The name “asparagus fern” is a strange jumble of terms. These plants are neither ferns nor edible vegetables. Although not even distantly related to ferns, asparagus ferns are, however, actually closely related to edible asparagus (Asparagus officinalis). Asparagus ferns are versatile, reliable, easy to grow and useful in a variety of gardening situations.
The most commonly grown asparagus fern is Asparagus densiflorus Sprengeri. This asparagus fern produces a mound of shiny, bright green, finely textured foliage about 18 to 24 inches tall and somewhat wider. (Although I use the term “foliage,” asparagus ferns do not possess true leaves. What appear to be small, needle-like leaves are actually modified, flattened stems called cladodes.) Showing its relationship to edible asparagus, the new growth looks remarkably like very tiny spears of asparagus. When the new growth opens and matures, the fine, lacey growth reminds people of ferns. So, the common name does make sense.
When the plants are old enough, tiny white flowers appear among the foliage. The resulting fruits are about the size of a pea, start off green and then turn an attractive red. Asparagus ferns are fairly easy to grow from seed. Remove the large, tan seed from the ripe, red fruit. Plant it immediately by pressing it into the surface of a container filled with damp potting mix. In fact, it’s not at all unusual to see seedling asparagus ferns growing in a landscape with mature, fruiting plants.
Asparagus ferns are very adaptable and will grow in full sun to shade. However, their foliage tends to look somewhat yellow in full sun. Their growth and color tend to be better if they receive shade for a part of the day.
Asparagus ferns will grow in nearly any soil and will thrive in both moist and dry conditions. They flourish in the hottest summer heat. Temperatures in the mid-to-low 20s may burn back the foliage in winter, but a trimming in the spring and abundant new growth will get the plants looking just fine again in no time.
They are among the most drought-tolerant plants we use in containers, which is a real advantage because containers can dry out so quickly. The secret to their drought tolerance is in the white fleshy structures attached to their roots. These structures store water to carry the plant through times of drought. You may see them when transplanting or repotting the plants.
No major insect or disease problem attacks asparagus ferns, so you never have to spray them. Fertilize them in spring and summer when you fertilize other plants in your landscape, and they will produce abundant deep green growth.
This plant is a sure bet even for novice gardeners and can be used in many different ways. The fine-textured, bright green foliage and low mounding growth habit of Sprengeri make it a good landscape choice. It is excellent as a ground cover, as a specimen plant or in groups. Its long stems hang down gracefully, making it an outstanding plant for hanging baskets and containers. Because it deals so well with poor growing conditions, asparagus fern will often grow where other plants won’t.
Because they tolerate more sun than true ferns, asparagus ferns are good choices where the fine texture of ferns is desired in fairly sunny locations. Their drought tolerance also lowers the need for supplemental irrigation during summer heat.
A Sprengeri asparagus fern needs to be repotted only when the roots are cramped to the point of raising the soil level an inch or so above the pot rim. At this point, the root ball will look like a solid mass of tough roots. And they are tough.
Either repot your asparagus fern into a larger container, or divide it and plant it into two or more containers. To divide the clump, use a saw – yes, a saw – to cut the clump into two or more pieces. Don’t worry about severing the water storage structures in the roots. Use any well-drained potting soil to repot.
Asparagus ferns also grow well indoors. Place your plant by a brightly lit window – morning sun would be ideal. Keep the plant evenly moist and fertilize it with a liquid fertilizer in summer. I find that asparagus ferns are generally easier to care for indoors than true ferns.
Another asparagus fern you are likely to see growing locally is Asparagus densiflorus Meyers. It is also called asparagus fern, but an even better common name used by gardeners is foxtail fern. It is a very different looking plant and has a more formal appearance. The tiny foliage is arranged densely along individual semi-erect stems that look remarkably like green fox tails. Altogether the effect is like a spiky hairdo.
This plant is sometimes harder to find and may be more expensive than Sprengeri, but it is well worth looking for. I also find the foxtail fern somewhat slower-growing than the Sprengeri asparagus fern. But it is just as tough and reliable in containers and in the landscape.
Dan Gill is a horticulturist with the LSU AgCenter. He can be reached at DGill@agcenter.lsu.edu.