Introduction

Aquatic stem plants offer a huge variety of colors and leaf shapes, however, hobbyists often shy away from growing them. A common experience for newer hobbyists is that the stem plants grows well for a time period, then after a couple of trimming cycles, the bottom stems deteriorate and the aquarist is at a loss of what to do. In this guide, we will explain how to maintain aquatic stem plants in good form long term.

A large number of plants in the aquarium trade can be categorized as stem plants. They come in a huge number of color variations and leaf forms. Stem plants grow taller continuously, while producing leaves along a vertical stem. The leaves come in many different forms and colors - some are finely pinnated to give greater surface area for gaseous exchange underwater, while others look similar to terrestrial plant leaves. For many aquatic stem plants, they will grow different leaf forms depending on whether the plant is growing above or below the water line. Our guide on non-aquatic plants have many comparison pictures of aquatic plants in their submerged form vs their emersed form.

Stem plants come in a huge variety of colors and shapes. Mastering stem plants open the doors to huge variety of possible plants to use in your aquarium.

Growth patterns of stem plants

Most stem plants continually grow upwards from the apical bud. This allows the plant to grow tall and gain an advantage over other shorter plants by growing closer to the light and shading their competition. For aquatic plants, this growth strategy also allows the plant to eventually breach the water line, giving the plant access to surface air. These are tremendous competitive advantages - perhaps this is why so many aquatic species come in the form of stem plants.

Stem plants grow continuously both vertically and often outwards as well. Here the slower growing red Xyris plant is in danger of being shaded by the faster growing stem plant bushes around it.

The downside of using stem plants in the aquarium is that many of them are fast and aggressive growers, with little limit on the maximum height that they can attain - most species will hit the top of hobbyist size aquariums given enough time. The tall growth of stem plants also shade surrounding species, stunting their growth if the tall stem plants are left untrimmed and unchecked. On the plus side, plant competition also affects algae - a tank with aggressive, fast growing plants creates an environment that is hostile to algae growth, and such densely grown in tanks tend to be very algae resistant.

Stem plants suffer from self-shading and overcrowding quickly in fast growing tanks, leading to the deterioration of the lower portions of the plant. From a layout perspective, stem plants that grow quickly also change the look of the planted area from a day to day basis. For all these reasons, growing aquatic stem plants pose a unique challenge for aquatic gardeners. Many aquascapers who are focused on hardscape will avoid using stem plants entirely due to the difficulty of managing them.

Basic propagation

All species of stem plant can be propagated in a simple fashion, by cutting off the top few inches of a stem plant and planting it directly into the substrate. New buds and roots both grow out from internodes. Internodes that are buried will naturally sprout roots. For matured stems that have already sprouted side shoots, these side shoots can also be cut off and replanted once they reach a couple of inches in size. Stem plants are among the easiest plants to propagate.

Trimming stem plants

Trimming can be done in 2 main ways.

Straight trimming

The first is by cutting off the entire top portion at once. This means shearing off the entire top couple/few inches and letting the bottom rooted portion regrow fresh new tops. For this to be executed successfully, the rooted portion must be healthy enough to sprout new buds after trimming. This can be very counter intuitive for newer aquarists as it seems we are removing the most colorful and healthy top growth while retaining the less robust base portions of the stems.

In this example the Ludwigia arcuata is straight trimmed; the top 2 inches are cut off and the rooted base portion is left to sprout new shoots. While the base may looks very bad after trimming, it will recover and sprout new shoots from the rooted base within days.

When straight trimming, one should always trim the front row of plants shorter than the back row, forming a slope. This allows the stems to line up better for front-facing view. It is best if the front stems are trimmed lower than plants in front of it, which allows older base portion to be hidden; only newer heads will be seen when they grow above the front plants.

By removing the apical bud, this encourages side shoots (lateral buds) to develop along the stem at the internodes. This allows single stems to branch and become more bushy. Factors that encourage bushier growth and increased branching include - higher nutrient, CO2 and light levels. Healthier, faster growing plants produce side shoots more readily, while plants in slower growing mode exhibit more vertical growth form and less branching. Branching is exhibited much more strongly in CO2 injected aquariums.

