I was initially attracted to this lily by it's rarity, reputedly hard-to-grow nature, and potential as an exceedingly attractive conservation subject. I made some enquiries to governmental institutions, and with their help was able to obtain a quantity of wild collected seed from an undisclosed location in Florida. This seed was used to set up a germination and plant cultivation experiment. Information from such experiments can be used to propagate plants for re-introduction into the wild on conservation sites and to produce nursery propagated plants to fulfill public demand.
Most of what is reported about seed germination is anecdotal and this species is considered difficult to grow in garden settings, although Mary Henry was able to grow it from seed to flower in 5 years in her Pennsylvania garden. The goals of this study are to elucidate an efficient germination protocol, and to determine optimum conditions for sustained growth in cultivation.
A simple seed germination experiment was installed. Seeds were sown on slightly moist perlite
and subjected to one of three temperature treatments: 70F in light for 5 days followed by incubation in darkness at 70F for 5 months, 70F in light for 5 days followed by cold stratification, and an "outdoor treatment" (seeds sown in 50/50 silica sand/peat medium and placed in a moderately heated playhouse). Excellent information on lily species germination can be found on the Pacific Bulb Society website:
Lilium iridollae seeds sown on perlite in plastic bags. The moisture level is critical and seeds/seedlings should be kept barely damp. Seeds at the sides of the bag appeared to benefit from extra moisture and produced the best seedlings.
A L. iridollae seedling 2.5 months after being sown on perlite and incubated for 5 days in light and the rest of the time in darkness at 70F. As suggested in the literature, the germination pattern of this species in delayed hypogeal, and the highest rate of germination and most vigorous seedlings were produced from seeds started at 70F. Seeds sown on perlite and cold stratified for three months germinated only after transfer to 70F conditions, but seedlings germinated irregularly and were not as vigorous as seed incubated on perlite at 70F.
From left to right, L. michiganense, L. superbum, L. canadense var. coccineum, and L. iridollae (note the long roots of L. iridollae) after three months of growth in the greenhouse.
To compare development among species, I also sowed seeds of L. canadense var. coccineum, L. canadense var. flavum, L. michiganense, and two accessions of L. superbum. L. iridollae germinated and developed more slowly than all other species. Although four months at 70F is the general recommendation before switching the plants to cold stratification, I kept the L. iridollae at 70F for an extra months (5 total months) and the seedlings continued to develop. After this they were transferred to 40F for three months.
On July 1, the seedlings were transferred to a 50:50 silica sand/sphagnum peat medium and irrigated with reverse osmosis water. Since it was quite hot at this time, the seedlings emerged immediately, grew throughout the summer and autumn, and are showing the first signs of dormancy as of this writing on November 29, 2011. We have about 200 seedlings at this stage.
Seedlings are now quite robust and are being separated from community pots to maximize growth next season. Progress of this work will be updated on this blog.
Lilium iridollae seedlings. Photo taken on November 28, 2011. Roots are 15-20 cm long!
Now, if I could only convince some kind soul to send me some seeds/plants of Lilium grayi and Lilium catesbaei.......