water. In summer, I would water every other day during dry periods, and skip rainy periods. In winter, I watered lightly, once a week (I didn't want much growth at that time, as it wasn't as good as summer growth).
Temperature. It took the variable outside temperatures quite well, and I brought it inside when the temps started dropping below fifty degrees Fahrenheit. Inside, I kept it an even sixty degrees. That was to give it a break from heavy growth.
Soil. I actually didn't use soil, but a mix of mostly coir, with some perlite. They require good drainage, but also enjoy water retention. Make sure the pH of the mix is around neutral (7.0) before planting.
Pot. This changed a lot (with the growth of the plant). They don't need a huge pot, even when quite large. I used plastic pots inside more attractive square wooden (to attatch support) decorative planter. I had a small reservoir inside the planter, and 6 locking castors underneath, to roll with.
Support. The plant will sprawl over everything if care isn't taken in providing a strong support. I used a four-legged tiered steel piping structure (painted to look like bamboo), which I built to fit onto my wooden planter. Each tier was removable, and reasonably attractive. The tiers themselves were crafted from bamboo.
Humidity. Outside, placement is necesary for humidity. On my property, this isn't a problem, but if you live in a dry area, you'll have to spray the plants with mist daily. Indoors, my old plant room stayed about 55% rh on it's own which was suitable.
Fertilizer. I was kind of cheap here - I used a basic 10-10-10 soluble fertilizer as a root drench once every two weeks while the plant was outside. Now and then I gave a micro-nutrient infusion, or sometimes tea from my vermicomposter, to keep things balanced.
As a side note, the plant died in less than a year after it left my hands. I'm not sure whether it was just spoiled, or the new owners just didn't have a green thumb...