Does Viagra really help preserve flowers?

If your beloved brings you flowers and Viagra for Valentine’s Day, it might not pay to get too excited. They could just be really into horticulture. Viagra, it is said, can preserve cut flowers from wilting.

However, tracking the scientific publication that demonstrates this is hard.

What is evidence that Viagra prolongs flower life?

It’s surprisingly limp.

If you search for a connection between plants and Viagra, it seems to start with a report in the British Medical Journal, Viagra makes flowers stand up straight. The report mentions work by Lesem and Wills on nitric oxide, published in Plant Physiology and Biochemistry on how nitric oxide can delay senescence. It looks like the Viagra discovery popped up during work in Ya’acov Leshem’s lab, and it was going to be part of a presentation at a conference. The key paragraph from the BMJ article is:

“An unexpected finding of Professor Leshem’s group is that Viagra has a similar effect on plant ripening as it does on men’s sexual organs. Viagra increases the vase life of flowers by retarding the breakdown of cyclic guanosine monophosphate (cGMP) (the production of which is mediated by nitric oxide).“

The BMJ article is behind a paywall, but the contemporaneous Wired article, Flaccid Flowers Bloom on Viagra, gets most of the details included in the BMJ. Leshem told Wired, “Aging in plants and in men is connected to the decrease in normal production of a molecule called cyclic GMP (guanosyl monophosphate),” Leshem explained. “This leads to a decrease in the plasticity of the spongy tissue in the male penis and in plants. This is part and parcel of the normal biological process.”

From the BMJ article, the ‘Viagra preserves flowers’ fact has worked its way into scientific literature – but with one exception the references are all back to Judy Siegel-Itzkovich’s article in the BMJ. The one exception is Pagnussat et al. 2003 in Plant Physiology. They say: “Some reports have described how small concentrations of sildenafil can double the life span of cut flowers delaying their natural senescence process” and cite both Siegel-Itzkovich in the BMJ and the Plant Physiology and Biochemistry article as the source. However, I’ve read the Plant Physiology and Biochemistry article and cannot find a reference to Viagra, or its chemical name sildenafil citrate. It is possible that the chemical is hiding in the paper under a different name. However, seeing as the Siegel-Itzkovitch news article refers back to the earlier publication there is, at best, one scientific publication on the effect of  Viagra on flowers. If that earlier publication does not refer to Viagra then the only reference is the BMJ article. I think it would be unfair to critique a 400 word news article as a peer-reviewed article, but at the same time I’m not willing to take it as proven fact.

How do you test if Viagra can prolong flower life?

I set out to test if Viagra really can keep your flowers perky longer, in a way that you can do at home – if you happen to have any Viagra lying around. Unfortunately real life got in the way during the experiment, so it’s going to need at least one replication.

The design is very simple. Get two vases with water in them. Divide the flowers evenly between the two vases. In one vase, add some Viagra and compare what happens in that vase with the other.

The flowers I used were carnations. There were a couple of reasons for this. One is, in the past I’ve better results with carnations than woodier flowers like roses. We need something that could flop over. The other reason is that, in the BMJ, Siegel-Itzkovitch mentions that Leshem’s team had already tested Viagra on strawberries, legumes, roses, carnations, broccoli, and other perishables. So the flower I have used should be similar to what Leshem’s team have used.

I bought carnations from the local florist, which proved to be a mistake that I’ll come back to. My first idea was that I could buy two batches, one white and one red. The flower colours would be a useful label for which flowers had the Viagra. The obvious problem here is that it probably means buying two different batches of flowers. They would then probably have different harvest dates. Any difference in longevity would then be down to differences in the supply chain, rather than anything chemical.

So I compromised and got one larger batch of pink and assigned the flowers to two vases at random. Or I should have. There was no point splitting them till I had the Viagra to put in a vase, so they sat together in a group until I got the Viagra. This took some time.

They don’t hand out Viagra willy-nilly in the UK. You have to go to the pharmacist and have a chat to get it over the counter. You can’t just dash and say “Can I have some Viagra? I’m in a rush!” Some family business meant I didn’t have time for a discussion with the pharmacist, and so the flowers sat in their vase for a week. Next time I’ll make sure I get the Viagra first.

It would be fun if I could report some humorous misunderstanding with the pharmacist when I went to get the tablets. Possibly with him thinking I was using ‘carnation’ as a euphemism. However, he was very cool. He (and the rest of the queue that had formed behind me while I was buying it) are interested to find out the results.

