what makes tomatoes ripen

Are you annoyed by tomatoes that are slow to ripen? If you want to speed up the ripening process for your tomatoes (on or off the vine), there are a few tricks of the trade that you can try. So, why are your tomatoes so slow to ripen? Too much water or fertilizer can make tomatoes ripen slowly. Intense sunlight overheats tomato tops, leading to green or yellow shoulders on the fruit. Heat or cold also delay tomato ripening – the ideal temperature for ripening is 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius). Of course, there are also ways to make your tomatoes ripen faster if you have already harvested them. In this article, we’ll talk about why tomatoes are slow to ripen. Then we’ll get into ways to solve the problem. Let’s begin. Why Are My Tomatoes So Slow to Ripen? There are a few main factors that can slow down tomato ripening: Variety (some varieties take a longer time to ripen, due to more days to maturity)Stress (over watering or over fertilizing can both cause it)Intense sunlight without shade (due to lack of leaves because of disease or pruning)Temperature (both heat and cold can slow things down) Temperature is an important factor in how long it takes tomatoes to ripen. If temperatures are too cold or too hot, tomatoes will be slow to ripen (or they may not ripen at all!). Temperature affects tomato ripening speed, whether they are red, orange, yellow, purple, or some other color! (You can see my illustration of ideal temperature ranges for tomato plants here.) The best temperature for tomato fruits to mature is 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius). When temperatures get too high, the tomato ripening process slows down or stops. This is because high temperatures cause the plants to stop producing lycopene and carotene (the pigments that make the fruit red). According to the Colorado State University, tomatoes do not produce lycopene and carotene above 85 degrees Fahrenheit (29 degrees Celsius). Tomatoes produce ethylene gas, and the chlorophyll that makes them green is released by the lycopene that makes them red. What Makes Tomatoes Ripen? Lycopene and carotene are the pigments that make the tomato fruit ripen and turn red. At first, a tomato fruit has lots of chlorophyll, which is a chemical that makes plants green. Over time, chlorophyll breaks down and is replaced by lycopene and carotene (these are carotenoids that make plants red and orange). However, this ripening process does not begin until the tomato grows to full size, which happens several weeks after pollination. Tomatoes ripen when chlorophyll breaks down and is replaced by lycopene and carotene. Depending on the variety, it can take a while for this growth to happen. According to Purdue University, an average tomato will grow for 40 to 50 days (6 to 7 weeks) and still remain green. Once the tomato grows to its full size, its color will start to change. As part of this process, the tomato will start to release ethylene. According to the New Mexico State University, ethylene is a natural plant hormone that plays a large role in fruit ripening. Ethylene is what triggers a tomato to start breaking down chlorophyll and producing lycopene and carotene to replace it. You might think that sunlight would help tomatoes to ripen faster, but this is not true. While tomato plants do need light to grow, excessive light won’t help to ripen the fruit any faster. So, don’t remove the leaves and branches to try to give the fruit more exposure to sunlight. Tomato plants need sunlight to grow, but excessive sunlight will not help the fruit to ripen faster. Not only is this unnecessary, but it may be harmful! For one thing, too much sunlight will heat up tomatoes, especially the top part of the fruit that is most exposed. If the tomato gets too hot, it will prevent the production of lycopene and carotene. This will slow down the ripening process. (It may also cause uneven ripening of fruit - you can read more about it in my article here.) One sign of uneven ripening is the classic green or yellow shoulders that appear on the top of your tomatoes. You can learn more about uneven ripening of tomatoes in this article from the Colorado State University Extension. Green shoulders on a tomato are unsightly, but a little patience may still yield good fruit. It seems reasonable to expect that moist, fertile soil would help tomatoes to ripen faster. Unfortunately, this is not true either. Although moist, fertile soil is important for the growth of tomato plants, you won’t be able to speed up the ripening process by adding water or fertilizer. For the most part, you just need to be patient and wait for your tomatoes to ripen. This is especially true for slower-maturing varieties. How Long Does It Take Tomatoes To Ripen? According