How to Preserve Your Summer Garden Harvest: Canning, Freezing, and What to Do With Too Many Tomatoes

By mid-July, most Zone 7a gardeners face the same problem in different ways. Your tomatoes are ripening faster than you can eat them. Your zucchini shows up the day after you promised not to pick another one. Your beans are going stringy in the fridge because you bought too many at the market. Your neighbor is knocking on your door with a bucket of cucumbers.

Preservation turns a flood of summer vegetables into food you use in November.

This guide covers the three methods that matter most for home gardeners: freezing, water bath canning, and pressure canning. It explains what each method is good for, what it is not good for, and which vegetables you should preserve in June, July, and August. The focus is on practical steps, not theory. If you have a garden producing right now, you should be able to use this guide today.

Why Preserve at All?

There are two reasons gardeners preserve food. The first is practical: vegetables have a season. Tomatoes grow in summer and stop in fall. Green beans produce for about three weeks and then decline. If you do nothing, your garden feeds your family for a few weeks and then stops.

The second reason is about food security. When you preserve a portion of your harvest, you have homegrown food on the shelf in winter. That does not replace shopping at the store. It means you have tomatoes for pasta sauce in January, green beans for Sunday supper in March, and pickled cucumbers in July of next year. It adds resilience to your household.

You do not need to preserve everything your garden produces. A good target is to preserve enough to last three to six months for the items you eat regularly. Start small. Learn one method. Then add more.

Freezing: The Easiest and Safest Method

Freezing is the simplest preservation method. It requires the least equipment, carries no food safety risk if done correctly, and produces results that are close to fresh in most cases. The trade-off is texture: frozen vegetables are not good for raw eating. They are best for cooking.

The Key Step: Blanching

You cannot just chop a vegetable and throw it in the freezer. Enzymes in raw vegetables continue to act even at freezer temperatures. Over time, they cause discoloration, off flavors, and texture breakdown. Blanching kills those enzymes before freezing.

Blanching means boiling the vegetable for a short time, then plunging it into ice water to stop the cooking. The timing varies by vegetable. Here are the most common ones:

• Green beans: 3 minutes in boiling water, then ice bath
• Corn kernels: 4 minutes in boiling water, then ice bath
• Broccoli florets: 3 minutes, then ice bath
• Cauliflower florets: 3 minutes, then ice bath
• Carrot slices: 2 minutes, then ice bath
• Peas: 1.5 minutes, then ice bath
• Spinach and leafy greens: 2 minutes, then ice bath
• Tomatoes (for sauce): 30 to 60 seconds in boiling water to loosen skins, then ice bath. Remove skins, chop, and freeze.
• Bell peppers: No blanching needed. Wash, seed, chop, and freeze raw.
• Herbs (basil, oregano, thyme): No blanching needed for most. Freeze whole or chop and freeze in ice cube trays with a little water or oil.

After blanching, drain the vegetable well and pat it dry with a clean towel or paper towels. Excess water causes freezer burn.

How to Freeze

You have two options:

Tray freezing (preferred). Spread the blanched and dried vegetables in a single layer on a baking sheet lined with parchment paper. Freeze the tray for two to three hours until the pieces are solid. Then transfer the frozen pieces to airtight freezer bags or containers. This prevents the vegetables from freezing into one big clump. You can scoop out just what you need.

Bag and freeze (simpler). Pack the blanched, dried vegetables directly into freezer bags. Squeeze out as much air as possible, label with the vegetable name and date, and freeze. The pieces will clump together, but you can break them apart later when cooking.

Both methods work. Tray freezing gives better results for cooking. Bag and freeze is faster and fine for soups and stews.

Storage Life

Frozen vegetables keep well for eight to twelve months at a steady 0 degrees Fahrenheit or below. After that, they are still safe to eat but quality declines. Use the oldest stuff first and label everything with the date.

What Freezing Does Well

Freezing works best for vegetables that will be cooked after thawing. This includes green beans, corn, peas, broccoli, cauliflower, carrots, spinach, and tomatoes (for sauce or soup). It works less well for vegetables you eat raw: lettuce, celery, radishes, and cucumbers do not freeze well and become mushy.

Water Bath Canning: For High-Acid Foods

Water bath canning is the method most people picture when they think of home canning. You fill jars with food, process them in boiling water, and seal them on the shelf. It is straightforward, but it only works for high-acid foods. The acid level is what prevents botulism spores from surviving the processing.

Water bath canning is suitable for:

• Tomatoes (with added acid)
• Pickled vegetables (pickles, peppers, relishes)
• Jams and jellies
• Fruit preserves
• Hot sauce and salsa (with tested recipes)

The Golden Rule: Add Acid to Tomatoes

Tomatoes are borderline. Their natural acidity varies widely depending on variety, ripeness, and growing conditions. To make them safe for water bath canning, you must add acid to every jar:

• Whole or crushed tomatoes: 1 tablespoon of bottled lemon juice or 1/4 teaspoon of citric acid per pint jar. Half the amount for quarts.
• Tomato sauce or paste: 1 tablespoon of bottled lemon juice or 1/4 teaspoon of citric acid per pint jar.
• Salsa: Must use a tested recipe that includes the proper amount of vinegar or lemon juice. Do not improvise salsa recipes.

