Q. I printed the hydrangea chart, but how do I know what zone we are in for selecting the right one? Please advise.
Anonymous from Poland
A. Zones are very important when selecting perennials, shrubs and trees for your landscape. I like to say, “Everything is a perennial…somewhere. Just not always here in the Mahoning Valley.”
To remember what zone we are in, start by thinking of the North Pole as No. 1 – the pole looks like a No. 1. Zones increase in numbers as they get closer to the equator, known as Zone 13. Thus, we are somewhere in the middle — mostly Zone 5 in the Mahoning Valley.
The US Department of Agriculture (USDA) keeps track of the average annual extreme minimum temperature in areas throughout the country. That is how zones are determined. The best, up-to-date zone map is here: http://go.osu.edu/USDAzones.
The average extreme minimum temperature in Zone 5 is between -10 and -20 ∞F. But the USDA also notes much of our area is warmer than Zone 5. It is in the colder part of Zone 6 (6a to be exact). Although this is the case, I recommend you stick with buying plants from Zone 5 and the zones lower than 5. Why? Well, many (maybe even most) Zone 6 plants are not suited for our area. Some Zone 6 plants will just die after one season in the Mahoning Valley. Others will survive, only to not bloom the next year. You can plant these plants, if you protect them or plant them in a protected area, but you still might lose them. Here is a great factsheet on protecting roses during the winter (which can also be applied to macrophylla hydrangeas and many other plants): http://go.osu.edu/winterprotection .
In general, choose Zone 5 plants (-10 to -20 ∞F on the plant tag) and other lower zones for the best success in your garden. (One perennial favorite, Sedum “Autum Joy” is listed as Zones 3-8.)
Eric Barrett is the Ohio State University Extension Educator for Agriculture and Natural Resources in Mahoning County. Call the hotline at the office 330-533-5538 Mondays and Thursdays from 9 a.m. to noon to submit your questions.