Rhubarb is an immensely popular summertime vegetable. You can find rhubarb made into smoothies, pies, desserts, and even savory dishes at the start of summer. It’s common to pair it with strawberry, so they tend to be in stores at the same time each year. But, when should you stop eating rhubarb? When is rhubarb too old to use? You may have heard people claim that rhubarb is toxic after a certain point.
Whatever drew you here, we’re going to go over when it’s too old to use, how you can tell it’s gone off, and much more below.
Rhubarb is a tart, tasty summer or spring vegetable that has bright red stalks and big leaves. It goes well with sweet dishes.
General Information About Rhubarb
Originally, rhubarb came from Asia, and European explorers brought it over to America not long after the 1600s. It grows very well in planting zones that offer cooler climates, and this makes it popular in northern gardens. Rhubarb is very easy to grow, but it requires a dormancy period to thrive and produce the larger stalks in the spring months. Rhubarb grows well when the summer temperatures sit around 75°F in the summer and 40°F in the winter months.
The stalks are the only part of the plant you eat, and they offer a very tart, rich flavor when you cook them. The leaves are toxic as they have an irritant in them called oxalic acid, so make sure you don’t eat them.
What’s so great about rhubarb is that it’s a perennial, and it’ll come back and produce for many years. For this reason, you want to plant your rhubarb in its own space in any corner of the garden where you can leave it to grow undisturbed. Rhubarb grows very well in any soil that is amended with well-rotted compost and manure, and many people choose to put it right by the compost pile.
With the umbrella-like leaves and the ruby or green stems, this plant adds structure and height to your garden, along with a splash of pretty color that comes back year in and year out.
When is Rhubarb Too Old to Use?
So, when is rhubarb too old to use? We all know that rhubarb is out of season by the time the middle of summer rolls around, and the leaves turn poisonous, but what are the signs that let you know when is rhubarb too old to use? A young and fresh rhubarb plant will produce a crisp, firm stalk with a uniform coloring, and it has a sweet but fresh smell. If you notice any odd brown spots, it’s mushy, you see mold, or it has a weird smell, these are all signs that your rhubarb is too old to eat. If this is the case, you want to get rid of it.
Rhubarb Ripens in Late Spring to Mid Summer
Due to the way it grows, rhubarb is great to harvest at the end of the spring. Most of the rhubarb grown and sold in the United States is from Washington and Oregon, and it grows in open-air fields. This means that you can expect to see it in stores from May to early July at the latest, and this is the general harvesting season. However, they’re also greenhouse cultivars available.
Rhubarb is well planted in hothouses, and they are ready to go early in the spring months. This crop won’t overlap with the open-air field harvest, and this gives you a rhubarb season from late March until the middle of July each year. So, if you want some rhubarb, you’ve got a few months to find it if you don’t grow it on your own. However, you do want to watch out for the leaves, and we’ll go over why below.
Rhubarb Leaves are Poisonous
Rhubarb leaves have oxalic acid, and this is toxic if you ingest it. This is the primary method of defense the plant uses. It can be fatal to animals too, so make sure none of your livestock or pets can get near it. Humans do have to eat a lot of the leaves to have severe symptoms, but it’s best to avoid them either way.
The poison is only found in the leaves, and this is why you always cut them right off at the stem level when you cook the stalks. Most of the time, rhubarb will be sold without the leaves, but it’s always a good idea to double-check. There’s also an old saying that you don’t want to eat rhubarb after mid-summer, and it is for two main reasons:
- By midsummer, rhubarb will have a woody, flavorless texture with the stalks
- There’s an old wives’ tale that claims the poison will seep into the stalks
While the first part is true, and rhubarb will get fibrous and lose the flavor towards the middle of summer, you can still harvest and eat it. However, it’ll be very bland.
