Q. What do I do with my 4 foot high amaryllis plants?  How much should I cut them back? What is Amaryllis? A.Amaryllis is a perennial flowering plant that comes from an underground bulb, much like a tulip. At 4 feet tall,yours is a large one. The size may vary with a variety and light exposure. If they are not getting enough light the leaves will be very succulent. With adequate light believes should be leathery and more durable.              Amaryllis is a fun plant to grow in the desert provided you amend the soil with compost and cover the soil surrounding it with an organic mulch such as wood chips that decompose and continue to improve the soil.Make sure you keep it away from late afternoon sun. You have your amaryllis in good exposure it sounds like with it in the East side with some filtered light during part of the day. Amaryllis does well with half-day sunlight. As you’ve already expressed I’m sure that you amended your soil with compost the time of planting and mulched the bulbs. Sometimes the flowers need staking because they can get a little top-heavy. They will die back at the first frost. At this time feel free to cut them back to the ground. Cover the bulbs with 4 to 6 inches of wood mulch through the coldest part of the winter. When all danger of frost has passed go ahead and uncover them and let them warm up. I would fertilize lightly once a month. You can buy Amaryllis in many of the stores like Home Depot and Lowe’s while they are in bloom. Enjoy them in your home while they are blooming and then transfer them outside and plant them in the ground or in a container. And planting them in the correct soil are both important with this plant. If you plant them in shade you might be disappointed when they don’t bloom the way they are supposed to. They need light but they should receive light during the cooler parts of the day and protected from sunlight when it is very hot. This means the Eastern or northern exposures are best as long as they avoid the late afternoon sun. Planting under trees that provide filtered light, but not dense shade, will also work. Soil improvement is extremely important. When you are planting make sure you add at least 50% compost to a desert soil. Soil amendments decides compost should include all meal or a high phosphorus fertilizer at the time of planting and mixed with the compost/soil mixture. You might need to stake the flower stalk at the time of planting if you fear wind damage. Use a thin bamboo stake and green nursery tape. As with any flowering plants in the garden, fertilize this plant with a good fertilizer for flowering like you might use for roses or gardenias. Fertilize them once a month lightly during their growing season. Amaryllis can also be used as a cut flower inside the home. More information on Amaryllis from the National Arboretum You will have to adapt this information to our climate.