5 Signs Your Spinach is Bolting (Plus The 3 Reasons Why!)
Seeing bolted spinach is frustrating after putting in weeks of effort to grow them. Is this just a normal occurrence or is there something the spinach needs? The truth is, it could be both.
Tall thick stems, small pointed leaves, and flowering stalks are all signs that a spinach plant is bolting. Factors like plant stress, 12 hours of sun, and temperatures over 70°F can cause spinach to bolt prematurely. Prevent bolting by providing spinach plants with adequate shade and water.
Bolting is nature’s way of ensuring the next generation of spinach plants will survive. But what exactly are the reasons behind this, especially if it happens too soon? Keep reading forward to learn why!
1. Green Flower Stalks
Young spinach plants with green flower stalks are bolting.
This, of course, is the biggest sign that spinach is bolting. The presence of flowers!
Check the top of the plant for flowers and seeds. These flowers are small and should be less than an inch wide, and may even blend in with the rest of the spinach.
2. Smaller Leaves
Spinach leaves that grow to be smaller in size is a sign of bolting.
Spinach leaves normally grow to be around 5-inches broad and are the perfect size for sandwiches.
If the leaves begin to develop in smaller sizes at the top of the plant with the flowers, the spinach is bolting.
3. Pointed Leaves
Pointed spinach leaves indicate the plant is bolting.
Not only will spinach leaves become smaller as they bolt, but they will also become more pointed and less ovate.
With most, if not all, of the plant’s energy going towards the production of flowers, you’ll find that the spinach leaves will grow to be less lush and full than they used to be.
4. Increased Height
Bolting spinach plants will grow tall and near 1 foot in height.
Spinach plants are usually low-growers and produce large groups of tasty leaves close to the ground.
However, if you notice your spinach is growing tall and close to a foot high, this is because it is trying to make its flowers more prominent to flying, pollinating insects.
This is usually a pretty obvious sign that your spinach is bolting.
5. Thick Central Stems
Spinach plants that grow thick, central stems and develop flowers at the top are typically bolting.
To help protect its new flowers from wind and damage, bolting spinach plants will grow one thick main stem in the middle.
Normally, this is where you will find all the other signs of bolting—tall, flowering stalks and small but sharp leaves. They will be located right at the top of this stem.
This is because the plant is now concentrating on reproducing and setting seed. So the usual spinach growth that you’re used to will quickly be halted as it focuses on its new priority.
The 3 Causes of Spinach Bolting
The 3 most common causes behind bolting spinach are:
- Increased temperature
- Increased light exposure
- Plant stress
So you now understand that bolting is completely natural and can be seen at the very end. But what exactly are the reasons why spinach bolts when they’re still so young?
To answer that, here are some of the most common causes of spinach setting seeds.
1. Increased Temperature
Spinach is a cool-season vegetable that survives by rapidly developing seed heads during hot weather. Temperatures over 70°F will signal the plant to bolt and grow flowers instead of leaves.
This plant thrives in cool weather. When temperatures become too high, however, it is natural for spinach to develop flower stalks and begin bolting.
Spinach prefers cooler temperatures, so if it is not grown with its desired conditions, it will instead focus on setting seed, and, as the term suggests, bolt as fast as it can!
Keep an eye on the weather in your area and prepare for spinach to potentially sprout flowers when temperatures consistently go beyond 70°F.
2. Increased Light Exposure
Because of its photoperiod sensitivity, spinach plants are more likely to bolt after 12 hours of daily sun exposure. This is the reason why spinach is not as commonly cultivated during the longer and hotter days of summer.
Long-day exposure can influence the growth of spinach plants and potentially cause them to bolt.
This is to help ensure the continuation of its species and make it more likely for the next generation to thrive.
When spinach absorbs full sun for the majority of the day, it will eventually adapt to this! Instead of growing foliage, the spinach will choose to develop flowers and seeds.
It can be amazing how quickly plants will respond to things. However, bolted spinach is usually undesirable.
Shade can effectively be used to help prevent this, but this is covered later on.
3. Plant Stress
Some of the most common causes behind bolting spinach are moisture stress and the crowding of plants. Factors like insufficient space and a lack of consistent watering can result in the plant feeling threatened and trigger premature bolting.
Stress can cause spinach to bolt prematurely. What’s unfortunate, though, is that stress can have its own myriad of factors behind it.
Moisture stress can be a significant factor behind spinach bolting, as spinach often has thin and shallow roots that require consistent moisture.
Spinach seedlings must also be planted at least 4 inches apart to prevent stunt growth. If they are not thinned out early on, this can lead to the spinach crops growing too closely together.
This stress can easily prompt spinach to start setting seeds and stop leaf growth too early.
5 Easy Ways to Prevent Spinach From Bolting
The 5 methods that can be used to prevent the spinach from bolting are:
- Water spinach more often in hot weather
- Remove spinach seed heads
- Grow spinach in cooler soils
- Provide spinach with some shade
- Plant spinach early
So, you’ve identified all the reasons why spinach may suddenly bolt. Now what?
To prevent this from happening again, here are some tips you can use to prevent your spinach from bolting.
1. Water Spinach More Often in Hot Weather
When average temperatures are above 70°F, spinach crops must be given adequate amounts of water. Excess moisture should additionally be avoided when there are more than 2 inches of precipitation per week.
