Fat Hen (not native)

Fat hen (Atriplex prostrata) is a widely spread, non-native annual of salt and brackish marshes, often growing at the upper edges of the pickleweed. In autumn, leaves, stems and seed sprays turn shades of gold, red, orange and purple, adding to the seasonal color of the marsh.

Like other salt marsh plants, fat hen has a mechanism for avoiding salt toxicity. Excess salt is transported away from growing tissues and deposited in microscopic bladder hairs on the leaf surface. When full, bladders collapse, excreting the salt from the plant and leaving behind small fragments, like dandruff, on the leaf surface.

This salty plant is a host for our smallest butterfly, the pygmy blue.

Description ^4,26,34

Fat hen is an herbaceous annual that produces one to several sprawling to weakly ascending basal stems up to a meter long. Stems are branching or not, angled or ridged, initially green, becoming striped with red before turning deep rose in fall.

Leaves are variable in size and shape. Larger (lower) leaves may be 3½ inches (9 cm) long and nearly as wide at the base; the upper (outer) leaves are smaller; many leaves are arrowhead-shaped (sagitate or hastate), but the smaller leaves are sometimes narrowly to widely triangular or lanceolate. The leaf petiole is shorter than the leaf. Leaf margins are smooth or irregularly toothed. Leaves are green, sometimes edged with red and turning golden to deep rose in the fall. The young growth of both stems and leaves are covered with specialized hairs (bladder hairs or salt hairs, further discussed under Ecology), highly modified hairs that excrete salt. These give the leaf a silvery sheen when young and a rough, scaly texture as the leaf ages.

Flowers occur in discontinuous clusters along branching spikes at the stem ends. The lower flower clusters are interspersed with small leaf-like bracts. The individual flowers are tiny and either male or female, with both occurring on the same plant, usually, but not always, in separate clusters. Male flowers are radially symmetrical, less than 1/16 inch (0.1cm) across. There are no petals and the calyx forms an open bowl with five, triangular lobes that curve inward; the calyx is reddish in the bud, becoming green on flowering. The pistil is absent; there are five stamens, with bilobed anthers with yellow pollen. The female flower consists only of a single pistil which is fully enclosed by two slightly unequal, ovate, leaf-like bracts that are joined at the base and that give the structure a flattened, asymmetrical shape, somewhat like a sunflower seed less than 1/8 inch (mm) long. The pistil has a one-chambered ovary with a two-branched style. Fat hen blooms from June to November.⁷

The fruit develops within the pair of enclosing bracts. The entire structure enlarges to about 1/4 inch  (0.5 – 0.6 cm) becoming deep pink to dark brown. The shape is distorted by irregular tubercles that develop at the base of bracts. There is one seed per fruit, but the fruits produce seeds of two types: brown seeds greater than 1/16 inch  (0.15 – 0.25 cm) wide and smaller black seeds. The size differences may reflect different germination times.³⁰⁵

Classification

Fat hen is a dicot angiosperm in the goosefoot family (Chenopodiaceae).² Plants in this family are often succulent or scaly; many appear weedy; many are salt tolerant. Typical flowers are tiny, greenish and lack petals.^11,34,44,143 This family is currently under study and genetic evidence may result in the Chenopodiaceae being merged with the related Amaranthaceae.^41,44,143 Well known members of the goosefoot family include beets, spinach, and Quinoa seed.^11,44,

In the Reserve, the most familiar species in this family is pickleweed (Salicornia pacifica) which dominates much of the salt marsh vegetation.⁴⁸

Atriplex is a genus of about 100 species,¹¹ 42 of which are found in California.⁷  Species of Atriplex are distinguished from other members of the family by the structure of the female flower, which is enclosed in two bracts that are fused only at the base.¹¹

Ecology ^236,545

Plants of saline and alkaline wetlands have one or more adaptations that allow them to persist in spite of toxic concentrations of salt in the surrounding environment. Exclusion of many salts by the roots (an adaptation of all halophytes), segregation of salts into special chambers within the plants (e.g. pickleweed, Salicornia pacifica) and excretion of excess salts through salt glands (e.g. salt grass, Distichlis spicata) are common mechanisms.

Species in the goosefoot family, including species of Atriplex, possess highly modified hairs on young stems, fruits, and leaves that serve a function similar to that of salt glands. These bladder hairs (or salt hairs or vesiculated hairs) consist of a few cells, one or more stem cells, and a bladder cell. Together they look like tiny balloons tethered to the leaf surface. The surfaces of young vegetation have a sheen from the tiny bladders. Salts that pass into the plant are moved out of the cell sap and into the bladders of the hairs. These can expand many times their original size, much like an inflating balloon. Once the bladder reaches capacity, it collapses, releasing its salty contents onto the leaf surface to be blown or rinsed away. The bladder hair does not regenerate, but the remnant fragment remains on the leaf surface, giving the surface of older leaves a rough, scaly texture.

Human Uses

We have found no clear record of use of this species by local native Americans, although there are references to use of the larger Atriplex shrubs (A. canescens ²⁸² and A. lentiformis ^{71, 282}). Some Atriplex species were used as greens by the natives in Baja California⁷⁶ and the Chumash may not have distinguished Atriplex species from California croton (Croton californicus) and used them both to make a hot tea to treat colds.¹⁵

A few reports are specific to the modern use of fat hen as a culinary green,¹¹ such as a substitute for spinach, especially palatable when cooked. “The leaves have a natural salt content that blends well with a little lemon.”³⁴

Interesting Facts

Fat hen, together with many other species of Atriplex and Chenopodium, is host for the western pygmy blue, the smallest butterfly in North America.¹¹⁶