Growing euphorbias successfully- Key success-factor: Watering
Rikus van Veldhuisen
Growing euphorbias successfully – key success-factor: Watering. Euphorbia World 10(2)2014, page 11 – 13.
This year spring arrived early here in Holland and as every year the question was; when can I water my euphorbias for the first time? Actually, it is the only time I really enjoy watering my plants. I guess the fact the long resting wintertime is over and expectations of fresh new growth and flowers are the reasons of this joy. For the remaining I do not like it at all. To fix the job as quickly as possible I use the hose and easily distracted as I am when seeing something of interest, I overwater them or even I completely spout one out of the pot, leaving everything in a mess. I won’t argue with you when you tell me I am very bad at it. Even so, I put some thoughts about watering euphorbias on paper for you.
Best way to do it.
I have visited some growers who had every single plant in a separate saucer. When watering every single plant is judged for its need of water. This judging is of course how the skills of the grower are measured by. Factors to come to a judgment how often and how much water is given to a plant are many. To give you some clues;
- Is the euphorbia a very succulent one like Euphorbia obesa of nearly not a succulent with big leaves like Euphorbia species ‘Lavasoa’, the one from the previous article.
- Is it a sensible species coming from a very arid region like Euphorbia turbiniformis or does it grow naturally in wet conditions like Euphorbia ampliphylla.
- Is it grafted or on its own roots.
- Is the plant in full growth, do you want to slow it down in autumn or is it (still) in rest.
If you go along all your euphorbias with the watering pot a few times a week and you make the correct decision about if and how much you water your plants, I am convinced you will grow superb plants. For me this costs me simply too much time, or I have too many plants. In my 50 square meter greenhouse it takes me in the growing season one or two times a week an hour to water them all. As said, if I could find a way to do this automatically, at a lower frequency or shorten the time spent, I would do it, of course maintaining a certain level of success.
How do I do it?
First thing is that all my plants are in trays on the table or in hanging gutters along the sides or above. When I water I water a lot. This way I make sure all the plants in a tray or gutter have the time to soak up water and the potting mix in all the pots gets well wet. The amount of water given is based on experience, but normally I overwater quite a few trays each time I water. If there is still a few centimeter of water in it the next day, I use a hose to get the water out, the way you get petrol out of the tank of a car.
The frequency of watering your plants depends of course on the weather, the season, etcetera, but also on the potting mix you use. Some mixes can absorb much more water than others and also dry out much more quickly. My advice is to use the same mix as much as possible a mix that fits for you for as much of your plants as possible. If you use a lot of different mixes for your plants, you have added another variable factor that makes a good judgment more difficult.
Also I love to add some lava to my potting mix (about a third). This lava is soaks up water very quickly, also after it has been completely dry, and it also disperses the soaked water over the whole pot. Another thing I love about lava is that it has a much lighter color when it is dry. In other words, the color tells you how dry or wet the mix is.
Size of the plant regarding the size and form of the pot.
Small sensible species trying to grow in large deep pots is not wise. Wide shallow pots dry out much quicker than deep narrow ones, which is also the fact for smaller pots. So I put my most sensible plants in relatively smaller and wider pots. On the other hand, plants which need more water are put in bigger and deeper pots. Especially pots in which roses and shrubs are commercially grown are highly appreciated by me for this reason.
Next thing is of course I try to place in the same tray plants together with the same needs as possible. Not only the amount and frequency of water but also need of light (direct sun) or shade comes into account.
From my experience some species are very particularly about the spot where they want to grow. Many years ago I acquired quite a few times Euphorbia radians. This Mexican tuberous rooted species never was growing well for me and if it did not die right away, it didn’t come back after winter because the tuber rotted. After many trials it grows now very well for many years now after I found out it loved to grow on a shelve against the wall of the barn where my greenhouse is built against. It is a bit higher and thus warmer, the wall is west facing, so it get only a few hours direct sunlight. And also the stonewall stays cooler during the day and warmer during the nights. Quite often I find myself with a plant in my hands, obviously not happy with the way it is treated, trying to find the perfect spot for it. More than once I was rewarded for this in getting a happy growing and flowering euphorbia.
When is the right time to water?
You are inclined to say; when in growth when the plants are dry. This is not entirely true I think however. I already mentioned I water my plants on a lowest possible frequency, so I can stretch the decision of when to water over several days. Of course depending on having the time, but it depends also on the weather. A lot of growers water when it is hot and sunny. I normally wait for the rainy and cloudy day. In our greenhouses the climate can be very extreme, especially temperature. On a warm and sunny day the plants and pots can get very hot. I guess plants react to this by getting in rest or at least not grow very fast. Also the potting mix dries out very quickly.
It is like in nature I think, where it also doesn’t rain when it is warm and sunny.
First time of watering in the season.
As said I use a hose with tap water to water my plants. This is not entirely true, as I also have a barrel with rainwater in my greenhouse. It stores the water from the roof in my greenhouse. It is placed inside, so that the water is heated up a bit and not too cold. However this is far too little rainwater for all my plants, but when I can I use rain water.
Watering with very cold water is a bad thing too. Succulent euphorbias in generally need 15 degrees Celsius to start growing and when you water your plants with water of about 8 degrees Celsius, it will decline the resistance of your plants against diseases and rot.
For more than 20 years now I water my plants the first few times in spring with very warm water. It is so hot that I cannot hold my hand in it when it comes out of the hose. No hazing or spraying before and at once the full amount making them totally wet. Fresh new growth and flowers appear within a week. Losses of plants in the period of waking them up are few when using this method. The reason I started doing it this way was however the fact that some plants started to bleed from the weak growing point. These plants are becoming very ugly this way, but also they are very difficult to get going normally again. When the weather allows it and it is not too cold in spring here in Holland, I start as early as possible. The shorter the resting period is, the better I think. It is normally during the resting period I lose most of my plants. Because of this I also try to keep them going (not fast growing) in autumn as long as possible.
There are a few reasons however to refrain from watering in spring. Some species want to flower first before starting the vegetative growth. Euphorbia pachypodioides is such a species. If you start watering an adult plant of this species in spring at first signs of growth, you will never get a flower. Also a lot of caudiciform species are very vulnerable to rot if watered to early. Especially the tuberous rooted species of the former genus Monadenium are late starters and might not be watered until early summer. Even better might be to wait for the first signs of growth before any water is given.
I must admit that that there is much more to watering than thought it would when I started to write this article. Some things you do by habit and some things there is a purpose too. It is not always easy to sort them out. Thinking it over I come to the conclusion the key word is balance. Balance between growth and rest, or flowering and growth, between time and attention, treating them in groups or as an individual. No matter where you find the balance in your way of cultivation, main thing is you are enjoying it.
Euphorbia leontopoda has formed a nice new segment in less than two weeks after been woken by watering it with hot tap water at the end of March.
When is this condition euphorbia abyssinica needs quite a bit of water for a short period of time. When you continue to water a lot the new grown segment becomes tapering and the plant loses its charm.
This tray of Euphorbia poissonii and relatives looks super at first, but the growth is too lush. These plants might be more vulnerable to rotting in winter.