BUD SAMPLE INFORMATION

The selection of spurs or canes to sample and send to us is the most important step in determining the accuracy of the results.  The sample must represent the kind of spurs or canes that will be left on the vines by the pruning crew.  A sample of the best possible spurs is likely to have better fruitfulness than you will see in your actual crop.  A sample of weak spurs you don’t want will have poorer fruitfulness than your vineyard average.  The person taking the sample should be familiar with pruning practices.

Some growers take samples from the same set of vines each year, for comparison. Others simply take a sample representing a range of vine types and different areas of the vineyard.

A typical sample size is 20 or more spurs or canes for each block or sample area.  Some growers send more for more precise results.  Others send fewer to save on cost and labor.  For more information see our discussion of sample size.

Be clear about how many buds you are cutting.  For example, if you want us to check three buds on a spur, cut off all the buds beyond bud 3.  If you leave extra buds and tell us to “start at bud 1”, our interpretation of bud 1 may differ from yours. 

For canes, we typically inspect the 3rd, 6th, 9th, and 12th bud on each.  Checking this sub-sample on a variety of canes is more accurate than checking all the buds on fewer canes.  If you want us to check more or different buds on each cane, just let us know.

If you want to know the location where each spur was taken, label each one with a tag or write on the wood.  We will return results with each spur identified.

Spurs from each block or sample area can be placed together in a labeled plastic bag.  Do not add wet paper.  Cut spurs will stay fresh enough for several weeks, as long as they are not left in the sun.  Canes can be shipped whole with or without a bag.

Our reports include statistics on standard deviation, margin of error, and precision.  These statistics show how much confidence you can have that your sample’s mean bunches per bud is close to the actual value in your vineyard, within defined limits plus or minus.  The statistics can also be used to estimate how many samples you should take to reduce the margin of error to a desired plus or minus around the calculated mean value.

Sample size is a compromise between accuracy and cost.  Accuracy increases with a larger sample, but so does cost.  Fortunately, the per-acre cost of our service is low, but it does take time and labor for you to gather the samples.

In general, we recommend a sample size of 20 or more spurs or canes for each block or sample area.  If you will be satisfied with only approximate percentage fruitfulness, you can send 10 or fewer.  If several blocks have the same variety and soil conditions, you might take 10 samples from each block, and we will give you the combined average with a sub-average for each block. 

If a block has an area with different conditions, such as a sandy streak, you can send a separate sample for that area.

Statisticians tell us that the sample size necessary for accurate results depends on the uniformity of the buds.  A vineyard with close to 100% fruitfulness has a low variance and a smaller sample size can be trusted.  The same is true of a vineyard where most of the buds are unfruitful.  Vineyards where close to 50% of the buds have fruit have the highest variance, and need the largest sample sizes to accurately predict the number of bunches per vine.

If you decide after you see your results that you need a larger sample size, you can send us more and we will recalculate the averages.

We do not collect the samples from your vineyard, for two important reasons.

First, we are not pruning experts.  You know better than we do which spurs and canes represent a good sample of what your pruning crew will leave in the vineyard.  So the results will be more accurate if you take the sample.

Second, we are too busy.  In 2017, we inspected over 23,000 buds in November, December, and January.  Our clients have vineyards in all of California’s growing areas, and some out of state.  Collecting samples is time consuming, and we would have to charge a much higher price.

However, we are happy to discuss sampling with you before you start.

Cost = $2.65 / Bud

Please send samples to:
746 E Dayton Ave.
Fresno Ca. 93704
Rob Weaver
559-977-2563