Hardiness

"Which Lily bulbs will do best in my Garden?"
 
This is a tough question because of varying micro climates within similar geographic areas,  but the different types of lily bulbs do tend to behave similarly.  The hardiness zone for an area is just a general guideline, many gardeners push the zone rating and are able to grow "tropical" in places where they would not survive otherwise.

Individual lily cultivars are discussed from time to time tagged as Garden Review.  Feel free to comment and add any information you might have to help other gardeners.


A Brief Overview of the Different Types of Lily Bulbs

Asiatics perform wonderfully in full sun or light shade in all areas, even in very cold climates of USDA Zone 3.  They also do well in most areas of the South, but prefer more winter chilling to reset the blooms. Soil pH is usually not a factor, they grow equally well in both strongly acid and alkaline soil.

Oriental lilies like cooler summer temperatures and so need to be planted in afternoon shade or all day dappled light in hotter climates.  In mild climate summers, where the average temperature doesn't usually exceed 90 degrees during July and August, Oriental lilies do equally well in full sun or light shade. No winter mulch is required if your climate is warmer than Zone 6, and they are very happy all the way up through Zone 9.

OT, Orienpet and Oriental-Trumpet Hybrids (all the same, just different descriptions) are lilies that  have some Lilium henryi and/or Trumpet lilies in the breeding line.  They are more heat resistant than purebred (or regular) Oriental lilies and tolerate alkaline soils better.  They can take full sun in most areas and are not affected by the occasional 105 degree heat blast, but the flowers will last longer on the stem with afternoon shade if it is over 100 degrees most of the summer.

Purebred Trumpet lilies (not bred with Oriental lilies) do not need as much winter chill as other types of lily, can be grown well in Zone 7 to 9b, and are pretty heat resistant for the south.  The stems can be damaged by deep freezing or heavy late frosts in the Midwest after the sprouts have emerged.

Species lilies (Lilium) have varying requirements based on the geographic area where they originate.  Our Knowledge Base of Lilium species found on our main website will give you an idea of their vast differences.



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.

 
General Guidelines for Lily Bulb Hardiness 
& Warm Winter Tolerance
 
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.

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. 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