Water, the Third Variable

By Tom Broome

The quality of your water source is just as important as the soil and the fertilizer used in growing your cycads. If you grow cycads in containers, you can change the brand of fertilizer, or change the soil mix, but many times you are stuck with the available water supply. In fact, when choosing a location for a nursery, after, "Is this land prone to flooding," your second question should be, "What is the quality of the available water source?" I have seen two nursery owners buy the same seedlings, use the same soil and fertilizer, but get totally different results. These two nurseries were only two miles apart, but the water supply was different.
Water can contain elements such as iron, sulfur, calcium, magnesium, sodium, and chlorine, as well as carbonates and bicarbonates. If concentrations of any of these chemicals are too high, there can be trouble. Compensating for these chemicals can be expensive and time consuming.
If your water contains sulfur, the pH can get on the acidic side. If so, add some dolomite. If you have alkaline water, which is very common in south Florida, add some sulfur to the soil Iron doesn't really hurt your plants that much, but the build-up will stain the leaves badly. There are various chemicals that can be used in an injector system to dissolve iron buildup. If drip irrigation can be used, at least then the leaves won't be stained. If your water contains high concentrations of calcium, magnesium, sodium, or chlorine, things can get a little more complicated. These elements are salts that can cause many different problems. Build up of salts can bum roots and kill your plants. Before discussing remedies, a few things need to be explained.
Dissolved nutrients in the soil, fertilizers, and certain chemicals, such as sodium, in the water are all types of soluble salts. Water is attracted from areas of low salt concentration, to areas of high concentration. The concentration of salts in the root system of plants causes water to move from the soil into roots. When salt levels become so high in the soil, wetter can be drawn out of the roots. Salts can be absorbed by roots as well as by leaves. If these salts accumulate to toxic levels, roots and leaves can be burned. High levels of sodium can cause other nutrients such as calcium and magnesium to be leached out, causing nutrient deficiencies in plants. If your water contains high salt levels, drip irrigation can at least keep the salts off the leaves. Newly emerging leaves on cycads are particularly vulnerable to burning.
As you water your plants, nutrients and salts are being leached out. As you fertilize, salts are being added. The secret to all this is the balance between the adding and leaching of salts. Soils with coarse materials in them, such as pine bark, can cause water to flow through too quickly. Soils with fine textured materials hold water longer, helping the leaching process. This is one reason why I suggested the soil mix in a previous issue. If salt levels are high in your water, another way to compensate is by using a time release fertilizer. That is why using Nutricote can be beneficial Many people like to keep cycads on the dry side when it comes to watering. When salt levels are high in the soil, the reduced water levels intensify the effects of salts on roots. Watering for shorter periods of time, but on a regular basis, will help with this. If salts are not being leached out properly from normal watering, once-in-a-while watering for two or three times longer than normal may be necessary.
While we are on the subject of water, I have noticed that one of the most common ways that people kill cycads is by rotting the stems or roots. Several years ago, I was talking to Larry Bussell about our native Zamia (Z. integrifolia), and he told me what would be the single most important clue in growing cycads: "Zamia likes to be uniformly moist, not dry, not wet." I have noticed at more xeric habitats that the apex of the plant was one foot below the surface. The soil was almost pure sand. The wetness of the rain never really reached the stem, but the capillary action of the sand drew down a uniform moistness. At the same time, at that level the sun never dried the soil completely. I have also observed Zamias growing in marginally wet areas. The bottom of the tuber would rot, harden off, then pull the apex below ground level As the plant grew above the surface, the process would repeat Even though you can't generalize about all cycads, if you keep your growing medium "uniformly moist," I think most cycads would benefit.
Here in Florida, growers of Zamia integrifolia have noticed that plants grown in full sun have a tendency to have curled leaflets. In the shade these same plants will have flattened out, out attractive leaflets. When the newly emerging leaflets are soft, they will curl to reduce the amount of surface facing the sun, thus reducing the loss of water in the leaflets. I have experimented with severed plants and found that extra watering while new leaves are still soft will flatten out the leaflets. Once the leaflets harden off, they will stay flattened. This procedure will make your plants a lot more attractive.
Sometimes I will have plants that push new leaves, but these leaves will abort before reaching fall size. In particular, I had a group of Cycas micholitzii in my hot greenhouse that would abort leaves on a regular basis. Last summer, I noticed they were all pushing new leaves again. One of them was pushing two leaves, and the first leaf to emerge was already half shriveled. I brought the plant into the shade and started watering it twice a day. The bad leaf started growing and hardened up beautifully, except for the few leaflets that were already damaged. After repeating this procedure on the rest of the plants, all leaves came up and hardened off normally. Since then, I have had six species of cycads try tx3 do the same thing, and I have saved all the leaf flushes after repeating this procedure. I have noticed that plants growing in a well-drained potting mix have a tendency to abort leaves more often. Sometimes, the aborting of leaves can be a sign of a reduced root system due to fungus, or a high water table, if the plant is grown in the ground.
This is the last article of a series of three. Once you have mastered the balance of soil, fertilizer, and water, everything else in culture becomes easier. There are many ways to speed up growth and to produce more seeds. Some of these techniques may not work for you unless this balance can be maintained. Keep in mind that certain soil components and fertilizer brands may not be available in all parts of the country. Also, climate can alter individual results, but the basics of these three articles should help all growers. If you are not all that concerned with fast growth, you will at least lose fewer plants. In many cases, some of these cycads are hard to find. At least by reducing the mortality rate of your cycads, these plants can become more common.