Chilling Hours for Fruit Trees
From Kent Ryun in Growing Growers, KC:
Being a former fruit tree inspector with the crop insurance program, I can tell you observation of where it did and did not frost is a very important consideration for orchards, vineyards, etc.
Normally, a hilltop or top of a steep slope is the right place. Only thing better is for this to be the highest hill around. Orchard placement to take advantage of temperature inversions (cold drops, heat rises) is called passive frost management. Orchardists call that "air drainage". NEVER plant them on flat land or where other land around you is higher than the planting site.
So, if you have a great site, you have a better chance of surviving borderline late spring freezes such as we had last few days. Stage of fruit bud development is huge at time of frost. Fruiting buds were much LESS developed on April 7, 2009 compared to the devastating effects of April 7, 07 when the fruiting buds had experienced at least 6 weeks warm weather in March and April before getting hammered. I have talked with some fruit enthusiasts this morning and looked at my own....stage of bud development and site selection is what saved my bacon. Some fruit bud development can be delayed a little with more dormant oil sprays, but you find proof of that by googling around the net.
That said, one young orchardist in Lafayette County did something the big growers chose not to a couple night around April 7, 2007 and he saved about 11 rows of peaches that year. While it is probably illegal according to DNR to burn old round bales of hay, he had them strategically placed between every other row of peaches and light some in a pattern when temps hit 31 and lower. They smouldered most of the night during that heavy fog, warming the orchard just enogh....most of the smoke fell with the coldest air right down to the MO RIVER channel because this orchard was right beside the bluff overlooking the mighty mo...Next night he lit some more. This was an isolated area and none of his neighbors turned him into DNR who I understand would have made him put them out.
Site selection is huge. Variety selection must be varieties compatible with this area based on chiilling hours.
Alot of orchard trees come from the many fruit trees near McMinnville, Tennessee. One of the oldest is Cumberland Valley Nursery. Google for "fruit tree nurseries, McMinnville, Tennessee and you should find a selection. CVN was not on the net, being the oldest, they have had alot of repeat business and got along without it.. CVN puts out a variety list and has a "Chilling Hour Chart" showing chill hours per variety. They have all sorts of peaches, nectarines, apples, plums, maybe pawpaw, etc
Bottom line, you want the highest chilling hour varieties for this area such as 750 - 1000 chilling hour. Why? Otherwise, when the variety gets its chilling hours, (lets say 500 hour for example) which may be in February, the first week of warm weather that follow will cause fruiting buds to swell, bloom all at a time when we know there will be more cold spells like the one we just had last two days. Thus, you will lose the crop about every year. I have witnessed this, unfortunately some orchards in the Carolinas experimented years ago with gulf states varieties like the Lafeliciana......a cajun variety. Trees were pretty but never produced a crop because you can produce fruit from a 350 chilling hour variety when placed in an area that required 600-800 chilling hours.
Bottom line, be sure you have a suitable site and seek 750 to 1000 hour varieties for your site. While you are at it, do some soil testing to be sure soil PH is right and nutrient needs are determined. Soil ph makes alot of nutrients available that otherwise are not available when the soil PH is wrong. ALso formerly worked in a university soils lab doing those tests.
Have some other thoughts if you want to contact me.