Have you been dreaming up a fresh batch of salsa or salad, only to discover that your cilantro has already bolted? Now what?!
"Why is my cilantro plant bolting?” and “What can I do to stop my cilantro from bolting?” are questions we field pretty regularly as Indoor Edible Gardening experts. If you’ve experienced this kitchen emergency, then you're in the right place.
Bolting cilantro is a classic culinary conundrum. When growing cilantro for the first time (heck, it even happens to experienced gardeners), you’re bound to discover it may have already started to bolt before you even made your first harvest. In this blog you’ll learn that timing is everything, and not everything you read about cilantro bolting online is true. So, what’s really going on with your cilantro plants when they bolt, and is there anything you can do about it?
What Is Bolting, And How Can I Tell If My Cilantro Is Bolting?
First off, let’s define the term bolting so you get a good handle on this developmental change in your cilantro plants. Bolting is when the plant shifts into its flowering phase, sending up an elongated flowering stem that develops into an inflorescence (a complete flower head that includes the stems, stalks, and flowers). The cilantro plant is doing this because it has sensed that it's time may be coming to an end, and it wants to create seeds (aka coriander) for the next generation.
The term “bolting” is most used when referring to biennial plants (ex. cilantro, broccoli) that live for one or two growing seasons, respectively, and then die after producing mature seeds for the next generation. Bolting and flowering are a totally natural part of your plant’s life cycle.
You’ll know your cilantro is about to bolt when you notice a thick central stem developing that has smaller, more deeply lobed leaves (very feathery looking). You may also notice some yellowing of the foliage, as the plant pulls nutrients from older leaves to fuel flower and seed development. Plants will then get very tall, very quickly. Once you notice this tell-tale sign of bolting, hold onto your herbs because these plants are off to the races!
What Causes Cilantro to Bolt?
How Temperature Impacts Cilantro Bolting
The first simple answer is temperature. Cilantro is an annual that thrives in cool to moderate temperatures and plants are triggered to bolt and flower when temperatures hit the 70s. Your best cilantro harvest will come when temperatures do not exceed 65-70°F. You’ll see plenty of generic recommendations for growing cilantro between 50-85F. If only it were that simple! It really depends on your local growing conditions…and importantly night temperatures.
- In New York City, grow cilantro from mid-April through early-November.
- In some parts of California cilantro can be grown year-round with harvests March-Mid-November.
- In southern California plant cilantro late-September-November and harvested late fall through early spring.
- In the Pacific Northwest, grow cilantro May through November.
- In Texas cilantro grow cilantro from September through February to early-March. You may also be able to get in a short crop from planting transplants in February, but it will be a short growing season with bolting occurring in March.
“But wait! You just told me I can grow cilantro at temperatures between 50-85°F….but didn’t you also just tell me it bolts at warm temperatures? 85°F is pretty warm! ”
Yes…but, you might not have considered the differences in night temperature between different growing regions. Warm days and cool nights result in a cooler day-night average temperature. In certain hot climates night temperatures are often just as warm or hot as day temperatures…causing plants to bolt, or bolt sooner.
Photoperiod or Day Length
The next trigger is photoperiod, or daylength. Once the day length exceeds 12 hours, as we head into late-winter or spring, your cilantro will set its sights on flowering. The longer the days the faster the flowering. For me in Dallas, TX a 12-hour day happens right about March 16…if you live in New York, you’re looking at about March 18.
Clearly, there’s nothing anyone can do to change the daylength. However, if you're growing cilantro indoors under grow lights then you do have significantly more control and it may be possible to delay the onset of bolting.
How Stress can influence Cilantro Bolting
A possible trigger for your cilantro to bolt out of season is stress. Plants that are under stress, say too little water or light, can sometimes – in a last-ditch effort to survive – pull all their existing resources to flower and make some seed before they die. Now, if you’re growing your cilantro under the right conditions this trigger won’t be as common a culprit as temperature and photoperiod. But it can happen, so just make sure your plants are getting plenty of light and appropriate amounts of water and nutrients.
Can I REALLY Stop My Cilantro from Bolting?
Because we’re here to deliver gardening advice that doesn’t suck, the truthful answer is…Unfortunately no, you can’t stop cilantro from bolting! Nor can you really slow it down in any meaningful way.
When cilantro is ready to bolt it’s going to bolt. Bolting isn’t a terrible thing! It’s what the plant is supposed to do. And there’s really no such thing as a cilantro plant that blooms “too early.” The plant is responding to temperature and day length and when those conditions are favorable for flowering that’s when it’s the right time for the plant to flower and produce seed. Who are we to argue with nature?
The bottom line is that unless you’re able to treat your cilantro plants with a plant growth regulator that suppresses gibberellin (a plant hormone that triggers flowering in cilantro in response to environmental changes like temperature and photoperiod)…there’s no stopping it! (Ok, WHEW that was a lot of botany, we’ll try not to do that to you again…unless you want us to!)
Does shading your cilantro keep it from bolting?
Growing cilantro in shadier spots or covering it with shade cloth is a method touted by some to prevent cilantro bolting. While a little shade - either from neighboring plants or shade cloth - or an inch or two of shredded mulch around the plant can keep roots a little cooler (this is especially beneficial in hot climates), remember that reduced light will also reduce the amount of leafy growth. These methods won’t prevent bolting, but they might buy you a little bit of extra harvesting time.
Can I Still Eat Cilantro When It Bolts?
If you’re a cilantro lover (and we know there are plenty of cilantro haters out there!), you’ll quickly notice an extra bitter flavor to cilantro leaves as soon as plants begin to bolt. Cutting off the flower stalk won’t reverse this unfortunate change. We recommend for the sake of all your dinner guests to put those pruners down, step away from your cilantro plants, and allow them to flower, feed the pollinators and beneficial insects (it’s a very popular pollinator plant), and harvest some coriander seeds! Yes, that’s right, cilantro seeds are known in the kitchen as coriander. Fill up a jar and keep it on hand to spice up your next curry dish.
What To Do When Your Cilantro Has Bolted?
It should not be pretty clear that there isn't really a whole lot you can do about it once your cilantro plant has bolted. Instead of dwelling on what can't be undone, we recommend:
- Starting over with some high quality cilantro seeds. Look for 'slow bolt' varieties.
- Check out our 5 Tips For Stopping Cilantro From Bolting, and
- Our comprehensive guides on how to grow cilantro either indoors or outdoors.
- If you're interested in learning more about cilantro and other plants that can be grow indoors, grab a free copy of our eBook titled 'How To Grow An Indoor Edible Garden' below.