Growing Aquarium Plants: Weeding with Wet Elbows

Daniel J. Hinkley, plantsman and longtime Horticulture magazine contributing editor, shares this guest post about his adventures in growing aquarium plants. You don’t want to miss how

even one of the most experienced plant explorers found a new way to garden.

The Adventure in Growing Aquarium Plants Begins

There obviously exists still a surfeit of fascinating plants on terra firma to keep me quite entertained for the remaining years of my life. I will continue to study those until my limbs no longer cooperate. However, quite by coincidence, I have developed a fascination for the under-earthly counterparts of many of the plants with which we gardeners are familiar, and along with it a hobby that keeps me “in the soil” throughout the winter months.

growing aquarium plants

Be sure to consult with a trusted local aquarium supplier before adding fish to your aquascape. Photo credit: MirekKijewski/iStock/GettyImages

A few years ago, in Germany, I encountered for the first time the elegant stems of Ranunculus fluviatilis, which thrives in fast-flowing streams throughout Europe. Just months later, I was intrigued to learn that the rare Lobelia dortmanna grows in the deep, cool lakes of the Olympic Mountains of Washington state—virtually my own back yard.

A few months later and after a very steep learning curve, I had become that weird guy in the basement with 275 gallons of freshwater aquariums. As each species thrives and ultimately flowers, I am reminded again of the magic and the diversity of the plant kingdom on Earth.   

The Basics of Growing Aquatics

Flowering plants in freshwater aquariums are the botanical versions of the marine mammals. They evolved in the oceans, moved to land and moved back to aquatic environments. Just as whales and seals depend on the same basics of living as all mammals, flowering plants that live beneath the water have the same needs as those on land.

Aquatics frequently thrive in areas that are subject to seasonally changing water levels, so most have the ability to grow both submersed and emersed (rising above the surface of the water). The plants will ultimately flower, however this will happen when the flowering stems rise above the water (generally during the seasons when the water level is at its lowest). The flowers will be pollinated in typical fashion by wind or insects, but the resulting seeds are weighted, forcing them to the substrate of soil where new generations will germinate.

Many aquatic plant species possess extremes in leaf shape and size depending on whether they are below or above water. The underwater leaf forms are an adaptation to capture as much light as possible, although it can present challenges in proper plant identification. And should this column inspire you to give an aquascaping a try, you will soon discover that most plants you purchase will have been produced above water; they will immediately die back upon planting. Submersive leaf forms will soon enough take their place as growth resumes.

Full disclosure here: As is the case with most hobbies, this can become as complicated or remain as simple as one allows. Enter carbon dioxide. In a natural system, this essential building block of life will always be found in quantities sufficient for healthy plant growth. CO2 plus H2O (and, duh, there is a lot of that around) plus a bit of light is the stuff of photosynthesis. In a designed system such as an aquarium, CO2 levels become deficient and growth will be stunted. It is quite easy to add liquid forms of CO2 to your underwater garden, or you can go the route that I have—adding a dribble of this gas to the water throughout the daylight hours, the only time it is useful. This is not nearly as complicated nor as expensive as one might imagine; a tank of CO2 refilled from a local welding supply costs approximately $40 for six months (and I’m growing a lot of plants).

You do, for the most part, need to keep the temperature of your water in the mid- to high range of 70˚F. And yes, as with all garden plants, they will need supplemental fertilization. Pretty easy stuff, really: a squirt of NPK with micronutrients once per week for every 10 gallons of water.

And what “soil” to put on the bottom of your tank for proper growth? You will read a lot of opinions on this. Do your research on this, and on proper lighting. Above all, visit a highly regarded, independently owned local fish store. You will find that they love their craft and will not steer you wrong.

A Few Favorite Plants

I have a long way to go to fully reveal the inventory of genera and species that I can successfully cultivate, but these are great beginner plants and generally commonly available.

My introduction to the European species of aquatic buttercup led me to the Australian Ranunculus inundatus. I find this a charming plant, appearing very much like a slowly spreading counterpart to the wood anemone (Anemone nemorosa), to which it is related. Increasing the temperatures and dropping the water level will encourage it to produce its pretty yellow flowers slightly above the water level, though I am content to simply grow it as low, textural groundcover.

I have long grown the ornamental crinums in our gardens in the Pacific Northwest for their colorful amaryllis-like flowers produced on tall stems in mid- to late summer. How astounding for me to discover there exist two species of fully aquatic Crinum.

Crinum thaianum, or the Thai onion plant, is now considered a very rare species that is endangered in its native haunts of Thailand from wetland draining and habitat destruction. Fortunately it is found firmly in cultivation and not wild collected. During the drier seasons, this species will send skyward stems of very pretty white lily-like flowers that open just above the water surface.

