Canning your own greens is a rewarding way to preserve the bounty of your garden or local farmers market. It allows you to enjoy fresh, nutritious vegetables year-round while controlling the ingredients and avoiding preservatives found in store-bought options. However, safety is paramount when it comes to canning, especially low-acid foods like greens. Inadequate processing can lead to botulism, a serious and potentially fatal illness. This guide provides comprehensive information on how long to pressure can greens safely and effectively, ensuring you and your family can enjoy your homegrown produce with confidence.
Understanding the Importance of Pressure Canning for Greens
Greens, such as spinach, kale, collard greens, mustard greens, and turnip greens, are low-acid foods. This means they have a pH level higher than 4.6. At this pH level, the bacteria Clostridium botulinum, which produces the botulism toxin, can thrive in an anaerobic (oxygen-free) environment, like the inside of a sealed canning jar.
Boiling water canning, which is suitable for high-acid foods like fruits and pickles, doesn’t reach a high enough temperature to kill botulism spores. Pressure canning is essential because it raises the temperature inside the canner to 240°F (116°C) or higher, which is sufficient to destroy the botulism spores and ensure the safety of your canned greens.
Preparing Your Greens for Canning
Proper preparation is a critical first step in safely canning greens. It ensures that your final product is not only safe but also tastes its best. This involves thorough cleaning, trimming, and sometimes pre-cooking the greens.
Selecting and Washing Greens
Choose fresh, young, and tender greens for canning. Avoid any greens that are wilted, discolored, or show signs of damage. Inspect the greens carefully and discard any leaves with blemishes or insect damage.
Washing greens thoroughly is essential to remove dirt, grit, and any lingering pesticides. Fill a large sink or tub with cold water and submerge the greens. Agitate them gently to loosen any debris. Rinse the greens several times, changing the water each time, until no sediment remains in the bottom of the sink. A salad spinner can be helpful for drying the greens after washing.
Trimming and Cutting Greens
Remove tough stems and ribs from the greens. These parts can be bitter and take longer to cook. Fold the leaves in half lengthwise and cut out the stem with a knife. Discard the stems or save them for making vegetable broth.
Cut the greens into smaller, manageable pieces. A size of about 1-2 inches is ideal. This will help them pack evenly into the jars and allow for better heat penetration during processing.
Hot Packing vs. Raw Packing
There are two primary methods for packing greens into jars: hot packing and raw packing.
Hot packing is generally recommended for canning greens. This involves cooking the greens briefly before packing them into the jars. Hot packing helps to shrink the greens, making it easier to pack more into each jar. It also helps to remove air from the tissues of the greens, which can improve the vacuum seal and the quality of the final product.
To hot pack greens, blanch them in boiling water for 3-5 minutes, or until they are wilted but still bright green. Drain the greens thoroughly and pack them into the jars while they are still hot.
Raw packing involves packing the raw, uncooked greens directly into the jars. While raw packing can save time, it can result in a poorer quality product. The greens will shrink during processing, leaving a lot of headspace in the jars. This can lead to discoloration and a less desirable texture. If you choose to raw pack, pack the greens tightly into the jars, leaving the recommended headspace.
Pressure Canning Equipment and Preparation
Having the right equipment is crucial for safe and successful pressure canning. Ensuring your equipment is in good working order and understanding how to use it properly is essential.
Essential Canning Equipment
You will need the following equipment for pressure canning greens:
- Pressure canner: A pressure canner is specifically designed to reach the high temperatures required for safely processing low-acid foods.
- Canning jars: Use only jars specifically designed for canning. These jars are made of tempered glass and can withstand the high temperatures and pressures of the canning process.
- Lids and bands: Use new lids for each canning batch. The bands can be reused, but make sure they are in good condition and free from rust or dents.
- Jar lifter: A jar lifter is a tool used to safely lift hot jars from the canner.
- Lid wand: A lid wand is a magnetic tool used to lift lids from hot water.
- Wide-mouth funnel: A wide-mouth funnel helps to pack the greens into the jars without spilling.
- Bubble remover/headspace tool: This tool is used to remove air bubbles from the jars and measure headspace.
Preparing Your Canner and Jars
Before you begin canning, inspect your pressure canner to ensure it is in good working order. Check the gasket, vent pipe, and pressure gauge. Replace any worn or damaged parts.
Wash your canning jars, lids, and bands in hot, soapy water. Rinse them thoroughly. Place the jars in a large pot of water and bring to a simmer. Keep the jars hot until you are ready to fill them. This helps to prevent the jars from breaking when they are filled with hot food.
Heat the lids in a separate saucepan of simmering water. Do not boil the lids, as this can damage the sealing compound. Keep the lids hot until you are ready to use them.
The Pressure Canning Process: Step-by-Step
This section provides a detailed guide to the pressure canning process, ensuring you understand each step and can follow it safely.
