Seed collection of annuals is an important aspect which needs scientific knowledge and special care in handling and storage. Maintenance of the purity of varieties which is highly technical requires the knowledge whether crop is self, self to partial cross or cross pollinated. Self-pollinated annuals which do not need any isolation distance are Lupins, Sweet pea, and Salvia.
The annuals which are self to partial cross pollinated require the isolation distance of 50-100 metres, are: Antirrhinum, Larkspur, Linaria, Phlox, and Pansy. Majority of the annuals are cross pollinated which require an isolation distance of more than 400 metres e.g. Balsam, Zinnia, Gomphrena, Cock’s Comb, Sunflower, Portulaca, Gaillardia, Sweet alyssum, Calendula, Corn flower, Sweet Sultan, Chrysanthemum, Cosmos, Dahlia, Helichrysum, Candytuft, Eschscholtzia, Marigold Nasturtium, Verbena, etc.
To produce seeds of different varieties large area for proper isolation is required. In some of the nurseries, sweet pea trained as an artificial curtain up to 2 or 2.5 m high is used to provide an isolation distance for self to cross pollinated crops. In limited space other devices like bagging and growing under glass houses are also used.
Other than isolation, removal of off types is also an important operation which should be done before flowering or flower opening. The improvement in seed set is also achieved in certain crops like large pansy and carnation by brushing. Now-a-days, the F1 hybrids are very popular due to uniformity in plant height, flower size, floriferousness and bigger size of bloom.
Similarly F2 hybrids are very popular in some crops like pansy, antirrhinum which bring out colour carnival in the garden. These F1 hybrids are produced every year by crossing two selected lines. The crossing involves emasculation, collection of pollen and pollination which is done manually; that is why the cost of hybrids is high. In crops like marigold, male sterile line is used as one of the parents which save above operation done by manual labour.
Seed collection should be done at proper maturity stage before splitting of seed pods. Seeds are generally thrashed by hand, winnowed, cleaned and screened. Dry and inert material, small, deformed and broken seeds should be removed from bulk. Seeds should be treated with insecticide to prevent the pest infestation during storage. Seeds packed in muslin bags with silica gel are stored best in air tight tins and glass jars. Cardboard boxes can also be used.
There are some difficulties in seed production business of ornamental crops in comparison to vegetable or field crops. The demand of annuals is not very large and seeds are small in size which does not permit the use of machines in handling. Thus, the cost of handling and packing becomes high.