Tissue samples may be collected at other times of the year if absolutely necessary. However, nutrient levels change rapidly outside the recommended time frame and make results more difficult to interpret. If sampling in the spring, sample in June and collect new upright tissue only. Tissue samples should be collected when a deficiency is suspected or diagnosis of a specific problem is needed. Soil samples can be collected in the spring when the bog is no longer water-logged.
Wet soils give falsely high phosphorus readings.
Soil samples may be collected in the late summer when collecting tissue samples. Use periodic soil sampling to monitor any change in soil pH. Fall samples are acceptable if no sanding is planned. Collect samples when the vines are dry. Do not strip off the leaves. Do not wash the samples prior to mailing them.