=Liriodendron tulipifera seed germination issues=
Temperature
The seeds need a period of cold to germinate. This simulates the seeds' natural conditions, lying amid fallen leaves through a cold winter. Germination rate varies with temperature and time, and increases with lower temperatures given over a longer period. When seeds are exposed to 36 degrees Fahrenheit for 140 days, you should get a 90 percent germination rate. A refrigerator will give the right temperatures to pretreat tulip tree seeds. Around 60 to 90 days cold treatment in a refrigerator crisper drawer should give you a reasonable germination rate.
Moisture
Moisture is essential during the pretreatment period. The moist chilling of seeds is called stratification. You can use several water-absorbent materials to keep seeds moist, such as vermiculite or perlite, paper towels or sand. The material should be moist but not soggy. When using vermiculite, perlite or sand, embed the seeds in the middle of the moist medium in an airtight container, such as a plastic refrigerator container. If you use paper towels, place several moist layers of towels under and over the seeds. Check periodically to make sure the materials remain moist enough. The seeds also need moisture after planting. They need to be kept constantly moist for several weeks. You'll get better germination in mineral soils or in soils composed of aged humus, like leaf mold.
Viability and Storage
Pretreated seeds remain viable for a long time if kept in cold storage. Tulip tree is notorious for low germination rates, due to the absence of embryos in the seed. Researchers R. E. Wean and A. T. Guard found about 80 percent of the seeds they investigated had no embryos, so were unable to germinate. Most of the viable seeds came from the middle of the fruit, rather than at the ends, so choose seeds from the middle section. Dry seeds that haven't been pretreated can be frozen and kept for years and then pretreated.