Description
of seeds belonging to the Angiospermae
Elaeagnus angustifolia L. oleaster (Eleagnaceae) The dormancy of the seeds depends on mechanical factors which block the development of the embryo for a certain period of time; it is overcome after warm stratification for 1-4 weeks (considered by some authors to be unnecessary) and cold stratification for 8-12. Before starting the thermal treatment, it may be useful to soak the seeds in sulphuric acid for 30-60 minutes, and then wash them. The use of peat as a substrate for stratification increases the effects of the treatment. Since the germination of pretreated seed is encouraged by the daily temperature range, sowing should be carried out at the end of the winter or in early spring. Alternatively, autumn sowing.
Eucalyptus spp. Gum tree, eucalyptus (Myrtaceae) Eucalyptus seeds are, in truth, made up of fertile seeds, sterile seeds, and various types of impurities in differing proportions. Germinability of the very many existing species, generally expressed as the number of germinable seeds per gramme of bought seed, varies enormously, depending on the degree of cleaning. In air-tight containers at temperatures between +3 and +5°c, with a water content of 5-8%, the seed will keep for long periods. Sowing usually takes place at the end of the winter (February-March) in warm seed beds, with transplanting of the seedlings into seed boxes in the spring (April). If pelleted seeds are used, that is to say, individual seeds coated with inert material to increase the volume, then sowing should be carried out in late spring (May-June).
(Celastraceae) Autumn sowing immediately after the harvest or spring sowing with seeds stratified in the warm for 8-12 weeks and in the cold for 8-16. Vegetative propagation possible.  Sowing in Euonymus europaeus
Fagus sylvatica L. common beech (Fagaceae) The endogenous dormancy of these seeds is greatly conditioned by the methods used for harvesting and storage; Indeed, it would really be necessary to work out a separate programme for the duration of cold stratification required to interrupt this physiological state, for each batch of seeds. In certain cases, within the same batch, the period of vernalization needed varies after a year or more of storage. In order to maintain the seeds’ quality, their water content must be reduced to 12% if the seeds are to be sown the following spring (at harvest the water content is generally around 25-35%, but may be as high as 50-55%.) If, however, the seed is to be kept for at least 5 years, at temperatures of between -10 an -5°c, in airtight containers, then the drying process must be staggered until a percentage humidity of 8% is reached, using heat regulated air at a temperature from +18-+20°c. Autumn mulched sowing if the position is characterized by well drained land, with no spring frosts. Alternatively, mulched spring sowing with seeds which have been cold stratified from 3 to 12 weeks (8 on average). Between the harvest and the beginning of stratification, the seeds should be kept in air-tight containers at temperatures of around +5°c, with a water content of 10-12 %. During vernalization, it is a good idea to check the swelling of the seeds, so that the treatment can be interrupted immediately at the onset of germination which occurs normally, even at low temperatures. Late spring sowing should be avoided, since ground temperatures over +15°c can induce secondary dormancy. Recent studies suggest the use of the following pretreatment techniques:
 Seeds of Fagus sylvatica
Firmiana simplex Wight (Sterculiaceae) Sow in the spring.
(Oleaceae) The seeds of this species show varying types of dormancy. In F. excelsior, for example, dormancy is due to the immaturity of the embryo added to physiological mechanisms of germination inhibition. In other species, it is a result of the presence of inhibiting factors in the pericarp. As we do not have complete knowledge of all of the factors involved, and since dormancy also varies so greatly depending on provenance, and methods of harvesting and storage, the pretreatments suggested are not always effective. The humidity level of the seeds should be reduced to around 8-10% in order to avoid any loss of germinability during storage.
Fraxinus americana L. White ash (Oleaceae) Sow in the spring with seed which has been stratified in warm temperatures for 30 days, and then in cold temperatures for 60 days. In some cases only cold stratification is carried out, for 60-90 days. See Fraxinus spp.
(Oleaceae) The seeds do not enter a true state of dormancy, but germination is more homogeneous if the seeds are sown in the spring with seeds which have undergone cold stratification for 2-8 weeks. See Fraxinus spp.
Fraxinus excelsior L. common ash (Oleaceae) Sowing can begin immediately after harvesting when the seeds are changing colour from green to brown (the end of the summer). If sowing in the spring, use more mature seeds which have undergone warm stratification for 8-16 weeks and then cold for 8-16 (if possible 16-16), beginning the warm stage in September and the cold one in January. Given the length of this type of treatment and considering that the seed companies do not often have the seeds available before October-November, it may be more practical to use matter which has been well-kept in cold storage at around -4°c with a water content of 8-10%. Stored in this way, the seeds keep well for at least 5-8 years, and the pretreatment can then begin at the end of the summer (August-September) so that sowing can take place in the second summer after the harvest. If the sowing of the treated material must be postponed, vernalization may be prolonged for a few weeks (3-8) , but the temperature should be set at -3°c. Germination in the nursery is encouraged by alternating temperatures (warm in the day and cold in the night), so we do not advise sowing in the late spring. Recent studies have made it possible to take the seeds out of dormancy before or during conservation. Once the warm and cold stratification have been carried out (16+16 weeks), the seeds should gradually be brought to a water content level of 8-10% , and then they can be kept following the same methods used for the dormant seed (air-tight containers at -4°c). See Fraxinus spp.
(Oleaceae) Sow in the autumn or in the spring with seeds stratified in the warm for 2-8 weeks and in the cold for 12. See Fraxinus spp.
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