Follow these procedures for sampling specific fruits, vegetables and trees.

Crop Stage of growth sampled Plant part or leaves to sample Approximate number
Apples July 15 to Aug. 15 Leaf from middle of current terminal shoot 60
Asparagus Mature fern (August) Fern from 17 to 35 inches up 20
Beans, snap Initial flowering Young mature trifoliate 50
Beans, table Mature Young mature leaf 20
Blueberries First week of harvest Young mature leaf 50
Broccoli Heading Young mature leaf 15
Cabbage Heads, 1/2 grown Young wrapper leaf 15
Cantaloupe Early fruiting Fifth leaf from tip 25
Carrots Midgrowth Young mature leaf 25
Cauliflower Buttoning Young mature leaf 15
Celery Half-grown Young mature leaf 20
Cherry Summer Mature leaves from new growth 50
Cucumbers Early fruiting Fifth leaf from tip 20
Grapes Veraison Petiole from young mature leaf on shoot (one petiole per shoot) 60
Lettuce Heads, 1/2 size Wrapper leaf 20
Onions Midgrowth Top, no white portions 25
Peaches and nectarines Spring at fruit set Midshoot leaf 20
Peas First bloom Recently matured leaflet 50
Pecan 56-84 days after terminal bud set leaflet pairs from new growth 25
Peppers Early fruiting Young mature leaf 20
Plum Summer Whole leaf from midshoot growth 25
Potatoes 40 to 50 days after emergence Young mature leaf 20
Pumpkin and squash Early fruiting Young mature leaf 15
Radishes Midgrowth to harvest Young mature leaf 40
Raspberries First week in August Leaf 18'' from tip 50
Spinach 30 to 50 days old Young mature leaf 35
Strawberries At flowering Young mature leaf 20
Sweet corn Tasseling to silk Ear leaf 10
Tomatoes First mature fruit Young mature leaf 20
Walnut, black Summer Mature leaf from new growth 5
Walnut, English Summer Center leaflet from mature leaf 25
Watermelons Midgrowth Young mature leaf 15