Fern asparagus (Asparagus setaceus, A. plumosus) grows well both outdoors and as an indoor houseplant, but wherever it grows this plant needs warm temperatures of at least 50 degrees Fahrenheit to thrive. This ornamental asparagus is grown for its graceful, dainty fernlike foliage and grows outdoors in U.S. Department of Agriculture hardiness zones 9a through 11.
Asparagus fern growing outdoors can withstand some light frost, but freezing temperatures, below 32 degrees Fahrenheit, often kill the plant to the ground. After a light frost, the plants do grow back from the roots. The fern asparagus' rate of growth depends on the amount of sunlight it receives. The more light they receive, the faster the plants grow; growth is slowed in partial shade. The plants are drought tolerant, so you can allow soil to dry out before watering. Over-watered fern asparagus develop brown or yellow leaves.
You can grow fern asparagus as a houseplant in any region. Indoors, the plant still needs warm temperatures, but not too warm. A good daytime temperature is about 72 degrees Fahrenheit with a cooler temperature around 60 degrees Fahrenheit at night. Fern asparagus are not true ferns and belong to the lily family, so you need to provide the plants with bright direct sunlight year round. Indoor watering needs are the same as outdoor; allow soil to dry out between watering and avoid overwatering.
Cold Temperature Effects
Fern asparagus are pretty tough plants, but once temperatures drop to 20 degrees Fahrenheit or below, the plant can suffer burn back of its foliage. If the plant is exposed to these temperatures for a few days, the plant can die. When the plant experiences a short time in cold temperatures it can recuperate if you trim back the burnt foliage in the spring. After trimming the plant back, healthy new growth appears quickly.
Fern asparagus require little care and grow well outdoors on the patio in pots or hanging baskets and in mixed planters indoors. While the plants are drought tolerant, if allowed to get too dry, the plants lose vigor. Given adequate growing conditions the plants grow up to 3 feet tall and wide, bearing slender, foliage and 1/4-inch fragrant, white flowers in summer and red, pea-sized berries later in the season.
- The New Illustrated Encyclopedia of Gardening Volume 2; T.H. Everett, Edtior
- ZipCodeZoo: Asparagus setaceus
- The New Sunset Western Garden Book; Kathleen Norris Brenzel,Editor
- Telly's Greenhouse: Asparagus Fern
- Purdue University Department of Horticulture: Ferns for Indoors