Growing euphorbia’s successfully; Intensive Care

Rikus van Veldhuisen

Growing euphorbias successfully – intensive care. Euphorbia World 11(1), page 11 – 13.

Some time ago, when presenting a slideshow on euphorbias, a guy asked me: ‘How on earth can you grow Euphorbia guillaminiana for a longer period of time?’ I replied that growing Euphorbia guillaminiana was easy. The audience was stunned and was ready to fire a lot of arguments in order to convince me of the opposite. But I continued; growing them in summer is easy and when you pay good attention if your plants flower with the between leaves hidden most of times green flowers, you are already well on your way. The rather large seeds germinate well and seedlings grow fast and without any problems in the first months. It is also quite certain that more than half of your plants will die in winter, mostly because of the roots start rotting, even when kept totally dry. So my explanation for easy was that you need at least five plants, loose most of them in winter, get seedlings in summer, so that the plants died in winter will be replaced.

One thing is for sure, some euphorbias are very hard to grow, especially getting them through the resting period in winter and/or getting them started again in spring. Needless to say, the ones we love the most are also the ones which depart the most easily. I have wondered quite regularly why put ourselves in this painful process of paying a lot of money for something we most likely will lose again most quickly and hating ourselves for it when lifting the dustbin once more.  It must be the few times a fellow lover of euphorbias shares his compliments and admiration for the beauties you managed to keep going.

However since I placed a special ‘intensive care’ area in my hothouse the death rate of for instance the above mentioned Euphorbia guillaminiana dropped drastically to well below a quarter and in some years even no plant or seedling died in winter of this species.

In winter my hothouse is kept at 15 degrees Celsius at the lowest. Most species are kept dry from early October to the beginning of March. The central heating system and the lack of watering the plants makes the micro climate rather dry in winter, which of course is good  for preventing plants to rot. But more fragile species can suffer from this and start to dry and wilt completely. When visiting fellow growers of succulent plants, I saw some them placing their plants under plastic cover with additional heating. A talk with a lover over Stapeliads convinced me to make my own ‘intensive care’ area, or normally referred to as a hotbox, when he said he had some species which required 20 degrees Celsius as the lowest temperature in winter in order to get them through wintertime. It would be far too costly the heat the whole hothouse to a temperature as high as this. He made some sort of tent of cusps plastic and on the bottom heating mats were placed. He furthermore argued that a lot of plants he usually lost in winter now were kept in cultivation by him for several years.

Soon after I went at work, made a frame of wooden slats, covered it with cusps plastic and on a layer of insulation material I placed a heating mat regulated by a thermostat. Not soon afterwards I faced the problem it was too small and was happy with the result. However some plants still died by the cause of completely drying back. When I kept them growing by watering more frequently the plants survived but etiolated too much and lost their good looks. In the end I removed the heating mat and placed a professional growth lamp, you know, the one we use here in Holland for growing Cannabis, above the plants. The growth lamp is switched on and off by a time switch. It is only switched on during the night twice for an hour. The last lighting period is just before dawn, as this is the coldest period. This way it is used both for heating the plants and providing some extra light. The drying of plants is not as harsh as when using a heating mat and plants need less watering and can be kept growing a little bit without etiolating.

So now my Euphorbia guillaminiana plants are placed in my hotbox and they seem to appreciate it. Also quite a lot of other special things are placed in it like fresh-rooted cuttings of tropical East-African spiny species, which so easily can dry completely in winter when still having thin thread-like roots. Also the seedlings of seeds sown late in the season, when kept a bit moist, survive the winter here. Some species do need higher temperatures in winter like Euphorbia neoarborescens (Monadenium arborescens) and a lot of the small tuberous rooted species of what is now Section Monadenium of the Subgenus Euphorbia. Also species of this Section, especially the arborescent ones, start growing after the height of summer or early autumn. Most of the times they are budding when other plants are going into dormancy. When these species don’t receive additional warmth and watering in autumn and winter, the flowers will wilt. Putting this type of plants in the hotbox or in your home on a windowsill will make it possible to harvest seeds of these self-fertile species of euphorbia. However not all these species are very difficult to get your hands on as they also propagate easily by cuttings and grow without any problems for you, I am quite happy to grow seedlings of Euphorbia torrei (Monadenium torrei), Euphorbia neospinescens (Monadenium spinescens), Euphorbia spectabilis (Monadenium spectabile) and Euphorbia magnifica (Monadenium magnificum).

I hope the advice and guidelines I put to you will be of use for you and will yield more success in cultivating euphorbias. As said before, what works for me doesn’t need to work for somebody else in different circumstances. Trial and error, when something learned, is the best way to get results in the end.

Figure 1

In my hothouse a central part is arranged as an ‘intensive care’ area for plants suspected not to survive winter without extra care.

Figure 2

Inside the hotbox not the tiniest little space is left unused. Above the plants a growth lamp is placed which is switched on and off by a time switch.

Figure 3

In my home on a window sill a selection of euphorbias with a very late growing season is placed in winter, so that they can finish their flowering and fruiting.