With its spiky leaves and myriad of color possibilities, flax plants can be a lovely ornamental addition to your garden. Ornamental gardeners typically plant the genus Phormium, which includes the New Zealand Flax and Mountain Flax species. Phormiums are recommended in USDA hardiness zones 7 through 11, so if you live in a mild climate you can plant your plants directly in the ground without much fear of losing them to frost. Growing them in the ground may mean that your plants get big and messy over time; that's when a good pruning job is in order.
Inspect the plant and look for leaves that are brown or wilting. These dead leaves are doing your plant no good and are contributing to its messy appearance. As you inspect the plan, you'll notice that it's made up of individual "blades" or leaves -- plan to get rid of any blades that are brown or unhealthy looking.
Snip off and compost all brown-tipped blades near the base of the plant. It's OK to remove a lot of the leaves of the plant if they are brown. This will encourage the plant to grow new leaves.
Step back, and inspect the shape of the plant. If your plant is already fairly established and large, you may want the plant to maintain a roundish shape. Look for any leaves that are sticking out beyond the general round shape, and prune them from the plant's base.
Remove any leaves or debris that have collected around the base of the plant. This will prevent mildew or excess moisture from collecting around its base, and clean up the appearance of the plant.