Growing Tuberous Sundews   Leaf of Drosera menziesii

Tubers
One of the extraordinary properties of the tuberous sundews is their ability to build tubers, which offers a very unique means of propagation!
In order to survive the hot and dry Australian summer in the south-west, the plants build subterraneous tubers, where they store energy and nutrients for the next growing season.
   Tubers of Drosera menziesii

Coming out of dormancy

At the beginning of the wet, mild winter in south- western Australia, the plants begin to bud from the tubers and emerge above ground. This process can occur quite rapidly, as demonstrated by the pictures below:

  Drosera erythrorhiza (above left) is very small (see the single grain of sand by comparsion) but quickly grew much larger in only 14 days! The pot size is 3*3 inch (7x7 cm).

Flowers

The flowers of the tuberous sundews are quite large for the size of the plant and are extraordinarily beautiful. They also normally have very pleasant-smelling aromas!

Drying out/Dessication
When the summer starts again, tuberous sundews begin to develop their tubers and their aboveground parts begin to dry out, as demonstrated in the pictures below:
   
      Drosera macrophylla at the end of the growing season and one month later

Climate and Habitat Information
Nearly all the tuberous sundews originate from semi-arid regions in the south-west of Western Australia. These areas become hot and dry in the summer months, but are wet with moderate temperatures in the winter. The plants adapt to this extreme variation of conditions by growing during the winter and then developing subterraneous tubers before the hot and dry summer in order to survive the dry period. As summertime begins, temperatures begin to rise above 70 °F (20°C) and the photoperiod reaches approximately 10 hours a day. At this time, all the parts of the plant above the ground begin dying and the subterraneous tubers are formed. Some species like Drosera gigantea form tubers up to 5 feet (1,5 m) deep in ground. At this depth, the temperatures are lower than on the surface and there is also residual moisture stored here, even though the surface is extremely dry, like a desert. When the winter time begins, bringing lower temperatures and substantial rainfalls, the tubers start to sprout again. At this time, the photoperiod is between 8 to 6 hours.
The areas in which tuberous sundews grow are usually very sandy.

Average Rainfall (mm)

Click on the chart for the full size
(This chart is based on Perth, Australia. The original data are from the Australian Government, Bureau of Meteorology.)

General Conditions for Growing

Cooler temperatures during the growing season
Tuberous sundews are picky about the temperatures. If temperatures drop below 32°F (0°C) the plant will die and you can only hope that a few roots survive to build a new plant and that this plant becomes strong enough to form a tuber, when the growing period is over.
On the other hand, if tuberous sundews receive temperatures above 75 °F (25 °C) for one week or longer, the plants will think the dry summer is approaching. In response, they will begin to remove nutrients from the aboveground parts of the plant in order to build a subterraneous tuber. At this time, it will appear that the plant is dying.
Therefore the temperatures during the growing season should be between 40 and 70 °F (5 to 20 °C). Mine are kept in the house at temperatures around 70 °F (20 °C) at daytime hold winter long and this works well.
In the dormancy season the temperatures should be above 70-75°F (20 °C) but also try avoid temperatures that are too hot. Don’t worry if there are some days with cooler temperatures, but this time shouldn’t be longer than a week or more, otherwise the tubers can start to sprout.

Average day- and nighttime temperatures
           Fahrenheit                             Celsius
Click on the chart for the full size
(This chart is based on Perth, Australia. The original data are from the Australian Government, Bureau of Meteorology.)

The Key to Cultivating Tuberous Sundews

The key for a successful cultivation of tuberous sundews is to closely mimic the conditions tuberous sundews are subjected to in nature. As you can see in the charts the temperatures in the growing season are less than 75°F at daytime (25°C) with relevant rainfalls and about 8 to 6 hours sunlight. In the dormant season the temperatures are above 75 °F (25°C) with nearly no precipitation.
If you can provide these conditions you will have fun time with your tuberous sundews :) 

Media Moisture
In the winter, while the tuberous sundews are growing, the media remains moist. The easiest way to keep the soil moist is by using the tray method- but make sure that the tubers remain above the water line. Usually this is not a problem since the tubers were planted mostly halfway up pot. But towards the end of the growing season, the secondary tubers develop and in some species (ex. D. gigantea), these tubers are formed deep in the pot. This is yet another reason to give your plants less water when the first signs of dormancy are observed. Usually, I put these plants in a separate tray, which is left completely dry. In the course of time, the watered tray becomes more and more empty and the dry one is filled up with pots, where the pots are left to dry.

