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Lily Bulb Hardiness & Warm Winter Tolerance
(The chart published by the USDA and complete interactive searching – link below – can be found on the website for the US National Arboretum, which is a good place to start when trying to determine in what type of climate you live.)
When researching your location, bear in mind that all map lines are not absolute and each garden has its own unique micro-climate."
Neighborhoods with many trees blocking wind, hills that "drain" away moisture faster, concrete bulkheads, sidewalks and driveways that tend to collect heat, as well as southern exposures will allow you to grow plants that might not be recommended for your area.
Asiatics – Zones 1-9. (Sweet Surrender, Tiger Babies, Lionheart, “Pearl Series”, etc.) No winter mulch is needed and they prefer colder winters to reset bloom.
Scented Asiatics – Zones 3-10. (LA Hybrids such as Red Alert, Nashville, Eyeliner, Party Diamond etc.) grow well in all areas, do not require as much cold to reset the bloom, and would not need an “artificial winter” in the fridge in southern areas. They start to grow immediately in spring after thaw, which is very helpful during short growing seasons, but a hard frost in late spring could damage sprouts.
Purebred Orientals – Zones 6-9, colder with winter mulch. (Casablanca, Star Gazer, Acapulco, Muscadette, Crystal Blanca etc.), but if heavily mulched for winter or with a good snowfall, down to Zone 3 or 4 easily. Oriental lilies dislike hot, dry areas, growing the bulbs in afternoon sun is recommended because the flowers will last longer.
Purebred Trumpets – Zones 7-10, colder with winter mulch. (Copper King Strain, Pink Perfection Strain, Golden Splendor Strain, “Angel Series”, etc.), heavily mulched, down to Zone 3 or 4, but can be subject to late freeze damage in May, cover emerging stems if temperatures below 30 degrees F. are expected.
Oriental-Trumpet Hybrids – Zones 6-9, colder with winter mulch. (OT hybrids like Conca ‘dOr, Cocossa, Tea for Two, Eudoxia, Scheherazade, Sweetheart, etc.), same as Purebred Orientals, down to Zone 3 or 4 if well mulched for winter, and seem to be more resistant to late frost damage, plus because of the “trumpet” genes, they do not require as much winter chill as Oriental lilies, thus are very suitable for southern areas and will take higher heat in summer.
Longiflorum-Oriental Hybrids – Zones 7-10, colder with winter mulch. (LO hybrids like Gizmo, Triumphator, etc.), about the same as Purebred Trumpets and are suitable for southern areas that have higher heat in summer. For colder areas and heavily mulched over winder, down to Zone 3 or 4 , but could be subject to late freeze damage in May, cover emerging stems if temperatures below 30 degrees F. are expected.
Find your USDA Hardiness Zone The following are examples of USDA Zones in the USA and Canada, if your location is not listed, look at the average low winter temperature listed (Fahrenheit, not Celsius). The general guidelines are based on average low temperatures. The general guidelines are based on average low temperatures are found below. To open a new browser window access the interactive map click USDA Zone Chart
Zone 1--- ( Below -50 F) --- Fairbanks, Alaska; Resolute, NW Territories (Canada)
Zone 2a --- (-50 to -45 F) --- Prudhoe Bay, Alaska; Flin Flon, Manitoba (Canada)
Zone 2b --- (-45 to -40 F) --- Unalakleet, Alaska; Pinecreek, Minnesota
Zone 3a --- (-40 to -35 F) --- International Falls, Minnesota; St. Michael, Alaska
Zone 3b --- (-35 to -30 F) --- Tomahawk, Wisconsin; Sidney, Montana
Zone 4a --- (-30 to -25 F) --- Minneapolis/St.Paul, Minnesota; Lewistown, Montana
Zone 4b --- (-25 to -20 F) --- Northwood, Iowa; Nebraska
Zone 5a --- (-20 to -15 F) --- Des Moines, Iowa; Illinois
Zone 5b --- (-15 to -10 F) --- Columbia, Missouri; Mansfield, Pennsylvania
Zone 6a --- (-10 to -5 F) --- St. Louis, Missouri; Lebanon, Pennsylvania
Zone 6b --- (-5 to 0 F) --- McMinnville, Tennessee; Branson, Missouri
Zone 7a --- (0 to 5 F) --- Oklahoma City, Oklahoma; South Boston, Virginia
Zone 7b --- (5 to 10 F) --- Little Rock, Arkansas; Griffin, Georgia
Zone 8a --- (10 to 15 F) --- Tifton, Georgia; Dallas, Texas
Zone 8b --- (15 to 20 F) --- Austin, Texas; Gainesville, Florida
Zone 9a --- (20 to 25 F) --- Houston, Texas; St. Augustine, Florida
Zone 9b --- (25 to 30 F) --- Brownsville, Texas; Fort Pierce, Florida
Zone 10a --- (30 to 35 F) --- Naples, Florida; Victorville, California
Zone 10b --- (35 to 40 F) --- Miami, Florida; Coral Gables, Florida
Zone 11 --- (above 40 F) --- Honolulu, Hawaii; Mazatlan, Mexico
Wild Lily bulbs making up the genus Lilium belong to the family Liliaceae comprising of approximately 200 genera made up of approximately 2,000 lily species. There are in the neighborhood of 110 to 120 Lilium species depending on whose classification you reference. For the full article, click Knowledge Base