Packing the Jars
Remove a hot jar from the simmering water using the jar lifter. Place the jar on a towel-lined surface.
Using a wide-mouth funnel, pack the hot, blanched greens into the jar. Pack the greens firmly, but not too tightly. Leave the recommended headspace, which is typically 1 inch for greens.
Add boiling water to the jar to cover the greens, maintaining the 1-inch headspace. Use a bubble remover or nonmetallic spatula to release any trapped air bubbles. Gently slide the tool down the sides of the jar to dislodge the bubbles.
Wipe the rim of the jar with a clean, damp cloth. This is important to ensure a good seal.
Place a hot lid on the jar, centering it over the rim. Screw on a band until it is fingertip tight. This means tightening the band until you feel resistance, then backing off slightly. Do not overtighten the band, as this can prevent air from escaping during processing and lead to a poor seal.
Repeat this process for all of your jars.
Loading the Canner
Place the rack in the bottom of the pressure canner. Add the amount of water recommended by the canner manufacturer. This is typically 2-3 inches of water.
Carefully load the filled jars into the canner, making sure they do not touch each other or the sides of the canner. Use the jar lifter to gently lower the jars into the canner.
Venting the Canner
Secure the canner lid and lock it into place. Turn the heat to high. Allow the canner to vent steam for 10 minutes. This is an important step to remove air from the canner, which can affect the processing temperature. A steady stream of steam should be visible from the vent port during this time.
Pressurizing the Canner
After venting for 10 minutes, place the weight or close the vent according to the canner manufacturer’s instructions. The pressure inside the canner will begin to rise.
Monitor the pressure gauge closely. Once the canner reaches the required pressure for your altitude, begin timing the processing time.
Processing Time and Pressure
The processing time and pressure required for canning greens will depend on the type of greens, the jar size, and your altitude. It’s crucial to follow tested and approved canning recipes from reliable sources like the USDA Complete Guide to Home Canning or your local extension office.
Here is a general guideline for processing times for greens in a weighted gauge pressure canner:
| Jar Size | Processing Time (Minutes) | 10 lbs Pressure (0-1000 ft) | 15 lbs Pressure (Above 1000 ft) |
| :——- | :———————–: | :—————————-: | :—————————–: |
| Pints | 70 | 10 lbs | 15 lbs |
| Quarts | 90 | 10 lbs | 15 lbs |
Adjust the pressure according to your altitude. If you live at an altitude above 1,000 feet, you will need to increase the pressure to compensate for the lower atmospheric pressure. Consult the USDA guidelines or your canner’s instructions for specific altitude adjustments.
Cooling and Depressurizing the Canner
Once the processing time is complete, turn off the heat and allow the canner to cool naturally. Do not attempt to speed up the cooling process by running cold water over the canner. This can cause the jars to break or the seals to fail.
Allow the canner to cool until the pressure gauge returns to zero. Once the pressure is zero, wait an additional 10 minutes before carefully removing the weight or opening the vent.
Unlock the canner lid and carefully remove it, tilting it away from your face to avoid being burned by any remaining steam.
Removing and Storing the Jars
Using the jar lifter, carefully remove the jars from the canner and place them on a towel-lined surface, leaving space between the jars. Do not disturb the jars for 12-24 hours. This allows the jars to cool completely and the seals to form.
After 12-24 hours, check the seals by pressing down on the center of each lid. If the lid flexes or pops up and down, the jar is not properly sealed and should be reprocessed with a new lid or stored in the refrigerator and used within a few days.
Remove the bands from the sealed jars. Wash the jars and label them with the contents and date. Store the jars in a cool, dark, and dry place.
Safety Considerations for Canning Greens
Always follow tested and approved canning recipes from reputable sources. Do not alter the recipe or processing time. Always use a pressure canner for low-acid foods like greens. Never use a boiling water canner for these foods. Ensure your pressure canner is in good working order and that you understand how to use it properly. Follow the manufacturer’s instructions for venting, pressurizing, and depressurizing the canner. Always use new lids for each canning batch. Inspect the jars for cracks or chips before filling them. Follow the recommended headspace guidelines. Process the jars for the correct amount of time and at the correct pressure for your altitude. Properly cool and depressurize the canner. Check the seals of the jars after cooling. Store the jars in a cool, dark, and dry place.
Before eating any home-canned greens, inspect the jars for signs of spoilage. Discard any jars with bulging lids, leaks, or unusual odors. It’s also a good practice to boil home-canned greens for 10 minutes before consuming them, even if they appear to be properly sealed. This will destroy any botulism toxin that may be present.
Troubleshooting Common Canning Problems
Sometimes, even with careful preparation and execution, canning problems can arise. Here are a few common issues and how to address them.