Rotala florida on the left, Bacopa salzmannii SG on the right.

White arrows above show lateral buds forming at the internodes of the main stem. These side shoots can have side shoots of their own as the bud matures. While many stem plants form lateral buds naturally when they are in fast growth speed, many species will only form more lateral buds when the apical bud has been cut.

Trimming by cutting off individual strands

The other method of trimming a stem plant bush is by picking out the longest individual strands of plants that stick out from the stem plant bush to even out the height of the bush as a whole. This technique is time intensive and requires some dexterity on the part of the aquascaper. The advantage of this technique is that for a stem plant bush that is already in relatively good shape, this does not require the cutting off the entire top of the bush. This technique preserves the shape of the bush while removing plant mass and giving the bush longevity before over-crowding sets in. Done skillfully, this can also reduce the height of the bush or change its shape while preserving the aesthetic tops of most of the bush.

More than 10 stems have been cut from the Rotala "blood red SG" bush in the left side picture, and the result (right side) looks almost the same except that plant mass has been reduced. This preserves the aesthetic of the tank for an extended period compared to straight trimming.

What species make good bushes?

Not all species can be shaped into nice bushes easily. How profusely a plant branches is heavily species dependent. Some species will not branch significantly and will never become a dense bush, regardless of how it is trimmed. Species that branch very readily and can tolerate overcrowding are the best for the straight trimming technique, as they will regrow the canopy quickly and in a neat fashion. Species that do not branch significantly should be trimmed by cutting off individual strands.

Examples of species that branch very readily:

Stem plant species that branch profusely after the apical bud has been trimmed off include: from left to right above - Pogostemon erectus, Rotala rotundifolia [and its many variants], Ludwigia arcuata, and Myriophyllum golden [and other variants]. These species recover from straight trimming easily, and form dense bushes. They are great for creating volume in mid and back ground. Other good species for dense bushes include Hemianthus glomeratus (pearlweed) and Limnophila aromatica. All plants on this page were grown with APT Complete in the water column and APT Jazz in the substrate.

Rotala rotundifolia (and its many variants) is one of the most popular background plants in the planted aquarium hobby due to its ability to be shaped into dense bushes easily. Rotala 'blood red SG' above takes trimming well and forms dense bushes with repeating trimming.

Ludwigia 'super red' and Ludwigia arcuata make great bushes and can be trimmed to contour around hardscape. Notice how steeply the plants are sloped (picture below) to give the nice frontal view (picture above).

Examples of species that branch loosely:

Some examples of stem plants that branch loosely include: from left to right above - Bacopa caroliniana/colorata, Rotala macrandra [and its many variants, the variegated version is shown here], Rotala ramosior 'Florida', and Ludwigia senegalensis. These plants can form good bushes but they are best used in the mid-ground rather than background of the tank. There will be more gaps in the bush and you may need a larger bunch of them to have a nice bush. However, with good trimming technique, they still make very nice bushes. 

Examples of species that branch sparsely:

Some examples of stem plants that do not branch much include: left to right above - Ludwigia pantanal/meta, Proserpinaca palustris, Ludwigia glandulosa, Persicaria 'sao paulo'. If the apical bud if cut off, only a couple of side shoots will form along the internodes; also, the distance between the side shoots is much wider compared to other examples previously mentioned. Thus, these species do not naturally form dense bushes just by being straight trimmed. They can forcefully be arranged into a dense clump by planting individual stems very close to one another, however, none of these species take over-crowding well. These species are best used in the mid ground or in large groups to give the appearance of density. They are best trimmed by picking off individual strands or by replanting the tops every time.

Ludwigia pantanal/Meta grows long stems that do not branch significantly. One can plant individual stems close together to get a more dense grouping.

Self-shading and over-crowding

Leaves generally do not last forever - stem plants will continually produce new leaves while the stem keeps growing towards more favourable areas (towards the light or to breach the water line to reach air), older leaves will be left to deteriorate if they are shaded/overcrowded and no longer contribute to the overall growth of the plant. Different species have different tolerances to over-crowding. Some species have leaves that are very hardy and can take long term overcrowding or shading, while other species face very quick deterioration of lower stems once they get shaded/overcrowded.

