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FOILAGE
SAMPLE COLLECTION GUIDE
General
Tips
Plant tissue samples must be collected properly and carefully
to be useful for evaluating the nutrient status of a crop.
Analytical results can only be as accurate as the sample.
The most critical objective of sample collection is ensuring
that it is representative of the area in question. If a field,
orchard or vineyard is not uniform regarding soil type, fertilization,
spray or disease conditions, separate samples from each distinct
area are recommended. Do not combine specimens from different
varieties, cultivars, ages or plantings. Best sample-collection
method depends on the type of plant or crop being submitted.
Recommendations for some crops are listed on this page. Please
contact our lab for sample collection recommendations for
other crops.
Field crops and vegetables - Leaf samples
During the morning hours, select the newest but fully expanded
leaves on the main stem. Typically, this will be the third
to fifth leaf branch from the growing tip of the plant. Avoid
atypical insect- or weather-damaged plants unless special
samples are being collected to assess a specific problem.
Place the leaves in a Foliage Sample bag. Collect approximately
10 leaves from each of 3 to 5 areas within the field to be
sampled. A minimum of 60 to 100 leaves should be submitted
for a complete nutrient panel. Place leaves in a labeled Foliage
Sample bag and submit to the lab within 24 hours for best
results. Sample on a 7 to 14-day interval.
 Field
crops and vegetables - Petiole samples
During the morning hours, select the petioles from the newest
but fully expanded leaves on the main stem. Typically, this
will be the third to fifth petiole from the growing tip of
the plant. Avoid atypical insect- or weather-damaged plants
unless special samples are being collected to assess a specific
problem. Strip away the leaf blades from the petioles and
discard them. Place the petioles in a labeled Foliage Sample
bag. Collect approximately 20 petioles from each of 3 to 5
areas within the field to be sampled. A minimum of 60 petioles
should be submitted for a nitrate analysis, 100 for a complete
nutrient panel. Sample on a 7 to 14-day interval. Submit the
samples to the lab within 24 hours for best results.
Tree and orchard samples
Sample trees between 60 and 70 days after the average petal
fall date. Select 60 to 100 leaves with petioles from the
middle of terminal shoots. Shoots should be of average vigor
representing typical trees in a planting with uniform soil,
fertilizer and spray conditions. Avoid atypical insect- or
weather-damaged shoots unless special samples are being collected
to assess a specific problem. Select 1 or 2 leaves per shoot
from shoots that are well exposed to light and 5 to 7 feet
above ground level for large trees, or 3 to 6 feet above ground
level for smaller trees. Beyond 70 days after petal fall,
select the first fully mature leaf from the shoot tip. Place
leaves in a labeled Foliage Sample bag and submit to the lab
within 24 hours for best results. Wash spray residue and dirt
from leaves before wilt if necessary.
 Berries
and small fruits
Strawberries - Sample first fully matured leaf blades
in June from fruiting plants or in early August from non-fruiting
plants. A minimum of 75 leaf blades is required. Raspberries
- Sample leaves on non-fruiting canes during August. A minimum
of 75 leaf blades is required. Blueberries - Sample
from July through August. A minimum of 150 leaf blades is
required.
Select healthy leaves that have been well exposed to light
that represent the average condition of the planting unless
special samples are being collected to assess a specific problem.
Collect 1 leaf per plant. A simultaneous soil pH test is recommended.
Place leaves in a labeled Foliage Sample bag and submit to
the lab within 24 hours for best results.
Grapes
Sample fruit-bearing grapevines during July to early September
or at bloom for nitrogen status. Select petioles only from
mature leaves opposite bunches. Immature or senescent leaves
should not be sampled. Remove the leaf blade from the petiole
and discard. Place 100 to 200 petioles in a labeled Foliage
Sample bag and submit to the lab within 24 hours.
Mint
During the morning hours, select petioles from the newest
but fully expanded leaves. Avoid atypical insect- or weather-damaged
plants unless special samples are being collected to assess
a specific problem. Strip away the leaves from the petioles
and place them in a labeled Foliage Sample bag. Collect approximately
20 petioles from each of 3 to 5 areas within the field to
be sampled. A minimum of 60 petioles should be submitted for
a nitrate analysis, 100 for a complete nutrient panel. Submit
the samples to the lab within 24 hours for best results. Sample
on a 7 to 14-day interval.
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