
I’m not a great fan of ferns as houseplants: although they grow very quickly and easily on the terrace in summer, I don’t think they’re good plants when brought indoors (indeed, the fronds tend to dry out one by one until the plant dies, a sad sight). I have to admit, though, that the shape of ferns, with their delicate, airy fronds, adds an enviable Victorian edge to any room. How, then, to marry the desire for a fern with its growing difficulties? The solution is indoor asparagus.
Origin
Indoor asparagus does not refer to a single plant, but rather to several species of asparagus in the genus Asparagus, whose growing conditions make them well suited to life as an indoor plant. Asparagus grows wild in southern Africa, but its cousins can be found in both Asia and Europe. In fact, there are some 300 different species of asparagus, including A. officinalis, the edible species often found in grocery stores and sometimes in our gardens. This article is not about growing asparagus for our plates, but about growing asparagus for our living rooms.
All these Asparagus species can be found in the genus Asparagus, itself a member of the Asparagaceae family. Here we find many very common plants, such as hostas (Hosta sp.) and common bluebells (Hyacinthoides non-scripta) of our gardens. To make things even more confusing, we also sometimes place these plants in their own family or subfamily (Agavoidea and Hyacinthaceae, respectively) and “real” asparagus in the subfamily Asparagoideae…
As for houseplants, other members of the Asparagaceae family are also grown, notably spider plants (Chlorophytum comosum) and dracenas.. These plants share with asparagus their ease of cultivation. This tolerance to forgetfulness (and pesticides) makes asparagus invasive in many countries, notably Hawaii and Florida, where it is forbidden to grow outdoors.

Description
Asparagus is a herbaceous plant, meaning it has no bark, and generally grows in the undergrowth. Their root system is particularly impressive: disproportionately large, the roots themselves are thick and punctuated with tough tubers that act as water reservoirs in times of drought. From the crown grow sarment-like stems, first arching then drooping, which appear to be covered with leaves.
This is not the case. The “real” leaves have abandoned their photosynthesis function, for the most part, and are shaped like scales on these stems. Some change and become particularly petty thorns, as they point downwards; so it’s easy to get your hand into the fluffy, inviting branches of indoor asparagus, but the thorns will make themselves felt when it’s time to pull it out again, like a plant trap.
The branches themselves look like ferns because they are covered with small twigs, known as cladodes. These are branches modified to take on photosynthesis functions. They are generally a soft, shiny green, becoming darker with age. Stems can reach over a metre in length in older specimens.
Indoor asparagus flowers irregularly, but frequently. The cladodes are then covered with small white flowers, slightly perfumed but often insignificant, which are followed by red berries.

Varieties
Indoor asparagus generally refers to Asparagus aethiopicus, the most common commercially available variety in Canada. Densely branched, its stalks can reach over a meter in height. It is still sometimes referred to by its former name of A. densiflorus ‘Sprengeri’ or Sprenger’s asparagus, in honor of Carl Ludwig Sprenger, a German botanist who contributed to its popularity in Europe.
The true A. densiflorus refers to this asparagus with more upright, conical stems, reaching up to 80 cm (32″). More compact in size, which explains its nickname of fox-tail asparagus, its leaves are a slightly softer green and its spines smaller. To distinguish it from A. densiflorus ‘Sprengeri’, it was given the cultivar name ‘Meyersii’, but this distinction is unnecessary now that it has been repatriated under A. aethiopicus. The name densiflorus is reminiscent of the dense habit of fox-tail asparagus, so it’s appropriate to distinguish them.
You can also grow A. setaceus, with its sturdy, densified stems and black berries. The stems of this indoor asparagus can reach three meters and eventually become climbing. It is sometimes used to garnish bouquets of cut flowers. Its former name is A. plumosus, for its feathery appearance.
Finally, it is possible to have success with A. falcatus, whose cladodes are larger and wider, and with A. retrofractus, which is very slightly reminiscent of conifers.

Growing Tips

Light
Indoor asparagus is quite flexible when it comes to light: if it prefers bright light, it can make do with medium light and, when well hydrated, tolerate direct sunlight.