Unstable or stressful conditions in the tank will greatly speed up the deterioration of lower stems. It is very common to see bare lower stems in non CO2 injected plants tanks for example, due to the stress of maintaining plant mass in a low CO2 environment. Repeated straight trimming cycles also causes bottoms portions of the stems to deteriorate faster.

Providing a good level of lighting and good growth parameters (ample amount of nutrients/CO2) can delay this deterioration, however, most stem plants will face it at some point of time. So for stem plants to be maintained in good form long term, replanting the tops is a necessity and unavoidable.

The mini macrandra type 4 has top growth that looks good, but the bottoms have begun deteriorating. This is normal when stem plant bushes get old and happens to different species at different speeds.  

Replanting tops

To refresh stem plant bushes, we will replant the fresh tops of the plants, while discarding the older bottom portions. Stem plants generally take very well to frequent replanting, compared to other types of plants. Most species regrow their root system readily.

The first step is to uproot the entire stem plant bush. To control the mess when kicking up the soil, we recommend using a water siphon to vacuum the area when uprooting plants. The siphon should be held very close to the point where the plant is being pulled up to capture soil debris. 

We will try to remove as much of the old root system as we can and also clear organic debris that has build up in the area. While organic debris does contribute small amounts of nutrients through decomposition, a build up of organic debris interferes with root formation for more delicate plants and also triggers algae. To stir up the organic debris, we use a turkey baster to blast jets of water at the substrate while vacuuming with a siphon. The aquasoil should look clean before we commence replanting.

Next we will sort the uprooted stem plant bush, and choose only the healthiest heads to replant. If the substrate is depleted in nutrients, we will add root tabs into the replanting spot to refresh the aquasoil. If you have followed the above steps, it will be like planting fresh plants into a new tank - except that these plants can skip the adaptation phase because they were taken from the same tank. By doing the steps above, stem plant bushes can be maintained in good form perpetually.

This tank is more than a year old, but looks as fresh as a tank that has just grown in from being freshly planted. All the stem plant bushes and even the carpet has been replanted more than once. Replanting fresh growth also makes the tank very algae resistant as fresh leaves on healthy plants are naturally algae resistant.

Which tops to replant? and other details:

When replanting, the right section matters. Above, we have three Myriophyllum guyana cuttings. A is older and less robust- observe the darker, stiffer, knobby stem. B is younger and more robust, but has several branches, which will give rise to uneven new shoots. C is ideal. A single, younger, healthy stem. It is also thicker than A and B.

Another example, using the Rotala macrandra mini type IV green. A is a middle portion and already has several branches. It is a poor choice as it will give rise to very uneven growth. B is a weak cutting- observe how thin the stem is, and the lack of colour. If replanted, it has a lower chance of success. C is ideal. A thick, singular healthy top with healthy new leaves.

Above: Myriophyllum guyana replanted the 2Hr Way. Observe the even spacing and the use of healthy single-shoots. Also notice how clean the substrate is.

Above: Rotala 'blood red SG' after trimming. When the bottom stems are so bare, we recommend replanting the tops, instead of straight trimming. This species is so hardy that in this instance, the tops have a good chance of regrowing - however, it may not grow to the ideal density and growth form.

When replanting:

• Choose the thickest, single stems.
• Avoid branches, older stems or portions with algae.
• Clean the substrate surface thoroughly before replanting.
• Plant evenly with space around each stem.
• Cleanliness is key.

Refreshing old layouts

Replanting stem plant bushes may seem tedious at first, but it also offers a good opportunity to change the tank's layout over time. The pictures below are all of the same tank across 2+ years. Most of the base species were maintained but moved around, and the stem plant bushes were replanted quite a few times. Between the trimming cycles and replanting opportunities, a stem plant focused tank is ever-changing, with never a dull moment.

All tanks and plants on this page were grown with APT Complete in the water column and APT Jazz in the substrate.