The second part about the poison from the leaves going into the stalks isn’t based on scientific facts, and there’s no evidence to support the fact that the oxalic acid from the leaves will seep into the stalks. However, there is one thing to keep in mind. As summer moves out and autumn creeps in, the first cold snap will bring a light frost. Rhubarb that survives a frost won’t be any good to you. The leaves will wilt and the stalks will go limp. At this point, you can’t eat the stalks, and this is where the old wives’ tale may come from.
You want to make sure you get all of the leaf remnants off of the stalks before you use them as the leaves are poisonous.
Frozen Rhubarb Toxicity
First, you have to differentiate between rhubarb that has succumbed to frost and frozen rhubarb. Frozen rhubarb that gets harvested early in the spring, chopped, and then flash-frozen is okay. It’s just the stalks from the plant without any leaves, and it’s as crispy and as healthy as you can find it in a peak growing season.
You’ll find frozen rhubarb in your frozen food section in your local supermarket. You can also make frozen rhubarb at home. As long as you grow a lot of healthy, fresh rhubarb stalks, you can chop them up, put them in a freezer bag, and keep them frozen for up to six months.
On the other end of the spectrum, rhubarb that has been touched by frost in unharvested rhubarb that is still in the ground. Once the rhubarb gets hit with the first cold snap and frost, the stalks will go limp, and the leaves will too. The texture will be very fibrous, and the flavor will disappear.
How to Tell if Rhubarb is Bad
When is rhubarb too old to use? You have to learn the common signs that let you know the plant is bad to figure this out. When spring comes, rhubarb is right behind, and you’ll find it throughout the summer. This quick guide will help break down whether or not your rhubarb is safe to eat and what to look for in your plants:
Fresh rhubarb stalks come in deeper shades of red to glossy, bright pinks, and they have a pinker hue closer to the leaf end. When you cut into the stalks, the stalk wil be a very pale green coloring, or you may even see white. As the rhubarb ages, the colors will start to darken, and they’ll also lose their sheen. The attached leaves usually get trimmed back and left for aesthetic purposes, and they’ll look less vibrant and paler in color.
Fresh rhubarb should never have any mold growing on it, and you shouldn’t see it in the leaves either. You can find small discoloration spots on the ends, down to where you take it from the mother plant or by the leaf end, but you can easily remove these spots before you eat it. If you see any mold, this is a sign that your rhubarb can be too old to use. You may also see other age-related signs like texture, appearance, and smell. If you do, it’s a good idea to discard it.
When your rhubarb is fresh and young, it has an acidic and sharp taste. This is very similar to the tanginess you’ll get with a fresh grapefruit, and the sharpness can be slightly overwhelming if you’ve never had it before. You should refrain from eating your rhubarb raw. While it’s not toxic in this state, it is very unpleasant. The delicate flavor will be overshadowed by the sheer tartness. However, once you cook it and add a little sugar to take the edge off, your rhubarb will give you a very pleasant, zesty taste that pairs wonderfully with creamy or rich desserts. But, if your rhubarb is too old and musty, you’ll get a dirty flavor on top of the sour tartness. The scent that comes from old rhubarb is very unappealing too.
Rhubarb stalks that are in-season and fresh are well-shaped and long, and they have a stiffness that is very hard to miss. They may even poke their way through the packaging. The stalks should be uniform in size and rigid, and they’ll bend without breaking. Also, when your rhubarb has seen better days or it’s gone bad, it will become limp and get soft. Rhubarb that you can’t keep upright is no longer edible, and you should throw it away.
It’s hard to describe rhubarb’s smell when it’s fresh. It has an earthy and zingy scent, and it smells like spring. It’s full of renewed zest for life, and it bursts from the colder winter weather. However, as it ages, this scent slowly disappears, and it vanishes before taking on a sour scent. This scent comes from the fibers inside the stalk because they’re breaking down, and the enzymes are changing the plant at this point.
When is rhubarb too old to use? You now know that there are several factors you can look for when you use your rhubarb to ensure it’s fresh.
