Spinach is versatile, nutritious, easy to maintain, and can add a vibrant pop of color to any garden, making it a perfect plant to grow. However, beginner and seasoned gardeners can still struggle to grow the perfect spinach plant, especially if they can’t provide optimal growing conditions. If this is your first time growing spinach, you might even feel worried about its sheer size, as the plant can quickly tower over your garden.
Your spinach is growing so tall because of issues like poor light, water, and temperature conditions and failure to harvest at the right time. It’s natural for it to grow to 1 or 2 feet (30-61 cm) tall, but if your spinach grows taller than this, it can be a sign that you have an inedible harvest.
There are many caveats to the explanation above, so let’s explore the topic of spinach growing too tall a little more in-depth. Below, I’ll answer whether a tall spinach plant is a good sign. I’ll also go over some of the most common reasons why the plant might be overgrowing, the best time to harvest spinach, and how the plant can be affected by bolting.
Is Tall Spinach a Good Thing?
Tall spinach is a good thing because it signifies that your plant is healthy and thriving in its environment. The only instance in which tall spinach isn’t a good thing is if you find it unsightly or if the spinach is excessively tall.
If you notice your spinach plant reaching 1 or 2 feet (30-61 cm) high right around the time of harvest, it’s a healthy sign. Most spinach species that reach this height are fully grown and ready to be eaten, meaning that the growth process has been successful and you have provided the plant with all the necessary growing conditions.
However, before determining whether excessive height is something to worry about, you first need to determine what “excessive height” entails in your particular case. That’s why, if you get your plants from your local nurseries, you want to save the informational label attached to them. That’ll give you a rough idea of how tall you can expect your spinach to grow.
If you’ve accidentally lost that information, you can still reach out to local nurseries and inquire about the specific species of spinach you’re growing. If you don’t know much about the type of plant you’re growing, you can reliably stick to 1 or 2-foot-tall expectations.
Excessively tall spinach is typically only a bad thing when the plant has overgrown so rapidly that it has surpassed all your set height expectations. While, in this instance, gardeners might believe that they’ve done something right to have their plant exceed any size expectations, they’d be surprised to learn that overgrowth can be just as dangerous as undergrowth.
Overgrowth results from a problem in the plant’s life cycle, and it can render your entire harvest inedible. It’s hard to pinpoint what the trigger of this issue might be without examining the plant itself.
But generally speaking, potential problems include the following:
- Poor growing conditions
- Failure to harvest at the right time
Reasons Spinach Might Grow Too Tall
Let’s take a closer look at the potential causes for excessively tall spinach. How do they exactly affect spinach growth, and how do they usually present themselves?
Poor Growing Conditions
Upon reading “poor growing conditions” on this list, you might feel surprised. How can incorrect growing conditions make a plant surpass its expected size? Surprisingly enough, it’s a common phenomenon.
Spinach can easily bolt and become bitter when the environmental conditions are suboptimal. Some parameters to pay extra attention to are the amount of sunlight per day, the air temperatures, and the soil moisture.
Spinach Needs Partial Sun
Ideally, a spinach plant needs 4 to 6 hours of sun per day. When the plant doesn’t receive all the light it needs, it grows taller and leggier in search of a light source, ultimately surpassing the 1-to-2-foot benchmark. That’s why you should ensure that all the plant’s light, nutrient, water, and soil needs are met.
Spinach Is A Cool-Season Crop
This leafy vegetable grows best when the air temperatures remain between 50 and 60 °F (10-15.6 °C).
Seeds and seedlings have better tolerance to the heat and cold, respectively. For instance, seeds have better germination rates when soil temperatures reach up to 75 °F (24 °C).
On the other hand, young seedlings with a couple of leaves can survive air temperatures as low as 15 °F (-9 °C). This sometimes happens when the seedlings sprout just before the last spring frost. Once the frost passes, the young spinach plant will continue to grow.
However, mature spinach plants that are over four weeks old will likely grow tall flower stalks if the air temperatures go above 70 °F (21 °C). This process is called bolting, which is a plant’s defense mechanism to produce flowers and seeds in case of stressful situations to ensure they survive the following year.
Moist Soil Prevents Bolting
Although some varieties, such as the Malabar spinach and Bloomsdale spinach, are heat and drought-tolerant, most spinach cultivars are cool-season plants.
