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Bok Choy Flowering – What Causes Bolting?

I recently went out into the garden to find that my bok choy plants were flowering. The small leafy greens started forming a tall spike topped with yellow flowers. Has this happened to you?

There are a number of reasons your bok choy (also known as bok choi) may be flowering. In this article, I’ll share the 5 most common reasons your bok choy is flowering. Hopefully, I can help you avoid flowering bok choi in the future!

Bok choy flowering in late spring hot weather
Bok choy flowering in late spring.

Quick note: Pre-mature flowering is also called bolting. This refers to the unwanted flowering that is triggered by hormones in your plants. Bolting is generally something we want to avoid (unless we’re saving seeds).


1. High Temperatures

The first cause for bok choy flowering is heat. High temperatures can cause many cool weather crops to bolt. This is a natural response from the plants to begin the reproduction phase.

To help avoid early flowering, make sure to plant your bok choy at the right time. Bok choi (and pak choi) should be planted in very early spring or late summer into fall. Most varieties can tolerate a light freeze (down to around 27°F), so don’t worry about starting seeds too early!

Bok choy flowering upright
Bok choy plant bolting with yellow blooms.

If you are expecting a heat-wave, you can provide temporary shade using shade cloth over your bok choy and other leafy greens. This can provide some much-needed relief from the heat, especially during the hottest parts of the day (mid-afternoon).

There are also heat-tolerant varieties that can better withstand high temperatures before flowering. If you suffer from early heat spells (like we do), then one of these types may be a good choice to grow.


2. Transplant Shock

Another cause of early flowering in bok choy is transplant shock. When you plant out your seedlings, be careful to avoid over-handling the rootball. This can cause unnecessary stress to your plants, potentially causing them to flower too soon.

Young bok choy plants growing in a raised bed
Young bok choy plants recently transplanted.

Another related issue is having root bound plants. This happens when your bok choy sits in a pot that is too small for too long. The roots out-grow the container and begin to circle around in the pot, causing stress.

Avoid both issues by transplanting seedlings outside as soon as they are ready. Also, try your best not to disturb the roots in the process.


3. Day Length

Some plants are ‘programmed’ to flower during certain times of the year. But how does my bok choy know what time of year it is?

One method plants use to trigger different growth stages is the day-length. Essentially, how long is the sun shining, and how long is it dark?

This is more common in regions where the day length is long, but weather is cold. If the plant ‘thinks’ it is mid summer, it may produce flowers to set seeds.

Unfortunately, there isn’t much to be done to avoid this trigger other than planting at the correct time of year. Again, early planting in spring or mid-late summer sowing are the best times to plant bok choy.


4. Water or Nutrient Stress

Bad watering habits or poor soil can cause stress in bok choy plants, potentially triggering flowering. Essentially, the stressful environment puts your plants into panic mode, causing them to reproduce.

First, make sure your garden soil is well-draining, meaning that water doesn’t pool on the surface. If you’re growing in pots, make sure they have drainage holes to allow excess water to flow out of the soil.

If you haven’t already, get a soil test from your garden. These tests look at what nutrients are in the soil, soil acidity, and composition to help make any necessary improvements for optimal growth.

You’ll learn things like how much sand, silt and clay are in your soil. You’ll also discover how much nitrogen, phosphorus, and potassium are in the soil, along with recommended actions to correct any issues.


5. Succession Planting (Is Not All That Effective…)

Since so many of the causes for bok choy flowering have to do with planting at the wrong time, why not succession plant? This is the process of sowing seeds every week so that harvests come regularly.

The problem is that bok choy will still often flower when the environment changes, regardless of the plant’s actual age.

Bok choy plant flowering
2 bok choy plants planted at different times, but both are flowering.

So, the better option is to find out the ideal time to plant in your region. In my personal experience, the earlier you plant, the better.

Of course this doesn’t mean you can plant in the dead of winter, but you may be surprised at how early you can get your bok choi outside in very early spring.

Experiment with planting times to see how early you can get away with planting. It is better to take a few risks to learn for yourself what works best for you.


Uses For Bok Choy Flowers

Since your bok choy is flowering, why not make use of those beautiful blooms?! Here are some great uses and benefits of bok choy flowers:

  • Flower stalks are edible. While they aren’t quite the same texture and appearance as the foliage, bok choy flowers are fully edible! Chop up the stalks and use them in stir fries, soups, or wherever you planned on using your bok choy leaves.
  • Allow plants to produce seed. If you like to save seeds, then you’re in luck. Bok choi flowers will eventually produce seeds which can be harvested, dried, and stored for planting later.
  • Attract pollinators. Like many flowers, bok choi blooms will attract pollinators to your garden. So, if you don’t mind them taking up your garden space, let them bloom and bring in the bees!

I hope this article helped you understand why your bok choy is flowering. Many of these same principles can be applied to other cool weather crops like spinach, lettuce, broccoli, and cauliflower!

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