Depending on where you live, you may be quite used to the ever-changing weather and temperature it brings. Spinach plants, however, are sometimes unable to adjust to such changes.
Temperatures close to 75–80°F will dry the soil out rather quickly. So make sure your spinach is given plenty of water during days of high heat.
Additionally, if your spinach is given more than 1–2 inches of rainwater a week, hold off on watering. To prevent triggering them to bolt, keep an eye on how much water you give it!
2. Remove Spinach Seed Heads
Seed heads can be removed on sight to help slow the ongoing bolting of spinach. However, this method will not halt the reproductive cycle completely and spinach plants are typically unable to convert back to normal growth.
Sometimes, bolting is inevitable. If this is the situation, you can help slow the bolting process down by snipping off and removing flowers and seed heads as soon as you see them.
This method can be used to try to maximize harvest but just keep in mind that this won’t stop the flowering entirely.
Bolting is an indicator that the plant is at the end of its life cycle. Once a spinach plant decides to bolt, there’s very little chance you can convince the spinach to act differently.
3. Grow Spinach in Cooler Soils
For optimum growth, spinach seeds should be planted in cool soils after the last sign of frost. Cover the soil with mulch to further prevent the spinach from bolting in the heat and help smother competitive weeds.
To help ensure your spinach leafy success, be sure to plant them in cool soils as soon as you can work the ground after the frost has left.
If you grow your spinach indoors or are growing it hydroponically, however, be certain they’re kept away from warmer rooms of the house.
Remember, spinach is temperature-dependent. Consider covering the soil with mulch to further help the soil from becoming too warm in the summer and protect them from weeds.
4. Provide Spinach With Some Shade
Spinach plants can tolerate full sun but are less likely to bolt if they are grown in partial shade. Prevent spinach from flowering by covering them with shade cloth or growing them in the shade of taller plants.
One gardener I know had an entire bed of spinach that was setting seed. To her surprise, she discovered the shaded half of her spinach crops were the only ones she found that were not bolting.
So, what’s the solution? To accommodate this cold weather plant, consider investing in shade cloth!
This shade cloth on Amazon is great for protecting spinach and is what I usually recommend.
Alternatively, you can purposefully grow spinach behind or under taller plants so they are hidden from the harsh rays of the sun.
You may even grow them under the shade of a tree or just prop something up in front of them, this will all provide you with the same benefit.
If you use grow lights, reduce the number of hours they’re left on.
This will essentially help trick the spinach into thinking the days have become shorter and that it is closer to winter. This is great if you happen to live in a hotter climate and still want to enjoy your leafy greens.
5. Plant Spinach Early
To minimize the chances of bolting, spinach plants should be grown as early as possible for them to flourish in cooler months. Cultivate spinach crops in spring and fall, when temperatures are lower and more consistent.
Prevent the spinach from becoming stressed and bolting by planting them as early as you can.
However, don’t wait more than 6–8 weeks when temperatures are predicted to go over 70°F. As we’ve discussed, this can increase the likelihood of spinach plants flowering!
Another thing to note, though, is that transplanting spinach can be quite difficult due to how delicately shallow its roots are. Consider planting spinach in the spring and fall, as these seasons are much more predictable.
Can You Eat Bolted Spinach?
Spinach leaves are completely safe for human consumption at all stages, including when it bolts. Bolted spinach is typically deemed inedible due to the plants’ increased bitterness but can still be consumed regardless.
Despite the popular belief that bolted spinach is inedible, it is completely harmless and safe to eat. It just has a sharper taste which many may find unpalatable!
The longer the spinach is allowed to bolt and develop seeds, the more pungent its flavors can become. This is because when it goes to seed, it is now producing different hormones that will affect the leaves’ overall flavor.
Its increased bitterness may play a part in the plant’s survival by making it less likely for wild animals to consume them.
This would explain why the seed heads are the most bitter, so try to avoid eating those! Eat some leaves to do a quick taste test and use them in stir-fries or soups.
Getting hungry? Read our article here on how to measure spinach.
Can animals eat bolted spinach?
Bolted spinach is completely safe for both human and animal consumption. Spinach is high in nutrients and can safely be fed to rabbits and chickens. However, large quantities of spinach must be avoided to prevent nausea and adverse health effects.
Are there bolt-resistant varieties of spinach?
There is no variety of spinach that is completely resistant to bolting. Bolting is a natural part of the plant’s life and reproductive cycle. However, some varieties are less likely to bolt prematurely, such as Olympia spinach and Bloomsdale Long Standing spinach.
Summary of Why Spinach is Bolting
Bolting spinach plants typically display small pointed leaves going up tall thick stems with flowering stalks. After the plant has experienced stress and high temperatures above 70°F, the spinach will begin its reproductive cycle and stop producing normal leaves.
Factors such as consistent moisture stress and long sun exposure can also contribute to premature bolting. To ensure success, spinach plants must be grown with partial shade and given adequate water to prevent the spinach from bolting.
- “Spinacia oleracea” by n/a in University of North Carolina
- “Bolting in vegetables” by n/a in The Royal Horticultural Society
- “Growing Spinach, A Cool-Season Vegetable” by n/a in University of Pennsylvania State