“A mysterious and occult phenomenon”. Believe it or not, that is how groundwater hydrology is described in Texas State law concerning groundwater use. Back when the law was written (Billy the Kid was still in diapers then) folks didn’t have a clue about where groundwater came from, how it got in the ground, or how you got it out, save for digging a hole. So groundwater was described as a mysterious and occult phenomenon that couldn’t be controlled by state law. This gave landowners complete and unrestricted control of what they could find on their land. Lately, Texas has been trying to catch up with the 20th Century at least, and has been updating the water laws, but as far as we know, the “mysterious and occult” part is still there. That’s probably why Frank was able to douse for our last well!

When it comes to the post harvest handling and vase life of zinnias, we think the same mysterious and occult phenomena are at work! Zinnias are one of the most widely used and popular specialty cut flowers grown by small farms and local growers, but so very little is really known about how to handle them. Every grower has a different method of handling them, but one story is common. “ My zinnias have been fine all season, but suddenly the petals are turning brown and I don’t know why.” This has happened to us, and to just about everyone we know, at one time or another. They’ll be fine for weeks, and even though nothing has changed (so you think) they suddenly start to go down. It can only be occult–our competition must be putting a Mojo on us!

After sunflowers, zinnias are probably our most important summer crop. We use a lot of them in bouquets, and we sell a lot of straight bunches. Lately they have been very popular at the new Austin Farmers Market. So we need to make sure they last for our customers. We set out this season to run some trials, and we have decided that zinnia post harvest handling is a much more subtle and sensitive process than most folks realize. We’ll go over what we found out, but first of all, here is a little basic post harvest handling info about field grown cut flowers and floral preservatives.

Floral preservatives are essential in any operation that wants to sell a flower that lasts for the customer. In a nutshell, a floral preservative does three things–it lowers the pH of the water, it kills bacteria and other organisms in the water, and it provides a food source for the flower. This food source is usually sugar, a point we will return to later. There are many different formulations of floral preservatives depending on the company and the type of flower you are using it with, but they all have the three basic characteristics.
A floral preservative is different from a “hydration” solution, which is used to help the stems take up water quickly after cutting. Hydration solutions can be something that acidifies the water to speed uptake, or they can be some type of surfactant (a soap-like compound) that breaks the water surface tension and allows the water to move more freely in the tiny little tubes that carry water in the stems. In either case, hydration solutions do nothing for the long-term maintenance of flowers, and flowers should be transferred out of hydration solutions and into preservative after they are properly hydrated. Floralife Hydraflor, Quick-Dip, and Chrysal OVB are examples of hydrators.

There are three basic problems with post-harvest handling of zinnias. One of them is the browning of the petals. This can happen sometimes overnight. Another problem is with bent necks, where the stem bends right under the flower and becomes very brittle and snaps off. The third problem is when the stem ends break down and decay rapidly in the bucket. All of these problems are related to each other in terms of proper preservative use.

Clean buckets a must
First, let’s talk about the stems rotting. This is a very basic problem that is at the heart of vase life problems with all flowers. A cut flower stem is an open wound that feeds bacteria, and as the bacteria grow and clog the stem, water can’t move up the stem and the flower wilts. It’s that basic. With zinnias it’s a bit more complicated because zinnias tend to rot quickly, so along with a clogged stem, you can get a meltdown that rapidly results in a smelly mess of glop where there once was a stem. Yuk.

Your first line of defense is to have clean buckets. VERY clean buckets. In case you didn’t hear that we said VERY CLEAN BUCKETS! We can’t say it enough. We have seen so many growers, wholesalers, and florists using dirty buckets, and then they complain about vase life. We wash and disinfect every bucket we use, every time we use it. Putting flowers in a dirty bucket is a sure way to ruin months worth of hard work. Always use fresh water and make sure that there are no leaves in the water to carry dirt and feed bacteria. If you don’t keep zinnia stems in clean water, the other concerns are a moot point.

