Growth Time. Caladium plants reach full size, up to 3 feet tall, in one season. The size of the plant and the leaves depend on the size of the tuber. Seeds take one to three months to germinate before the plant begins to grow. Grown from tubers, leaves usually emerge within three to four weeks.Caladiums do not begin to grow until the soil temperature reaches 70 F, so cooler soil will mean a longer wait for the plants to emerge.rowth Time. Caladium plants reach full size, up to 3 feet tall, in one season. The size of the plant and the leaves depend on the size of the tuber. Seeds take one to three months to germinate before the plant begins to grow. Grown from tubers, leaves usually emerge within three to four weeks.