Itís smart to know heat-zone number

February 15, 2011 03:03 pm
In 1998, the American Horticultural Society (AHS) published a book titled “Heat-Zone Gardening,’’ describing its purpose as “how to choose plants that thrive in your region’s warmest weather.’’

Included were two maps. One is the familiar USDA Plant Hardiness Map, and the other not-so-familiar but equally useful map designated Plant Heat-Zones as determined by the AHS. There are also 120-plus pages of plant profiles that assist one in making sound decisions when entertaining the thought of installing new flowers, shrubs or trees. Both the USDA and AHS map zones are included in the plant profiles.

The important difference between the two maps, and planting information, is the designation of average heat-days per calendar year that are above 86 degrees Fahrenheit. The reasoning behind the choice of 86 degrees has to do with plant transpiration and plant ability to adjust to the rapid loss of water, which results in damage to cellular proteins (growth regulators), or the point where plant stress stops active growth and blooming.

This time of year is a good opportunity to do a little added research when selecting plants for your landscape. Visit the AHS website at for additional information. There is also an online tool to find your specific heat-zone number to correspond with the map, also available to download, purchase or view online from the website.

“Heat-Zone Gardening’’ can also be purchased or ordered from your local bookstore.

Master Gardener classes are currently ongoing at the Extension office in Island City. New this year is the opportunity to take just one, or a few, of the sessions instead of the entire course. A small fee is charged, but the information gained is well worth the expense.

Although the program has already started for this year, call Robin Maille, the local Master Gardener program coordinator, at 541-963-1010 if you’d like to attend any of the remaining sessions. They continue to April.

The Union County Extension Service has an informative and attractive web page with information posted for gardening, forestry and youth activities all within our local areas. It’s worth your visit at

A local reader asked if it’s too early to start seeds indoors. No, it isn’t, depending on what seeds you have in mind. Some smaller seeded varieties, such as annual lobelia, petunias and eustoma, need three to four months to reach flowering size, so seeds started now will be in the blooming mood when the first of June rolls around.

It’s too early to plant most vegetable seeds. Just remember, if you want your seeds to sprout and thrive, you have to be able to give them auxiliary heat and light, especially once they have sprouted. Some seeds need dark to sprout.

Seed packets are an excellent source for growing instructions, and at least one local store in the La Grande area has its spring seed display set up already. I have to admit, I couldn’t resist and added seeds to my shopping basket. Am hopeful now to get the little greenhouse set up and get some spinach, lettuce and green onions going soon. Please don’t remind me again that it’s February. I see spring just around the corner! But then again, most gardeners are a hopeful bunch, aren’t we?

Until next time, if you plan for the best, that’s probably what you will end up getting. Still have seeds from last year? Give them away or plant them anyway, it can’t hurt!

Jennie Lu Hagen is a La Grande gardener.