to Cornell University, it takes 6 to 8 weeks after pollination until a tomato reaches full maturity. This time frame can change with the variety of tomato you choose. Tomatoes take 6 to 8 weeks after pollination to ripen. However, the variety and the weather can both affect the time. For example, the Fourth of July tomato from Burpee takes only 49 days to reach maturity. On the other hand, the Celebrity tomato from Burpee takes 70 days to reach maturity. Keep in mind that for tomatoes, the time to maturity (or days to maturity) is the amount of time between transplanting into the garden and harvesting ripe fruit. The weather will also have an impact on how long it takes tomatoes to ripen. Remember: when the temperature is too hot or too cold, ripening will slow down or stop. However, tomatoes can continue to ripen when temperatures return to the optimal range, as long as they were not damaged by frost or excessive heat and drought. How To Make Tomatoes Ripen Faster Now that we know what makes tomatoes ripen, let's figure out how to speed it up. There are four main ways to make your tomatoes ripen faster: Choose a fast-maturing tomato varietyMaintain proper temperatureProvide shade if necessaryUse ethylene to your advantage Start your tomato plants indoors to give them a bit of a head start! We’ll start off with choosing a fast-maturing variety, since this comes before the growing season even begins. Choose A Fast-Maturing Tomato Variety A fast-maturing tomato variety will ripen faster and be ready for harvest sooner than other tomatoes. This is important if you live in a cold climate with a short growing season. Here are a few fast-maturing tomato varieties you can try: Summer Girl Hybrid – this tomato is a fast producer, yielding round fruits that weigh 5 to 6 ounces. At only 49 to 53 days to maturity, you can look forward to a harvest in about 7 weeks! You can learn more about the Summer Girl Hybrid tomato on the Burpee website.Mighty Sweet Hybrid – this determinate grape tomato variety produces tiny tomatoes that weigh 2 ounces each. They mature in only 55 days, so you will have a harvest less than 8 weeks after transplant. You can learn more about Mighty Sweet Hybrid tomatoes on the Burpee website.Bloody Butcher – this heirloom tomato produces fruits with a deep red color that weigh 3 to 4 ounces each. They also mature in 55 days, so you will be picking ripe tomatoes in under 8 weeks. You can learn more about Bloody Butcher tomatoes on the Burpee website.Early Girl Hybrid – this tomato starts to produce very early in the season, yielding fruit that weighs 5 ounces. At only 59 days to maturity, you can harvest these tomatoes less than 9 weeks after transplanting to the garden! You can learn more about Early Girl Hybrid Tomatoes on the Burpee website. Smaller tomatoes will often ripen faster than big ones. Choose fast maturing varieties to get ripe fruit sooner. Of course, after you choose your tomato variety, you still need to make sure the plants don’t get too hot or too cold. Let’s talk about that now. Maintain Proper Temperature If you can control the temperature, you will ensure that your tomatoes ripen as fast as possible while they are still on the vine. Extreme high or low temperatures can cause slow growth of tomato plants and delay fruit ripening. Avoid Cold & Frost Tomatoes will not survive frost, whether they are young transplants or established vines. In fact, according to the University of Idaho Extension, tomatoes are susceptible to cold damage at temperatures below 45 degrees Fahrenheit (7 degrees Celsius). Frost will kill tomato plants, and temperatures below 45 degrees Fahrenheit (7 degrees Celsius) can harm them. So, you need to wait until after the danger of frost has passed to transplant tomatoes outside. However, in an area with a short growing season, you will lose fruit to fall frosts if you transplant too late. To avoid this problem, use cold protection for your tomato plants. Some ways to protect tomato plants from cold include: Cloches – these are covers meant to protect young plants from cold, wind, and pests. A cloche is often made of plastic, although glass ones exist as well. You can even use a wire cloche, but you would need to cover it with a blanket or towel to provide any cold protection. You can learn more about cloches in my article here.Row Covers – a row cover is made of a fabric that keeps plants warm, but still allows sunlight through. They are large enough to cover an entire row of plants, but you can cut them into pieces to cover individual plants if you like. You can learn more about row covers in my article here.Greenhouses – a greenhouse keeps plants warm and protects them from late spring frosts or early fall frosts. In cold climates, an extra week at the beginning and