About the bent necks. We are convinced that the problem of bents necks lies with hydration, specifically with too much hydration. One of the hard things about zinnias is that depending on the weather, they can be a different crop to pick each time you pick them. In our hot Texas summers, we need to use a hydrator to pick everything into, including zinnias. But on the rare cool rainy day, or late in the fall, a hydrator can over-hydrate a zinnia. In Northern areas where the climate is typically cool and rainy, (or even in Texas after too much rain) the stems can be so turgid with water that when they are cut and put in water, they take up more water than they need–the stems curl just like a dandelion stem would curl when you split the stems and dropped them in water as a kid. We have even seen zinnia stems curl on the plant after a very wet period.

We have found that although we have to use a hydrator, we really can’t leave the zinnias in a hydrator for more than an hour. We use Chrysal OVB, and with most other flowers, we can leave them in the solution until we can process them, even overnight. But with zinnias, the stems will absorb so much water that the flower heads will curl over just like a hook. So we always transfer our zinnias into new (CLEAN!) buckets when they come out of the field. The next morning we can always tell the bucket that got passed over and not changed. They are so curled that they are unusable!

The hydration problem is, in our opinion, closely related to the next problem: browning petals. And here we really do step off into what is our “opinion”. We have heard so many possible causes for the brown petals from so many different people that it truly does enter the realm of “mysterious and occult”. Right up there with UFO’s and Tarot cards. (Maybe the bent neck problem is really our competition bending them with their minds like Uri Geller used to bend spoons!)

If you haven’t seen this problem (yet) it looks like this. You’ve been picking zinnias for weeks. They’ve all looked good, but one morning you go out to process the flowers that you have picked the day before, and on random flowers in the bucket, parts of petals, or entire petals will have turned a dark tan color, like someone held a match under them just long enough to scorch them. Some flowers are unaffected, and some flowers have it bad. It will continue to develop, and in another 24 hours the whole bucket looks like it’s a week old. If you are lucky, this problem will happen while you still have the flowers. If you’re not, your customer will call you in a day or two and tell you that they have the problem! A flower grower’s nightmare!
We have yet to see any definitive research on this problem, but here is what we think: We often hear that this problem is exacerbated by hot weather (but not always). This is the case for us. We also saw this problem much more when we were using a full strength, universal flower food with all 3 basic components. What we have decided is that in hot weather we are seeing the stems use a lot of water (actually floral preservative) after cutting, even after transferring them out of the hydrator. We suspect that the volume of water being used is so great that the stem is carrying up and concentrating in the petals anything that is in the water–chemicals, dissolved solids or micronutrients, or sugar. Sugar was the culprit that we had our eye on first.

Sugar is an important component in floral preservative, especially in flowers like glads or tuberoses that have many buds still to open. But it is also known to burn foliage in high concentrations in flowers such as roses. Another problem with sugar is that it feeds the bacteria that you are trying to kill with the biocide in the preservative. We began to suspect that too much sugar was burning the zinnia petals, and we decided to change our procedure. Instead of transferring the zinnias from hydrator to floral preservative, we began transferring the flowers into plain water.

This partly solved the problem. The sugar was gone, and the burned petals seemed to go away, but now we had problems with bacteria and shorter vase life. Zinnias are not one of the longer lived flowers in the best case, but we need to get a week from them if possible. But in plain water they would begin to go down in 4 or 5 days. This wouldn’t do.

We solved this problem by switching from a universal floral preservative to something called a “holding solution”. We use a product called Chrysal Professional 2, but there are many other companies that offer similar products that might work for you. Basically a holding solution is 2 out of the 3 components of a floral preservative–a biocide and a pH reducer. There is very little sugar in a holding solution because it is meant to “hold” or keep flowers from developing while in storage or in transit. We had switched to Professional 2 for all our flowers in order to slow them down while they were on display at the stores, but we were still transferring the zinnias into plain water. This season we ran a comprehensive trial of all the preservatives, hydrators, and other floral treatments that we had on hand (such as biocides) and all possible combinations of the above. The best combination by far was a 1 hour hydration in OVB followed by an immediate transfer into Professional 2 holding solution. Our zinnias are now lasting at least 7 days, and farm market customers are telling us that they last even longer for them!

