Growing euphorbias successfully – getting more of them: Sowing

Rikus van Veldhuisen

Growing euphorbias successfully – getting more of them: Sowing. Euphorbia World 10(3)2014, page 22 – 25.

I guess it is true for all lovers of plants: After managing the skill of growing your beloved plants and having multiplied them by taking cuttings, the next thrill is to raise them from seeds. Most of you will not argument with this hypothesis and think back about the time, not long after taking up growing succulent euphorbias as a hobby, with much pleasure when for the first time a batch of seedlings was repotted.

Some species don’t produce cuttings and for a lot of species sowing is the only way is producing a plant looking like the original natural specimen. The number of species with a tuber or a many angled central stem are too many to mention and these species are only reproduced by seeds as an original looking plant. So the skill of harvesting the seeds and raising euphorbias from seeds is a necessary skill for a grower of succulent euphorbias. Unless of course you buy your plants at a succulent sale, but then you refrain from the joy and pride to witness the amazing development of your own sown euphorbia from a single little seed to a full grown adult plant. In many cases a seedling looks very different from the adult plant. I remember all too well the first time I had sown Euphorbia borenensis. The fiercely spined, beautiful marked, 6-ribbed stems looks totally different 4-ribbed, nearly spineless stems of the adult plants. It is just an examples the surprises you are in for, when you start sowing euphorbias. And of course the other result will be magnificent additions to your own collection and happy fellow collectors made happy with your spare seedlings. Are there more reasons needed to get started.

Getting seeds.

For by far the most species of euphorbia are grown from seeds easily. The problem is to get the seeds. For nearly all species the fruit explodes when ripe and the seeds are thrown away for meters. On top of this the ripening of the fruits may take a long time and just as easy go very quickly. This may mainly depend on the weather, but also be genetic. I grow a new species of the milii-type, a very robust plant with thick stems and large white flowers. But the fruits ripen in a just a few weeks and are hardly visible between the large cyathophyls, which is of the same color as the fruit and is incredibly small for such a robust plant. So it is easily overlooked and it took me several years before I noticed the fruits at all and was able to harvest some seeds. After that getting seedlings was very easy.

Another annoying habit of our euphorbias is that when the seeds are packed somehow or the plant is put in a closed container, the fruit stops growing, the seeds don’t ripen or the fruit wilts away totally. I have no solution for this problem any other than use an open material to put the fruit in. I have seen many possible materials for doing this trick, such as cotton wool or a piece of lace curtain. Cotton wool is very effective for catching the sticky seeds of Euphorbia obesa and E. meloformis. Also it is easy to use for these species as the fruits are quite often closely pressed together in large numbers and the cotton wool can be placed simply over the fruits. I use very frequently a pyramidal Lipton tea bag, of which I have taken away a small portion of one side. This lets the tea out and make it possible the tea bag is placed over the fruit. I even let the little rope attached to the tea bag, as this rope is quite handy. The rope can be attached to a branch of the fruiting plant and can pull the tea bag so that the opening is pulled side- or upwards and the seeds can’t fall out of the tea bag when the fruit explodes. Very conveniently quite a few species of euphorbia have a long peduncle bent downwards when the fruit is not yet ripe, but when ripe the peduncle stretches upwards and signaling, please put the tea bag over. What also suits me that using this method, the motherplant can be left on its original place on the table or in the gutter. It has happened more than once that a nice plant, loaded with fruits, was taken out of its place and put somewhere in the shade in a bucket, rotted away when left too long waiting for the fruits to ripen. This doesn’t mean I don’t use this method, I have a whole collection of plastic boxes of all sizes, which I can close with a lid. Jaap has a lot of success with some large old aquaria.

Sometimes the fruits develop seemingly normal, but after ripening they don’t blow away their seeds. Normally this means the seeds are not viable, but not always. I have successfully raised a lot of plants from seeds I had to peel out of the fruits myself, amongst them also very rare ones. This year I had some fruits on my Euphorbia odonthophora. I grow two different clones for many years and as they were flowering at the same time, I had high expectations. However I had poor result as only a dozen of fruits ripened and even so, the fruits didn’t explode when ripe. I broke the fruits myself and there was something in it, but I had never seen such small seeds of any euphorbia. I was about to throw it all away, but wanted E. odonthophora seedlings so badly, I thought; ‘What the heck, I try it anyway’. I am now happy to grow five seedlings of Euphorbia odonthophora, not only for having them, but also for seeing my stubbornness being rewarded. So don’t be too hasty to throw away not exploded fruits. To peel out the seeds I use a knife and I don’t need to mention it is a weary and time consuming job to do.

As a rule, with some exceptions, euphorbias have only three seeds in a fruit and the difficulty of harvesting them, you know now why the seeds of euphorbias are so little offered in trade and when, they are expensive and little in numbers. Your Society had several attempts to start a seedbank, as there was always a great demand for such a service, but the scarcity of seeds led every attempt to a failure.