Much different in appearance is C. calamistratum from Cameroon. This species displays an intriguing characteristic commonly found among many families and genera of aquatics, much to the delight of the gardener. The leaves elegantly and tightly spiral, ostensibly to increase the leaf area’s surface in order to gather sunlight. It creates a fanciful appearance not seen in many, or maybe any, terrestrial plants.

Many of us grow Cyperus, or Papyrus, in the sedge family, as a wet-loving “temperennial” in containers, especially in the warm and sultry states of the East, but Cyperus helferi is a truly elegant underwater addition to the aquarium. It will form thin-textured stands of foliage; with water movement they look much like a field of grass in a summer breeze.   

If there is a queen of the aquatic landscape, the genus Aponogeton offers up an amazing number of sensational species (provided you have sufficient room). All species are native to the tropical regions of Asia and Africa. Aponogeton madagascariensis, the so-called Madagasgar lace plant, produces broad, strappy upright leaves; the tissue between the leaf veins immediately dissolves, leaving a specimen appearing more a creation of a Flanders lace factory than the plant kingdom. Aponogeton ulvaceous must hold a record (I have not researched this fact) as one of the fastest-growing plants in the world. Its elegantly twisting leaves will easily fill a 20-gallon container in only a week once established. It blossoms consistently for me, with fragrant white flowers that appear slightly above the water level on long willowy stems.

Those enamored with Arisaema, Calla and other aroids might be surprised to learn that one of the most popular and diverse plant genera in the hobbyist’s aquarium comes from the same family, the Araceae. It is rather hard to come up with a favorite from this group, as it is a matter of apples and oranges. Cryptocoryne wendtii, in its red-foliage forms, is easy, dependable and stunning. Cryptocoryne spiralis has elegantly long and narrow leaves that will rise and lie across the surface of the water while flowing in water movement from the outlet of the water filter or supplemental pump. All will ultimately form the flower familiar to many of us as the water level drops: a rather charming spathe surrounding a squat spadix, looking all the world like a cobra lily cultivated by Neptune himself. The cryptocorynes are the ideal beginner’s plant as they tolerate low light levels and less than ideal water conditions.

Equally easy and certainly widely available are the so-called Amazon swords, in the genus Echinodorus. Though these will blossom above water with spires of white flowers, they have also evolved to form plantlets along stems that will break free and float downstream—a great way to propagate and share. A top choice here is E. angustifolia ‘Vesuvius’, which, unlike its bolder-textured, wider-foliaged cousins, forms beguiling specimens of extremely narrow and spiraled foliaged; a must-have in my mind.   

Moss and More

Of course, not all freshwater aquarium plants are higher plants—moss, algae and ferns are also good additions. Several ferns and mosses have evolved to live submersed, with the most popular and dependable to cultivate known as the Java fern (Microsorum pteropus). Like the above-mentioned Echinodorus, this species has the desirable habit of forming plantlets on the ends of each leaf that can be harvested to increase your own populations or share with friends. (Although it too will ultimately produce a sexual population through spores when the foliage exists above water during dry seasons.)

Perhaps the strangest of the plants that I grow, and the one my non-aquatic-geek friends ask about most, is the cool-loving marimo moss (Aegagropila linnaei), which is in fact an algae discovered in highly separated populations in Iceland, Scotland, Japan and Estonia. Appearing to be a perfect green velvety ball, about the size of a small orange, each is indeed solid and quite easy to cultivate. These love to bounce along the substrate as if in a slight current, so water movement using a small submerged pump will help. And if yours for unknown reasons goes south, simply put it in a jar of water in a dark refrigerator for a month; it will fully recover.

Before closing, a quick but important plea: I feel that fish should not be added to a tank until one fully understands the conditioning cycle that must take place over a period of several weeks in order to make it safe for them. (Plants are not so fussy!) Please do not experiment with living creatures to see if your tank is ready to receive them; instead, take water samples into your local fish store.

Lastly, in acquiring plants, I have found that seriously minded local fish stores will sell properly identified and labeled plants; this is not the case when one is ordering on online. For reasons I do not understand, the standard for online aquarium plant sales is simply and terribly below par. Be prepared to receive bags of often times unrooted and unlabeled plants; indeed, ask the supplier if they label their plants before you order.

Yes, aquascaping represents a topic quite outside of the realm of what would be expected from a notorious hardy-plant enthusiast. Yet it is an immensely satisfying addition to get you through the winter months. I hope some of you might give it a try, and report to me through my website your own successes and failures.

You can read more about Hinkley’s adventures at danieljhinkley.com.

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