Avoid letting your tubers rot!
The first time I grew tuberous sundews, I made the mistake of keeping them in an active growing state for as long as possible. I thought as long as the plants are growing it is better to keep them moist, and I only stopped watering them when they were nearly brown. The result was that many of the tubers rotted. Keep in mind that at the time the first leaves becomes brown, the tubers have already started to form. I know it’s hard to see a healthy plant to die of thirst and not to give it even one drop of water, but they expect and need this.

Humidity
Generally tuberous sundews are not so picky about the humidity. In the growing season (in habitat) there is between 60 and 80% relative humidity and that’s the range you should try to attain. Humidity can be controlled by a range of options- for example, there is about 100% humidity in a closed glass container and 20-50% in an open glass container in the house (depending on the time of year). While tuberous sundews can grow in very low humidity, it is not recommended to let them grow open in the house without the tray method because they will produce little to no dew, and won't be able to digest insects/food as easily.

Feeding
Tuberous sundews should to be fed, too. You can follow these guidelines for feeding.
If your plants have small leaves, it’s generally better to use very small portions. The small leaves usually have the strong tendency to die after they have digested something, regardless of if they are fed or have caught a meal by themselves. Therefore I don’t feed seedlings or small plants until they have at least 5 or more leaves. I usually feed one leaf of each plant every two weeks.

Feeding Rosetted Tuberous Sundews

Light
Like nearly all sundews, tuberous sundews need a lot of light, but they don’t have very high requirements because they are usually growing in the cold season, when the light intensity is low. Plus, as you see on the chart below, the natural photoperiod is between 6 and 8 hours during the period that they are growing.

Growing tuberous Drosera in a greenhouse (or using additional lighting)
Therefore, if you grow them in a greenhouse at an appropriate temperature during the winter, you probably do not need any additional light. If the plants don't obtain full coloration under these conditions, this is not necessarily harmful (as long as the plants are still producing dew). If you desire to provide supplemental illumination, it is better to add the additional lighting while the sun is shining rather than extending the photoperiod.

Solely Using Artificial Light
Tuberous sundews can be grown very well under artificial light, but in this case, the temperature needs to be monitored carefully. Most artificial lights produce heat (most notably T-5 fixtures). This can be a problem, since heat seems to be the most important factor that controls the biological clock of tuberous sundews. Under artificial lighting, a constant photoperiod of 8 hours in the growing season works well.

Average Hours of Sunlight (Photoperiod)

Click on the chart for the full size
(This chart is based on Perth, Australia. The original data are from the Australian Government, Bureau of Meteorology.)

How to Plant and Unpot the Tubers
There are good advantages for either letting the tubers remain in the pots or digging them out. I usually dig them out, which has the following advantages:

• If you have the tubers in bags, you have the control to diagnose problems if/when they arise (such as if the tubers start to rot or dry out).
• You can be happy about the secondary tubers when they form! That’s always a bit like X-mas :)
• Sometimes the secondary tubers are all clumped together. Next time you can plant the tubers at an appropriate distance from each other.
• Last but not least, tubers make great trading material!

On the other hand, in the nature, nobody digs tubers up (apart from poachers) and they still grow very well. In any case, the disturbing of the tubers is unnatural for them. Once someone asked me whether I dig out the roots of some African sundews, too, if they die back above the ground for the summer dormancy. Hmmm ….. that’s an argument.
Anyway, if your collection of tuberous sundews becomes huge enough it’s simply a question of time to dig them out or not.

