Drainage

• Beds must provide adequate drainage so they don't collect water after irrigation or rainfall. Standing water and waterlogged soils cause aster roots to suffer from rot and decline, which kills the plants. A 12-inch deep hole filled with water that drains within 24 hours has the proper amount of drainage for the asters to grow. Adding compost to poorly drained soils may help improve the drainage. Building a raised bed above the native soil also improves drainage in the gardening site.
  
  

Soil Quality

• Asters grow best in rich loam soils. These soils have a high organic matter content that helps the soil remain moist without becoming soggy. The organic matter present in the soil also provides nutrients to the aster plants. Sandy soils drain too quickly so that not enough moisture remains for healthy plant growth and flowering. Clay soils tend to become soggy or compacted, which prevents aeration to the roots and eventually kills the asters. Improving the drainage with compost amendments or a raised bed also improves the soil quality.
  
  

Potted Plants

• Container-grown asters need a potting mixture that provides the same qualities as those required in a garden bed. Soil mixtures combine soil with peat, vermiculite, perlite and other non-soil amendments to provide drainage. Soilless mixtures mainly consist of peat or compost combined with perlite and similar amendments. A soilless mix supplies good drainage, doesn't compact and also provides a sterile medium that helps prevent disease and fungal problems.
  
  

Fertility

• Garden-grown asters only require light fertilization to replenish the nutrients already available in the soil. A 1/2 cup of a balanced slow-release fertilizer applied two weeks after planting supplies all the necessary nutrients for the aster's entire growing season. Nutrients leach out of aster containers quickly so potted plants require monthly applications of a water-soluble fertilizer, applied at the rate recommended on the label.