How to grow Sphagnum

How to grow Sphagnum

How to grow Sphagnum

The essential element in the cultivation of the sphagnum is water.

The water has to be strictly demineralised (or, if you live in the countryside or in places without smog, you can use also rainwater). Instead, for what concerns the choice of the substrate, it depends on what you want to obtain. Here follow the examples:

Cultivation in vase:

If you need just a small quantity of sphagnum to use for some carnivorous plant, it might be enough to put the heads in vases of the plants you already have, as long as they have a substrate of peat, or a mix of peat and perlite. To make sure that the heads don’t die in a short period of time, you have to spray them with water at least once a day to clean off the accumulations of tannins which tend to blacken the tips of the sphagnum. If you don’t clean them off, they will keep to accumulate to the point that they will block the growth and kill the plant in a couple of weeks. 

Cultivation in sphagnum box:

Creating a sphagnum box is best choice if you want to start your own production of sphagnum and then use it for different purposes: cuttings, nursery, to make the substrate lighter, to produce big quantities to put in bigger vases or to use it as alive elements in a humid terrarium. The point is to have always ready a growing sphagnum box so that you can take the sphagnum you need at any time.

The sphagnum boxes can be made in 3 different ways (I personally think that the 3rd method is the best one).

1 - Classic immersion sphagnum box:

This is the first type of sphagnum box used by growers of carnivorous plants, and is the one that best recreates the natural conditions of a peat bog. Some people call it floating sphagnum box, but it is quite different from the floating sphagnum box illustrated in point 3. The aim is to create a floating peaty substrate on which the sphagnum will grow. In order to build it you will have to use a plastic net, like the one used for mosquito nets, and place it at the bottom of the box to create a sort of tank with the same shape of the container. You will have to put the substrate inside the plastic net as follows: fill half of the box with 100% perlite (that will make the whole thing float), fill the remaining half of the box with a mix of 50% peat and 50% perlite. Place on the surface a layer of 1 cm (0.4 inches) of crushed dead sphagnum heads. After you put water in the container, the plastic net with the substrates will float.

Substrate of Perlite                        Immersion S. Box recently started                        Representative cross section

Pros: abundant water reserve; fertile for possibly a long time; can be used as a nursery for carnivorous plants.

Cons: the high presence of peat facilitates the accumulation of tannins on the tips of the sphagnum. The substrate tends to dissolve over time, making the underlying perlite emerge, especially on the edges. It tends to lose buoyancy. It is easy to build for its large dimensions, but once it is built it can’t be easily moved from the container. There is a risk for anoxia and rottenness of the substrate.

2 - Water sphagnum box

This is a good solution for those who need to cultivate sphagnum just for a short time, waiting for a definitive arrangement, or for those who simply want to preserve it, keeping it alive. In this type of sphagnum box the substrate doesn't have a floating purpose and the regulation of the water level is left to a tank or to the grower that will have to refill the sphagnum box with water every day. To build it just place a layer of peat (not thicker than 1 cm – 0.4 inches) at the bottom of the container or of a flowerpot saucer and making sure that is always hydrated with a thin layer of water (not more than 1 cm – 0.4 inches). Place the sphagnum on top of this moisturized peaty substrate and, over time, new sphagnum heads will grow to fill any available space. To make sure to have a minimum water reserve, take a bottle and make a small hole at the bottom (0.5 mm), place it in a corner of the container and fill it with demineralised water. This way, when the water will evaporate, some water will be dispensed from the bottle in order to maintain a constant level of water.

Water S. Box recently started                                                 Schematic drawing

Pros: Extremely easy to build; very rapid growth in the first few weeks; little accumulation of tannins; it is possible to make it in smaller versions; well-oxygenated substrate.

Cons: Difficulty in maintaining the water level stable; it can lose fertility in short time; little water reserve and impossibility to make water changes; it can’t be used as nursery.

