Research Question on Zephyranthes grandiflora

Tony Avent
Sun, 07 Dec 2008 09:03:38 PST

There seems to be two factors at work with rain lilies.  First, each 
species and hybrid has a flowering window, outside of which they will 
not flower under any least not normal circumstances.  
Within the flowering window, there is a factor, moisture, but more 
likely atmospheric pressure, that causes the plants to flower.  If it 
was only rainfall, then plants grown in covered greenhouses wouldn't 
flower at the same time as plants growing outdoors and exposed to the 
rain. I know that Carl at Yucca Do had cataloged the flowering window of 
each rain lily, but it doesn't seem to be posted on their site 
currently.  Good luck.

Tony Avent
Plant Delights Nursery @
Juniper Level Botanic Garden
9241 Sauls Road
Raleigh, North Carolina  27603  USA
Minimum Winter Temps 0-5 F
Maximum Summer Temps 95-105F
USDA Hardiness Zone 7b
phone 919 772-4794
fax  919 772-4752
"I consider every plant hardy until I have killed it least three times" - Avent

patty allen wrote:
> Hi Martin.
> I have always heard that it is the chemicals (nitrogen?) in the lightening and thunderstorms that causes a large burst of blooms to emerge. 
> In my experience just as a gardener, if the rainlilies are allowed to stay dry for a period of days (2-3 weeks), then a very generous amount of watering will induce another flush of blooms. This goes on sporadically throughout the growing season, sometimes into the fall months here in southeast Texas.
> Patty
> Humble, Texas, about 20 miles north of Houston, Texas
> -----Original Message-----
>> From: "J.E. Shields" <>
>> Sent: Dec 6, 2008 3:22 PM
>> To: Pacific Bulb Society <>
>> Subject: Re: [pbs] Research Question on Zephyranthes grandiflora
>> Hi Martin,
>> That sounds like an interesting problem.  There is clearly something 
>> associated with rainfall that triggers bloom in rain lilies.
>> I too grow my rain lilies in pots here in central Indiana.  The pots spend 
>> the summers outdoors in full sun and the winters inside a greenhouse, 
>> usually dry and out of the way under a bench.  Their winter treatment is 
>> very probably suboptimal to say the least.  In summer, I can get  markedly 
>> increased flowering of my potted rain lilies by standing the pots in 
>> saucers and keeping the saucers full of water.  Even so, a natural rainfall 
>> does a better job of triggering flowering.
>> I wish you luck in your study.  I will be eager to hear what conclusions 
>> you can draw when it is finished; I'm sure others in this group will be 
>> equally interested.
>> Best regards,
>> Jim Shields
>> in Westfield, Indiana -- a suburb of Indianapolis.
>> At 12:39 PM 12/6/2008 -0600, you wrote:
>>> My name is Martin Stone and my student, Shelton Slack, and I are working
>>> on a research project growing _Zephyranthes grandiflora_.  We are at
>>> Western Kentucky University in Bowling Green, about an hour north of
>>> Nashville,  TN.  We experience warm summers and cold winters and are
>>> located in USDA hardiness zone 6 which means in an average winter we
>>> will experience at least one low temperature between 0 deg F and
>>> negative 10 deg. F.  We have divided my large, old, potted clump into
>>> smaller pots and are growing them  in a greenhouse with temps no cooler
>>> than 65 deg. F.  We want to observe their flowering and try to answer
>>> the old question about what induces flowering.  They are growing well
>>> after having been potted since September.  We would like to know:
>>> 1.  Is there a period after transplanting during which flowering does
>>> not occur?  How long do we wait?
>>> 2.  Is flowering sensitive to the daylength?
>>> 3.  and the big question:  Does anyone have clues into the nature of the
>>> flowering?  There is not much scientific literature out there and the
>>> two main sources are a little dated and conflict.
>>> On a personal note, I have grown a potfull for the last dozen years from
>>> a single corm.  They are all clones of the original plant, which is a
>>> bonus in this  study.  They stay outside until winter, when I bring them
>>> into the greenhouse.  But in the summer, I water my pot with the hose
>>> every day and I see sporadic flowering.  After a rain, there is a burst
>>> of flowers a day or so afterwards.  I believe the flower buds are
>>> pre-formed and staying dormant until something about  a rain event
>>> triggers them to elongate and open.  Is it temperature fluctuation
>>> associated with a rain event?  Is is cool rain water?  Is it a drop in
>>> barometric pressure (seems unlikely but who knows?).  What do you  think
>>> and what are your observations?
>>> Thanks in Advance and I look forward to your advice and thoughts.
>>> My Best,
>>> Martin
>>> --
>>> Martin Stone, Ph.D.
>>> Assistant Professor,
>>> Leichhardt Professor of Horticulture
>>> Department of Agriculture
>>> Western Kentucky University
>>> 1906 College Heights Blvd. #41066
>>> Bowling Green, KY 42101-1066
>>> Office (270) 745-5963
>>> Fax (270) 745-5972
>> *************************************************
>> Jim Shields             USDA Zone 5             Shields Gardens, Ltd.
>> P.O. Box 92              WWW:
>> Westfield, Indiana 46074, USA
>> Tel. ++1-317-867-3344     or      toll-free 1-866-449-3344 in USA
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