Cool-season spinach plants can cope better with higher temperatures and excess sunlight if the roots remain cool with adequate moisture. If the soil is allowed to dry out, it can become a stress signal that will trigger your plant to bolt.
Failure to Harvest at the Right Time
This is usually the main cause of spinach overgrowth, and it, unfortunately, comes as a result of human error. Keep in mind that “human error” in this instance doesn’t always mean that you were negligent toward your plant. Sometimes, you can watch your spinach like a hawk and still miss important signs due to inexperience.
Lack of knowledge or previous experiences can also make you uncertain, even if you do notice a sign or two. Not wanting to risk an early harvest, you wait, and you wait until it’s too late—a scenario every gardener can relate to.
Unfortunately, as I’ll also explain in one of the following sections, once the spinach starts bolting, the leaves become bitter or tasteless, meaning your hard work will have gone to waste.
That’s why it’s imperative to find the right time to harvest your spinach—neither too early nor too late. However, sometimes even the most careful gardeners miss the cues the plant sends when it’s ready for harvest.
When to Harvest Spinach
Experienced gardeners may tell you that it only takes about six weeks for spinach to be ready for harvest. Unfortunately, there’s no mathematical equation that can help you determine when your spinach is ready to harvest.
With that said, there are still plenty of signs and methods you can rely on to make an educated guess. There’s an overall consensus that spinach is ready to harvest once its height surpasses its width and the outer leaves reach a length of about 6 inches (15 cm).
Remember that different spinach species have different-sized leaves, so always keep the informational pamphlet that came with your plant on hand to refer back to it whenever you need to.
Moreover, if you’re growing your spinach in spring and notice that the plant is about to bloom (or bolt), you’ll want to harvest it immediately. As I’ll explain further below, spinach that has bolted has already gone to waste, so you should act as quickly as possible.
Another technically correct but less precise suggestion is to harvest spinach leaves as soon as they’re large enough to eat. Though this approach might seem vague initially, if you’re an avid spinach eater, you already know what your harvest should look like without even needing to measure the leaves.
I recommend harvesting spinach in layers. It’s best to remove the outer layer of leaves first, as this gives the smaller ones an opportunity to grow. As soon as they’re big enough, you can harvest the inner leaves too.
I know that this process is more tedious and time-consuming than if you were to just harvest them all at once, but your effort will surely pay off in the final taste of your dishes.
Keep in mind that this suggestion doesn’t apply in those instances when the spinach is about to bolt. Once the blooming process has taken place, the plant will grow even taller, but its leaves will quickly turn tasteless or, even worse, bitter.
So, if you find yourself in this situation, removing all the leaves or pulling out the plant is the best course of action. Bolting is also a consequence of failing to harvest at the right time, and it can cause the plant to grow even taller. I also urge you to taste as you harvest to make sure the spinach you’ll be bringing home is pleasant-tasting. In some instances, the leaves might turn bitter faster than expected.
How Does Bolting Affect Spinach Size?
Bolting (or going to seed) is a term used to refer to the phenomenon where a plant prematurely develops a flowering stalk due to environmental stress brought about by high temperatures, low soil moisture, and too much sunlight.
With spinach, you want to harvest the leaves and not the flowers. It’s inconvenient when it bolts because the plant starts redirecting a great deal of nutrients and energy to the new growth, leaving the rest of its structure underfed.
When the plant blooms unexpectedly, a surge of nutrients and energy goes toward its growth as its organism tries to sustain the new flowers. That’s why when your spinach starts bolting, you’ll notice it growing way taller than usual.
Bolting is an issue that most gardeners, especially amateur ones, have to deal with at one point or another. What casual growers might not know, for example, is that all garden vegetables can bolt if left unharvested for long enough, and spinach is no exception.
This phenomenon can often negatively affect your harvest, which is why you’ll want to avoid it at all costs. So, while you wait that extra day or two to ensure your crops are fully ripe, remember that waiting too long might make all your harvest go to waste.
Now that you know what bolting is and why it’s important to prevent it from occurring, it’s time to learn about the signs to look out for before it’s too late. Once you notice one or more of the occurrences listed below, act quickly and harvest your spinach as soon as possible.
