Flowering – GreenUpside – Learn how to grow a green garden with us!

Potatoes are a cool-season crop - but after warmer weather, you may see the plants start to flower. At that point, you start to wonder if it is a cause for concern or a normal part of the growth process. So, why is your potato plant flowering? A potato plant flowers when close to maturity so it can reproduce. Pollinated flowers will produce green fruit with seeds. A potato plant flowers as it gets closer to maturity – a signal that "new potatoes" (small tubers) are ready for harvest. Cold, wet weather can also make potato plants flower. Flowers on a potato plant indicate that its tubers (the edible part of the plant that grows underground) are starting to form. After you see flowers form on your potato plant, you know that the plant is doing well, and that it is getting closer to harvest time. In this article, we'll take a closer look at why potato plants flower, when they flower, and what they look like. We’ll also get into how and when to harvest your potatoes. Let's begin. Why Is My Potato Plant Flowering? According to Michigan State University, a potato plant will flower near maturity, as part of its process of reproduction (producing new plants). After flowering, a potato plant will sometimes produce green fruit (seed pods) with seeds inside. Potato plants produce flowers as they get closer to maturity. The flowers may turn into green fruit after pollination occurs! These fruits look like green cherry tomatoes. In fact, potatoes and tomatoes are related, since both are members of the nightshade family (Solanaceae). Potato plants are more likely to produce fruit when the weather conditions are cold and wet. Potato plants also need proper pollination to produce these green seed pods. The flowers on potato plants may turn into green fruit with seeds inside, like the one seen here.Image courtesy of user:H. Zell via:Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Solanum_tuberosum_004.JPG Potato flowers are self-pollinating (just like tomatoes). This means that their flowers contain both male and female parts. However, self pollination does not mean guaranteed pollination. The flowers still need some sort of stimulation for pollination to happen. Wind, birds, bees, and other insects can provide this stimulation and pollinated potato flowers. Each seed inside the green fruit on a potato plant can grow into new potato plant. However, the new plant is unlikely to have the same traits as the parent plant (that is, the seed will not "grow true" to the parent plant). The seed you get from potato fruit above ground will likely grow into plants that are not similar to the parent plant.Image courtesy of user:MidgleyDJ via:Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Potato_fruits.jpg For this reason, most home gardeners use seed potatoes (sprouted potatoes) to grow new potato plants. (You can learn how to plant sprouted potatoes in my article here!) Just remember that you should not eat the green fruit on tomato plants! These fruits (and the stems and leaves of potato plants) contain solanine, which is a toxic substance that will make you sick if you eat it. (Sprouted potatoes also contain solanine in the sprouts, so avoid eating the sprouts as well!) What Do Potato Plant Flowers Look Like? Potato plant flowers usually have white, purple, or pink petals, along with a yellow center. However, the petals on a potato plant flower can also be blue or red. A potato plant flower is often purple, although white is also a possibility. (By the way, you can find some interesting houseplants with purple flowers in my article here.) The structure of a potato plant flower is similar to that of a tomato plant flower. (This makes sense, since they are relatives in the nightshade family.) Potato flowers can also be pink, like this flower on a Yukon Gold potato plant. According to the University of Arkansas Extension, potato flowers are often aborted before they are pollinated and produce fruit. Most of the time, the flowers fall off in the summer heat. However, proper pollination combined with cold, wet weather can encourage potato flowers to produce fruit (the green fruits that look like cherry tomatoes, which we mentioned earlier). When Do Potato Plants Flower? Potato plants flower towards the end of their growing season, when the plant is close to maturity. It is nothing to be concerned about – in fact, it is a sign that the potato plants are doing well! A potato plant flowers near the end of its growing season as it gets close to maturity. However, you should not harvest the potatoes right when the flowers start to form. In fact, the time after a potato plant flowers is when the bulk of the tubers (potatoes) form underground and experience the most growth. Remember that potatoes can take 10 to 17 weeks to mature, depending on the variety. You should check the time to maturity when you buy seed potatoes from a seed company. (If you are interested in early potatoes that mature faster, you can find several such varieties here). You can also find information on choosing potatoes from the University of Minnesota Extension. Also, be sure to keep track of the date you planted your seed potatoes (mark it on your calendar!) This will help you to figure out an approximate harvest date. For example, let’s say you plant seed potatoes on May 1. If you planted a potato variety that takes 13 weeks to mature, then the mature potatoes will be ready for harvest around July 31 (sooner for new potatoes – more on this later). In colder northern areas of the U.S., some gardeners plant potatoes in mid-April, about 6 to 8 weeks before the last frost date. This extends the growing season, but increases the risk that a hard frost in late spring will kill any potato plants that emerge. To decrease this risk, wait until 1 to 2 weeks before the last frost date in your area to plant your seed potatoes. Use this frost date calculator from the Old Farmer’s Almanac to find the last frost date in your area. Knowing the last frost date in your area helps you to plan for your potato crop. Ideally, the soil temperature should be 50 degrees Fahrenheit (10 degrees Celsius) when you plant your seed potatoes. Avoid planting when the soil is still too wet from spring rains (the soil should not stick together). You can see the life cycle of a potato plant on this page. How Long After Potatoes Flower Are They Ready? You should not harvest potatoes while the plants are