Test the soil

• 1). Test the soil where your hostas are planted if they don't look their best. Don't fertilize sluggish plants before you know what is going on at the heart of the hosta - its roots. Knowing what is or is not in your soil is paramount to diagnosing a treatment plan. Soil-testing kits can be purchased at home-improvement retailers, or you can send a sample of your soil to your local agriculture extension office.
  
  
• 2). Know when to fertilize. When you apply your fertilizer is almost as important as knowing what type of stimulant to use. Fertilize hostas in the fall if you are using a treatment that is high in nitrogen. The soil test will help determine whether a liquid or a granular fertilizer should be used on your hostas. If you apply fertilizer in the fall, water the hostas adequately to help the fertilizer reach the roots. Fertilizing hostas in the spring is best with a fertilizer that is lower in nitrogen. This will ensure that they get the right amount of boost before they bloom.
  
  
• 3). Use composts to boost your hostas' health. Horse manure is one of the best options because it is high in nitrogen and is absorbed into the roots more quickly. Decomposing leaves also make a good compost for poorly performing hostas. Cover the soil around hostas with compost in the winter to help ensure they will be ready to look their best come spring.
  
  
• 4). Look insects that can stunt a hosta's growth. Slugs, grubs and weevils can damage hostas, especially in the spring. Insecticides can be found at any home improvement retailer that will help keep your hostas free from harmful pests. Move winter mulch away from the base of your plant in warmer months to discourage slugs.