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Since this is only hardy to Zone 9, the chances are slim that it will survive in your garage. It needs sun, too. Some people try - it costs nothing to experiment. It will need watering, too, since it will not be dormant. Do not trim off leaves.

Culms are the stems. Which you remove depends on what you are going for. It sounds like the instructions wanted to make the surrounding plants more visible, so I would think they would want the outer area trimmed back.

They are not likely to survive winter and may not come back. Generally, they are treated like annuals in cold climates; however, some people have had luck with overwintering these plants indoors. In ground plants can be dug up and transplanted to a pot. Clip the foliage down to about 3 inches from the top of the pot and stick it in a sunny window in a cool room. Keep it moist, (but not wet) because it can die very easily from drying out. It will revert to green coloration and won't look like much for the winter, but when it goes back outside in the spring, it should come back.

Dig and pot it up. Clip the foliage down to about 3 inches from the top of the pot and stick it in a sunny window in a cool room. Keep it moist, (but not wet) because it can die very easily from drying out. It will revert to green coloration and won't look like much for the winter, but when it goes back outside in the spring, it should come back.

Unless you have a cold-hardy variety, it is very difficult to successfully overwinter these plants. However, since yours is in a pot, you can try bringing it in the house. Clip the foliage down to about 3 inches from the top of the pot and stick it in a sunny window in a cool room. Keep it moist, (but not wet) because it can die very easily from drying out. It will revert to green coloration and won't look like much for the winter, but when it goes back outside in the spring, it should come back.