We've got a couple of these plants but have no idea how to look after them. Watering them regularly (every 2-3 days, or when the soil seems dry) seems to help. The pot rims are about a foot at their widest part. However, we're concerned about the lower leaves drying up. Is this a normal part of this plant's growth process and does it continue this way and produce a 'trunk' of sorts? As a follow-on question, do we need to re-pot these plants?