How to Unpot, Collect, and Store Tubers

When to Collect Tubers
The important question is when to unpot tubers. The right time is about one or two months after all the aboveground parts of the plant became brown and dry. Then the media should be nearly dry. Raise the pot a little to feel the weight. If it is dry it’s much lighter.
Turn the pot around so that the media comes out. Carefully tear the media into 2 chunks. Usually you will see the first tubers, because it seems that the media prefers to break at the parts where the big tubers are.

Hunting for Tubers in the Pot
Now a very difficult part starts, the tuber search. You have to crumble all the media and look carefully for small tubers. If you have a species that has dark red tubers, you are lucky. If the tubers are white, the little ones will look just like the sand grains. It is a good idea to orient yourself with the dried parts of the plant and then follow them until you hopefully find a tuber.
If you start hunting for tubers too early, the formation of the primary and secondary tubers will not be complete and the roots will still be white and thick. If you disturb the plant in this condition, it’s usually not possible to “re-pot” it. In this case, treat the whole tuber-root like a normal tuber and hope that the tuber-development process will continue. If you don’t break the root in the process, it will usually work out just fine.

Storing the tubers during the Summer
At this point you have 2 options:

Option 1- Leave the tubers in their pots for the summer
If they should remain in the pot the media may not become totally dry. In nature the tubers are formed deep underground, where there will be residual moisture to keep them alive. So the key is to maintain some residual moisture in the pots- but not too much! This isn't a problem- store the pots somewhere that is protected from sunlight and will not become too hot. A dark place under the shelf in a greenhouse or somewhere in a room is good (or in the garage). During the dormancy period, you should give the tubers daytime temps of at least 75°F (20 °C). This is easier than it sounds...

Option 2- Dig up and collect the tubers for summer storage 
If you dug out the tubers, separate them from bigger clumps in order to avoid rotting-- but do not try to separate them forcefully. This can cause damage to the tubers. Some tubers form a papery cover, which are the remains of the former tuber. This is to protect the tuber and should not be removed. If it does fall apart, then it will usually still be alright. Once you have the tubers, store them according to the following directions:

• Keep them in a dark place
• Keep them in closed containers. Plastic zip bags or small plastic containers work very well
• do not forget to label the bags- or better, put the plant label into the plastic zip bag
• Store them at about 70 to 75 °F (20 to 25 °C)
• Check up on the tubers from time to time (weekly to monthly) in order to see whether they are drying out, rotting or start to sprout
  

Only in very rare cases do problems occur. If they are drying out then you can put a well squeezed-out piece of moist spagnum moss into the bag. in order to rehydrate the tuber. I've made this some times and in one case, when I controlled the bag, mould developed and already had overgrown the tuber. In the end, the tuber did not survive. In other cases it works well. So be very careful, and practice makes perfect!
Next time I will try to sterilize the sphagnum before use, maybe by treating it in the microwave oven. OK, that's not a sterilization, but it surely will reduce the microbiological contanimation.
Some others use to put some nearly dry media together with the tubers into the zip bag. Alternatively, you can re-pot the tuber into nearly dry substrate.

Potting up & Planting Tubers
Pot Height- Use Tall Pots
In the literature, it is commonly mentioned that tuberous sundews need tall pots. This is very true for adult plants. The height should be at least 4 inches (10 cm). In my experience, this height works very well for almost all tuberous sundews. It has been reported that if the pot is too short, roots may grow out of the holes in the bottom of the pot. These longer roots usually form tubers, too, so be careful not to break them. However, I've grown tuberous sundews since 2005 and have never had this occur. For seeds and young tubers, smaller pots will work just as well. I usually sow the seeds in about 2-inch (5 cm) tall square pots and repot them in 3 or 4 inch (7.5 to 10 cm) tall pots. That works well for many winter growing drosera species as they initially have only short roots and can be placed on fresh substrate easily. Exceptions for this are all Drosera menziesii ssp. and Drosera bicolor. These species produce a long, fine root approximately 1 cm long before showing their first leaves. Still, re-potting these is not a problem if the sowing mix contains lots of sand and just a little peat. At least the top ½ inch (1cm) should not contain too many long fibers which can make repotting a time consuming business. It sounds complicated but it becomes routine in a short time. The tuberous sundews don’t require wide pots as long as they don’t form large rosettes (such as Drosera erythorhiza). The 40 tubers in the picture at the top of this page were collected from a single 4-inch-tall (10cm) square pot with a width of 3x3 inches (7x7 cm).