Bottled lemon juice is preferred over fresh lemon juice because the acidity is consistent. Fresh lemon juice varies in acid content from fruit to fruit, and consistency is what makes canning safe.

Basic Water Bath Canning Steps

1. Prepare your jars and lids. Wash jars in hot soapy water. Keep them hot until filled (place in a pot of hot water or run through a dishwasher). Lids go in a small pot of simmering water (not boiling).
2. Prepare the food. Chop, crush, sauce, or pickle as your recipe requires. Follow a tested recipe exactly.
3. Pack the jars. Leave the headspace specified in the recipe (usually 1/2 inch for vegetables, 1/4 inch for jams).
4. Wipe the jar rims with a clean damp cloth. Place the lid on the jar and screw on the band until fingertip-tight. Do not overtighten.
5. Lower the jars into the water bath canner or large pot. The water should cover the jars by at least 1 to 2 inches.
6. Bring to a rolling boil and process for the time specified in the recipe. Process times range from 35 minutes for pickled vegetables to 40 minutes for tomatoes.
7. Remove the jars and let them cool undisturbed for 12 to 24 hours. Do not retighten the bands while hot.
8. Check the seals. Press the center of each lid. If it does not flex up and down, the jar sealed. Store sealed jars in a cool, dark place. Refrigerate any jars that did not seal and use them within a few weeks.

Pressure Canning: For Low-Acid Vegetables

Low-acid vegetables like green beans, corn, carrots, squash, and beets cannot be safely canned in a water bath. The acid level is too low. Botulism spores can survive boiling water temperatures and only die at the higher temperatures reached in a pressure canner.

Pressure canning reaches 240 degrees Fahrenheit (at 10 pounds of pressure), which is hot enough to destroy botulism spores in low-acid foods. This is not optional for these vegetables. There is no shortcut.

Equipment: A Pressure Canner, Not a Pressure Cooker

You need a pressure canner. A pressure cooker from the kitchen drawer is not a pressure canner, even if it looks similar. Pressure canners are larger, have a heavy gauge body, and include a weight or dial gauge for monitoring pressure. They are designed to process multiple jars at once.

There are two types:

Weight-gauge canner. Uses a weighted disc that jiggles or rocks to maintain pressure. You read the pressure from the gauge or by the rate of rocking.

Dial-gauge canner. Has a dial that shows the exact pounds of pressure. These require annual calibration checks to ensure accuracy.

Both types work. Weight-gauge canners are more common and generally less expensive. Dial-gauge canners give a precise reading but need regular calibration.

Basic Pressure Canning Steps

1. Prepare jars and lids the same way as water bath canning.
2. Pack the raw or pre-cooked vegetables into jars. For green beans, pack them tightly into jars. For corn, you can use raw or hot pack (briefly boiled before jarring).
3. Add boiling liquid. For green beans, add boiling water, leaving 1 inch of headspace. For corn, add boiling water or leave dry (dry pack is an accepted method for sweet corn).
4. Wipe rims, apply lids and bands fingertip-tight.
5. Place jars in the pressure canner. Add 2 to 3 inches of hot water to the canner base.
6. Heat the canner with the vent valve open until a steady stream of steam escapes for 10 minutes. This vents air from the canner.
7. Close the vent valve and heat until the canner reaches the correct pressure (usually 11 pounds for weighted gauge or 10 pounds for dial gauge at most altitudes).
8. Start timing when the correct pressure is reached. Process times vary:
   • Green beans (pint): 20 minutes at 11 psi (weighted) or 10 psi (dial)
   • Green beans (quart): 25 minutes at 11 psi or 10 psi
   • Corn (pint): 20 minutes at 11 psi or 10 psi
   • Corn (quart): 25 minutes at 11 psi or 10 psi
   • Carrots (pint): 25 minutes at 11 psi or 10 psi
   • Squash (pint): 25 minutes at 11 psi or 10 psi
9. Turn off the heat and let the canner depressurize naturally. Do not force-cool it. When the pressure reads zero and the vent valve drops, open the lid away from you.
10. Remove jars with a jar lifter and cool undisturbed for 12 to 24 hours. Check seals the same way as water bath canning.

Altitude Adjustments

Pressure canning times and pressures change with altitude. At higher elevations, water boils at a lower temperature, so you need more pressure to reach the same internal temperature. Here are the adjustments:

• 0 to 1,000 feet: Use 10 psi (dial gauge) or 11 psi (weighted gauge)
• 1,001 to 4,000 feet: Use 11 psi (dial gauge) or 11 psi (weighted gauge)
• 4,001 to 6,000 feet: Use 12 psi (dial gauge) or 11 psi (weighted gauge)
• 6,001 to 8,000 feet: Use 13 psi (dial gauge) or 11 psi (weighted gauge)

Louisville, Tennessee is at roughly 900 feet elevation, so the standard 10/11 psi applies. If you move or visit at higher elevation, adjust accordingly.

