Growing tomatoes specifically for preservation requires precise planning. Successful home canning starts with calculating the number of plants needed to meet a specific goal. This focused approach ensures the gardener produces the right quantity and type of fruit necessary for efficient, large-batch processing.
Setting the Canning Goal
The first step in calculating plant requirements is defining the desired annual output, including what products will be canned and in what quantity. This goal depends on a household’s consumption habits, so reviewing usage helps set a realistic target. For example, a small family aiming to replace store-bought staples might target 40 quarts of thin sauce, 15 quarts of whole tomatoes, and 10 pints of salsa for the year.
The goal must be broken down by the final product type, such as whole tomatoes, sauce, paste, or juice, because each requires a different volume of raw fruit. Specifying the target number of jars provides the necessary input for subsequent conversion calculations. A clear, itemized list of preserved goods serves as the blueprint for the entire growing season.
Tomato Yield Conversion Rates
To convert the canning goal into a raw weight requirement, specific conversion rates determine the pounds of fresh tomatoes needed per final canned quart or pint. These ratios are based on the water content cooked off during the reduction process. Whole or crushed tomatoes require the least processing, needing about 3 pounds of raw fruit to yield one quart of preserved product.
Sauce requires more reduction, meaning more raw weight is needed to achieve the finished volume. For a thin tomato sauce, about 5 pounds of raw tomatoes are needed for one finished quart. A thick sauce, reduced by about one-half during cooking, requires 6.5 to 7 pounds of tomatoes per quart. Tomato paste is the most concentrated product, requiring the most raw material. Approximately 14 pounds of paste-type tomatoes are needed to yield 8 to 9 half-pint jars, which equates to roughly 8 to 9 pounds per quart of paste.
Plant Selection and Estimated Yields
The choice of tomato variety significantly impacts the yield calculation due to varying fruit characteristics and growth habits. Paste varieties, such as Roma or San Marzano, are preferred for thick sauces and paste because of their lower moisture content and small seed cavities. This dense, meaty flesh retains a higher percentage of raw weight after processing, making them more efficient for cooked-down products.
Slicing tomatoes, like Beefsteak, have a higher water content, yielding less finished product per pound of raw fruit. However, they often produce a greater total weight per plant. Paste varieties typically yield 15 to 25 pounds per plant, while slicing varieties generally offer a higher total weight, often 20 to 35 pounds per plant.
Growth Habit
Understanding the plant’s growth habit is important for managing the harvest schedule. Determinate varieties grow to a fixed height and ripen most of their fruit within a short two-week period. This makes them well-suited for the bulk processing sessions required for canning. Indeterminate varieties grow continuously, producing fruit over the entire season until frost, which is better for fresh eating but less ideal for large, single-batch canning projects.
Calculating the Number of Plants and Safety Margin
The final calculation synthesizes the desired volume, the conversion rate, and the estimated plant yield to determine the necessary number of plants. The first step involves multiplying the target number of quarts or pints of each product by its raw weight conversion rate to find the total required pounds of tomatoes. For example, aiming for 40 quarts of thin sauce at 5 pounds per quart requires 200 pounds of raw tomatoes.
Next, the total required pounds are divided by the estimated yield per plant for the chosen variety, which gives the base number of plants needed. If a paste variety is selected with an expected yield of 20 pounds per plant, the calculation is 200 pounds divided by 20 pounds, resulting in a base of 10 plants. This calculation provides the theoretical minimum needed to meet the canning goal.
It is prudent to include a safety margin to account for unpredictable factors like pest damage, disease, poor weather, or spoilage during processing. Adding a buffer of 15 to 25% to the base number of plants ensures the final canning goal remains achievable even with minor losses. For the example of 10 plants, applying a 20% margin means planting an additional 2 plants, bringing the total number of plants to 12.