Good seed is one of important elements in longan plantation. For fruit production purpose, good seed is derived from vegetative propagation, which may be obtained by shoot grafting, air layering, bud grafting, or stem cutting. Propagation by seed is done to obtain rootstock or for breeding purpose. Of those vegetative propagation methods, shoot grafting has higher percentage of successful graft than bud graft has. Compared to other fruit crop such as citrus and mango, shoot grafting on longan is more difficult due to uncertainty of cambium activity. Nevertheless, it is shown that the higher the skill the higher the percentage of successful graft. The steps for grafting are as follows:
Rootstock preparation Variety used for rootstock should have strong root and good vigor. However, in Indonesia, due to the seasonal characteristic of longan and low plantation area, it is expensive and difficult to get seeds. Moreover, longan seed is a recalcitrant seed, which means it has short shelf life. It requires specific treatment to prolong the shelf life, e.g. stored in sand or saw dust. Seed germination could be done in the germination bed or polybag. Those in germination bed have to be transplanted at the age of 2-3 months. On the other hand, those on polybag do not need it. Seeds are planted about 1-2 cm deep; later after one week the seeds start to germinate. The germinated seeds are given ZA 2 gr/l and NPK 2 gr/l alternately once every two-week. The seedling then ready to be grafted when the stem diameter reaches 0,8-1,5 cm.
Grafting The steps are:
- Choose good variety of scion which shows high yield and high economy value
- Use budwood taken from Foundation Block or Budwood Propagation Block which has mature leaves (no young or old leaves)
- Rootstock is cut around 10-15 cm above the media on polybag.
- Make a V shape incision on rootstock
- Omit the leaves from the scion. Also cut the scion tip to increase the probability of success.
- Make a V shape incision on the base of scion
- Insert the scion on the rootstock and tie it with plastic rope.
- Put a plastic cover on the scion.
Caring for the graft Successful graft will form shoot in 2-3 weeks after grafting. When the shoot appears, open the cover and do routine maintenance such as fertilizer application and watering. The fertilizer given are ZA 2 gr/l and NPK 2 gr/l alternately once every two-week. The plant is ready to transplanted when it reaches 50 cm in height and has at least 14 leaves (tr:bq).