end of the growing season can make all the difference for tomatoes.Mulch – most people think of using wood chips for mulch as landscape decoration. However, mulch can also prevent weeds and insulate the soil to keep plants a little warmer at night. You can use a layer of mulch as compost if you like! Mulch helps to keep soil warmer. You can use wood chips, grass clippings, or leaves as mulch. You can learn more about how to protect tomato plants from cold and frost in my article here. Avoid Excessive Heat If you live in a warm climate, excessive heat will be what slows down the ripening process for your tomatoes. To avoid this, don’t plant your tomatoes in a greenhouse where they can’t escape the heat. Tomatoes need plenty of sunlight to grow properly. However, try to avoid having your plants exposed to full sunlight during the hottest part of the day (around 3pm). Instead, plant them in a place that gets shade from trees from about 2pm to 4pm. This will spare your tomato plants from some of the worst heat when the sun is at its hottest. You can use shade cloth to protect tomato plants from sunlight and intense heat.Image from Wikimedia Commons, courtesy of T. R. Shankar Raman: https://commons.wikimedia.org/wiki/File:RJDRP_Nursery_DSC0282.jpg If there are no convenient trees nearby, you can set up an awning or some other type of shade that protects your plants for part of the day. Not only will this prevent excessive heat for the tomato plant, but it will also prevent sunscald on the fruit. Provide Shade If Necessary As mentioned earlier, excessive sunlight can heat up the tops of tomato plants and prevent ripening. This causes the unsightly "green shoulders" on your fruit. This often happens as a result of a lack of shade from leaves. Normally, a tomato plant's own leaves provide shade for the fruit. However, if you prune off too much foliage or lose leaves to diseases (like blight), this natural shade will be gone. Instead, your tomato plants may suffer sunscald or green shoulders due to excessive sunlight. Tomato fruit may suffer white or tan spots due to sunscald, caused by direct exposure to intense sunlight. Try using a shade cloth to provide tomato plants with a little extra shade protection. Depending on the rating, you can let most of the sunlight through the cover or block most of it out. If blight is a problem for you, check out my article on 10 blight resistant tomato varieties. Use Ethylene To Your Advantage Sometimes, you are forced to harvest your tomatoes before they are ripe. This may happen because of a looming frost, hungry pests, or because you are impatient. No matter what the reason for the early harvest, you can still make tomatoes ripen a little faster off the vine - even after they have already been harvested. Earlier, we talked about ethylene gas and the role it plays in causing tomatoes to ripen. Well, as it turns out, you can use that idea to your advantage to make tomatoes ripen faster. Ethylene is given off by tomatoes, but also by some other fruits, including: ApplesAvocadosBananasMelonsPeachesPears Peaches and other fruits give off ethylene gas, which can make tomatoes ripen faster. If you store your tomatoes near any of these fruits, the ethylene will cause them to ripen a bit faster. You can also store your unripe tomatoes near ripe red tomatoes to help them ripen faster (after all, tomatoes release ethylene too!) According to the Michigan State University Extension, you should store harvested tomatoes at 55 to 70 degrees Fahrenheit (13 to 21 degrees Celsius). Do not refrigerate them, since this will reduce their quality. Instead of harvesting unripe tomatoes, you do have another option. If the plants are small enough (such as container or patio tomatoes), you can move the plants and store them somewhere warmer when a frost threatens. If your tomato plants are in a container and small enough to move, bring them inside to give them more time to ripen in fall. A less extreme solution is to cut off the tomato branch at the stem, along with the fruit. Then, store the stem and fruit inside your house where it is warm, to give them a chance to ripen. Of course, tomatoes that ripen fully on the vine before harvest will always taste the best. However, garden tomatoes ripened after harvest will still taste better than most grocery store tomatoes. Conclusion Now you know why your tomatoes are slow to ripen. You also know how to speed it up if you want to harvest a little bit sooner. You might like to read my article on when to pick tomatoes (to optimize for ripeness). You might also want to read my article on why tomatoes grow deformed. I hope you found this article helpful. If so, please share it with someone who can use the information. If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy! ~Jonathon