Description
of seeds belonging to the Angiospermae
Gleditsia triacanthos L. honey locust (Leguminosae) After harvesting, the seeds are dried out and then put in air-tight containers at temperatures of between +1 and +7°c . Under these conditions, the seeds keep well for at least 4 years. Sow in the spring with seeds which have been scarified or treated with hot water. See Acacia spp.
Hibiscus syriacus L. mallow hibiscus (Malvaceae) Spring sowing with no pretreatment. As far as propagation of the many strains is concerned (Ardens, Blue Bird, Jeanne d’Arc, Woodbridge, W.Smith etc.) Vegetative propagation is commonly used.
Hippophaë rhamnoides L. sea buckthorn (Eleagnaceae) Sow in the autumn or in the spring with seed which has undergone cold stratification for 4-12 weeks. After the third week of vernalization, it is a good idea to check the state of the seeds. For spring sowing, an alternative method is the use of chemical scarification using sulphuric acid for one minute, followed by washing. Germination is encouraged by temperatures of around +20°c.
Hypericum calycinum L. rose of Sharon (Hypencaceae) Sow in the spring with no treatment. Commonly obtained with vegetative propagation.
Ilex aquifolium L. common holly (Aquifoliaceae) There are no known treatments against dormancy. We suggest warm stratification for 40 weeks followed by cold stratification for 24, with spring sowing. Vegetative propagation preferred.  Seeds of Ilex aquifolium
(Juglandaceae) These seeds are considered by many to be orthodox, and a water content of 15% is deemed sufficient to keep them in good condition. In practice, nuts with a moisture level higher than this give better results when sown. Sow in the autumn, with protection against rodents and other predators or in the spring with seeds which have been under cold stratification since their harvest. In the latter case, pregerminated or ‘still’ nuts may be used. It is very important to maintain the water content of the seed during stratification, so the soil must be checked periodically to avoid dehydration, and, at the end of the winter, to assess the seeds’ swelling. In many cases it is advisable to remove the hull while it is still soft, otherwise it becomes much more difficult to do, especially in J.nigra. This also allows a reduction in volume which makes handling easier and facilitates the application of fungicide treatments. The seeds should be sown in a horizontal position in well-drained beds. To produce the fruit variety, grafting is essential.
(Juglandaceae) See Juglans spp.
Juglans regia L. common walnut (Juglandaceae) See Juglans spp.
(Sapindaceae) The dormancy of these seeds is due to the impermeability of the integuments and , probably to embryonal immaturity too. Sow in the autumn with seeds which have been scarified either mechanically, or by soaking in sulphuric acid for one hour, or those which have not been treated at all. Spring sowing is better with scarified seeds which have been vernalized for 2-3 months.
Laburnum alpinum (Miller) Berchtold & J. Presl Scotch labernum (Leguminosae) See L. anagyroides
Laburnum anagyroides Medicus common laburnum (Leguminosae) Sow in the spring with scarified seed or seed treated with hot water. See Acacia spp.
(Lythraceae) Vegetative propagation common. Also obtained from the seed which germinates easily. May benefit from cold stratification for 30-45 days before spring sowing.
(Lauraceae) The seeds rapidly lose their germinability, so it is therefore advisable to sow in the autumn straight after the harvest, or in the spring using seeds which have been stratified during the winter. Whole fruits may be used, or those with the pulp removed by 2-7 days soaking in water.
(Oleaceae) The size of the seeds varies enormously according to the species. The pulp of the fruit is usually removed by steeping, before sowing or storing. Sow in the autumn immediately after harvesting or in the spring using seeds which have been vernalized for 4-8 weeks. Embryo plants raised in seed beds are often transplanted into containers. Vegetative propagation is very widespread.
Liquidambar styraciflua L. sweet gum (Hamamelidaceae) The fruit is harvested in autumn, from September to November, when it is turning from bright green to yellow. After a short drying period, the seeds fall away from the fruit and can be easily retrieved . As far as conservation is concerned, these seeds are orthodox and keep their vitality for up to 5 years if they are stored in air-tight containers at temperatures of between 0 and +5°c, with a water content of 5-10%. At a temperature of -18°c, the quality of the seeds is maintained for even longer periods. These seeds show a state of dormancy which can easily be interrupted by vernalization for 15-90 days (usually 30). Cold stratification may also be adopted, without a substrate, but in this case the temperature must be maintained at a low level (from +2 to +3°c). Another type of pretreatment often used is to soak the seed in cold water (+5°c) for 2-3 weeks. Sow in the spring with vernalized seed. The seedlings are prone to fungal infections. Vegetative propagation is widespread.  Fruits of Liquidambar styraciflua
Liriodendron tulipifera L. Tulip tree (Magnoliaceae) The winged seeds keep well for a few years if they are placed in air-tight containers at temperatures ranging from +3 to +5°c with a water level of less than 10%. Sow in the autumn or in the spring with seeds which have been vernalized, with or without substrate, for 4-12 weeks. A variety of ornamental cultivars propagate vegetatively.
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