The green bean, scientifically known as Phaseolus vulgaris, is one of the most common and rewarding garden plants to grow. Identifying the seedling correctly is important for new gardeners to ensure they are tending the desired crop and not a weed. Germination is relatively quick, typically resulting in the first signs of life pushing through the soil within 5 to 10 days. This initial growth phase features several distinct characteristics that confirm the plant’s identity.
The First Sign of Life: The Emerging Arch
The first structure a green bean plant sends above ground is a curved stem, often described as a shepherd’s crook or a loop. This arch is the elongating hypocotyl, the segment of the stem below where the seed leaves attach. The stem bends into this tight curve to protect the delicate growing tip and folded seed leaves as they are forced upward through the soil. This method of emergence is known as epigeal germination.
The arch is usually pale or whitish-green, sometimes exhibiting a slight reddish tint. As the hypocotyl lengthens, the curve straightens out, pulling the attached seed and its contents completely above the soil line. This upward thrust sheds the seed coat, allowing the seedling to fully emerge.
The Seed Leaves: Cotyledons
Once the hypocotyl arch straightens, two thick, fleshy structures unfold at the top of the stem, which are the cotyledons, or seed leaves. These cotyledons are typically oval or kidney-shaped and have a smooth texture. Their appearance is distinctly different from the subsequent true foliage.
The primary function of the cotyledons is to serve as the plant’s initial food source. They are packed with stored nutrients, such as starch and protein, which fuel the seedling’s growth until it can produce its own energy. They are temporary organs that will naturally yellow, wither, and drop off once the plant establishes its permanent leaves.
Defining Features: The True Trifoliate Leaves
The definitive feature identifying the green bean seedling appears shortly after the cotyledons have unfurled, growing from the top of the stem between the two seed leaves. These are the plant’s first true leaves, representing the start of full, independent growth.
The true leaves emerge in a characteristic trifoliate structure, meaning they consist of three separate leaflets attached to a single leaf stalk. Each of these three leaflets is typically heart-shaped or pointed, and they have a darker green color and a more textured or veined surface. This set of three leaflets confirms the identity of the young Phaseolus vulgaris plant, as all subsequent mature leaves will continue to display this three-part form.