Epá, não falem com tanta certeza do que não sabem a 100%.
A parte da planta que fica, naturalmente voltará a rebentar se tiver condições para isso, em muitas plantas até se dividirá, formando assim moitas mais compactas.
A restante poderás plantar, para enraizar melhor arrancas as folhas de baixo na parte do caule que vai ficar enterrado no substrato.
Poderás aprender um pouco mais sobre como podar plantas aqui um muito bom artigo do Just Me, sem dúvida o utilizador deste forum com maiores conhecimentos na área da botanica.
Sobre a cabomba, retirado do site da apc
Green Cabomba, or Cabomba caroliniana var. caroliniana, is a popular aquarium plant which exists in generally acidic lakes, ponds, and rivers in regions in both North and South America. It has been commonly available through most pond and aquarium plant retailers for years. The ease with which this species chokes out native flora through its rapid formation of massive colonies has led to its status as a noxious weed in Australia and other countries.
Under optimum conditions, the stems of C. caroliniana var. caroliniana can easily reach the surface of an average-sized aquarium within a week or so, even after a substantial pruning. The shoots will then drift below the surface, where limbs with oval- to diamond-shaped floating leaves and diminutive, white flowers will develop. However, if the temperature is too hot (70-76F is best) or there is not enough light, the plant will exhaust itself quickly and growth will slow to a crawl. This plant seems to relish light above all else, as pH and hardness seem to play only a minimal role in its upkeep. Micronutrient fertilizers promote larger, more robust growth. Limiting nitrate fertilization can cause the plant to darken and take on an almost brownish hue, especially under very high light. CO2 supplementation is not required but will boost growth.
C. caroliniana var. caroliniana can be propagated like other stem plants, but it should be noted that the bottoms of pruned shoots that remain in the gravel can take a little longer than other species to form new growth. Lateral branching is not common but it does occur; more so in long shoots allowed to float below the surface than in submersed ones.
In aquascaping, this species seems to be most effective as a backdrop. Its lime-green, furcate (forked) leaves offer up an interesting texture to which other plants with different leaf shapes and colors may be contrasted.