The four o’clock plant (Mirabilis jalapa), often called the Marvel of Peru, is a common garden favorite recognized for its prolific self-seeding habit. Gardeners frequently encounter its young sprouts where they were not intentionally planted, making accurate seedling identification necessary. Knowing the distinct features of this plant in its earliest stages helps determine whether a sprout should be nurtured or removed as a weed. This guide provides a detailed visual analysis of the Mirabilis jalapa seedling.
The First Sign: Cotyledon Appearance
The seed leaves, or cotyledons, are the plant’s first energy source before true leaves form. These cotyledons are notably large compared to many other garden seedlings, often measuring 20 to 25 millimeters wide and 30 to 45 millimeters long, making them distinctly wider than they are long. Their surface is characteristically smooth and the color is a uniform, bright green, lacking complex veining or texture.
These seed leaves appear directly opposite each other on the tiny stem, spreading flat to maximize light absorption immediately after germination. The cotyledons are temporary and will eventually shrivel and drop off as the plant establishes its permanent leaves. Their spatulate or broadly oval shape is a reliable early indicator.
Characteristics of the True Leaves
The first set of true leaves develops between the cotyledons and offers the most definitive visual cues for identifying the four o’clock seedling. Unlike the simple, broad cotyledons, these leaves display the plant’s mature morphology, described as ovate-acuminate. This refers to a pointed oval shape, often with a subtly heart-shaped, or cordate, base where the leaf meets the petiole.
The true leaves are a vibrant, deep green and possess a smooth, somewhat fleshy appearance that can look slightly glossy. They grow in an opposite arrangement along the stem; as the seedling matures, the pairs of leaves may appear slightly staggered at each node. These leaves lack any serration, featuring completely smooth, entire margins that help distinguish them from many weed species that exhibit toothed edges. The first pair of true leaves quickly expands, allowing the seedling to transition to independent photosynthesis.
Stem Structure and Early Growth Habits
The physical structure of the stem and its initial growth pattern are key identifying features. The stem of the four o’clock seedling is notably thick and fleshy, often described as “juicy,” which provides early structural support. It maintains a light or bright green color, but a slight reddish or pink-purple tinge may be visible near the base or at the swollen nodes where the leaves attach.
The seedling exhibits an upright posture and a vigorous, fast-growing habit, quickly developing multiple branches even in its early stages. This rapid growth is supported by a significant subterranean structure: an elongated, tuberous taproot. While the taproot itself is hidden, its presence firmly anchors the young plant, making established seedlings difficult to pull from the soil compared to many shallow-rooted annual weeds.