3 - Floating sphagnum box

This option combines all the pros of the previous sphagnum boxes and it can also be widely personalized. As in point 1, it based on the principle according to which to obtain a water level as stable as possible (which is essential for a good growth of the sphagnum) the substrate has to float on the water like a raft. To avoid problems related to the poor compactness of the perlite, it will be used a styrofoam slab instead. Its thickness can vary from 1.5 to 2.5cm (0.6 to 1 inch) according to the water need of the sphagnum species: 1.5cm (0.6inches) are suggested for very hydrophilic species, and 2.5cm (1 inch) for those that bear low humidity conditions. You will have to place a cloth on top of the slab, with the edges hanging loose on at least two sides, so that they can absorb water for capillarity. As an option you can delimit the slab with edges: use four cut to size polystyrene strips applied to the slab, on top of the cloth, using toothpicks. They will help preventing the substrate and the sphagnum from falling into the water. You will have to place the substrate on top of the cloth: 1cm (0.4 inches) of peat and perlite, or just peat, and cover it with a layer of dead sphagnum to avoid, at least partially, the accumulation of tannins coming from the peat.

    6 months old s. box (edges removed)                        Sphagnum boxes with edges just started                Representative cross section

Pros: maximum stability of the substrate; abundant water reserve; little accumulation of tannins; well-oxygenates substrate; easily removable “raft”; can also be made in smaller size; more than one sphagnum box can be placed in one container.

Cons: it can’t be used as a nursery because of the little layer of substrate.

Growth conditions

The sphagnum is a plant that adapts to different environmental conditions as long as water is present. This adaptation results in a different morphology depending on how it is cultivated: changing light, temperature, water level and atmospheric humidity you can obtain different types of growth.


The more light there is, the more the sphagnum will grow compact, rapidly increasing the density.

In shady conditions it will grow rapidly in volume while maintaining a very low density. In the long term the plants will be subject to dehydration in the terminal areas here the water will find it hard to reach by capillarity.


In the cold (average temperature <15°C - 59°F) the sphagnum tends to grow slowly and to produce very small compact heads with many small twigs clumped around the apical meristem. At warmer temperatures the heads will be bigger, more widespread and they will grow faster. Exceeding the 45°C (113°F) could be fatal for some warm-sensitive species (e.g.: fimbriatum and papillosum). On the other hand, there are no limits for what concerns the cold since the sphagnum can freeze without any problem. Many species (especially the magellanicum and most of the Acutifolia section) assume a red colour if kept in direct sunlight and exposed to high thermal excursions (<15°C - 59°F at night and >30°C - 86°F during the day).

Water level:

A very high water level practically submerging the heads, allows a very rapid growth of the sphagnum with many twigs, but its structure will be soft and it won’t grow straight up. It is important to avoid the water getting overheated or polluted with too many nitrogenous substances because this will favour the growth of algae instead of the sphagnum. The species of the Sections Sphagna, Subsecunda e Cuspidata are especially suitable for these conditions.

If the water level is too far from the heads (>5cm – 2 inches gap), the sphagnum will grow more compacted in order to optimize the capillarity. The more the sphagnum grows compacted the more it will be able to grow over the water level.

The maximum compactness is achieves in high brightness conditions but not in direct sunlight: if there is too much shade the growth tends to be widespread but not compact; if there is too much sunlight, the excessive evaporation will create accumulations of tannins on the heads and on the tips of leaves and twigs, blocking the growth.

Atmospheric humidity:

Atmospheric humidity probably is the most important element for the cultivation of the sphagnum. When the atmospheric humidity drops below 50%, the evaporation increases and with it starts the process of accumulation of salts and tannins on the heads, the leaves and the tips of the twigs of the sphagnum. It is very common for it to happen also in nature. However, with the first rain, any accumulation of salts and tannins is diluted and carried away. If the sphagnum box has reached sufficient stability and compactness it can be left to the weather allowing the rain to do its job. If it is not possible (for example when you cultivate it in a greenhouse) you should frequently spray it with water or a watering can, to eliminate the accumulations paying more attention to the darker areas of the sphagnum. Normally it is advisable to do it once a day in summer and once a week during the rest of the year.


