Some additional notes on the cultivation of euphorbias
Rikus van Veldhuisen
Some additional notes on the cultivation of euphorbias. Euphorbia World 14(1)2018, page 30 – 32
The knowledge that articles about the cultivation of succulent euphorbias are generally highly appreciated by our readers made me, after long hesitation, write a series about this subject for Euphorbia World. The amount of reactions and even a reprint in another succulent journal made the effort quite rewarding and I intended soon afterwards to write a next part on this subject. Again this proved to be a step postponed many times. Rereading the articles made me always conclude I had little more to add. Finally I made up my mind by concluding I had since then indeed some experiences, which might be of some use to our readers.
The easiest way of pollination.
In Euphorbia World volume 10, issue number 1, I wrote about the multiplication of Euphorbia species nova ‘Lavasoa’. The argument made was that pollination of the very small insignificant green flowers is time consuming and with a very low success rate. Growing new plants from cuttings taken of the thick rootstock proved to be a much more easy way to get more plants looking very similar to a seed-grown plant. I must admit now that this isn’t true. The year after I had put my plant next to the open door of my greenhouse. The plant was visited frequently by bees and flies and the result was it was loaded afterwards with fruits. This plant grows easy from seed and the result was I had many seedlings to spare next year.
Since then I have repeated the procedure many times for several species of euphorbia. For instance Euphorbia ambovombensis, with the small nodding flowers, is also time consuming to pollinate, however the success rate is usually very high. Placing my large plants a few days in between the flowerbeds of my garden yielded huge amounts of seeds without using the brush at all.
Better results in sowing euphorbias.
In Euphorbia World volume 10 issue 3 I have already explained how I am sowing my seeds of euphorbias. The seeds are planted in a commercial sterile sowing and cutting mix as soon as the seeds are harvested during the season. Normally germination is within weeks. Of quite a few species the seeds can be considered lost when they do not germinate instantly. A good example of this are the species of the Madagascan Milii-group, better referred to as the Section Goniostema of the Subgenus Euphorbia. But some species germinate very erratically, such as the Medusoïd species, or now called the Section Medusa of the Subgenus Rhizanthium. I have already explained it is a good trick to place the sowing pot out of the hot and humid area and place it sometime in a colder and shadier place. This sometimes leads to an astonishing wave of seedlings. But sooner or later one has to repot the bigger seedlings, or one waits to long repotting them and you find out the roots or the complete seedlings are rotted.
I found out now that repotting the seedlings one by one is not necessary and I place the whole clump of potting mix with the seedlings in a bigger and much deeper pot. One has to keep this in mind when sowing the seeds and not put to many seeds in one pot, thus preventing the seedlings are standing too close together for healthy growth later.
I suppose the accompanying pictures show clearly the benefit for this procedure and especially for the rarer species this is very rewarding. And as a result the roots are not damaged by repotting the seedlings, so the growth in the first year is better. Seedlings of Euphorbia punicea in figure … are sown 4 months before the picture was taken. The tallest ones are 10 centimeter high, but even more important, look at how small the smallest ones are. I guess these are only a month old or so and these seeds would most likely have been thrown away in the process of repotting the larger seedlings.
Propagating euphorbias, a very unusual method.
Some species of euphorbia are considered very hard to grow on their own roots in cultivation. For this reason these species are normally grafted on a less demanding stock. Some East African species are very vulnerable of drying away during the resting period in winter. You give them some water and they rot. If you don’t water them they just dry away, especially smaller plants. For this reason I grow some of them as a grafted plant. Not for reason of esthetics, but just to be more sure to keep some material alive. Sometimes the grafted plants throw out new roots where the graft has grown onto the stock. I have never fancied this phenomenon, however it doesn’t occur very often. I normally cut away the roots hanging useless in the air or even sometimes root the graft after cutting off the stock.
I also grafted some branches on my favorite stock, Euphorbia candelabrum, of a yet to be named euphorbia from Kenya. This plant looks like euphorbia turkanensis, but comes from Maktau, a very different area. The normal procedure, when repotting grafted plants, is to sink the stock a bit in the bigger new pot. For some reason I didn’t cut off the roots of the graft this time, but put the plant back on the shelve. Later I noticed that on every place, where the roots touched the potting mix, little new plants emerged. It reminds me of the way how strawberries are propagated. where the runners touch the ground a new little plant grows. However in this case the air born roots, and not runners, make the new plants. As it is now too late in the season, I will not do a thing just now, but I intend to cut off all the tiny new plants in spring. Also I will not cut off the roots of grafted plants anymore, but when repotting, I will lower plant and leave the tips of the roots just above the soil. I hope to repeat this trick some more times.
So far my experiences this time. I hope they will benefit you in some way, not in the least place to increase your joy in growing euphorbias.
Young seedlings of two medusoïd species. Not the different age of the seedlings. I wouldn’t be surprise if these still will more seeds germinate eventually.
Four month old seedlings of Euphorbia multifolia (in front) and Euphorbia punicea. Note the different size (and age) of Euphorbia punicea.
A grafted plant of Euphorbia species nova, Maktau, Kenya, with the stock lowered in the soil when repotting.
The same plant as in figure 3. It is clear to see this is a grafted plant and where the roots start growing out of the graft.
On one side of the same plant the stock has completely disappeared behind the roots and a serious amount of little plants are borne where the roots touch the soil.