Propagation
There are several ways to propagate Ginkgo biloba and its cultivars.
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Seed
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Air Layering
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Cuttings
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Budding
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Soft Tissue Grafting
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Hard Tissue Grafting
1. Seed – only buy seed from a reputable source. Option 1, sow in the autumn outdoors (protect from rodents) and it will usually germinate freely in spring. Option 2, buy in the autumn, mix with a 60/40 mix of damp peat and sand. Place into a zip lock freezer bag and write the date on it. Close the bag and put into a warm place at 15-20 degrees centigrade (room temperature is fine) for approx. 4 weeks. Then place the bag into a fridge at 40 degrees centigrade for 8 weeks. During both the warm and cold pre-treatments, it is important that the peat/sand mix does not dry out. At the end of the 12 weeks of pre-treatment the seeds are ready to sow.
2. Air Layering - this is a simple method carried out in the dormant season. Find a suitable stem, wound it below a node by removing a sliver of bark, treat with hormone rooting powder and wrap moist sphagnum moss around it . Wrap carefully with plastic and seal it, then cover in foil to prevent sun scorch. Wait until the autumn, then detach the rooted plant material and pot it up. (Acknowledgement - The images below were found on the internet)
3. Cuttings - take semi-ripe cuttings in early summer from terminal shoots, just as the wood begins to become firm. Cuttings should be 100 -150mm long. Remove the lower leaves and dip the base of the cutting into rooting hormone powder. Insert 50% of the cutting into a well-drained open cutting compost and firm in. Water well and then place on a heated propagator or warm windowsill. Check regularly and re-moisten as necessary. The cuttings should root in about 12 weeks. Leave them in the pot or tray over winter and pot up in Spring into 9 cm/3 inch using a suitable potting compost. Grow on until well established. Plants grown in this way are slower growing when compared to plants that are hard tissue grafted.
4. Budding – it is possible to bud cultivars of Ginkgo biloba onto two/three old root stocks. In trial undertaken by the collection holder Chip Budding has been the most successful. Material which has begun to harden is taken from the cultivar to be budded in July or August. A chip is prepared, inserted into the stem and bound with polythene budding tape. In approximately 8 weeks the tape should be removed carefully. The root stock is headed back during the dormant season and the bud (if taken) grows away in late spring. At that point it will need to be potted on, caned and tied in. Plants of upright cultivars can grow a stem 60 - 90 cm high.
5. Soft Tissue Grafting – it is possible to soft tissue graft cultivars of Ginkgo biloba onto one-year old seedlings, but this is a very difficult process requiring a higher level of skill, special grafting clips and suitable environmental control (keeping high levels of humidity) to be successful. It should be noted that soft tissue grafts are very slow to grow away. Because the method sacrifices growing points of the cultivar to be grafted and is inherently difficult, it is not considered to be a viable method of propagation.
6. Hard Tissue Grafting – this is the usual methods used to propagate Ginkgo cultivars. Two-year-old, pot grown root stocks are grafted using one-year old scion material of the desired cultivar. This is carried out in February and March. The type of graft used is immaterial, however the cambiums must match. After the graft has been completed, it is tied and waxed. The completed grafts are then stood down in a cold glasshouse. Once the grafts start to grow away in the late spring/early summer, they are potted on into a larger container. If an upright growing cultivar, they are caned and tied to form a straight stem.
A video clip of the National Collection Holder grafting Ginkgo biloba
