Four Questions: Wonder Why Every Rose Has Its Thorn?

In the spirit of Valentine's Day, a UA Master Gardener answers questions about romantic roses' thorny nature and how you can keep cut flowers from your sweetheart fresher longer.
Feb. 13, 2017
The rose garden on North Campbell Avenue in Tucson includes 85 plants.
The rose garden on North Campbell Avenue in Tucson includes 85 plants.

Valentine's Day is the busiest day of the year for florists, and no flower is more popular on the occasion than the quintessential red rose.

We asked rose expert Lauren Kettenbach, an Arizona Master Gardener who oversees the rose garden at the University of Arizona Cooperative Extension Office at 4210 N. Campbell Ave., Tucson, to share some of what she knows about the rose.

Kettenbach has been a Master Gardener for 20 years. When she's not caring for the UA rose garden's 85 plants, she's busy with 150 of her own at home. She also teaches classes throughout the community on rose gardening.

Master Gardeners are volunteers and community educators who work with the UA to provide research-based information on gardening and landscaping to the public. They are trained through UA Cooperative Extension in the College of Agriculture and Life Sciences. The program includes a 50-hour training course and an internship and is open to anyone with an interest in gardening and landscaping.    

In addition to her work with the UA, Kettenbach also is a master consulting rosarian for the American Rose Society and is a member and past president of the Tucson Rose Society.

Q: Why do roses have thorns?

A: Scientists think roses have thorns to protect them from being eaten by animals.

Q: For people who receive cut roses on Valentine's Day, what is the best way to keep them fresh?

A: To keep roses fresh, change the water daily and recut stems at a 45-degree angle every day. There is a lot of folklore about what keeps roses fresh — aspirin, 7 Up, ginger ale, vodka — because of the sugar content. A lot of people put those sorts of things in with their roses, but I don't. I sometimes use the packets that you get with florist roses, but if you change the water daily and recut the stems and put them in the refrigerator at night, you'll get them to last. … A cut rose cannot be transplanted.

Q: Where do roses grow best, and in what conditions?

A: They do really well all over the country, but they need a minimum of about six hours of sunlight a day. They do not like to compete. You can't grow them underneath trees — they need some open space. And they need a minimum of eight to 10 gallons of water per watering if they're in the ground. This time of year in Arizona, I would say to water them twice a week, and in the summertime at least every other day. A lot of people grow roses in pots, and they do beautifully in pots here in Arizona, but you need the biggest pot possible — 24 inches and up is ideal — and roses in pots need to be watered every day.

Q: How many different varieties of roses are there, and where do most of the roses we buy come from?

A: The American Rose Society has 37 classes of roses, but there are thousands of varieties, and they change yearly as people breed them and come up with new ones. Roses in the commercial market are predominantly grown in South America in greenhouses. The roses that are in the commercial market today have all been cross-bred to create different varieties. It's a real science to how they develop them now, and they're completely different from what was found in the wild thousands of years ago.