Planting Season

• Canna lilies are sensitive tropical plants and suffer in frosts. Plant them outside in mid-spring, after all threat of frost passes. If you're planting in a moderately shady area, where soil remains cooler, wait until the soil warms to 65 to 70 degrees Fahrenheit. Canna lilies grow and bloom in their first year and every year thereafter, with mid-summer, late summer and early fall flower production.
  
  

Considerations

• Black walnut trees produce a toxin called juglone, which causes wilting, yellowing and eventual death to many plants in the vicinity. According to the Purdue University Plant and Pest Diagnostic Library, though, not all plants fall prey to this problem. Canna lilies are not particularly sensitive to this toxin and can grow around black walnut trees with certain considerations.
  
  

Site, Sun and Space

• Canna lilies do best in full sunshine but do grow in sites with partial and filtered sun. Plant them under a walnut tree but away from the trunk, to avoid deep shade. The Purdue Plant and Pest Diagnostic Laboratory suggests moving any plantings even farther from the base of the tree and out from under the canopy to avoid walnut drop, stems and leaves. This placement helps the plants avoid black walnut toxins. Give them sites that get filtered, dappled or partial sun, with complete drainage. Space the canna lilies at 1 1/2 to 3 feet to give them space for growth.
  
  

Soil and Fertilizer

• As bulb plants, cannas require deep, rich and loose soil for root expansion and growth. This is especially true when they don't get full, bright sunshine all day. Amend the soil under any black walnut tree before planting to decrease the toxins from the black walnut and to give plants a better chance of survival. Fresh soil restricts the chances of juglone exposure. Mix 3 to 4 inches of organic compost into the top 8 to 10 inches of soil through the canna bed to warm the soil and build a moist, loose foundation. The Alabama Cooperative Extension System notes that cannas enjoy fertilizer and recommends feeding them with 5-10-5 fertilizer in spring or at planting, and monthly thereafter.