Are My Flowers Dropping?

photo by @mytinyharvest

 

Many times, I have seen new hydroponic growers frantically asking for suggestions how to help their plants (primarily tomatoes) that are dropping flowers... only to post pictures, and they aren't losing flowers at all.  Quite the opposite!

To get to the bottom of this, you first need to understand a bit about how fruiting flowers work. 

I'm sure most of us recognize a chart of this nature from our school days.  Don't worry, there won't be a quiz!  But in a so-called "perfect" flower, meaning a flower with all the needed parts, pollen needs to get from the stamen (aka 'antler'), to the stigma.  This is why shaking or 'buzzing' the flowers with a Be the Bee wand or something similar is all that is needed - the pollen only has to get a tiny distance.  From there, it moves to fertilize the ovules, which eventually become seeds.  In fruiting plants like tomatoes, peppers, eggplants, etc., the successful fertilization triggers the ovary to turn into fruit, containing the fertile seeds.  Once this job is done, it no longer needs the decorative bits that attract pollinators - in other words, the blossom.

So!  Back to our primary question.  

Whether your flowers are successful or not, the blossoms are going to fall off.  But how do you know whether to worry or not?  Luckily, it's very simple.

If the entire flower segment, including the stem and cap, comes off, that is a dropped or fallen flower.  If, however, it's just the actual flower petals part, that is actually a good sign, as it means your flower was fertilized and it is now in the process of turning into edible fruit!

Two healthy post-fertilized flower shed, and a dropped flower

As you can see above, it's a very distinct difference.  If it has a green 'cap', it is a dropped flower.  If it's just the petals, all is good.  

It can feel worrisome since you can't necessarily see a little tomato, but if you get down to look inside the green 'cap' that is left behind, it's there.

Dried up flower petals about to pop off a baby tomato

As an amusing aside, those tiny black 'strings' on the bottom point of tomatoes?  That's the dried up leftover flower stigma.

I have an actual dropped flower!  Is it time to panic now?

No! Even healthy, well-producing plants will drop a flower now and then.  It could be from damage (getting bumped, etc.), it could be due to a simple error in the flower's production, it may have grown in a position that it didn't manage to get fertilized, or it could be something as simple as the plant already has too many fruit forming, so it shed a couple of extras.  Only if you start getting multiple dropped flowers over a short period, is it time to start worrying and trying to track down the problem.

In AeroGardens, when there is substantial flower drop, the vast majority of times it is due to insufficient pollination.  Relying on a fan or gently shaking the bush will get you tomatoes, but most of the flowers will drop.  Trying to hand pollinate, with a brush or a q-tip, is stressful, time consuming, and still has a poor success rate.  Using the Be the Bee wand on each flower for a couple of seconds each day results in almost perfect fertilization rate.

The next most common cause is insufficient nutrients.  Tomatoes are very heavy feeders; it is one of the reasons it is important to have empty spaces for each plant you're growing — it means that 3 smaller plants' worth of nutrients are available for each one.  However, if your plants get very large, and especially when they're trying to set a lot of fruit, even that may not be sufficient.  In these cases, I generally recommend adding a second, half-strength feeding halfway through your 14-day feeding cycle.  It makes more nutrients available for them, and alleviates some of the feast-and-famine effect. 

Hand in hand with this, incorrect pH can cause a lot of blossom drop.  An inexpensive pH meter is a very useful tool when you are trying to grow fruiting plants.

If you are reasonably certain you are successfully pollinating and your nutrient and pH levels are good, other causes of flower drop are temperature (either below 55F regularly, or extreme fluctuations), stress (such as routinely allowing the tank to run dry), and - as mentioned before - simply having too many flowers/fruits already.