A last loose remark about euphorbia seeds. I have noticed several times a rather large variability in size, color and or form of euphorbia seeds. However the varying seeds were viable and also frequently from a single plant. Many years ago there was put a large value to characteristic features of seeds for determinating species of for instance of cacti. In euphorbia this was never the case, perhaps of this reason.

Sowing the seeds.

As we have the seeds now, the most difficult part has been done and we have to raise the seedlings now. For by far the largest number of species of succulent euphorbias this is easy. For most of the species the seeds are large, the seedlings are not vulnerable and grow fast.

However a lot of species have seeds which do not stay viable for a very long time, especially euphorbia  species from Madagascar have to be sown within weeks. I normally sow the seeds right after harvesting them.  Only from around oktober to march I store the seeds, but this already yields me poorer results in terms of germination rates. This also means I sow seeds a few times a week and don’t do this a few a times year and then in larger numbers. And as with watering I prefer to put in as little effort as possible. I normally use square 6 centimeter pots and fill these with a commercially produced ‘sowing and cutting mix’ bought at the garden center next door. This mix is always available and always more or less the same, so I know how it behaves regarding water saturation and also important, it has been sterilized.

In my glasshouse is a section, which I call ‘intensive care’, I hope to come to that in later chapter of this series. In this ‘intensive care’ area I have plastic trays. In one of them is a tempex box in which perfectly fit 20 square 6 centimeter pots. After the pots have soaken up plenty of water from the bottom for a day or so, the freshly sown batches are put here first. This is a kept a bit more wet than the rest of my plants, but not too wet, and certainly less wet than what I have seen a lot of fellow euphorbia growers do. Also the freshly sown seeds are not more protected than my other plants, no extra bottom heat, neither are they put in closed conditions such as a plastic bag or under glass. I am convinced the result is that I get mot hardy and resistant seedlings than when they are raised in too favorable conditions. Sometimes the seeds take a long time to germinate, especially the medusoïd ones. If they don’t I place the pot with the not germinated seeds in a colder place. More than once germination started right away. I guess it is like in nature, rain normally comes with colder temperatures.

Another thing I am used to is that I plant the seeds one by one, the smallest ones not more than 25 in one pot. This way the seedlings can grow bigger before they have to be repotted and can be potted in a 5,5 or 6,5 round plastic pot in one move.

Having said the tempex box is kept a bit wetter, when good germinated the pots with seedlings are taken out of the box and placed next to it in the tray and kept dryer. Never let the pots dry out totally, as it will take an effort to get them growing again and also this will result in loss of seedlings. The seedlings are never placed in full sun, but are having a good amount of light.

I mentioned before euphorbia seedlings are easy to raise in general. But of course there are exceptions to this rule. I only managed to raise Euphorbia immersa sown in pure clay. When there was just a trace of peat in the potting mix the seedlings rotted away. Using the method with success for Euphorbia immersa, I have tried it also for Euphorbia turbiniformis, piscidermis and horwoodii. Several attempts over the years have yielded batches of small seedlings as big as the pin of a needle. But that’s as far as they came, staying in the pot for years, but never I was able to get them growing any bigger. Recently good seedlings of Euphorbia horwoodii are offered in trade, so there is somebody around, far more skilled than I am, and this person is invited to write additional lines for Euphorbia World on this subject.

One final little story I must add as a conclusion. Many years ago I was always amazed by the fact seedlings were popping up everywhere in the collection when visiting Jaap Keyzer. Some of the species just growing around everywhere (in my memory) I was even unable to grow. I guess this is a very natural thing and is proof to the fact the grower has been able to get near natural conditions in his greenhouse. Since I have built a bigger and higher greenhouse myself this is also case for me. Once I had forgotten about a fruiting Euphorbia micracantha and the seeds were blown all over my collection. For several years I have found seedlings of Euphorbia micracantha by the dozens. Recently I even found a seedling of Euphorbia immersa in a pot destined for Euphorbia celata. Of course this was a surprise and I took the seedling out with care, potted it up and placed it in the ‘intensive care’ area. It immediately rotted. What I want to point out is that they have a mind of their own, there is no way of getting a hundred percent success rate, no matter how skilled you are. Sometimes it seems to go very easy, sometimes it seems impossible. That makes it interesting and keeps us busy.


Figure 1

The pots with the older seedlings are standing in front of the tempex in which pots, kept a bit more wet, with germinating seeds are kept.

Figure 2

Clearly is to be seen here the seeds are planted and every one of them has the space of growing until nearly one centimeter in diameter before it has to be repotted.

Figure 3

A Lipton tea bag has been put over a fruit of Euphorbia transvaalensis. The string attached pushes the opening against the peduncle in order to prevent the seeds falling out of the tea bag.

Figure 4

A seedling of Euphorbia (Monadenium) torrei sown in spring and pictured in at the beginning of October and already 7 centimeters high.