Mini Climates
(also called "mesoclimate")
Note: mini- climate, in botanical terms, refers to the goings on inside the cell.

Humidity: It has been observed in some parts of northwest WI that are rated a zone three, that it is best to use the hardiest zone three plants, as, according to Gordon Snyder of Glidden, WI, longtime resident and nurseryman, "you have to add about 10 degrees onto ratings that are suited to some other regions classified as zone 3" (such as NW New York state), in other words, apples that survive 50 below in NW NY have only survived 40 below where Gordon lives. He suspects that the air is drier in NW WI but I wonder if wind might also be to blame as he lives in a farmed rather than wooded area. My nursery in Minocqua is rated a zone three but is sheltered by tall pines. Trees do a little better there than in the open. If you have dry air and also very windy conditions please read the next section.

Extremely Windy Conditions: If you live in the Dakotas, CO, Western Nebraska, and states considered semi- arid. (or in the High Plains), where dry winds blow constantly and fiercely all winter, it would be best that you choose your varieties with caution. For example, for those living in western Nebraska rated a zone 4, it is best to stick to zone 3 plants. Generally, the hardier a tree is the more resistant it is to desiccation . This is especially important if your soil is shallow or dry and you have dry summers as well as winters. I would recommend that you consider trees that are rated at least one zone colder than your USDA zone and to plant smaller trees that don't require as much water as large trees, to choose drought resistant rootstocks such as 111 or interstem Bud 9/111, and to avoid trees like Melba which naturally put out a lot of leaf surface area.

Erratic temperatures: If you live in an area with wide swings in temperature in the spring and fall, consult your extension or your neighbors to see what they are growing. Trees that go dormant earlier in the fall and stay dormant later in the spring can escape the damage caused by low temperatures when the tree isn't completely dormant. Generally the trees that are classed into the lower zones can endure such fluctuations better but this is not always the case. It depends on the number of 'chill hours' a tree requires, that is how many hours or days it must be exposed to the temperatures between 33 and 41 degrees F before it breaks dormancy. In the fall it depends upon how early it begins to shut down for winter. Generally earlier ripening fruits will begin dormancy earlier. If you have late spring frosts you may decide to restrict your choices at first to those that bloom late in the spring. (See "Bloom Dates" under 'Tables')
The extreme in erratic temperatures is what is called a "Chinook", a phenomenon familiar to many Alaskans where warm temperatures regularly appear in late winter, signaling a far- northern tree to start growing in February only to zap it with hard freezes later on. Few trees can survive such abuse, those that do stay dormant longer and don't begin to grow in February. Check with your extension for varieties suited to your area.

Mountainsides and Mountain Valleys: As I approached Valley Nursery in Montana from higher up the mountainside, in mid September, the thermometer in my van read in the mid- 50's; by the time I descended the mountain, only a few minutes later, however it read 32 degrees! Clayton Berg, owner of Valley Nursery, has grown fruit trees there in that valley for many years and recommends only a few varieties, fewer than the folks way up north of him in Edmonton, Alberta. Check with your neighbors to see what they are growing and/or consult your extension. Generally you will need to choose early ripening, cold hardy plants. Pre- plant forethought is of utmost importance for mountain growers The location of your tree on your property and more generally, on the mountain itself can have profound effects on your tree's success. A good example is Bear Creek Nursery in the state of Washington which was situated on a mountainside bench that is rated a zone five. But just UPHILL is a basin in the mountainside that sometimes receives winter temperatures that are 20 degrees colder! This is due to the cold air currents coming down the mountain, being funneled into the basin uphill but deflected around Bear Creek's property. (You can feel the cold air streaming by the edge of Bear Creek's land, Bear Creek's site received the heat rising from the valley below during the day but was protected from the cold air currents which streamed down the mountain at night.). So because these two sites are so close to each other the USDA hardiness maps lump them into the same zone even though there is a drastic difference in temperature.
If you live on a mountainside you may be able to control air currents by careful landscaping, using hardy evergreen trees to block or divert cold air coming down the mountain. Most typically, those who grow fruits in the mountains will have to pay less attention to the zone maps and more to the factors listed above, specifically- Erratic Temperatures, Late Spring Frosts, Early Fall Frosts, Short Seasons, and Total Summer Heat.
Rely more on your neighbors experience rather than the hardiness zone charts to see what trees they are growing and choose varieties that have a similar bloom time and ripening period. (This isn't to say you shouldn't experiment with marginal varieties or yet untested varieties)
The location of your tree on your property and more generally, on the mountain itself can have profound effects on your tree's success. Once planted you have only a few "tricks" at your disposal to alter your mini- climate.

