|MadSci Network: Botany|
It will depend on how you measure the speed of growth, the cultivars (cultivated varieties) you are comparing and the environment. Speed of growth can be measured in several ways, including increase in height, gain in fresh weight and time to maturation of the bean crop. Climbing or pole types grow taller than bush type beans so a climbing lima bean might grow faster in height than a bush type of kidney bean and vice versa. If you are growing lima beans and kidney beans, you can determine for yourself, which of the two cultivars you have grows the fastest under your conditions. If you buy packets of garden seeds, the cropping time in days is usually printed on the package. Kidney beans are certain cultivars of Phaseolus vulgaris. Lima bean is Phaseolus lunatus. The first website says broad bean 'Express' is the fastest maturing cultivar of broad bean, but there are many types of beans. References Thompson and Morgan bean seeds Lima bean production guide Dry edible beans
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