still flowering. According to the Old Farmer’s Almanac, when you harvest will depend on what type of potatoes you want: If you want new potatoes (small, tender potatoes with thin skin that rubs off easily), then harvest your potatoes 2 to 3 weeks after the plants stop flowering. If you want mature potatoes (larger potatoes for long term storage, with thick skin that does not rub off easily), then harvest your potatoes 2 to 3 weeks after the plant dies back. Mature potatoes are ready for harvest 2 to 3 weeks after the potato plant dies back. During the growing season, be sure to use “hilling” every so often to keep potato tubers covered and out of the sun. Hilling simply means using extra soil to cover some of the new growth on a potato plant. Hilling also helps to suppress weeds from growing and can be used to bury weeds that have appeared near your potato plants. The last hilling of the season should be done before your potato flowers start to bloom. Hilling helps to prevent potato tubers from getting exposed to sunlight (which can make them turn green and toxic). Without hilling, some of the potato tubers may work their way to the surface of the soil. If they are exposed to sunlight, they will turn green and produce solanine. As mentioned earlier, solanine is a toxic substance that makes you sick. It is also found in the green fruit that sometimes grow above ground on potato plants, as well as in potato sprouts, leaves, and stems. Remember to keep your potatoes watered when they are flowering, since maximum tuber formation occurs during this time period. Stop watering shortly before harvesting mature potatoes (1 or 2 weeks before harvest). This will keep the soil dry and prevent rot. (Dry potatoes will also store better over the winter.) Plan to harvest your potatoes before the ground freezes. A thick layer of unexpected snow will make it difficult to harvest your crop, so watch the weather forecast if you live in a colder region with a short growing season. Should I Let My Potato Plants Flower? You can let your potato plants flower - a flowering potato plant is nothing to worry about. There is nothing wrong with a flowering potato plant – it is just trying to reproduce. A potato plant produces flowers to reproduce - but tubers can also make new plants. Flowering means that the plant has been successful in absorbing the water, nutrients, and sunlight it needs from the environment. If you like, you can pinch the flowers off of your potato plant when they appear. This may allow the plant to put more energy into the tubers underground, resulting in larger potatoes. Can You Dig Potatoes Before They Flower? You can dig potatoes before the plant produces flowers. There are likely to be at least some new potatoes (smaller, thin-skinned potatoes) that form before the potato plant flowers. If you dig potatoes before they flower, you might get smaller tubers ("new potatoes") instead of large ones. However, potato plant flowers are a good indication of how mature the plant is. Another option is to use your hands to dig in the soil around one of your plants to search for new potatoes. If all of your seed potatoes were planted at the same time, then they should be at about the same stage of development. Harvest your new potatoes on a dry day, and be careful with them! The skins are very thin, so it is easy to cut or bruise the potatoes by mistake. The skins on new potatoes are so thin that you might accidentally rub them off if you handle the tubers too roughly. Remember that new potatoes don’t store well – this is another drawback of their thin skins. Harvest as many new potatoes as you need for the next day or two. Leave the rest of the potatoes to keep growing until you harvest them later. Another thing to keep in mind: you may want to dig your potatoes if temperatures get too warm. Tubers stop forming when the soil temperature gets up to 80 degrees Fahrenheit (27 degrees Celsius). What Happens If Potato Plants Don’t Flower? Potato plants can still produce large and perfectly healthy tubers, even if the plant never flowers at all. You can wait until the plant itself dies back (leaves turn yellow, and plant dries up) and harvest mature potatoes 2 to 3 weeks later. Do Potatoes Keep Growing After The Plant Dies? Potatoes do not continue growing after the plant dies. However, before you harvest, make sure that the potato plant really is dead! Otherwise, you will be missing out on some growth of the tubers. Tubers do not continue growing after the potato plant's vines and leaves have died. How Do You Know When To Dig Up Potatoes? Harvest new potatoes 2 to 3 weeks after your potato plant stops flowering. If there are no flowers, then check the soil with your hands to see if there are any new potatoes to harvest. Harvest mature potatoes 2 to 3 weeks after your potato plant dies back. This extra time underground will allow their skins to become thicker (called curing). Thicker skin means that the potatoes will last longer in storage. Harvest the potatoes with your hands, or do it carefully with a pitchfork. A shovel might cut into your potatoes! A pitchfork is a good tool for harvesting potatoes if you don't want to use your hands. Usually, you will find your potatoes in the first 6 inches of soil below the surface. After harvesting, you can use a rag or brush to remove dirt. Do not wash your potatoes until you are ready to use them. Washing will decrease their shelf life in storage. Use damaged potatoes first, since cut or bruised potatoes will be the first to rot. Store the intact potatoes for later. Do not refrigerate your potatoes, since the humidity levels in the refrigerator will lead to faster sprouting. You can learn more about the best way to dig potatoes in my article here. Conclusion Now you know why potato plants flower, when to expect potatoes from your plants, and how to harvest them. Flowers on your potato plant are nothing to worry about – in fact, they signal good health, and they help you to figure out when to harvest new potatoes. A potato plant flower is nice to look at, but they may not always appear. They are something to look forward to in the garden! For more information on potato growing, you might want to check out my article on planting sprouted potatoes. You might also be interested in reading my article about a potato's life cycle (they are technically perennial!) I hope you found this article helpful – if so, please share it with someone who will find the information useful.