it gets one hour of light?? .. and/or medium bright light ...

plz explain more fully ...

and how about a pic of the whole plant ...

ken

@tapla (mid-Michigan, USDA z5b-6a) Thank you for this very informative answer, you seem to know you stuff quite well :-) I will pay closer attention to watering of this plant, I have been giving it water when the pot felt light or when the top Inch of the soil felt very dry. I will use my moisture meter from now on though. The soil is airy and fluffy so compact soil can not be the culprit. In case adjusting my watering has no effect, is there any way for me to increase Ca intake or ‘fertilize‘ it with Ca?

best regards

@ken_adrian Adrian MI cold Z5

The plant gets indirect bright light the whole day and one hour of evening sun

M - First, the hooked leaves with misshaped margins isn't due to issues related to light.

You need to be careful about trying to increase uptake of a single nutrient by adding more of it; this, because an excess/toxicity of Ca can cause a deficiency of Mg (magnesium). If the reason for the deficiency was/is culturally caused, and I suspect it was/is, the best path to resolution is by way of correcting the cultural cause. The reason I suspect there is no actual deficiency of Ca in the medium is, the medium would almost certainly have been pH adjusted with dolomitic lime, which contains Ca and Mg in a favorable ratio, and your plant hasn't been in the medium long enough to have depleted the Ca. Not only that, but the Mg fraction contained in the liming agent/dolomite is about 125x more soluble than the Ca fraction. This means a Mg deficiency would very likely appear precedent to a Ca deficiency.

The best way to resolve this issue isn't by focusing on fixing a Ca deficiency; rather, by focusing on ensuring your nutritional supplementation program is holistically appropriate. I'm not sure if you live in the US, but Foliage-Pro 9-3-6 fertilizer is an excellent source of nutrients and all your plant needs for normal growth and vitality. Everything I currently grow is fertilized with FP 9-3-6 with the exception of tomatoes and (when I grow them) hibiscus. For those I still use FP 9-3-6, but I doctor it with soluble forms of P and K from other products.

If you do decide to treat the deficiency rather than correct the cultural cause, I suggest you use a product that also contains Mg ...... something like Cal-Mag (click link), which will help keep the Ca:Mg ratio balanced to prevent the antagonistic deficiency I explained somewhere above. If you use it, use it as a soil drench only; this, because the Ca fraction of the solution is not mobile in the plant, so it will not provide added Ca to new growth as it appears. As a soil drench, it would be constantly in the nutrient stream. But again, the best way to address it is with a fertilizer that has all essential nutrients (including all micronutrients) in an appropriate ratio.

Last, moisture meters don't measure moisture levels, they measure electrical conductivity. Clean the probe, add distilled water to a clean cup, insert the probe, note that it reads DRY. Sprinkle a little table salt in the water to add a few ions, and the needle moves to WET. A wooden "tell" will tell you accurately when it's time to water. I'll leave you with something I wrote about using a tell.

Using a 'tell'

Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.

Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.

In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.

Edited to say: This thread might be of interest as it talks about the likelihood more harm than good will come from trying to treat a deficiency of a single nutrient.

Al

@tapla (mid-Michigan, USDA z5b-6a) Wow, I am overwhelmed at how much you scientifically know about plants. If I understood right the issue is not a Ca deficiency in the soil but in the plant? I am from Germany so excuse me if I didn't understand fully. What I am taking away is that the cause is 'cultural' (I'm not so sure what that means) and I should focus on supplementing my plant with a stable fertiliser in a steady and continuous way while trying to make sure I don't overfertilise? I use a moisture probe on my bigger pots and overwatering is not an issue for me usually, I don't equate water with love for my plants like some people do :-D I also pick up smaller pots or stick my finger in and I never water without checking a Plant first. I repotted the Syngonium from Terracotta into a nursery pot I keep in a cache pot now, the roots were healthy and bouncy when I repotted. Thank you very much for you expertise and for sharing your quite impressive knowledge with me. Cheers!

Thanks for the kind words, Malin.

You're on the right track, but let me say the reason there is a calcium deficiency IN the plant is not necessarily because there is a calcium deficiency in the grow medium. The calcium is probably there and available for uptake, but a waterlogged medium is culturally limiting the plants ability to take up that nutrient, calcium.

"Cultural" conditions which affect a plant's ability to function normally include but aren't limited to: too hot, too cold, compacted grow medium that holds an insufficient amount of oxygen, over/under-watering, too little/ too much light, high salinity in the medium, too much of one nutrient limiting uptake of another, ..... others. Some examples - cold medium temp limits uptake of phosphorous, no matter how much phosphorous is in the medium. High medium salinity (too many salts accumulating from fertilizer solutions and tapwater limits water uptake and therefore nutrient uptake as well. VERY commonly, excess water in the root zone limits uptake of water and nutrients, but particularly calcium. Availability of too much magnesium can also limit uptake of calcium and potassium.

So as far as nutrition goes, the easiest and most effective way of making sure your plants get all the nutrients they need to grow normally is to make sure you're using a medium that allows you to flush it thoroughly to eliminate an increasing accumulation of nutrient salts and to reset the medium's fertilizer content to zero before you fertilize again. I make my own media from very high % of coarse materials so I never need be concerned about over-watering, and I have complete and easy control over nutrient supplementation. Having to fight your grow medium at every turn denies the grower of an immense amount of the personal satisfaction that comes from growing well and the unshakable knowledge of being a good nurturer.

Al