When you grow spinach in your garden, one thing you want to avoid as much as possible is flowering. Also known as bolting, it changes the taste of your spinach for the worse, making it bitter and unpalatable. Not only does this reduce your yield, but you may also not get to enjoy your harvest.
You can keep spinach from bolting by planting it in early spring and fall. Spinach plants start flowering with increasing temperatures and daylight. Using row covers, ensuring the soil isn’t dry, thinning young plants, growing slow-bolting varieties, and applying fertilizers can tackle this problem.
Depending on the growth stage of your spinach plants, there are several ways to keep them from flowering. This simple guide highlights everything you should know about this topic, so the spinach growing in your garden takes a longer time to bolt.
1. Start Off With Slow-Bolting Spinach Varieties
You should plant slow-bolting varieties if you haven’t started growing spinach in your garden. Generally, these leafy greens are divided into three categories:
- Fast Bolting
- Medium Bolting
- Slow Bolting
Of all the varieties, slow bolting will work well because it takes longer to flower than others. You can go for types like Bloomsdale Longstanding, Indian Summer, Melody, Space, Whale, Winter Bloomsdale, and Tyee.
Bejo 1369 and Splendor are also excellent alternatives due to their exceptional tolerance to bolting.
Consider growing a species that tolerates heat well. Examples include New Zealand spinach and Malabar spinach. The former’s leaves are edible and can withstand drought-like conditions easily, with the latter falling under a different family of spinach, i.e., basella. Despite this, it tastes similar to regular spinach after cooking. You can identify Malabar spinach thanks to its heart-like leaves and green or red stem.
2. Sow the Seeds in Early Spring or Fall
One major factor that keeps your spinach from flowering is when you sow the seeds. Ideally, early spring and fall are the best seasons to plant this leafy green in your garden. However, if you plant too early—i.e., when there’s still frost on the ground—premature flowering will still be a problem.
This is because of a process known as vernalization, meaning you planted the seed when the temperature was low. Although older plants can survive temperatures as low as 20°F (-6.6°F), this isn’t the case for seeds and younglings.
When To Plant Spinach in Spring?
You have at least four weeks before the average last frost to sow the spinach. Now, it isn’t necessary to plant all the leafy greens in one go. This can be detrimental as all the spinach can flower simultaneously, which means you won’t get to harvest most of the leaves.
A better option would be to follow succession planting, where you space out the sowing period every 1-2 weeks. This is beneficial as you get a continuous harvesting period lasting a long time. It also ensures that not all leafy greens flower at the same time.
You can use a raised garden bed if you’re planting early in spring. This structure benefits leafy greens, allowing the soil to warm up faster than usual.
Ideally, you should plant slow-bolting varieties in spring as they have a higher tolerance to warmer temperatures.
When To Plant Spinach in Fall?
Another way to keep your spinach from flowering is to sow the seeds during early fall—well before it snows. This provides adequate time for the leafy greens to produce their foliage before they halt growth to withstand the lower temperatures.
On average, you have up to 6 weeks before the first average frost.
For this season, you can go for fast-bolting varieties, as the chances of spinach flowering are almost zero. Planting in mid-August works great, giving you adequate time to harvest the foliage before winter starts.
You can also sow the leafy greens in late September. This ensures there is time before winter for the foliage to grow. Once the temperature drops significantly, the plant will stop growing. At this stage, you can cut the flora one inch (2.54 cm) above the soil, essentially the point from where the plant grows.
This allows the leafy green to survive winter and start growing in spring. For this technique to work, you’ll need to plant a variety like Bloomsdale Longstanding, which has excellent tolerance to lower temperatures.
What About Transplants?
If you’re planning on getting spinach transplants from a nearby nursery, keep a few things in mind. Like seeds, you can sow them in spring or fall. However, you must check the transplants’ health before buying them.
For instance, if you notice any signs of stress, i.e., the plant doesn’t look healthy, or there are discolored leaves, avoid the leafy greens. Stressed spinach plants are more likely to flower earlier than their healthier counterparts.
Similarly, avoid older spinach plants, especially those with thick foliage. A sudden change in the growing conditions may induce stress, resulting in the plant flowering prematurely.
