Germination, establishment, and spread ofSoliva valdiviana(Compositae)

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Abstract
Achene production in So/iva occurs from mid November until the end of January but germination in the field is usually delayed until the first heavy rain in autumn. Two species of Soliva, S. valdiviana and S. pterosperma, occupy very similar ecological niches. Both species have a prostrate growth form which enables them to compete successfully with perennial lawn grasses in close-cut turf. Laboratory studies showed that whereas achenes produced early in the season take a long time to germinate, those produced later germinate rapidly. This feature is particularly marked in S. valdiviana. Germination is also greatly stimulated by light. About 40 days elapse from the first readily observable signs of capitulum formation to mature achene production in S. valdiviana. A central capitulum is produced first and under favourable circumstances capitula will subsequently develop on the laterals. Achenes will mature on detached capitula if given sufficient moisture and light. Presumably summer conditions in Auckland will not usually provide adequate moisture for sufficiently long for achenes to germinate. However, even if germination does not occur at this time, the achenes produced early in the season will be subjected to wetting and drying cycles. Experiments suggest that these are unlikely to affect viability. By the beginning of autumn it is probable that most of the achenes produced during the season will be capable of germinating rapidly. The seedlings will then occupy the open areas caused by summer die-back of the parents.