Signs That Spinach Is About to Bolt
Here are the most common signs your spinach is about to bolt:
The Plant Is Growing Too Tall
As mentioned previously, as soon as your spinach grows uncommonly tall, you should stay alert for the possibility of bolting. Generally, spinach grows horizontally rather than vertically, although when it’s ready to be harvested, it’ll be slightly taller than wider.
However, when it starts growing uncontrollably with a central stalk becoming taller than the rest of the plant, it’s a telltale sign that there’s an issue.
The Main Stalk Suddenly Becomes Thicker
A spinach stalk is typically fairly narrow, as the well-established nutrient transport system has plenty of space to reside within it. However, when the plant becomes ready to bloom, the surge of nutrients wouldn’t be supported by the narrow, delicate stalk. That’s why, right before the plant bolts, you’ll notice this part getting visibly thicker.
The Leaves Change Shapes
If you’ve grown spinach before, you know that its leaves are quite rounded around the edges, creating an oval shape. However, when the plant’s about to bolt, you’ll notice the leaves becoming more angular at their edges, creating an arrowhead shape. This change is a tell-tale sign of bolting.
What to Do if You Notice Bolting
If you’ve noticed one, or worse, several of these signs, it’s time to take action. If you ignore the warnings that the plant is giving you, you might end up with an inedible harvest. The best solution is to harvest the leaves immediately or pull the plant altogether. While you might lose some under-grown leaves in the process, it’s still better than being left with no harvest at all.
There are some approaches you can try to salvage your bolted spinach. However, those come with no guarantees. That’s why it’s best to move the harvesting date closer and save the leaves you can.
If your plant hasn’t shown any of these signs yet, you’re in luck! You can still take some steps to prevent or delay bolting as much as possible so that you can comfortably harvest your spinach on your own schedule.
How to Prevent Bolting in Spinach Plants
After knowing the downsides and signs of bolting, you can prevent the issue from occurring in your future crops by following the tips below:
Keep the Soil Moist But Not Wet
Hydration levels play an essential role in the well-being of any plant, spinach included. While beginner gardeners may consider watering the easiest part of the process, it can actually be quite complex. Striking a balance between over and underwatering is difficult.
Spinach has a deep taproot with lateral roots that enable it to access water from the soil. Giving it 1 inch (2.5 cm) of water weekly should be enough to keep it well hydrated. That means a mature plant with a 1-foot (30 cm) diameter should receive about 0.6 gal (2.3 L) of water weekly.
You can increase the volume to 0.9 gal (3.4 L) when the temperatures go around 70 °F (21 °C).
Make Sure the Temperature Is Ideal and Consistent
The optimal growing temperature for spinach ranges between 50 and 60 °F (10 and 15.6 °C).
Although the plant can thrive even when the climate is a bit cooler or hotter than that, you still want to make sure you’re protecting your spinach plant from extreme temperature fluctuations, as those can quickly cause stress and, in turn, cause it to bolt.
You can place a shade cover over your spinach row during the hottest parts of the day to keep them cool.
Choose Bolt-Resistant Varieties From the Start
Not all spinach species are created the same. They differ in taste, size, color, and bolt resistance. Getting good-quality, non-stressed seedlings that are bolt-resistant can make your job much easier.
Excellent examples of bolt-resistant or slow-bolting spinach include the following:
- Indian summer
I cannot stress the importance of using mulch enough. Mulch helps the soil retain moisture without becoming waterlogged, helps keep weeds at bay, and, as it turns out, can help prevent bolting too.
Applying a 2-inch layer of straw mulch can keep the roots cool during hot days. Since the extra material helps insulate the soil and roots better, your spinach will be less prone to temperature fluctuations and less exposed to the elements and, in turn, less likely to experience stress.
If it’s your first time trying to grow spinach, know that it’s normal for it to grow up to 1 or 2 feet (30-61 cm) tall. However, if it gets any taller, there might be an underlying issue. Potential reasons include failure to harvest at the right time and improper growing conditions.
Knowing the right time to harvest spinach is imperative when it comes to keeping it from overgrowing. So, if you want to enjoy your fresh, delicious spinach, make sure to harvest it as soon as its height surpasses its width.
If you found this guide helpful, I recommend my complete guide on trimming spinach. I’ll discuss the many tips and tricks to properly trim your spinach to keep it growing after harvesting: How to Trim Your Spinach to Keep it Growing