3. Take Extra Precaution To Ensure the Soil Isn’t Dry
Another reason your spinach starts to flower early is that the soil is too dry. When the leafy green is under drought stress, the plant will shift its priority from growing new foliage. Instead, it will focus on producing the seed stalk, an indicator that the flora is ready to flower and produce seeds.
As a result, you want to ensure the soil isn’t dry. Not only does this delay flowering in the spinach plants, but it also ensures you get better yields.
How Much Water Do Spinach Plants Require?
The rule of thumb for these leafy greens is at least an inch (2.54 cm) of water every week.
However, you won’t have to irrigate your garden as frequently if the area you live in also receives at least one inch (2.54 cm) of rainfall per week.
Now, this doesn’t mean you should stick with this irrigation schedule. How much water the spinach plants require also depends on your soil type.
For instance, spinach does well in sandy, loamy soils. However, this type of soil has excellent drainage properties. As a result, you’ll have to increase the irrigation frequency to ensure the soil doesn’t dry up.
Let’s look at another type of soil with more clay content than sandy, loamy soils. In this case, the clay allows the soil to retain water. Also, water doesn’t penetrate as deeply as it does with the sandy variant. For example, an inch (2.54 cm) of water poured into soil with high clay content goes down six inches (15.24 cm). Sandy loamy soil will allow the same volume of water to penetrate up to a depth of 10 inches (25.4 cm).
What is the point of allowing the water to go deep into the soil? The roots of the spinach plant will grow to reach the water deep inside. This benefits the leafy greens, allowing the flora to survive arid weather conditions.
The spinach plants will survive even if you are out of town and can’t find someone to water your garden. In addition, they won’t flower prematurely, preserving the taste of the leaves.
Always make sure there is sufficient moisture in the soil at all times. Dig two inches (5.04 cm) into the soil and see how far the water penetrated. If it is below two inches (5.04 cm), you must continue irrigating the garden soil.
Avoid light watering, as this only promotes shallow root growth. Also, as water can evaporate quickly from the surface, your leafy greens will face water stress.
How To Stop the Soil From Becoming Dry?
As long as you follow the best practices highlighted above, you should be able to prevent the spinach plants from flowering due to water stress.
You can also use other techniques to ensure you never face this problem in your garden. One of the best ways to retain soil moisture is to use organic mulch. In other words, you need to cover the top of your soil with fallen foliage, grass, or straw.
Once you cover the soil, it takes longer for moisture to evaporate, which is beneficial for leafy greens. Also, it prevents weeds from growing and competing with your spinach plants.
When adding materials to your mulch pile, ensure it is free of diseases and contaminants. If you don’t take this necessary precaution, you will infect your spinach and cause problems in the future.
4. Keep an Eye on the Temperature and Daylight
If you want to keep your spinach plant from flowering for as long as possible, you must pay attention to the temperature and daylight. Spinach grows well when the weather is cool, i.e., 40°F (4.4°C) – 85°F (29.4°C). For best results, keep the temperature between 60°F (15.5°C) – 65°F (18.3°C).
You should plant spinach in early spring because the temperature is usually below 80°F (26.6°C). These temperatures don’t stress out the plant, allowing it to focus on producing edible foliage.
Should the temperature go beyond 85°F (29.4°C), you should be wary, as your spinach can flower at any time. Generally, the temperature will reach this point during summer.
How hot it is isn’t the only factor that induces flowering in your leafy greens. Another element at play is daylight, or how long there is sunlight during the day. You may have noticed that the length of daylight increases during spring while peaking in summer.
Having more than 12 hours of daylight during the day triggers spinach to switch to flowering instead of producing foliage.
How To Deal With Increasing Temperatures and Daylight?
Is there anything you can do once the temperature goes beyond 85°F (29.4°C) and daylight exceeds? Luckily, there are several ways you can prolong foliage production, even when the environmental conditions aren’t favorable.
1. Sow Summer Vegetables for Natural Cover
An easy way to deal with this situation is to grow another vegetable with your leafy greens. Generally, you should plant the summer vegetables before you sow the spinach seeds in the soil. This gives enough time for the summer vegetables to grow and develop thick foliage.