I re-cut the carnations to freshen the stems and divided them between the vases. Now it was time to add the Viagra to one of the vases. 

In the BMJ article Siegel-Itzkovitch writes: “In this latest research they found that 1 mg of the drug (compared with 50 mg in one pill taken by impotent men) in a solution was enough to prevent two vases of cut flowers from wilting for as much as a week longer than might be expected.”

If I had access to raw sildenafil citrate and a reasonable pipette or scale at home, then I might have added 1mg too. But most of us don’t. We have the tablets. So I added the tablet. It’s tempting to think that if 1mg works well, then 50mg will have a really dramatic effect – but drugs don’t always work like that. If you have a headache, then 2 aspirin tablets are a good idea, but taking 100 tablets would be a spectacularly bad idea. So when you see the results, bear in mind the flowers may be overdosed.

Another problem is, as I mentioned above, that I got the flowers from the local florist. And my local florist is good. The first week, waiting to start the experiment didn’t visibly pre-wilt the flowers. As the second week passed and both displays were going strong I wondered if buying the flowers from a good florist was part of the problem. If I’d bought a petrol station special bouquet, would that have wilted faster and given clearer results? If you want top-quality, long lasting flowers then I can heartily recommend Flower Workshop of Wootton. If you want rubbish flowers that start shedding petals after a couple of days, so you can test drugs on them, then you should look elsewhere.

After three weeks, how do the flowers look?

For a while I thought the Viagra treated flowers were doing visibly better, but I suspect that’s the eye of someone who wants to justify an expenses claim to his boss. If there is a difference, it’s not dramatic. The three best flowers in the control sample are performing close to the flowers in the Viagra sample. If you look below, and compare to the image above, you can decide for yourself.

Were the tablets themselves a good batch? There’s a fairly obvious experiment to perform in order to find out if the Viagra works. You need a male with erectile dysfunction who isn’t on clashing medication. But identifying a subject and observing them requires a little more dedication than I’m willing to put into the project.

Another possible factor was the heat, or lack of it. It’s been cool in the conservatory, where I’ve been leaving the flowers to sit. A bit more heat to help them wilt might be useful. So a second test in the summer might be a good idea.

How might the Viagra be affecting the flowers?

The key to Viagra’s interaction with flowers might be down to how sildenafil citrate affects the production of nitric oxide (NO) in plants.

Nitric Oxide is a bit of a puzzle in plants. It’s been studied a lot in mammalian cells but, when you look at plant cells, things get more difficult. There’s no single source of NO, and no clearly identified sensing molecule in plants, according to a recent review by Claude Bruand and Eliane Meilhoc. However experiments have shown that nitric oxide is definitely a major element in the signals plants send around their bodies.

In human bodies there’s an enzyme that we’ll call PDE5 to save time. This breaks down another molecule called cGMP. What Viagra does is get in the way of the PDE5, meaning that the nitric oxide can bind to the cGMP. The increased amounts of cGMP go on to relax muscles, increase blood flow and let the magic happen.

In plants cGMP is an important chemical in stress response. It can, for example, affect how stomata open and close. If Viagra interferes PDE5 in humans, it’s reasonable to test to see if it’s doing the same to whatever breaks down cGMP in plants, leaving the nitric oxide free to bind to the cGMP and allow it to keep working in the plant for longer.

Why would you want to give plants something like Viagra?

The moment a plant is harvested, it starts to decay. Being ripped from the parent plant is a stressful experience for a plant organ and it starts working its best to protect what it can. The same plant parts are also susceptible to hormones, as before.

One particularly potent hormone is ethylene. Ethylene is the reason why storing other fruits with bananas will cause them to ripen. Bananas emit a lot of ethylene, and this is picked up as a signal by some other fruit that it’s time to ripen. Ethylene can do a lot of damage if you’re carrying fruit or flowers. Leshem and Wills found that nitric oxide and nitrous oxide can help combat the effects of ethylene. So ideally, if you have fruit or flowers, then fumigating the atmosphere with nitric oxide should help reduce spoilage.

In reality it’s a bit more difficult than that. Nitric oxide is very reactive, so relatively soon it will be exhausted from wherever you flush it into. Ron Wills has been working on more solid systems for delivering nitric oxide over longer periods. In a similar vein, a Viagra-like compound in the water for flowers might help nitric oxide fulfil its role in combating ethylene.

As it stands, using Viagra to preserve flowers is probably a waste of time for the amateur, and prohibitively expensive for the professional. But exploring how it might work could help learn how to encourage flowers, and fruits, use their own techniques for self-preservation between field and home.