Tomatoes, although botanically they belong to the fruits, are a remarkable vegetable. Not only are they a superfood rich in vitamins and minerals, but they are also incredibly easy to grow and remain a high-yielding crop. There is nothing more frustrating than being confronted with a green or yellow “collar” on your plants that stubbornly refuses to ripen while awaiting the tomato harvest. These spots are aptly named yellow and green collars and feel hard, especially compared to the rest of the ripe parts of the fruit. Discover helpful tips on how to avoid yellow and green collar on tomatoes here. Fortunately, it’s quite simple.
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What are green collars on tomatoes?
Green and yellow collars on tomato plants are a physiological disorder characterized by discolored areas under the skin that affect fruit quality. It is not a case of delayed ripening, the yellow and green areas are an actual disease of the affected tissue.
There are several reasons why some parts of tomatoes remain green or yellow while the rest of the fruit ripens. The first has to do with lycopene production. Lycopene is a plant pigment that gives tomatoes their red color. The ideal temperature for lycopene development is 18 – 24 ºC. When the temperature rises above 24 ºC and continues, lycopene production is inhibited.
The irony here is that tomatoes like heat. The plants can tolerate temperatures higher than 24 ºC throughout the summer. But it is direct sunlight that determines what happens on the fruit. The upper parts of the vegetable are usually the most exposed to heat or sunlight . When the sun hits the tops of tomatoes, temperatures in the fruit rise and inhibit lycopene. Without precautions, these parts cannot produce lycopene and they remain green.
Another reason parts of vegetables stay green has to do with chlorophyll, the pigment that gives plants their green color. Excessive heat prevents chlorophyll from breaking down. So when ripening green tomatoes are left in direct, hot sun for hours, the chlorophyll is preserved. Combine the tenacity of chlorophyll with the inhibitions of lycopene, and the vegetable turns green where red should break through.
Tomato deficiency symptoms: the yellow collar.
Carotene, which is another pigment in tomatoes, produces yellow and orange. It is less affected by heat. When higher temperatures and hot sun hit tomatoes, carotene (yellow) shines through while lycopene (red) is suppressed. The lower part of the vegetable is often protected from direct sunlight by the upper part of the fruit. This allows the upper parts of your tomatoes to remain yellow while the rest ripens red.
Can you eat tomatoes with green and yellow collars?
If you have ever eaten an unripe tomato, you know that it is usually sour and hard. This is also how green and yellow collars taste on tomatoes. Fortunately, the rest of the vegetable remains unaffected and is completely safe and delicious to eat. Just cut off the collars and it will feel like your green issues never existed.
Avoid yellow and green collars on tomatoes
Tomatoes that already have green or yellow spots can’t be corrected, so it’s best to prevent the discoloration from occurring during the next harvest. Fortunately, there are ways to avoid these tomato problems before they occur.
Pruning tomato plants is optional and, in most cases, an aesthetic decision. Some gardeners prune back some leaves to keep the plant in order or to affect fruit size. Keeping pruning to a minimum will help protect your tomato fruit. Foliage from a more heat-tolerant tomato plant can shield tomatoes as they ripen.
Green collar on tomatoes: shade is important
Partial shade on your tomato plant, especially during high heat, can maximize photosynthesis and reduce heat buildup in the plant. One way to provide shade is to plant tomatoes in areas of your garden that provide natural shade during the day. You can plant them against an east-facing wall so they get full morning sun but are protected from the harsher afternoon sun. As a temporary solution, you can add a shade cloth. Depending on how much shade the plant needs, you can adjust the density of the fabric.
Choose the right variety
Some tomato varieties are more susceptible to green collar than others: It’s better to use hardy varieties. When buying your seeds or seedlings, pay attention to which varieties are susceptible. The seed package may also indicate resistance to the disease – ideal for extremely hot climates.
Pick your tomatoes early
To prevent green and yellow collar, let your tomatoes ripen on the vine by picking them early. This method is only for extreme cases, as you may accidentally pick the tomato before it is fully ripe, compromising its flavor. The best time to pick early is when the red pigment begins to show through the green. After picking, you can leave the tomatoes on the counter where they will continue to produce ethylene gas that will help them ripen. To speed up ripening, store them with fruits that also produce ethylene gas, such as bananas or apples.