How To Tell if Rhubarb is Bad When You Cook It
Even though it’s technically a vegetable, it’s common to serve rhubarb as a dessert. It usually gets prepared by cooking it in sugar water until it’s soft and then served with other fruit, like apples or strawberries. In this context, it’s much harder to tell if your rhubarb is bad, so you have to pay close attention. A few key things can help you tel when is rhubarb too old to use, and they are:
Raw, fresh rhubarb has a very pretty and vibrant scarlet coloring on the outside with a more lime-green coloring on the inside when you cut into it, cooked rhubarb has a different color profile. When you cook it, rhubarb loses a lot of the bold scarlet coloring, and you can transfer this color to other ingredients or the cooking liquid if you braise or stew it. However, if your rhubarb has a grayish-green hue, you should be careful. Rhubarb takes on this hue, and a grayish-brown tone when it starts to go bad and rot. If you cooked your rhubarb and it looked like this, it’s a good idea to toss it out rather than try to eat it and potentially get sick.
Just like with fresh rhubarb, you shouldn’t see any mold. However, what you’re more likely to see is a liquid separation. This starts to happen when the rhubarb begins to break down and the enzymes change inside of the stalks. A visual clue is spotting a clear liquid that floats on the top of the cooked rhubarb, and it can even have a secondary white growth appear along the edges of the liquid. You should immediately toss your rhubarb if you see this when you cook it.
As you’d imagine, cooked rhubarb should have a slight tartness to it that is slightly sour but not completely unpleasant. This is why a little sugar is usually welcome. Once your cooked rhubarb goes bad, this will dramatically change. The flavor becomes unbearably sour, rotten, and it may even feel “fizzy” when you bite into it. You don’t want to swallow rhubarb that has gone bad. If you ingest it, it can cause an unpleasant upset stomach. In the worst case scenario, you’ll need to seek medical advice.
Freshly cooked or fresh rhubarb has a certain stiffness to the stalks. Even when you cook it, the fibers inside of the rhubarb stalks will be stringy and have a little structure to them. However, if your rhubarb is too old and has started to go off, your texture will be vastly different. Cooked rhubarb feels and looks slimy because the fibers are very soft, and you get an unsettling mouth-feel. If you’re in doubt, toss it right away.
Forget having the pleasant, zesty, earthy smell with your cooked rhubarb if it’s gone bad. Generally speaking, if it has gone bad, it’ll smell bad too. It’ll still offer that very sour note, but the enzymes inside of the rhubarb stalk will start to break down, and this will take the pleasant smell and turn it bad. The fresh scent does naturally fade as your rhubarb ages, but you’ll get a much more sour, rotting cabbage or citrus smell that is extremely unpleasant to be around.
It’s a little bit harder to tell if rhubarb is bad when you first cook it, but you should be able to tell when you bite into it.
How Long Rhubarb Lasts
Before we touch on how to store your rhubarb, you’ll want to carefully trim away and discard the leaves before you store them. This is true whether you bought your rhubarb at the store or local farmer’s market or if you grew it.
If you only need your rhubarb stalks to last a few days, up to four or five max, allowing them to sit on your counter or in the pantry is okay. They will start to dry out, but these small changes won’t be a big deal. This is especially true if you plan on making it into a pie. If you want to eat it raw, you should put it in the refrigerator when you get home to help prevent it from drying out.
To keep your rhubarb fresh for longer periods, you’ll want to put it into your refrigerator. One way of doing this is to put it in a plastic bag and pop it into the refrigerator. This way, your vegetable will retain the original quality for up to two weeks. You want to poke a few small holes into the bag to allow the ethylene gas to escape to ensure that your rhubarb doesn’t get overly ripe too quickly.
If you need it to last for slightly longer than that, you can keep it for up to three weeks in the refrigerator if you wrap the stalks loosely in aluminum foil without crimping the ends. This will help keep the plant’s stalks moist, and, at the same time, the ethylene gas will have plenty of opportunity to escape.