Another factor that adds to the vase life of zinnias is recutting the stems. We always recut when we are bunching the flowers that have come from the field, or when we’re making bouquets. We also advise our customers to recut the stems mid-week or if they see any signs of deterioration on the stem ends.
We feel confident that we have found and eliminated our problem, but you will still need to test things for yourself. Everyone’s water is different, and so are everyone’s growing conditions. One thing to watch out for, though, is that zinnias don’t like cold storage. Cold storage can bring on the same symptoms of the brown petals, and vase life after cold storage goes down fast. We almost never hold zinnias, but if we do, we bump the cooler temp up to 50 degrees. Anything lower could be trouble.

Problems may be in the cooler
There is one place that you can enjoy all of the problems we just mentioned at one time, and lose money too! At your local florist! We have seen and heard of many florists that use dirty buckets, don’t use floral preservatives, and put zinnias in coolers that are dirty and way too cold. So when your florist calls you up and says that your flowers didn’t last and that they need a credit, your best defense is to help them analyze their post harvest handling procedures. You’ll often find dirty coolers and buckets and improper storage temps. Chances are they are having problems with their other flowers too. Help them fix it and you’ll have a customer for life! Even wholesalers and topnotch florists can be guilty of this. We saw some filthy buckets at the wholesalers in the San Diego flower market last year. And we used to sell to one of the best florists in Austin. Some of our flowers were not holding up, and then we found that they didn’t use any floral preservative or hydrator in any of their arrangements! They said they were too expensive. These people should know better!

As a last word we spoke with Rudolf Sterkel, the head of the North American office of Benary Seed Co., the German company that breeds the Benary’s Giant (Blue Point) zinnia strain. Benary’s Giant is without a doubt the most popular cut flower strain of zinnia (We planted 3 pounds of seed this year!) and Rudolf gets a lot of zinnia questions. Among many other experiences , Rudolf ran a large cut flower operation in Zimbabwe at one time and has considerably more cut flower experience than most folks in the seed business.

“Always test your water at least once a year” is the first thing Rudolf stresses. “You need to know what you are working with”. The other thing that Rudolf points out is the pH of your water. He said in Zimbabwe they would always check the water and try to get the Ph down to about 3.5 or 4.0. As we mentioned, acidic water is more easily taken up by flowers and a low pH also inhibits bacterial growth. Citric acid is most commonly used, and Rudolf said most floral preservatives will do a good job lowering your pH, but it is still a good idea to check it. Many preservative companies, such as Floralife, will test your water as a service to growers.

Rudolf also agreed that two things he would watch for is cooler temperature, and using a biocide. Again, a good preservative should take care of the biocide, and cooler temperature is easily monitored. Sometimes microelements can cause petal burning, and Rudolf has worked with growers that have had high levels of boron in their well water. Zinnias are sensitive to boron, and again Rudolf stresses to test your water so you know what you are working with.

Rudolf agrees with us that there has been very little research done on zinnia post harvest handling. It is such a tough subject that “Nobody really dared to do anything!”, Rudolf says. There is some research going on with Dr. John Dole and Lane Greer at North Carolina State University and they presented some amazing results at the last cut flower growers conference. They we able to get up to 3 weeks vase life on some cultivars of zinnias using distilled deionized water. They also found that there are vase life differences between cultivars and colors in a series. Zinnias are becoming a very important crop for a lot of growers, so we hope we will see a lot more research like that being done at NCSU. There is hope for all of us out here in the heat!

On a completely different subject, we are once again looking for some winter help here at our tropical paradise in sunny Texas! We plant a lot of bulbs, perennials and plugs all winter here, and we have space for two people to work here from November 1st to the end of February. It’s hard work, and you’ll probably never want to see a tulip, iris, or lily bulb again in your life, but you’ll learn a lot, and the weather is nice (usually). Look for our ad in the classifieds for more info.