Preparing the Appropriate Soil for Tuberous Sundews
Tuberous sundews generally require a loose, sandy substrate. I grow nearly all my tuberous sundews in a mix of one part sieved peat to one or two parts white silica sand (with a grain size of 1 to 5 mm). If you do not want to sieve the peat in order to obtain the finer powder, try to collect some that is not too fibrous. Sometimes the addition of perlite and vermiculite is recommended, but my plants grow well without them. White silica sand (or light colored) is recommended. When you are looking for small secondary tubers, later, the sand color becomes important. When I first started planting my tuberous sundews, I used sand that consisted of small green, red, white, beige, brown, black opak and transparent grains. While this coloration is nice for an aquarium, it is a pain if you are looking for small secondary tubers! When I pot tubers, the top 0.2 inch (0,5 cm) of the media is pure white silica sand because of the following:

• light is a better reflected, keeping the roots cooler
• algae, moss etc. are discouraged, or will grow more slowly
• it simply looks better

Preparing the Soil in Pots
The following is meant for tubers that have already built a stolon and have started to grow. If you want to plant tubers while they're still in dormancy, then use soil that is nearly complete dry and start to water once the first signs of life are seen:
First prepare the pot with the media from directly above. The media shouldn’t be sopping wet, but just slightly moist. I usually prepare just enough media for the pots I'm going to use (don’t forget to rinse the media first if using low quality peat). I then press the water out of the media as much as possible and loosen it back up again before putting it into the pots. Don’t press the media too much into the pot - it should be compact, but a little bit light, too.


Planting the Tubers
Tubers have an eye! From that eye the tuber will start to grow and if the tuber didn’t build a stolon by the time you want to pot it, then this eye should be potted facing up. If not, the tuber will still grow, but the new stolon have to grow around the tuber in order to reach the surface, wasting energy and nutrients. Planting the tuber in the right direction is somewhat challenging. I use a tweezers, but you have to avoid pressing the tubers too much in the process.
When the tuber is positioned correctly in the hole, fill the hole with pure sand. Don’t press the sand down- let it only trickle into the whole, so that the new stolon will not be damaged and can easily grow towards the surface.

Tuber of Drosera tubaestylus with an eye that is only slightly observable.

Raising the Tubers
Now you can put the pot somewhere. If you potted tuber, which already started to grow, then put for instance with a pipette a few drops of water onto the sandy hole. If the tubers you potted did not have stolons, don’t water the pot at this stage. The residual moisture in the pot will be enough for the tuber. Until the stolon reaches the surface, the pot will not need light.
When the first green part of the plant is seen emerging from the soil, put it somewhere that suits the recommended growing conditions and start to water it. I used to adapt them slowly to more water by watering a little from the surface of the soil at first. Several days later, I used more and more water until after about two or three weeks, they were standing permanently in the water (about ½ inch (1 cm) deep) until the growing period is over. This is a safer method, but you may find that your tubers will be able to handle standing water immediately after budding from the surface.

How to Adapt tubers from the Southern to the Northern Hemisphere
Because of the tilt of the earth's axis towards the sun, the seasons of the northern and southern hemisphere are reversed. When there is the summertime in down under the north Americans and Europeans are cold and when the Northern’s are having barbeque in a hot summer night the Aussies are wearing winter clothes.
Because the tuberous Drosera are heavy adapted to the climatic conditions of the southern hemisphere, they need to be acclimated to the reverse seasons if they are brought to the northern hemisphere, which can be quite challenging.
If you are getting tubers from Australia, you will usually get them from January to March and then there are three different possibilities:

1. The tubers won't sprout until the next growing season (happens rarely to never).
In this case, you’re very lucky! If the tubers remain without getting rotted or shrivelled because of dehydrating and didn’t sprout, then let them remain like this. If they don’t sprout during the next autumn, then pot them and very lightly water them (dropwise!) to coax them to sprout. This is a hypothetical situation, since this has never happened to me and I never heard about it happening before.

