Whether you are producing young plants or preparing to transplant them, keep a close eye on your crops, as nutrient deficiencies are common at this time of year, especially in northern locations.
These symptoms generally appear when young plants are grown under low-light conditions that limit transpiration (water uptake), including high humidity [low vapor pressure deficits (VPD)], over-misting or excessively dry substrates, cold substrates, little to no air movement, and excessively low or high air temperatures.
Symptoms are appearing on the newly developing leaves and stems of calibrachoa, gerbera, pansy, and petunia propagated from seeds and/or cuttings, with some cultivars being more susceptible than others.
The first signs appear as stunted growth, followed by crinkled, twisted, thickened, and leathery leaves, leading to terminal growing tip abortion and poor rooting. Once the shoot tip aborts, lateral branches may develop, giving the appearance that the young plants were pinched or have a "witch's broom" effect, while in some cases, laterals do not develop. Most notably, depending on the severity of the deficiency, these plants may not grow after transplanting and will eventually die.
How can we determine if it is a calcium (Ca) or boron (B) deficiency? Although Ca is a macronutrient and B is a micronutrient, both are immobile, meaning that they are passively taken up as plants transpire water. Therefore, these elements cannot be reallocated to other parts of the plant. As with other immobile nutrients, symptoms of both Ca and B deficiencies typically appear in areas with rapidly growing cells, such as the growing points and on new leaves.
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