The Sundew Flowering and Seed-collecting Process: 

One of the most rewarding parts about growing sundews is spreading seeds around to other growers who are anxious to grow these amazing plants. For beginning sundew growers, it is also very exciting to harvest your first sundew seeds, since seeds can make great material for trades and they can also be used to grow trade material that you can use to acquire more carnivorous plants. Collecting seeds from your Drosera is very easy once you get the hang of it, but often, newer growers are concerned about the appropriate time that seeds should be collected. All of these questions and more are explained below :).

Encouraging Your Sundew to Flower
It took me quite a while to realize that flowering is primarily influenced by the amount of food that the sundew is able to catch (or is fed). Visit my sundew feeding page if you want to increase the amount of flowers your sundews produce, or if you have a full grown plant that has not yet flowered for you.

Increasing Seed Size and the Amount of Seed Produced
Most sundews will increase the number of flowers produced, seed pod size, seed amounts, and seed size in proportion to how much food they're able to catch. For example, D. intermedia 'Cuba' produces 2-4 small flowers on a short stalk if it is not fed. The seeds are very tiny and not very viable. However, if fed constantly every other week for 3 months, the plant gets much larger and produces large scapes with 10-15 flowers and comparably huge flower pods. The seeds are around 10 times the size of the miniscule seeds produced by unfed plants, and are extremely viable. This is because the plant is able to package more nutrients into the seeds, allowing them to grow faster and larger. Visit the sundew feeding page linked in the paragraph above for more feeding information.

Above- these aren't the greatest photo examples, but you can see in the top left picture of an unfed D. intermedia 'Cuba' that the flower stalk has 2 flowers on it and in the picture of the same plant on the right (fed often), the flower stalks are nearly 2x the sze and there were 8 flowers total (the picture is cut off).

While many Sundews self-pollinate, others- such as the Petiolaris sundews or some varieties of D. binata- are self-incompatible and require cross-pollination before any seeds will be produced. Other sundews, such as some of the South American varieties, are self-pollinating, but aren't very efficient at self-pollination unless extra help is provided (by manually rubbing the pollen onto the receptive part of the pistil (the female flower part). Aiding in pollination will increase seed set, and will generally always increase seed production, even with efficient self-pollinators, although they will normally produce ample seeds on their own.

The Flowering Process
Flowers
The flowers of Drosera species are classified as "perfect" and "complete" in plant biology because they contain both male and female reproductive organs in the same flower and can produce viable seeds by self-pollination (unlike Nepenthes). Sundew flowers are "complete" because they have all four types of flower structures, or "whorls":
1.) sepals, 2.) petals, 3.) carpels, and 4.) stamens (all can be seen in the diagram below).


All rights for the above diagram belong to EnchantedLearning.com

Flowering
Sundew flowers can remain open from anywhere between a few minutes to all day long. Don't be suprised if you miss your sundew flowering since it can be extremely brief! One way to tell if the flower has opened is that the petals sticking out from the sepals will

The flowers on your sundew may not open fully, but do not be worried. They will usually still produce plenty of seeds, but this can reduce the amount of seed that is produced. Bright light intensity and other factors, such as temperature and humidity can encourage the flowers to open fully. Some species, like D. binata or D. sp. "Lantau Island Hybrid" have flowers that will remain open for several hours, and can put on quite a show!

Sundews generally produce 3-20+ flowers on a single scape. In the extreme, D. capensis can have as more than 40-50 flowers per stalk when it's very healthy/fed! The flowers of the majority of sundews in cultivation are self-fertile and will self-pollinate without the need of any addtional help.

Pollination
The mechanism of the self-pollination process:
The anthers rub over the stigmas as the petals fold inwards while the flower closes. Pollen is then able to travel through the style into the ovary, where they will fertilize the many eggs that will eventually mature into seeds.
There are some exceptions, such as the Petiolaris sundews, which either require cross-pollination with a genetically different member of the same species or crossing with a different Petiolaris species in order to produce viable seed.

Why is cross-pollination beneficial?
Although it seems counterintuitive for a plant to be self-incompatible and produce few or no seeds on its own, the Petiolaris sundews and some South American Drosera, among many others, have evolved mechanisms for encouraging cross-pollination. Cross-pollination encourages genetic diversity and "fitness" or survivability of the organism. For example, consider a D. graomogolensis that is capable of tolerating warmer temperatures, but is succeptible to attack by a species of fungus. If self-pollination was the primary means of reproduction, then the plant would be able to produce many offspring, but if the fungal invader were to attack, all the offspring nearby would likely also be infected and die. However, if cross-pollinated with a D. graomogolensis several hundred feet away with a resistance to the fungus, but no tolerance for heat, then some of the offspring may inherit tolerance of warmer temperatures AND resistence to the pathogen. In this case, hybrid vigor would allow these offspring to thrive and the species will have a better chance at surviving and competing long-term.


Aiding in Pollination
When is aid of pollination necessary?
For self-fertile Drosera species, no help is required, but it can increase seed set. For example, some South American sundew are self-compatible, but their stigmas and anthers don't brush against each other as the flower closes. Thus, very few to no seeds will be produced when left alone. In this case, aiding in pollination will allow for a much larger seed set. But in the case of D. capensis, D. spatulata or D. burmannii (etc.), they are so efficient at self-pollination that aiding will only increase the seed set minimally.

