Growing euphorbia’s successfully; In boxes
Rikus van Veldhuisen
Growing euphorbias successfully – in boxes. Euphorbia World 17(2)2021, page 21 – 23
In my greenhouse there is still an intensive care area, about which I wrote before in Euphorbia World (2015). The use of this few square metres insulated with plastic foil is intensive and very much appreciated. I would be crippled without it. I also still have my sewing batches in it without further protection. After germination the seedlings must not be grown to profusely in my opinion, so that they become stronger and more robust. It seems a bit odd that my usual treatment now is that after transplanting I put the seedlings in a closed small box. In the following I will try to explain.
What boxes do I use?
I use the storage boxes which you can buy at any general shop. They must be translucent and I prefer the ones without wheels and have lids which can be closed well. These boxes are available in various sizes and can vary considerably in price. It took me quite some time to figure out which kind of box fitted well in my greenhouse combined with the pots I use fitting also well in the box with not too much space left unused (Figure 1).
When do I use these boxes?
Seeds harvested of my plants or given are always sown right away, even when autumn is already well on its way. From late autumn to winter I normally store the seeds until spring before I sow them. The seedlings of seeds sown in winter are normally big enough to survive winter without much problems, when given a longer period of time no or very little water.
For many years I had problems that losses during winter of seedlings of seeds sown in late summer or autumn. When these seedlings are watered in winter time they rot and when not watered they wilt away. I must add here that I keep my greenhouse in winter 15 degrees Celsius as minimum. I am also convinced that extra heating and artificial light also will solve the problem, but I never did this, as space and costs prevented me of constructing such a device.
When I started growing seedlings in boxes I used them especially for the smaller seedlings, mostly just transplanted, sown late in the season and for which I guessed they wouldn’t make when left unprotected (figure 2).
For which species of euphorbia I use these boxes?
Especially euphorbia species related to Euphorbia milii respond very well to this treatment. The closed box prevents the seedling to evaporate too much water, which they do easily with their little succulence and large leaves. The freshly potted seedlings are watered moderately, put in the boxes, the lid is closed and the box is put on a sun protected but light place. If direct sunlight can reach the boxes, the inside temperature gets too high and the seedlings are ‘boiled’. So it is very important you find a shaded, but light spot to store your boxes.
The seedlings don’t lose their leaves and keep on growing until late autumn, or even longer. In winter I try to keep the seedlings not too wat, but for sure not dry. Best thing is they maintain the leaves, but don’t grow.
It is a bit of job to inspect the wellbeing of the seedlings in the boxes. Taking the boxes from the piles, lifting the lids, water them and if necessary remove mould and deceased seedlings is time consuming and boring. But I must say, this way of cultivation is so successful, I don’t pay any attention to them for months.
Taking the plants out of the boxes also needs some care, because if you take the seedlings out of a closed box and put the plants on the tables in the greenhouse, they will wilt and often dry out quickly and die. When I guess it is time to take the seedlings out of a box, I put the lid skewed on the box, so that fresh air can get in the box, but that there is still some protection, after a week or two plants can be put in the greenhouse when watered amply (Figure 3).
Increased use of the boxes.
Being a collector of species of euphorbia I also try to grow species of euphorbia not exactly a succulent and fit for my greenhouse. I can mention for instance some species of the milii-group from Madagascar such as; euphorbia robivelonae, mangelsdorfii and elliotii. These species are very difficult to grow in a succulent greenhouse, most likely quite easy in a greenhouse suited for Tropical orchids. Nevertheless it is tempting for me to grow these kind of euphorbia’s as well. I grow these species now in boxes all year round without much problems.
The group of species of the milii-group, growing on the forest floor in Madagascar, is well known and highly appreciated by the lovers of euphorbia’s. These are species such as Euphorbia decaryi, crassicaulis and ambovombensis. A feature of this group is that they are easy to grow, especially in home on the windowsill. Big plants grown in the succulent greenhouse sometimes start fading away and getting less and less leaves, the plants don’t die and the process might last for years, resulting in the death of the plant in the end. The reason is that the plants are stressed by too much heat, direct sunlight and spells of too little water. Needless to say these plants are old, affectionately taken care off for a long time and when in good condition; show plants. From my experience I must admit the recovery of such a plant is difficult and often with no success. I now put such suffering plants also in a box. Though it takes time, plants make leaves again and recover (Figure 4).
Positive side effect.
Storing your seedlings in piles of translucent boxes is a very efficient way to cope with the lack of space in your greenhouse. And I have still to meet the first lover of euphorbias with plenty of space in his greenhouse.
A recent visitor in my greenhouse mentioned casually it looked like a plant factory, which felt a bit awkward, but it saves me plants, place and time, what am I complaining about.
Out of direct sunlight in a corner of my greenhouse a wall from piles of translucent boxes has appeared, the seedling factory.
Little pots with small seedlings of Euphorbia ambatomenahensis just survived the winter and are starting to grow. The pots have a diameter of 5,5 centimetre.
Seedlings of Euphorbia leuconeura and lophogona are about to find a place in the greenhouse.
An old plant of Euphorbia boiteaui (decaryi) var spirosticha is on its way to recovery. Note; the new leaves are starting to grow at the tips of the branches.
Euphorbia mangelsdorfii and elliotii is not suited for growing in a succulent greenhouse, so these fragile species grow in a box all year round.
Veldhuisen, Rikus van (2015): Growing euphorbia’s successfully – intensive care, Euphorbia World 11(1): 11 – 13.