The lima bean, Phaseolus lunatus, is an edible member of the legume family, Fabaceae. Originating in Central and South America, it has been a cultivated food source for thousands of years. It is also known by popular names like the butter bean (for larger varieties) or the sieva bean (for smaller types).
The Two Primary Growth Forms
The lima bean plant develops in two distinct forms: the Bush (or dwarf) type and the Pole (or climbing) type. Bush varieties are compact, self-supporting structures that typically reach 1 to 2 feet in height. These types mature faster and produce their harvest within a condensed period, making them suitable for smaller gardens. Pole varieties are climbing vines that use twining stems to ascend support structures, such as a trellis or pole, reaching heights of 10 to 15 feet. This climbing habit requires external support but allows the plant to produce a higher overall yield over a longer period.
Stages of Development: From Seedling to Flowering
The journey of the lima bean begins with germination, which requires the soil temperature to be at least 65°F for reliable emergence. Once the seedling breaks the soil surface, it first displays two cotyledons and a pair of simple, opposing leaves. Subsequent leaves are compound, forming the characteristic trifoliate structure (three distinct leaflets). As a true legume, the plant develops specialized root nodules that house nitrogen-fixing bacteria, enriching the soil.
The vegetative stages continue until the reproductive phase, marked by small, typically white or pale violet flowers in loose clusters. Lima beans are largely self-pollinating, which quickly leads to the formation of the pod. The plant typically requires 60 to over 90 days from planting to reach the stage where the immature pods are fully formed.
Harvesting and Preparing the Mature Bean
The seed is the ultimate product of the lima bean plant, harvested at two primary stages. The first is the “green” or shelling stage, where the pods are plump, firm, and bright green, but the beans inside are still tender and soft. These fresh, immature beans are often picked approximately 60 to 80 days after planting, offering a sweet, creamy texture. The second stage is for the “dry” bean, where the pods are left on the vine until they have completely dried, turned brittle, and changed color. This process allows the seeds to fully mature and harden, concentrating starches and proteins for long-term storage.
Raw or undercooked lima beans contain linamarin, a cyanogenic glycoside. Proper preparation, typically involving soaking and thorough boiling, is required to break down this compound and ensure the beans are safe and nutritious for consumption.