Dalbergia sissoo shows a great degree of variation, both within and between populations. In natural stands it typically exhibits a crooked and forked stem and a high occurrence of ramicorn branching. These traits, which are undesirable for timber production, are thought to be highly heritable: Selection against them should improve productivity considerably.
Unless the results of locally conducted provenance trials indicate otherwise, seed should be collected from local stands to ensure that trees will be well adapted to local conditions. To maintain genetic variation, seed should be collected from at least 25 superior trees exhibiting the desired traits.
Limited provenance testing has been undertaken in most of the countries where D. sissoo occurs naturally or has been widely established in plantations. These tests may have indicated that an exotic seed source is superior to local seed. Growers should contact local or regional research centers for information on testing results.
Flowering and seed characteristics
Dalbergia sissoo normally flowers between February and April. Following the appearance of buds, the flowers take from 13 to 15 days to come into full bloom and a further 20 to 25 days to develop pods. Although the trees usually flower abundantly, the seed harvest can be greatly diminished by severe storms during the flowering period.
There are at present conflicting reports regarding the pollination of D. sissoo. The species appears to be insect pollinated, and trees can apparently both self- and outcross to varying degrees, depending on local conditions. Bees are commonly thought to be important pollinators, although a recent study in Nepal noted that trees were effectively pollinated at one site in the complete absence of bees.
Most pods are fully developed by late May, and seed is generally harvested between November and January. Mature pods can contain up to four seeds, though commonly they contain only one or two. They are light brown, flat and thin-5 to 9 cm long and 8 to 12 mm wide. Seeds are kidney shaped, glossy and 6 mm long. There are about 50,000 to 60,000 seeds per kilogram or 18,000 seeds in one kg of dry pods. Mature seed that has been properly dried, cleaned and stored should germinate at a rate of 80 to 90%.
Seed should be collected as soon as possible after maturity, when the pods have turned brown and are dry. In most countries this is between November and January. Although, D. sissoo begins to produce seed from a very early age, seed should not be harvested from trees less than five years old, when final stem form can be observed with reasonable assurance. Neither should seed be collected from over-mature, declining trees, as such trees often produce seed that germinates poorly or grows into poorquality seedlings.
Seven- to ten-year-old plantation-grown trees usually produce 0.5 to 1.0 kg of pods per tree. Plantation-grown trees of 15 to 20 years with average to good form produce about 2.0 kg of pods per tree. Old trees grown at wide spacing can produce up to 7 kg of pods per tree. The timing of seed maturity varies somewhat from year to year and location to location. For this reason, it is important to assess seed maturity before collection.
Seed processing and drying
Dalbergia sissoo seed is difficult to separate from the pod; this is usually only done to produce seed in research quantities. Normally, seed is stored with the pod attached. Before storage, the pods should either be broken up into sections containing one seed each, discarding the empty pod sections and other foreign material, or they should be rubbed between the hands and then winnowed, discarding the empty pod and other foreign material.
Under favorable conditions seed can be harvested that is already dry enough for storage (moisture content 7 to 9%). Generally however, drying is necessary. The pods should be spread out on a clean surface in the shade and allowed to air-dry until they can be broken crisply between the fingers.
Because abundant seed is generally available every year, long-term seed storage is generally not required for tree planting at the village or communty level. Clean, dry seed should be stored in sacks just like rice, maize, beans or pulses. If the stored seed is kept safe from mice or rats and the storage area has adequate air circulation, the seed will easily maintain its viability for up to one year. In sealed containers at stable ambient temperatures, well cleaned and dried seed retains 60 to 70% viability for up to five years.
A seed orchard is a plantation established from selected seedlings or cuttings that are derived from mother trees with desirable traits. The seed orchard is planted in an isolated site to reduce the risk of pollination from outside sources and managed to produce frequent