- Jars not sealing: This can be caused by a number of factors, including a damaged lid, food particles on the jar rim, or not enough headspace. Reprocess the jars with new lids, making sure to clean the jar rims and leave the correct amount of headspace.
- Siphoning: Siphoning occurs when liquid is lost from the jars during processing. This can be caused by overfilling the jars, fluctuating pressure during processing, or removing the jars from the canner too quickly. Be careful to leave the correct amount of headspace, maintain a steady pressure during processing, and allow the canner to cool completely before removing the jars.
- Food discoloration: Discoloration can occur due to oxidation or enzyme activity. Hot packing the greens can help to minimize discoloration.
Canning your own greens is a fulfilling and cost-effective way to enjoy fresh, healthy vegetables throughout the year. By following these guidelines and prioritizing safety, you can confidently preserve your garden’s bounty and savor the taste of homemade goodness. Always consult reliable sources like the USDA Complete Guide to Home Canning for the most up-to-date information and safety recommendations. Happy canning!
Why is pressure canning the only safe method for canning greens?
Pressure canning reaches temperatures high enough to kill Clostridium botulinum spores, which can cause botulism, a deadly form of food poisoning. Low-acid foods like greens require these high temperatures because botulism spores can survive in boiling water bath canning, which only reaches 212°F (100°C). Therefore, pressure canning is absolutely essential for ensuring the safety of home-canned greens.
Boiling water bath canning is suitable only for high-acid foods (pH of 4.6 or lower) like fruits, jams, and pickles, where the acidity inhibits the growth of botulism spores. Greens, being low-acid, lack this natural protection, making pressure canning the only method that guarantees a safe and shelf-stable product, free from the risk of botulism.
What types of greens can be safely pressure canned?
A variety of greens are suitable for pressure canning, including spinach, collard greens, kale, mustard greens, turnip greens, and beet greens. It is crucial to follow tested recipes from reputable sources, such as the USDA or your local extension office, as processing times and procedures can vary depending on the specific type of green.
While you can mix some types of greens together, generally keep them consistent within a single batch. For example, you can combine collard and turnip greens. Always wash the greens thoroughly and remove any tough stems before packing them into jars for processing.
How do I properly prepare greens for pressure canning?
The preparation of greens before pressure canning is crucial for safety and quality. Begin by thoroughly washing the greens in cold water to remove any dirt, grit, or insects. Then, trim away any tough stems or damaged leaves.
Next, blanch the greens by steaming or boiling them briefly. This helps to reduce their bulk and improve their color and texture. Pack the blanched greens loosely into canning jars, leaving the recommended headspace as specified in your chosen recipe. Add boiling water, following the headspace requirement, and remove any air bubbles before sealing the jars.
What is the correct headspace to leave when pressure canning greens?
Proper headspace is crucial for creating a proper vacuum seal during the canning process. For greens, it’s typically recommended to leave 1 inch of headspace between the top of the packed greens and the lid of the jar.
This headspace allows for expansion of the contents during processing and helps ensure a tight seal forms as the jars cool. Insufficient headspace can lead to jar breakage or improper sealing, while excessive headspace may result in the food not being adequately processed. Always follow the specific headspace recommendations provided in your tested canning recipe.
How long do I need to pressure can greens, and how does altitude affect this?
Processing times for pressure canning greens vary depending on the type of greens, jar size (pint or quart), and pressure canner type (dial gauge or weighted gauge). Generally, pint jars of greens require approximately 70 minutes for processing, while quart jars require 90 minutes. Always consult a reliable canning resource for precise processing times.
Altitude significantly impacts pressure canning because water boils at lower temperatures at higher altitudes. Therefore, you must increase the pressure to achieve the necessary internal temperature for safe processing. Adjust the pressure according to your altitude, using the guidelines provided by your pressure canner manufacturer or your local extension office. Failure to do so can result in under-processing and potentially unsafe canned goods.
How do I know if my pressure canned greens have sealed properly?
After the jars have cooled completely, which may take 12-24 hours, check the seals. The lids should be concave and not flex when pressed in the center. You can also gently tap the lid with a metal spoon; a properly sealed lid will produce a high-pitched ring, while an unsealed lid will sound dull.
If any jars haven’t sealed, you have two options: reprocess them immediately, using new lids, or refrigerate them and use them within a few days. Never consume food from jars that show signs of spoilage, such as bulging lids, leakage, or an off odor.
What is the shelf life of properly pressure canned greens?
Properly pressure-canned greens can be safely stored for at least one year, and potentially longer, if stored in a cool, dark, and dry place. However, for optimal quality, it’s best to use them within that timeframe.
While the food may still be safe to eat beyond one year, the color, texture, and flavor may deteriorate over time. Always inspect the jars before opening and discard any that show signs of spoilage, even if they are within the recommended storage period.