Although the sphagnum requires a low quantity of nitrogenous substances sometimes it may be necessary to fertilise it.

To avoid stressing the plant, it is advisable to fertilised it only when it has reached a density of 1 per  or greater. The approximative dosages can start from 1ml of liquid fertiliser per orchids per 100 (0.2 ) of surface, to be diluted in demineralised water and then sprayed on the heads. Wait 2-3 weeks to observe the growth effect, then repeat the process adjusting the dose accordingly. At the first sign of intoxication (blocked growth, death of the heads or development of algae) change the water and stop the fertilisation. If a sphagnum boxes has very low water reserve, it is advisable to change the water every 2 months.

Handling the cultivation:

Pruning and transplant:

To obtain a dense layer of sphagnum in the shortest time possible, it is necessary to monitor and to take care of the cultivation through “pruning” and “transplant” of the heads. In other words, in the initial stages there are few heads growing on a very large surface, they will become upright growing plants relatively isolated from the others and once they have reached an average height of 2-3 cm (0.8-1.2 inches) they will deteriorate due to accumulations of tannins. To avoid this, it is advisable to begin the spread of the sphagnum starting from a small surface on which will grow as many heads as possible. Those will develop into a small “cushion“ of tightly woven fibres. Once this “cushion” of heads has reached 2-3 cm (0.8-1.2 inches) it will be possible individually cut the heads using a nail scissors and tweezers. The trimmed heads can then be placed at the edges of the “cushion” to increase the surface covered by sphagnum. Within a month, 2-3 new heads will be born from each point where the heads were cut, and the transplanted heads will be as high as the other ones. Then, it will be possible to repeat the procedure until the surface is completely full. At this point, you will need to optimize the growth to make the sphagnum box as compact as possible. It will therefore be necessary to repeat the pruning and transplant operation by placing the trimmed heads at the base of the fibres, trying to fill the less covered areas. After 3-4 series, the heads’ density will have reach a sufficient level to let the sphagnum grow, which will tend to form a compact “cushion” capable of maximizing the hydration of the upper layer thanks to the high capillarity.

Spraying and Irrigation:

If the sphagnum boxes are not kept in a greenhouse and are therefore subject to relatively low atmospheric humidity, it is necessary to spray them with water very often (or, in case of very compacted sphagnum boxes, using a watering can). The water in the water tank can be changed, entirely or partially at the grower’s discretion, when there are too many insects’ larvae and algae.


The ideal exposure greatly varies according to the species but, in general, the best results are obtained by placing the sphagnum in a well-lit place, as long as possible under direct sunlight. During summer the direct sunlight has to be avoided for the most sciaphilic species (papillosum, platyphyllum), and for those sensitive to high temperature (fimbriatum, capillifolium, subnitens, cuspidatum). However, it is advisable to avoid putting the sphagnum in the sun if you can’t water it several times a day. You will still obtain a good growth of the plant but it won’t have its red colour.


The greenhouse is convenient for the cultivation of sphagnum, especially during winter time. However, when summer is approaching, you have to pay attention to the temperature peaks. If they reach the 40°C (104°F) you will have to ventilate.

You can obviate the decrease of atmospheric humidity watering the plants more often.


Despite his innate antifungal and antibacterial properties, the sphagnum can still be vulnerable to the attack from certain moulds, which, if you don’t promptly recognized them, can lead to the death the whole sphagnum box. This can happen especially in winter, in the sphagnum boxes kept in a greenhouse. To reduce the risk it is advisable to periodically ventilate the greenhouse and to check if there are moulds at the base of the sphagnum. If you notice a sudden yellowing of the heads, you have to immediately spray a sulphur-based antifungal on the sphagnum.

Your Comments

>>Hi, Would you say that Sphagnum cultivation is possible without a peaty substrate?<< Yes, it is possible to replace the peat with other similar substrates. The coconut fiber is fine (but not fertilized).

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