As your spinach grows in the garden, the foliage from the summer vegetables provides shade, bringing down the relative temperature and exposure to sunlight.
You don’t have to worry about growing spinach under shade, even though it grows best under direct sunlight. Your leafy greens will still thrive as long as they receive at least 4-6 hours of daylight.
2. Row Covers Can Also Provide Shade
What if you have already planted spinach in your garden? Well, you can still reduce the relative temperature in your growing space with row covers.
Made from lightweight materials like polypropylene or polyester, they provide shade to spinach plants. Row covers work well in gardens as they allow water, sunlight, and air to go through.
You should be able to use them for 2-3 years before you have to get new ones. Don’t worry if you don’t find any that meet your requirements, as you can always cut and reshape them as necessary.
How Do Row Covers Help?
Using a row cover in early spring provides some protection against frost as it allows the soil to warm up faster. It also works well during the fall. This is because it reduces the soil’s relative temperature, allowing it to germinate without putting it under stress.
Also, it extends the vegetation period for the leafy greens, allowing you to harvest as late as early winter. This is because row covers will keep temperatures below them warmer than the environment.
You can go for light or medium-weight row covers as they provide the best protection for leafy greens.
Another reason you should use row covers in your garden is their ability to prevent temperature fluctuations. Sudden temperature changes don’t fare well for spinach as they increase the chances of spinach flowering out of the blue.
Make sure to use the row covers as soon as you notice seedlings emerge or when you sow transplants into the soil. When it rains, water will penetrate the cover. However, this doesn’t mean you should also irrigate your garden by pouring water on the cover. Instead, remove it and irrigate the soil directly.
Finally, row covers deter various pests, reducing the amount of stress the flora face. However, they can allow weeds to grow underneath, which can be a problem. Spinach doesn’t do well when competing for resources with other flora. Consequently, you should check underneath the row covers regularly and pull out any noticeable weeds.
5. Thin Spinach Leaves As Required
A common mistake among home gardeners is that they allow the spinach foliage to grow unchecked. This can be a problem as they can overcrowd the garden, reducing growth and eventually resulting in premature flowering.
Generally, spinach requires at least 4-6 inches (10.16-15.24 cm) of space between each plant for the best growth. When the flora reaches a height of two inches (5.04 cm), you should thin the foliage. This encourages new leaf growth, prolonging the vegetation period.
For more information, check out my complete guide on how to trim your spinach to encourage growth: How to Trim Your Spinach to Keep it Growing
6. Only Use Fertilizers When Necessary
Home gardeners love spinach because of its low resource requirements, thanks to its small size. However, this doesn’t mean you shouldn’t use fertilizers at all. In fact, if the leafy greens don’t have access to the necessary nutrients, the plants will be under stress, resulting in premature flowering.
Now, you should only use fertilizers after a proper soil test. Getting one for your garden is essential to know what the soil requires.
After a soil test, you should apply fertilizers to the soil. Ideally, you need to do this 3 months before you sow anything into the ground. Also, you must till it regularly, at least to a depth of 6 inches (15.24 cm).
Following this practice will ensure sufficient nutrients throughout the soil for the leafy greens. When using fertilizer after the plants have been established, make sure you apply the fertilizer at least 4-6 inches (10.16-15.24 cm) away from the plant. This ensures the roots don’t get damaged.
Also, after harvesting the outer leaves, you can apply a side-dressing of fertilizer to encourage new growth. For example, in this stage, you can use ammonium nitrate or sulfate. Not only will it boost growth, but it also increases your yield.
Premature flowering or bolting in spinach plants changes their taste, making the leaves bitter. This is why you should try to prolong the vegetative period as long as possible to have a better yield. If you’re planting in early spring, choose slow-bolting varieties, whereas you should go for quick-bolting varieties when planting in early fall.
Using row covers and planting warm-season vegetables can help deal with unfavorable weather and daylight conditions for spinach. Also, using fertilizers after thinning the plant and ensuring the soil is wet ensures the leafy greens continue to grow new foliage.