June 4, 2016
1 - Although New Mexico soils often have surplus calcium, calcium deficiency in plant tissues may be observed and treated with proper cultural techniques such as the Three Sisters Garden or shade and wind protection.
Yard and Garden June 4, 2016
After last week's column about blackening around the edges of pear leave, I received the following comment from Jeff Anderson, NMSU Extension County Agent for Dona Ana County: "Curtis, the black edging on the pears could also be a sign of calcium deficiency, that is, calcium not moving to the edges of leaves during rapid growth. I have seen this before and corrected it with calcium nitrate. Just some thoughts. Jeff"
Jeff's comment is very interesting because people often do not realize that we can experience calcium deficiency symptoms in New Mexico. Most soils in New Mexico have a surplus of calcium minerals, so how can there be a deficiency of calcium in New Mexico?
In arid Southwestern soils, calcium minerals have not been dissolved and washed away from the soil (leached) as it has in soils from regions with more rainfall and more acid soils to dissolve the calcium. However, in order for calcium to serve its function in plants, it must first be dissolved in water, taken up with the water through plant roots, and move in the transpiration stream as water moves from roots to leaves and fruit in the upper parts of plants. Our problem is based on getting the calcium into the plants and to the places where it is needed. Calcium is an important mineral for several plant functions. One of these is that it forms a glue-like material (middle lamella) that holds cells together in plants. When plants are growing, but calcium is not reaching newly forming parts of plants, such as the edges of leaves or the blossom end of fruit, the middle lamella cannot form and cells do not "stick" together properly.
The greatest problem seems to appear in newly forming cells at the greatest distance from the root system - newly forming leaves or fruit. As wind blows and hot, spring days dry our plants, the water carrying calcium (and other minerals) may not reach these distant points of the plant in sufficient quantity. The result is development of these plant parts with a poorly formed middle lamella. The end result will be calcium deficiency symptoms in these plant organs. Blackening of the edges of newly formed pear leaves may be a symptom of a poorly formed middle lamella.
Blossom end rot in tomatoes, melons, cucumbers, and other fruits is observed by New Mexico gardeners. We are coming upon the time in New Mexico gardens when this problem will be created in tomatoes and other susceptible plants. The problem develops long before the symptoms are seen. Susceptible plants need calcium just after flowering while forming their fruits. If the plants wilt at this phase of fruit development, there is a possibility of blossom end rot development. This appears later as the end of the fruit away from the stem collapses and turns black because the cells were not properly "glued" together by a poorly formed middle lamella.
Some gardeners utilize shade and wind protection to reduce the drying due to our intense sunlight and drying winds. The traditional Southwestern three sisters garden with corn plants shading and protecting lower growing plants such as squash, tomatoes, chiles, and beans is another method of moderating the drying effects. Corn, due to the characteristics of its photosynthetic pathway, can utilize as much sunlight as it can receive. The other plants cannot utilize the full intensity of sunlight and benefit from light shade. The corn plants also protect from wind while the lower-growing plants serve as a living mulch to shade the soil and conserve water for all the garden plants. The combined effect is reducing the potential for blossom end rot in the shaded plants.
So, in New Mexico we can experience calcium deficiency in plant tissues although the soil contains adequate calcium minerals. We can also reduce the potential for problems by building or growing shade for the garden. Prepare and plan now to avoid midsummer development of plant tissue calcium deficiency symptoms.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!