Will figs grow in Delaware?

USDA Har­di­ness Zone changes

Last week, the revised USDA Har­di­ness Zone Map was released. The revi­sion is the first change since 1990. Most loca­tions were moved one-half of a zone higher. The USDA attribute the changes to these criteria:

• They used data mea­sured at weather sta­tions over a 30 year period (1976–2005), while the 1990 map used data from a 13-year period (1974–1986).
• They used new mea­sure­ment meth­ods, includ­ing algo­rithms that con­sid­ered changes in ele­va­tion, prox­im­ity to large bod­ies of water and extremes of ter­rain (peaks and val­leys), which all affect temperature.
• They drew data from more weather sta­tions than in 1990.

Some addi­tional changes are zones 12 and 13 were added, and Puerto Rico is now included on the map. There is an inter­ac­tive map that can be down­loaded and printed. The new map is avail­able at planthardiness.ars.usda.gov. You can sim­ply type in your ZIP code to see your zone.

The zone map was cre­ated as a tool for gar­den­ers and grow­ers to deter­mine which plants are likely to sur­vive and thrive in any loca­tion. The map is used by mag­a­zines, cat­a­logs, books and the nurs­ery indus­try. The Plant Har­di­ness Map splits the United States into zones that rep­re­sent the aver­age annual low­est win­ter tem­per­a­ture in that loca­tion. Each zone spans 10 degrees faren­heit and is fur­ther divided into five-degree “a” and “b” sec­tions. For those of us in the Delaware and the Cen­tral Ohio areas, we are now con­sid­ered 6a and not 5b — a dif­fer­ence of about 5 degrees.

So what does this mean to the aver­age gar­dener? Not much. We still look at our gar­dens the same way as we did last year. The aver­age gar­dener has always tried to grow plants labeled for higher zones, with some success.

The U.S. National Arbore­tum list of cold har­di­ness woody plants can be found at usna.usda.gov/hardzone/hrdzone4.html/#5.

Almost all of Ohio is Zone 6a, with a few excep­tions around Lake Erie and small areas in Knox County and the Mans­field area.

The bot­tom line is some plants may be expected to have a bet­ter chance of sur­viv­ing win­ter in our region than they did in the past. Jim Chat­field, a hor­ti­cul­ture edu­ca­tor with the OSU Exten­sion Cen­ter in Wooster, said the changes have moved the zones a bit and there is evi­dence plants can sur­vive a lit­tle far­ther north than they did a few decades ago. When asked if they will carry new types of plants just because of the zone change, it appears that most nurs­eries will answer “no.”

It does mean, at least to me, we now have the sup­port of a zone har­di­ness map to rein­force us to push the enve­lope a lit­tle bit more. Try to grow that Mimosa, fig or banana tree.

It’s for the birds …

Bird Source is a fun activ­ity for this win­ter when things are dark and dreary out­side. The Bird Source orga­ni­za­tion will again count birds from Feb. 17 through Feb. 20. All you need to do is visit birdsource.org, get reg­is­tered and count away. The Great Back­yard Bird Count is an annual four-day event that engages bird watch­ers of all ages in count­ing birds to cre­ate a real-time snap­shot of where the birds are across the con­ti­nent. It’s so easy to do and a great project for stu­dents, your kids or even you. Bird Source gets us out of the house and into the fresh air. It’s free, fun and easy and it helps the birds.

The project is led by the Cor­nell Lab of Ornithol­ogy and National Audubon Soci­ety, with Cana­dian part­ner Bird Stud­ies Canada, and spon­sor­ship from Wild Bird Unlim­ited. Visit birdsource.org and reg­is­ter today.

Susan Liechty is an OSU Exten­sion Mas­ter Gar­dener volunteer.

Posted by Master Gardener on Feb 4 2012. You can follow any responses to this entry through the RSS Feed. Comments can be made below.