I have an artichoke agave on my desk in New York. I have had it for just over a year, during which time it has really thrived, sending out chutes & offspring, and the center cone "peels off" a new leaf every few months. Actually, that just happened last week, but now, this week, all of the bottom leaves are yellowing, and the ones at the very bottom have actually turned black. I'm wondering what's wrong with it. I water it once every 3-4 weeks. The last time was 5/8 or so. I've attached a photo.
Yellowing, or black leaves is one of the signs of over-watering. Even though you don't water that much, the soil could still be moist down by the roots. The soil may need to be more airy, lighter, faster draining. Use a good cactus soil and plenty of Perlite, or lava rock to help it drain better.. Make sure the pot has drain holes and is a size that's only an inch larger then the root-ball. Clay pots which are porous, will dry faster (which is good for cactus and succulents) then ceramic, or plastic.
