Monday, December 2, 2013

Ginkgo from Seed

A few years back in October, on a trip to Japan, I picked up half a dozen Ginkgo biloba seeds that had fallen around a huge old tree at Washinomiya Shrine in Saitama. I cleaned off the pulpy, foul-smelling outer seed coats, and stuck the seeds in a plastic bag to keep them moist for the trip home. Ginkgo seeds don't remain viable if they dry out too far, and also don't germinate much at all unless they receive slightly unusual treatment.

Once back in Connecticut, I planted the Ginkgo seeds in a loose, airy soil mix, not more than a centimeter deep. The embryos inside develop for some time after they are detached from their mother tree, so Ginkgo seed pots should be kept warm and moist for a month after sowing. After their warm period, the pot went to the refrigerator for two months of stratification, a period of cold (but not quite freezing) and damp conditions that many temperate-climate plants need for proper germination. In early spring, I moved the pot out to the greenhouse, and after a fairly long wait, eventually got three healthy seedlings.

Ginkgo seedlings quickly develop a robust tap root, even while the above ground shoot is small and spindly, so I separated out the young plants early on and put them in relatively large, deep pots. All three seedlings survived and are now well-branched and waist-high. There are interesting variations in Ginkgo leaf shape and size, and the Washinomiya trees have leaves that are more deeply bilobed than the "American" Ginkgoes growing next to them in the greenhouse, derived from seeds from UConn campus trees. The three seedlings from Japan are also noticeably different from each other, with the one in the foreground in the autumn photo below having very large but classically-shaped Ginkgo biloba leaves, while a shorter plant visible in the background has small, deeply lobed and tattered leaves.

For now, the new Ginkgoes are staying in the cool greenhouse in pots, for display and use in class demonstrations. Possibly they would like to be planted out in the ground at some point, if a good spot can be found for them.