Zinnias and Dahlias

I have to admit some confusion with identifying dahlias and zinnias and I hope I’m not alone. With seemingly hundreds of varieties of each, they can look extremly similar. I was recently reading a book and came across a picture with two zinnia varieites and one dahlia. I could not tell which is which without a bit of further research. I tend to second guess my first reaction over some plants–Was that really a dahila, or could it actually be a dahila-flowered zinnia?

Both dahlias and zinnias are generally planted every spring, and showcase a long display of colorful blooms. They both have a plethora of varieties that vary in size, color, flower form, etc.

They are very different plants, even if at first glance they appear similar. Dahlias develop tubers, and are actually tender perennials. The tubers can be lifted and stored for succeeding years in colder climates. Zinnias are annuals grown from seed. Dahlia varieties can be larger than zinnias (although both come in a huge variety of sizes). Zinnias are more tolerant of heat and drought.

So how can you tell them apart? Zinnia flowers are supposedly more two-dimensional, but I think your best bet is to look at the leaves. Zinnia leaves are attached directly to the stem, with little visible petiole. Dahlia leaves have a petiole and are generally more serrated. (For non-botanist readers, there’s some botanical terms to look up. And they are good to know so go ahead a google away.) With that said, the picture at the beginning is definitely a zinnia.