Watering
It’s a good idea to let the soil dry out slightly between waterings. That said, asparagus is a thirsty plant. Despite their tuberous roots, which store water, asparagus always seems to need water! This is because their particularly imposing root system leaves little room for the potting soil to water them.
This means that for a newly-potted indoor asparagus, you’ll want to wait for the soil to dry out over the first few centimetres, but very quickly, you’ll need to water it frequently to ensure its high water requirements. Watering in basins is often required.
Fortunately, it recovers rather quickly from periods of drought.

Atmospheric Humidity
Comme beaucoup de plantes d’intérieur faciles, une humidité atmosphérique est appréciée, mais pas forcément nécessaire.
Potting Soil
Asparagus can be grown in the usual potting soil for houseplants, as well as in potting soil for cacti and succulents (which is more difficult to keep moist, but avoids the risk of over-watering).
When repotting, it’s important to choose a pot large enough to contain its dense root system. It’s also advisable to choose a pot that you don’t attach any sentimental value to: roots are so dense that they can sometimes break pots if left in for too long. Similarly, it is sometimes necessary to break the pot when repotting, especially for plants that have been ignored for too long.

Fertilizers
If you choose to fertilize asparagus, an all-purpose fertilizer at the recommended dose can be used during the growing period. For plants whose overgrowth is to be limited, fertilization can be avoided altogether.
Temperature
A temperature between 12°C and 18°C (54 to 64°F) is optimal for the plant. It can tolerate higher temperatures, but generally likes cooler rooms. Don’t worry if temperatures drop further: the plant can survive gradual drops in temperature, as long as they don’t fall below freezing.

Maintenance
Unless the size becomes a nuisance, there’s no need to prune indoor asparagus. However, it should be placed where it’s easy to sweep up all the thorns it drops! Some stems eventually dry out: it’s only when they’re very dry that they’re easy to remove from the crown.
Propagation
Indoor asparagus can be multiplied by dividing it. You’ll probably need a saw to trim the tuberous roots and separate the plant. It’s also easier to remove some of the foliage, lest you be scratched by the prickly leaves.
The fruit can also produce seedlings, provided a few conditions are met. Most asparagus is either male or female, which does not make it self-fertile (and who buys two asparagus plants to put side by side?). On the other hand, some specimens may be hermaphroditic, but there’s no way of knowing until the flowers have been fertilized.
After fruiting, the seeds can be harvested. They can be soaked in lukewarm water for 12 hours before being planted in moist soil. Germination takes between one and two months.

Problems
Few problems affect indoor asparagus. They are occasionally bothered by insect pests (mealybugs, aphids, spider mites) and excessive watering can cause root rot. Plants affected by various common problems (insufficient light, too high a temperature or too low humidity) show this by yellowing cladodes. For asparagus with finer cladodes, such as A. setaceus, it can be beneficial to increase humidity a little, especially in winter. That said, all these problems are fairly rare.
Specimens that are too big, with roots that no longer leave room for potting soil, can be adversely affected by inconsistent watering. Indeed, despite their thick, water-storing roots, asparagus cannot tolerate drought for long. They make the forgetful gardener pay by rapidly dropping their cladodes. Left unwatered, the branches can dry out completely. That said, a good pruning a few inches from the ground and the plant will take off again… provided it’s watered more regularly!
Toxicity
This plant is slightly toxic for pets. The fruits, also toxic, can be attractive to children. In any case, it’s best to keep the plant out of everyone’s reach because of its thorny leaves.
Conclusion
For fern lovers who can’t keep their ferns alive indoors, the asparagus is an easy, trouble-free alternative to more temperamental houseplants. Its delicate foliage contrasts with its sturdiness: it’s a solid, easy-care houseplant.

Asparagus setaceus was the most popular when I was a kid in the early 1970s. It was everywhere. The others might have been less popular as houseplants because they grow like weeds outside. Asparagus setaceus was a bit more manageable if it tried to get invasive in the garden.