2. The tubers start to sprout after you receive them (happens often).
This happens quite often because the internal biological clock of the tubers triggers them to start sprouting in April or May, which is the beginning of the growing season in Australia. When this happens, you need to pot the tubers as described above.

Above a tuber of Drosera whittakeri ssp. aberrans with stolon read for planting

The key is to give then a short growing period. Water them and let them grow, until they reach their full size. Let them grow for about one or two months and then stop watering. Because of the short growing season, the plant can’t collect enough energy and as a result, the tubers will be smaller than when you received them.
Because of the summer temperatures, it is possible that they will start to dry out even though they are still in wet media. In this case, immediately stop watering when you see these first signs. I have lost some tubers because they've rotted at this point. Now let the pot remain like this until you see a new sprout coming out of the soil. If everything works well, this could happen when the temperatures are dropping in winter. But usually, they are a month or two later for the first or second seasons. So don’t worry if the others are emerging and the new ones are still in dormancy, possibly dreaming of flies and cold, wet weather :). If the new plant is coming out during the winter, then you've managed to adapt them to your conditions!

3. The tubers grow continuously until the next summer (happens occasionally).
If you are at the point that the tubers start to grow, you potted them, let them grow, and even if you stop watering the leaves don’t become brown, then you have 2 choices:
a. Water them again in order to let them grow the whole summer long OR
b. Wait until they will dry out
This is a difficult choice to make. Apart from some species, which are known to grow whole year long like Drosera gigantea and Drosera auriculata, I would recommend not watering them again. However, it depends on the circumstances.
An example/experiement:
This winter, I got some tubers from Australia and there were 3 tubers of Drosera zoneria, too. As normal, all of them started to grow, so I potted them. Following the things I wrote above, about three months later, most of the pots were totally dry apart from Drosera zoneria. These plants didn't show any sings of drying out even though I hadn't watered them for a month. Because all the other tuberous sundews standing next to this pot dried out and this one didn't, I decided to give it very small amount of water. Next winter I will write about the results.
Next winter: It was hard not to cry! I lost all three tubers of D. zoneria. ASt the end the plant became brown, the media was nearly but not totally dry, and they were standing at a place where all the others were standing, too. In the mid of january I could not bear it anymore and carefully look for the tubers and found only three shrivelled hulls. Probably the media was to dry.

Propagation Techniques for Tuberous Sundews

Propagation with Tubers
The easiest way to propagate tuberous sundews is via tubers. This is because the only thing you'll have to worry about is meeting the conditions for good growth of mature plants, stated above.
At the end of the growth period, when the aboveground parts of the plants are dying, one larger tuber is usually formed along with some little, small secondary tubers.
Depending upon the species, varying amounts of small or large tubers will be formed. Three years ago I got one adult tuber of Drosera menzisii. This year, I dug out 40 tubers of different size (probably some of them were grown from seeds which fall onto the ground). On the other hand I got a tuber of Drosera stolinifera. Year by year its single tuber becomes bigger and bigger, but it never formed little additional tubers (the five tubers on the pictur are from different sources).
Of course, the formation of additional tubers depends on how much energy the plant have. As expected, providing your plants with better conditions and feeding them regularly will increase the likelihood of obtaining material for propagation, such as seeds, offshoots, or small tubers.

Tubers of Drosera stolinifera                        Tubers of Drosera macarantha

Tubers of Drosera gigantea                           Tuber of Drosera andersonia

Obtaining Seeds from your Tuberous Sundews
Apart from tubers, seeds are the only other easy way of propagating tuberous sundews. While it can be quite tricky to germinate some tuberous sundew species (sometimes taking over 3 years for the more difficult species), seeds have the advantage that all the resulting plants will be genetically different. If you want to obtain seeds from your tuberous sundews, this is important to consider, since most tuberous sundews need to be cross-pollinated with genetically different plants of the same species in order to produce seeds (or with a different species that is compatible, which will sometimes create a hybrid). If you have multiple plants that were formed from the same parent or if one plant is the off-shoot of the other, then cross-pollination will usually not work.

