Cultivation of Agavaceae - Some How-To Hints
There are sufficient publications available where at least one chapter is dedicated to the adequate cultivation of plants. That's why we only would like to address six topics that we believe very important for the successfull cultivation of agavaceae, or rather that we have noticed in our own garden and greenhouse work.
1. Sun and Shade
In their natural habitat most agavaceae are exposed to extreme solar radiation all day long, but there are also species that prefer locations where the influence of the extremely strong sun is limited. It is not very difficult to simulate this situation with plants in cultivation if you are living in moderate climate zones and cultivate your plants in a greenhouse. Agavaceae are not particularly sensitive to high temperatures, but it's nonetheless recommendable to work with shading cloth when temperatures rise too much in the greenhouse. If you have the possibility to grow agavaceae outdoors and are living in hot climates, the leaves of your plants may burn in the very hot afternoon sun.
In nature wind has the capacity to considerably lower the surface temperature of plants in sunny locations. Wind is therefore very important, but it is difficult to accurately simulate in a greenhouse. Stagnant air and high humidity are a deadly combination for agavaceae in cultivatiion. Most agavaceae die because of fungi that let them rot slowly from the inside out. With high temperatures and stagnant air various pests such as mealybugs can multiply explosively as well.
In the cultivation of our plants (outdoors and greenhouse) we have discovered over the years that our plants had problems with our water but that they looked great again during the rainy season. An article in several parts in the journal of the American Cactus and Succulent Society had the answer to this mystery. In short words and a few pictures we would like to explain how we proceeded and what results the new watering system brought about. If you would like to know all of the details you should consult the entire article.
3.1 Determination of the original ph value of the water
In a first step we measured the ph value of our well water. We bought an electronic ph meter that had to be calibrated with different solutions. It is also possible to hire a professional laboratory to determine the correct ph value of your water. Our water has a ph value of 8.2. It is extremely hard and the roots of our plants don't like it at all. For comparison: Rain water normally is very soft and acidic with a ph value between 5.5 and 6.5.
3.2 Correcting the ph value to 5.5
According to the instructions in the CSSA journal article we filled a barrel with 114 liters (30 gallons) of our hard well water and tried to lower the ph value to 5.5 little by little. We added cheap white vinegar to the water. The vinegar has to be added in small quantities and after every addition of vinegar you need to stir the water well to find our what amount of vinegar you need to reach a ph value of 5.5. We reached it by adding 300 ml (~ 1 1/3 cups) vinegar to 114 liters (30 gallons) of water. The authors of the CSSA article write that the water should be used up soon because the ph value will slowly rise again. It is therefore advisable to mix only quantities you are going to use the same day.
3.3 Addition of ammonium sulfate
Ammonium sulfate is frequently used in agriculture to keep the root system of crops healthy and increase their ability to absorb water and nutrients. We use two level tablespoons of ammonium sulfate for 114 liters (30 gallons) of water. We dissolve it in one additional liter of water (~ 4 1/2 cups), add it to the barrel and stir very thoroughly. Here, ammonium sulfate it is only available in granulated form and it is very cheap. Ammonium sulfate is also used as a fertilizer (although in much higher concentrations), but it only contains nitrogen but neither phosphorus nor potassium.
3.4 Results according to our own experiences
Within days the plants look healthier and greener. They flower more willingly and are more resistent agains pests. After only a few weeks we were able to see the difference. We are now using this water since many month outdoors and in the greenhouse.
In our garden the plants grow in a mixture of 50% garden soil and 50% pumice to increase the drainage of too much water. In the garden we cover the ground with red volcanic pumice, protecting the surface from the sun and from drying out too quickly. In the greenhouse we use a mixture of 30% peatmoss and 70% pumice and cover the surface of the pots with coarse white granite sand. We don't recomment pure garden soil because it is too rich and the plants grow unusually fast.
The use of fertilizer with succulent plants can often result in unnatural growth form. After personal conversations with Kelly Griffin, San Diego, who is an expert in growing succulent plants, a combination of 10-20-20 (N-P-P or Nitrogen-Phosphorus-Potassium) should be used that is diluted down to 2-4-4 or something similar. This additional nutrition should not be used more than twice a year to avoid growing etiolated plants.
Pests are a tiresome topic in the cultivation of agavaceae. The best thing are systemic insecticides which are absorb by the plants through their roots and help them to form their own protection against most pests.
We hope that we have contributed a little bit to your successful growing and cultivating of succulent plants with these explanations.
Julia Etter & Martin Kristen
- Cactus and Succulent Journal US: 82(4) (Jul-Aug 2010): Ammonium Nitrogen and Acidic Water for Xerophytic Plant Growth (Burleigh & Roberts)
- Cactus and Succulent Journal US: 82(6) (Nov-Dec 2010): Watering Systems for Success in Growing Plants, Using Low pH and Ammonium Nitrogen (Roberts & Burleigh)