River basins: So, air currents flowing down mountains can create vastly different temperature readings but it also seems that as cold air flows horizontally, it too can cause some dramatic contrasts: There are claims that some areas of the Kickapoo Valley of Western WI have some of the coldest winter temps in the US despite being surrounded by a zone 4 on all sides. It is suspected that the cold air which is collected by the nearby river system funnels into the Kickapoo Valley creating winter lows that are occasionally fifteen to twenty degrees colder than the surrounding region. Once again, this illustrates the point that USDA zone maps are useful but are only a general guide.

Short Seasons: (Contact your local extension to find out your growing season length or ask local gardeners). If your frost- free growing season is fewer than say 90 days, you are further limited in your selection of fruit varieties. Click on Tables, 'Ripen Sort" in the index to your left for a list of ripening dates for apples.

Total summer heat: "Growing Degree Days" is a formula used to roughly determine the total summer heat for your area. It is calculated by averaging the high and low temperature for the day and subtracting 50. This has has served as a good guide for growers who want to find out what fruits, nuts, and vegetables will ripen in their area. (It has also proven an excellent way to predict the arrivals of such insects as leafhoppers and plum curculios) Heat- loving plants such as grapes, will not ripen when they don't get enough total summer heat. Plant in full sun (and/or against a building or wall where they will get additional light and heat). If you can't find the Growing Degree Days for your area you may be able to find the Cooling Degree Days which is calculated the same way except that the average is subtracted from 65 rather than 50. Consult with your local weather bureau to determine this information. For more info see http://www.wunderground.com/about/bios.asp

Late spring frosts: Blossoms can be damaged by late frosts. When you are planting different kinds of fruits its good to note which need the spring protection most so that you can prioritize prime locations for the most frost susceptible types. The general order from earliest to latest to bloom is as follows: apricots, plums, peaches, sweet cherries, sour cherries, pears, and finally apples. There is some overlap in that order since there is a range of bloom time between different varieties. (See 'Bloom Sort' under 'Tables'. Also, note descriptions under each variety for any info on frost tolerance, some will tolerate lower temperatures during bloom.)
Pre- planting strategies: Plant on the north side of a building or in an area under a roof overhang (or a shade- producing line of conifer trees, a fence, a wall or the like.) that provides shade for the tree (and/or soil under the tree) during the spring when late frosts are a danger, (in Madison, WI that is until about May 20 but in N WI that is until about June 20th or whenever it is considered safe to plant corn) But make sure that you choose a location where sun exposure is maximal during late summer when the fruits are ripening. When deciding what to plant where, save your most frost- susceptible fruits for such prime locations.
Post planting strategies include- consider covering them with blankets or spun poly (floating row covers) when frost threatens. Application of a fine spray of water also helps to a degree. And finally, there is a product out made of soy oil apparently which is supposed to help in some way. (Please e-mail me if you have any info on this).

Early fall frosts: Fruits may not ripen before hard fall frosts turn the fruits to mush on the tree. It is important to know the ripening dates of your trees if you live where early fall frosts shorten your season. The general order of earliest to latest to ripen is as follows: Juneberries, sour cherries, sweet cherries, peaches, apricots, plums, apples, pears. There is considerable overlap in amongst the fruits since there is a range of ripening dates between varieties. (Red June and Lodi for example are two apples which will ripen before most plums. See Ripening Times in Tables) Take note that some apples can stand considerable frosts on the tree without loss of quality (such as Ashmead's Kernel and Red Sparkle). To ensure that your trees aren't delayed in their ripening time make sure that they get plenty of sun and heat. With heat loving fruits like grapes, planting in front of a wall or other heat- giving or light- reflecting surface may help as long as it doesn't cause your plants to bloom too early. In Japan, where early- ripened fruit means huge profits, they use elaborate methods to ripen fruit early using plastic draped over the plants. (However, you really need to know what you're doing as this tactic can easily fry your plants on a sunny day.)