How to grow Sygonananthus species (S. Macrocaulon, S. 'lago grande')

Above: Syngonanthus 'Lago grande' has light green foliage that contrasts well with red/orange colored plants. 

Introduction

Syngonanthus macrocaulon has a distinctive mop / umbrella shaped top. Planting them at staggered heights will produce beautiful clusters.

Syngonanthus macrocaulon is the most commonly traded species in the hobby and it is found in the Amazon in very soft black water rivers. It was first introduced to the hobby as "Tonina sp. belem", but was later confirmed by botanists as belonging to the genus Syngonanthus. Some dealers mistakenly call it Syngonanthus belem, combining old and new names. The plant develops branched stems densely populated with narrow, delicate leaves measuring 2-3 centimeters in length. These leaves arrange themselves in distinctive rosette-like formations at the shoot tips, resembling the crowns of tropical trees. Unlike Tonina fluviatilis, which develops short-stalked flowers in leaf axils, Syngonanthus species produce distinctive long-stalked, head-shaped flowers appearing in groups on shoot tips, similar to Eriocaulon species. This morphological difference demonstrates the plant's closer evolutionary relationship to other pipewort genera.

In higher light systems and good carbon availability, the plant preferentially directs energy toward developing lateral shoots rather than pure vertical extension, which makes the species great for forming dense bushes. Its pale green colour contrasts well with red/orange plants.

How to grow

This plant has a long history in the hobby, but in the early years when its requirements were not well understood, it had a reputation for being difficult to keep. With the development of aquasoil substrates - which are acidic and buffer the KH/pH in tanks - this plant can now be considered fairly easy to grow as long as the tank has very soft water and aquasoil. Alkalinity should be low (less than 2 dKH) and pH should be on the acidic side (less than 7.0). In nature, such species are found growing in acid bog swamps with pH in the 3.0-4+ range.

It needs good light levels to grow well, so Syngonanthus species should not be shaded. CO2 injection should be present but does not need to be high. A nutrient rich, acidic soil substrate is a significant advantage in growing Syngonanthus species.

Similar Syngonanthus species

Similar plants in this category are Syngonanthus 'Manaus', which looks similar to Macrocaulon but is considerably taller/bigger, and 'Lago grande', which is similar in size but has a spiked top compared to Syngonanthus macrocaulon. Syngonanthus "Giant" is larger than the other varietals. All have similar growth requirements. 

Syngonanthus giant is significantly larger than Syngonanthus macrocaulon/lago grande. Syngonanthus manaus and Syngonanthus giant are the 2 larger Syngonanthus species.

Key success factors

• Soft water ( <2 dKH )

• pH 4.0-7.0

• GH is flexible (1 to 10dGH+)

• Sufficient light (medium level onwards)

• Rich, acidic aquasoil substrates makes it easy

Trimming and propagation

This species does not take straight trimming well - the apical growth heads should not be all cut off at once. The plant should be trimmed either by topping and replanting or by cutting off longer individual heads. New plants are produced by both methods which is the method to propagate this plant.

Topping and replanting

For topping and replanting - cut off the top 4 to 6 inches to replant as new plants. Look to gather long individual stems. Uproot and discard the older rooted portion. Plant the new tops in a staggered fashion with taller plants in the rear and shorter plants in the front. Leave a finger's width space between each plant as the plant will produce side shoots over time to fill the space. This approach should be used when the bottoms are deteriorated or infected badly with algae.

Cutting off individual heads

To trim a bush without replanting, look for heads that stick out the most, then trace the individual stem down to where it connected to the main stem and cut off the individual stem at that point. Large bushes can be regularly thinned by using this approach without up rooting plants. Over a longer horizon, this approach can give very neat, dense bushes as the plants will fill in available space with new heads.

In fast growing tanks, 10-20% of the heads can be trimmed away each week so that the bush does not get overly crowded. 

Syngonanthus 'Lago grande' has a spikier top than Syngonanthus macrocaulon. It is good for forming dense bushes over time.

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