Germinating Tuberous Sundew Seeds

The "Easier" Tuberous Sundew Species that don't need Stratification
Drosera macrantha, Drosera peltata and Drosera auriculata
The best time so sow seeds of these species is from August to September. About one month after sowing, the average daytime temperatures should be kept under 20°C (70°F).
Keep the seeds wet and with natural (shortening) day length. Seeds will germinate when the photoperiod and the temperatures are appropriate, mainly from October to December.
Besides the photoperiod and temperature requirements in this paragraph, you can follow the seed germination guide.

Hot Stratification of Tuberous Sundew Seeds- 3 options
In nature, the seeds of tuberous sundews will remain for at least one season on the hot surface of the ground, where occasionally bush fires break out because of the hot and dry climate. It seems that nearly all species of tuberous sundews require these hot temperatures and bush fires in order to germinate.
Again, the key to successfully cultivating of tuberous sundews is to closely mimic the conditions tuberous sundews are subjected to in nature.

Option 1: Sow them in august and keep them hot (about 85 °F (30 °C)) and dry until mid-end of September. Then Keep them wet and at natural (shortening) daylight. Seeds will germinate when light period and the temperatures are appropriate, mostly from October to December.
This year I tried to see whether it is possible to store the seeds from August to mid-September at around 85°F (30°C) before sowing them. This should work just fine and seems to be an easier alternative to keeping all of the sown seeds in pots at this temperature...

Option 2: Pack the seeds in some "tea-bags"-like material. I fold small envelopes out of filter paper from the coffee machine. Don’t forget to label the filter paper.
Now burn some plant debris. I use the dried parts of the tuberous Drosera, which I collect. Extinguish the fire with hot water and filter off the larger remains for instance through a coffee filter. Wait until the water has cooled down to about 140 °F (60 °C). Then put the seedsbags into the hot water for 30 to 60 seconds. You can sow the seeds right now, but it is easier to sow them when you first let them dry. Sow the seeds and keep them wet and at natural daylenght. Seeds will germinate when light period and the temperatures are appropriate, mostly from October to December.
I did not try to leave the fire part out. I expect it should work as well, but that remains to be shown.

Option 3: I am sure there are more options for the stratification like soaking with GA3 (Gibberellic acid, a plant hormone that stimulate rapid root grow and increase seed germination rate), but those are the ones I use and which I find quite easy to use even with larger numbers of seeds/species.
 
      Drosera menzisii var. basiflora with flower and seed vessels

Leaf Cuttings
There is only one species of tuberous sundews, Drosera auriculata, with which successful leaf cuttings have been reported. I've never tried this and would not recommend it, because tuberous sundews usually have only a few and/or small leaves in comparison to other sundews. Plus, tuberous sundews need the nutrients and photosynthetic products from the leaves in order to develop tubers.

Root Cuttings
It seems that root cuttings are not possible for tuberous sundews. I've never heard about anyone doing this successfully. Therefore, I would strongly discourage taking root cuttings from tuberous sundews, since you will probably end up harming the plant.

Literature
If you are interested in literature about tuberous sundews you will always read one name: Allan Lowrie. He discovered many species of tuberous sundews and other carnivorous plants in Australia.
He has published three books about the carnivorous plants of Australia. The first volume of this series is solely devoted to tuberous sundews.
Unfortunately, the first two volumes are sold out worldwide and the last one is as far as I know, not available, either. Sometimes these books are offered on the web for extremely expensive prices. Some carnivorous plant societies have a borrowing service for members, where you maybe can get them for a while. They're also available at quite a few libraries.

One species is named after Allen Lowrie: Drosera lowrie

Additional Questions or Suggestions?

Contact me at: sundewman(at)yahoo.com