Just like with papayas, mangoes, and a range of other vegetables and fruits, you need this gas to help the produce ripen. Then, you need to allow it to escape so the produce doesn’t ripen too much or too soon.
- Another way you can make your rhubarb last longer is to wrap the stalks in a damp cloth. This will help ensure that they don’t dry out as quickly. The only downside of this method is that you’ll have to remember to get the cloth damp every couple of days to keep the stalks moist.
How To Store Rhubarb
There are a few ways you can store your rhubarb to help prevent it from going bad before you can use it. These ways include but are not limited to:
Put your fresh rhubarb stalks out of the direct sunlight, and preferably somewhere dark and cool if you can. A pantry or larder is better than right on the kitchen counter because any rhubarb you keep here won’t last very long. However, it’s fine to store it here if it’s only for a few days.
To store your rhubarb in your freezer, there are a few easy and quick steps to follow. You start by peeling and trimming away any leaves and roots from each stalk. Next, you’ll blanch your stalks for a few minutes in boiling water, and then chill them in ice water. Once you drain them, pack them into freezer bags or airtight containers and freeze them.
Ideally, you won’t wash your rhubarb until you’re ready to use it. Instead, kepe the rhubarb inside of a plastic bag, and put it in the crisper drawer of your refrigerator. When you keep it here, it should last for five to seven days. However, you can also put your rhubarb stalks on the shelf inside the refrigerator, making sure they’re unwashed and in a plastic bag. They may only last for four to five days due to the fluctuating temperatures when you open the door.
You have several options available when it comes to storing rhubarb, and the method you choose will depend on how long you need to keep it before you use it.
Risks Of Eating Old Rhubarb
Most people don’t like the thought of wasting food, and they would rather give leftovers away or eat them once they go past their expiration date. However, this isn’t a good idea when it comes to rotten food. Eating food that has spoiled can have severe consequences because it gives a range of bacterial pathogens a direct way to get into your digestive system, and this can cause a reaction in your body.
However, this doesn’t mean you’re risking your life if you’re eating rotten rhubarb. If you do eat old rhubarb, but you stopped relatively quickly due to the taste or smell, you may experience unpleasant symptoms like dizziness, severe stomach pains, or uncontrolled diarrhea. It’s a good idea for you to book an appointment with your doctor just to be on the safe side.
Is it Safe to Harvest Flowering Rhubarb?
While you should avoid using the seed stalks or flowers, the leaf stalks are edible. However, you want to pull and discard the flower stalks as soon as you see them. If you leave them on the plant and allow them to develop, the flower stalks will reduce next year’s overall growth. Flower stalk formation can be caused by infertile soil, drought, and extreme heat. Also, if you’re wondering when is rhubarb too old to use, flower stalks may be an indicator. Old plants tend to flower much more than younger ones.
You can discourage flower formation using good cultural practices. You want to water the rhubarb plants once each week when it’s dry, and sprinkle a ½ of a cup of all-purpose garden fertilizer with a 10-10-10 ratio around each plant early in the spring months. If you don’t want to use commercial fertilizer, manure is another option. Apply a two or three-inch layer of well-rotted manure around your plants in the spring. Divide any old, large rhubarb plants early in the spring or late in the summer.
Putting Rhubarb Leaves Into the Compost Pile
While the rhubarb leaves have poisonous substances in them you can put them into your compost pile. Oxalic acid and other soluble oxalates aren’t readily absorbed by plant roots. Compost that has decomposed rhubarb leaves in it can be safely worked into your vegetable or flower bed soil without any negative consequences.
If you like rhubarb, it makes a delicious and tasty treat you can eat and enjoy every spring and early summer. Remember, don’t eat it if it’s gone bad. If you’re wondering when is rhubarb too old to use, our short guide gives you great pointers to follow to ensure you only get healthy, young plants.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.