What to Preserve: Monthly Guide for Zone 7a

Here is a practical timeline for what to focus on each month, based on typical Zone 7a harvest patterns.

June

• Garlic scapes. Blanch 1 minute and freeze in bags.
• Strawberries. Freeze or make jam.
• Early beans. Freeze or pressure can.
• Lettuce. Do not preserve. Eat it or give it away.

July

• Green beans. Peak harvest. Freeze in batches. Pressure can several dozen jars.
• Corn. Freeze kernels after blanching. Can whole ears or cut kernels.
• Tomatoes. Water bath can (with acid), freeze for sauce, or make salsa from tested recipes.
• Zucchini. Does not freeze well raw. Use in baked goods, make zucchini relish (tested pickle recipe), or share.
• Peppers. Freeze raw (chopped). Water bath can pickled peppers.
• Cucumbers. Pickle them. Water bath can pickles from tested recipes.

August

• Tomatoes. Late varieties continue producing. Can, freeze, or make sauce.
• Eggplant. Does not freeze well. Roast and freeze, or share.
• Late beans. Last batch before plants decline.
• Squash. Can or share. Does not freeze well.
• Okra. Pressure can or freeze (blanched 1 minute). Okra is slimy when frozen raw but fine canned.

September

• Pumpkins and winter squash. These store well without canning. Keep them dry and cool and they last months.
• Sweet potatoes. Store in a cool, dry place. They do not need canning.
• Apples. Make sauce (water bath can) or freeze slices.

Non-Negotiable Safety Rules

These are not suggestions. They are the difference between safe food and botulism poisoning, which is rare but can be fatal.

Only use tested recipes. From the USDA Complete Guide to Home Canning, the National Center for Home Food Preservation at UGA Extension (nchfp.uga.edu), or extension services at land-grant universities. Do not adapt recipes from blogs, Pinterest, or non-expert sources. Do not change the amount of acid, vinegar, or processing time because a recipe seems too conservative. The safety system depends on the exact ratios and times.

Use bottled lemon juice, not fresh. Fresh lemon juice varies in acidity. Bottled lemon juice has a consistent acid level that makes the safety calculation reliable.

Do not substitute vinegar. If a recipe calls for 5 percent acidity vinegar, do not use cider vinegar, wine vinegar, or homemade vinegar. The acid strength differs, and you cannot test it at home. Stick to what the recipe specifies.

Do not half-reduce a recipe. Canning is chemistry. Halving a recipe changes the acid-to-food ratio and the heat penetration time. Make the full batch or do not can it.

Do not use oven canning, microwave canning, or open-kettle canning. These methods do not reach the temperature or hold it long enough to be safe. Water bath and pressure canning are the only approved methods.

When in doubt, throw it out. A swollen lid, a spurting seal, a cloudy liquid, a yeasty or off odor, or mold on the food after opening means the food is spoiled. Do not taste it. Do not try to salvage it. Discard it and the jar.

Store jars properly. Keep canned goods in a cool, dark, dry place. Ideal storage temperature is 50 to 70 degrees Fahrenheit. Light fades color and nutrients. Heat speeds quality loss. Cold below freezing cracks jars. Do not store canned goods in an unheated shed in winter or a garage that gets hot in summer.

Label everything. Write the food name, the method (frozen or canned), the date, and the variety if relevant. Canned goods last one to two years for best quality. Frozen goods last eight to twelve months. Eat the oldest first.

Getting Started: Your First Batch

If you have never preserved food before, start with one method and one vegetable. The simplest path is:

1. Buy a quality freezer bag and a label maker (or use masking tape and a marker).
2. Blanch and freeze a pound of green beans or corn. It will take you about 30 minutes from harvest to freezer. You will learn the blanching process without any safety pressure.
3. Can a single batch of tomatoes. Use bottled lemon juice, follow a tested recipe, and make four to six pints. This teaches you the water bath process, the jar handling, and the seal-check routine.
4. Pressure can a batch of green beans. This is the most important skill to learn because green beans cannot be water-bathed. Buy two or three pounds of beans, process four to six pints, and you will have learned the core pressure canning steps.
5. Taste what you made. Frozen beans in a stir-fry. Canned tomatoes in pasta sauce. Pressure-canned green beans with a little butter and pepper. If it tastes good, you will want to do more.

A Final Word

Preservation does not have to be a full-time summer job. You do not need to can every tomato that ripens or freeze every green bean that shows up. A few dozen jars on the shelf, a few bags of frozen corn in the freezer, and a batch of pickled cucumbers in the fridge is enough to make a real difference.

Start with what your garden is producing right now. Pick one method. Follow the safety rules. Learn the routine. The next year, you will add more. The year after that, you will have shelves full of food from your own ground, and you will never buy canned tomatoes from the store again.

That is what preservation is for.

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— C. Steward 🍅