Taking vital signs in your garden
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Marty Nelson
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We are all familiar with the routine vital signs that begin a visit to the doctor’s office.
Temperature, pulse, respiration and blood pressure are indicators of our basic body functions and, if abnormal, signal the need for further examination.
Are there “vital signs” that might be helpful in assessing the health of the plants in your garden? In fact, there are. Like humans, plants need to carry out essential life processes in order to survive. These include the intake of water and minerals, the transport of carbohydrates to cells, and the exchange of oxygen and carbon dioxide. Unlike humans, plants also manufacture their own food through photosynthesis. Interruption of any of these processes can threaten the health of a plant. It’s these important plant functions that are the focus of a “vital sign” assessment.
First, there is the intake of water and essential minerals which is work conducted by the roots. A plant is approximately 85 percent water so a lack of water becomes apparent in wilted leaves and drooping stems, a significant vital sign. However, this can be tricky because wilted leaves and drooping stems can be caused by a lack of available oxygen in the soil, a condition resulting from overwatering. If a thirsty-looking plant doesn’t perk up when watered, then it’s time to check beneath the soil surface. Use a shovel to check for drainage at the root level. Soggy roots cannot absorb nutrients or water and are susceptible to disease.
Plants depend on a circulatory system to transport water and nutrients from one part of the plant to another. Damage to vascular tissues above the root level can appear as distorted or dying leaves and stems on a portion of an otherwise healthy plant. This is a signal to look for injury to stems or branches. The explanation could be physical, such as a broken branch, or there might be evidence of disease or insect infestation. Bacteria and fungi can plug up a plant’s vascular system blocking the flow of water and nutrients to leaves and shoots. The pattern of the damage is significant in determining whether the cause could be biological or environmental.
Another important vital sign is the color and condition of the leaves of a plant. Leaves are the location of the plant’s food production and gas exchange and often the first place we notice a problem. Color changes, such as yellowing or browning of normally green leaves, can be signs of a number of plant disorders including nutrient deficiency, pH problems, herbicide toxicity or exposure to extreme weather conditions. There can be additional signs when pathogens or pests cause leaf damage. Mildews, molds and rusts are forms of fungi that can be visible on leaves. Insects chew holes in leaves and some roll the foliage to shelter eggs and larvae. Sucking insects such as aphids and mealy bugs cause leaf distortion and leave a sticky honeydew that attracts ants. Careful inspection of leaves, especially the undersides, can provide the clues needed to discover the source of the damage.
Could some of your plants use a check-up? Think roots, stems/trunks, and leaves as a guide to remembering the vital signs you want to assess. Your goals are to detect changes that can signal threats to the health of your plants and to use your observations to guide further assessment and diagnosis. Fortunately, there are some excellent resources available to assist you in problem solving. Visit the Marin Master Gardener website at marinmg.ucanr.edu to find current gardening information and a link to the statewide integrated pest management system. You can also bring a sample or photo of your plant problem to the UCCE Marin Master Gardener Help Desk in Novato.