General demonstration of paintbrush method on a strawberry flower, courtesy of GAP photos

To aid in self-pollination of a sundew flower, all that is needed for is a fine paintbrish. Gently rub the brush on the pollen contained on the anthers, and then stroke the brush on the styles of the carpel (the female flower organ, to right in diagram above). Alternatively, the stamens can be individually removed with tweezers and directly rubbed onto the stigmas. This method is especially useful in cross-pollination, described directly below.

Making Sundew Hybrids
Under Construction...
Some crosses, like D. brevifolia (2n=20) and D. rotundifolia (2n=40) produce a sterile but vigorous hybrid, while others can have the same chromosome counts, (ie 2n=20) and will not be viable (such as D. filiformis x D. burmannii). This is likely due to their positioning on the Drosera phylogenetic tree, which shows the relative genetic relatedness between different species of sundews.

There are a ton of different crosses that Ivan Snyder tried in this CPN paper (scroll down to the bottom) and you can compare that with the "phylogeny of the sundews" paper online, or send me an email and i'll send you a compilation of different Drosera chromosome counts.

You can see in the paper that 2 different people who try the same cross can get different results using the same plants (ie D. capensis x D. spatulata, which is a common sterile sundew in cultivation failed to germinate for Ivan, while others usually have had success). This can depend on the soil used, the conditions they're growing in, temperatures at which the seed were produced, and more...

It's usually standard to make both crosses (D. adelae x D. spatulata and D. spatulata x D. adelae) since some "mother plants" (or the seed-bearing parent) produce more seeds than the other potential "mother" in a cross between the same plants.

Drosera burmannii flower anatomy diagram Click here for the full filesize of this photo

Some sundew flowers are extremely small and you may need a magnifying glass or loupe in order to see what you're doing.

(Under Construction...)



Seeds: Ripening/Drying, and Collecting Drosera Seeds

Waiting for Sundew Seeds to Ripen
If left untouched, sundews will usually open each flower on a scape over a span of 1-3+ weeks. The flowers will self-pollinate (or be pollinated by insects), and then develop seeds in the ovary (or ovaries), which can take a while to fully ripen. In high humidity it can take anywhere from 1 to 3 months. The pods usually become dessicated and assume a brown coloration. The brown color is the indicator you should look for to determine whether or not the seeds are ready to be harvested. The drying process usually breaks down the protective barrier at the top of the bud, allowing seeds to fall out and disperse freely when the flower stalk is blown by the wind or struck by raindrops (etc.). Some Drosera species have extremely unique methods of dispersion (ie splash cups or water dispersion). I usually let the stalks on my sundews (besides D. capensis or D. burmannii) turn completely brown before collecting them. For the weedier species (including D. capensis, D. spatulata, D. burmannii, and others) you may want to harvest the stalks earlier and keep them wrapped in paper or newspaper to allow them to completely dry out before collecting the seeds. This is mentioned briefly in this youtube video.

Below is a seed ripening progression of D. sp. "Lantau Island Hybrid"


The Proper Time to Collect Sundew Seeds
Since many sundews open a scape of flowers, with one flower opening each day (or every few days) the flowers that open earliest will often be near maturity by the time the last flower opens. This isn't always the case, but it holds true for D. capensis, D. burmannii and other sundews that produce many flowers on a single flower scape. If you are concerned about losing some of the seeds, you have several options:
Option 1. Harvest the flower stalk early by snipping the stalk off at the base of its attachment to the plant, and folding it inside of a full sheet of paper. Then, you can wait for several weeks for the stalk to completly dry out, and you can unwrap it carefully to collect the seeds. Many of the seeds may fall out during this process, so they will be ready to packetize or be planted immediately (unless cold stratification is required).
Option 2. Carefully pull off dried flower buds with ripe seeds and leave the rest of the younger buds to open or ripen on the plant. Packetize or store, or plant, as desired. I have decapitated flower stalks before when using this method, so be extremely careful.
Option 3 (best). Collect the seeds early by flicking the stalk on a "hot dog" folded piece of 8.5 x 11" paper. This way, you won't risk harming the flower stalk and most of the seed can still be collected from the older ripe seed pods.

Otherwise, if you don't have time to worry about dinking with seeds,  you can allow the seeds to completely ripen on the stalk while attached to the plant, and then carefully snip off the flower stalk from the plant by holding the upper part with the ripened buds while you gently cut halfway down the stalk (or wherever you feel comfortable cutting-it doesn't really matter). Be sure to hold the talk straight up without tilting it to the side, or many seeds may fall out (depending on what species it is). Once you've prepared the seed packets or packages you're going to use, you can turn the stalk upside-down, and if the pods are completely ripened, many seeds will fall out immediately. Further shaking of the stalk will release many more seeds. If nothing falls out on its own, you will have to coax the seeds outwith your fingers by gently squeezing the base of the bud. See my youtube video on collecting sundew seeds for a more detailed explanation.

Below- early seed pod harvesting is often a good idea when growing Drosera brevifolia, since, when ripe, the seeds start to "overflow" from the pod.


Planting Sundew Seeds
One of my favorite things about sundew seeds is that a vast number of subtropical Drosera species produce seeds that can be immediately planted without having to wait a for period of cold stratification (or vernalization). This means that many sundew seeds can be sown immediately and can germinate in less than 2 weeks (if seed is very fresh---if seed is older, it can take anywhere from 2-7+ weeks).
Be sure to check out the sundew germination guide for more information.


Packetizing, Storing, and Trading Sundew Seeds
Under construction...

Additional Questions or Suggestions?

Contact me at: sundewman(at)yahoo.com

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