The asparagus fern is not a fern at all but a plant in the asparagus family. It is loved for the graceful, ferny texture of its foliage. The feathery stems can grow to 20 feet long in the wild and are an appealing shade of emerald green. They turn yellow when their cultural care is inadequate.
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Meet the Asparagus Fern
The asparagus fern (Asparagus setaceus or plumosus) is a plant with feathery, flattened sprays of bright green stems. They look like ferns, and it is this resemblance that gives them their common name. In summer, they offer tiny white flowers that develop into deep purple berries in fall. The plant is a longtime favorite for adding texture to spaces both indoors and out.
An asparagus fern produces long, branching stems that are green or brown. The stems are rounded and arching with fine foliage that gives a soft or fluffy appearance. This "soft" foliage can be used as a very effective contrast to other plants. Mature stems develop sharp spines in the leaf axils.
The stems can be upright or trailing, and they carry cladodes — short, flattened stems that look and act like leaves. The true leaves are found at the base of these cladodes and look like scales.
Care for the Asparagus Fern
The asparagus fern is picky about light and water. A houseplant should be placed in a site with medium to bright light. Outdoors, light shade or partial shade works better. Hot, direct sun can injure the plant.
The asparagus fern needs water and needs it regularly. This can come in the form of moist soil or humidity in the air. Plants grown in hanging baskets are also in particular need of moist soil. In the house, you might even place one in a sunny bathroom shower. The sunnier the plant's location, the more water it takes to survive.
Asparagus ferns only thrive as outdoor perennials in U.S. Department of Agriculture plant hardiness zones 9 and above. They propagate easily from cuttings.
Diagnose Yellowing Leaves
The asparagus fern is grown for its green foliage that, with its light, delicate appearance, provides interesting texture in a mixed flower bed. When this ferny foliage turns yellow, it is a clear sign that the plant is not getting its cultural needs met.
Too much sun can cause the asparagus fern's foliage to yellow. On the other end of the spectrum, anyone trying to grow these plants in deep shade is also likely to see yellowing foliage. Likewise, a plant getting too little water will also turn yellow.
If you are fertilizing the plant and its leaves turn yellow, you may be giving it too much fertilizer. Use a water-soluble houseplant fertilizer at half strength for asparagus ferns, even for those grown outside.