Bamboo seeds are short-lived, and generally most of the species will lose viability within one to two months. The size, shape and number of seeds per kilogram will vary from species to species. Once a flowering bamboo clump is identified, it is important to determine the right age of seed maturity through frequent visits, and maturity can be assessed by cutting test of representative seed samples using a sharp knife.
The seeds can be collected after spreading a polythene sheet over the ground under clumps, and collected seeds can be processed by winnowing, sieving, and handpicking impurities. All non-seed materials like branchlets, leaves, and other easily removable debris must be removed, and the collection bags must be properly labeled with the date and species details.
The cleaned seeds must be sown immediately after collection without losing their viability. Before sowing, the cleaned seeds can be soaked in normal water overnight, and the floating seeds can be removed. The seeds can be sown either in seedbeds or in trays.
Based on the seed production behavior bamboos can be classified as
- Abundant or profuse seed forming: Species have abundant seed formation after gregarious flowering and examples are Bambusa bambos, Dendrocalamus hamiltonii, D. strictus, Melocanna baccifera, Ochlandra travancorica, etc.,
- Sparse or diffuse seed forming group Species with the production of a limited quantity of seeds, examples are Dendrocalamus giganteus, Bambusa nutans, and B. tulda, etc.,
- Sterile group: Species with sparse flowering as found in B. vulgaris, B. balcooa or species with profuse flowering in Pseudoxytenanthera monadelpha and Dendrocalamus stocksii. Seed formation is not reported in any of these species.
The number of seeds per kilogram of different species is given below,
| # | Species | No. of seeds/kg |
|---|---|---|
| 1 | Melocanna baccifera | 10 - 20 |
| 2 | Ochlandra travancorica | 45-50 |
| 3 | Thyrsostachys oliveri | 15000 - 18000 |
| 4 | B. tulda | 20000 – 25000 |
| 5 | D.hamiltonii | 26000 |
| 6 | D.strictus | 35000-50000 |
| 7 | D.giganteus | 40000 |
| 8 | B. nutans | 65000 |
| 9 | Bambusa bambos | 65000 -75000 |
| 10 | Dendrocalamus asper | 75000 - 80000 |
| 11 | B. polymorpha | 125000 |
| 12 | D. brandisii | 145000-20000 |
| 13 | D.sikkimensis | 180000-185000 |
Seed Germination
In most bamboo species, seed germination is epigeal, while hypogeal germination is also observed in the genus like Ochlandra. There is no dormancy for bamboo seeds, and a high percentage of seed germination is noted if seeds were sown immediately after collection. However, a rapid decrease in seed viability and germination percentage is also noted with seed ageing. Seed viability shall be evaluated as rapid viability tests (Tetrazolium test & Hydrogen peroxide test) and germination test. The seed germination test is carried out under laboratory conditions in a vermiculite medium in which a hundred seeds in four replications can be used for the experiment. The germination medium is maintained in moisturized condition till the test is over, and seed germination commenced from the 3rd day after sowing and completed in 18-20 days. Germination percentage can be recorded by using the formula given below:
- Germination (%) = (Total number of seeds germinated / Total number of seeds sown) x 100
Pre-germination treatment
In order to prevent fungal infestation, seed pre-germination treatment with biological extracts and fungicides will minimize the fungal incidence, and the rate of germination will be enhanced properly. Treatment with biological extract (leaf extract of Neem) and fungicide (Indofil/Thiram) will be able to control fungal infestation the treatment is as follows: Initially, mix the seeds with the requisite amount of fungicide and shake mechanically for 20 minutes for proper coating. Similarly, air-dry the fresh leaves of Azadirachta indica at room temperature and prepare extract by crushing the leaves in a mortar and pestle using distilled water in the ratio of 1:1 (50 g leaves crushed in 50 ml water). Soak seeds in the leaf extract for one hour and air-dry the treated seeds on filter paper.
Sowing of Seeds
Seeds can be directly sown in nursery beds or dibbling of seeds in polybags can be done for raising seedlings. If it is in seedbeds, sufficient drainage should be ensured, waterlogging should be avoided and partial sunlight by providing a shade net is also preferred. The size of the seedbeds can be 10 x 1.5 m. The seedbed should have proper protection from rats and rodents by using nets. The medium can be a mixture of soil, sand, and compost or fully decomposed Farm Yard Manure (FYM) (3:1:1), and this can be altered depending on the type of soil. A shallow trench or holes with 5mm depth can be created in the seedbed using twigs or fingers, and seeds can be sown in these shallow trenches and refilled with dispersed sand. Sufficient moisture should be created by regular watering using a sprinkler. Depending on the species, seed germination will start after five to seven days and will continue for 25-30 days.
If seedlings attain stages of 4 to 6 leaves, plants can be transplanted to polybags (6 x 8 inches or bigger with small holes in the sides) filled with poly bags with a mixture of soil, sand, and organic manure in 1:1:1. In the case of sandy loam soil, the potting medium can be soil, and manure mixture (3:1). The polybagged seedlings can be kept in partial shade (50 to 75 percent) or under trees or shade nets for one to two months before transferring to direct sunlight. Daily watering should be done and 3-4-month-old seedlings are most suitable for planting in the field.
If germination is in trays, vermiculite can be used, and generally using this method will allow for maximum germination and easy to poly pot the seedlings without any damage.
Note: The species like Bambusa balcooa, B. vulgaris, Dendrocalamus stocksii do not produce viable seeds and they can be propagated either through culm cuttings or splitting rhizomes. The seed-producing species have long flowering intervals varying from 30 to 70 years (Bambusa bambos, B. polymorpha, Dendrocalamus strictus, D. brandisii, D.giganteus, etc.,). Some of these species flower gregariously and then the entire clump will die whereas the species like Ochlandra setigera, O. wightii, O. setigera, flower sporadically with or without parent plant deaths.