The answer -- they can't. Unless something breaks in this pattern, don't expect a good pollination cycle or a lot of fruit to set. Here in the Detroit area, the only thing blooming yet is apricot, with Japanese Plum and Serviceberry showing color but not out. I keep hoping for better weather, but every day is cold, wet, colder, and wetter. Right now, not raining, but only 53 degrees at 2:00 in the afternoon. My poor bees have hardly gotten in any decent flight time. Most days are so cold that only a few are out at any one time. I have given them sugar syrup and pollen substitute patties in the hives just to help make sure they don't starve at this crucial time of the year when they should be bringing in tons of pollen and nectar and building up the population. One of the worst springs I can remember, a handful of decent hours of weather here and there. Our fourth wettest April on record in the Detroit area. Don't know how the numbers will play out for cold for the spring period, but both March and April were way below normal, and May certainly doesn't hold out much promise for even attaining normal temps, at least in the first half of the month.

The 4in1 pear tree that I bought from Lowe's contains mostly Asian pears. The varieties are 20th century, chojuro, shinseiki and european bartlett. I know we don't get enough chill hours for the bartlett, and over time this branch may die out, but I'm hoping for the best. I planted the 4in1 tree in the coldest section of yard. Two years ago I planted a single shinseiki pear and it has grown considerably. It's had flowers but I did not allow it to set fruit - I will let it produce this year (here's hoping for some more cold weather). I know asians need 350-400 chill hours, so I'm pushing it and will have some unfruitful years. I am also looking for the low-chill european/hybrid pear varieties you mentioned. I wish more local nurseries would carry the floridahome/hood combo. Bakers has received comice pear (I've read various information with chill hours around 300). They have jiro-fuyu and hachiya persimmon if anyone is interested. These should be available for sale in a week. Baker's received their shipment a week ago and are potting them up for sale right now. I suspect other nurseries are gearing up with fruit trees too - so if anyone sees any european pears out there, please let us know! Thanks, June.

For anyone that happens upon this rather extensive question and wonders about possible answers, see a similar thread posted in the Fruit and Orchards Forum, linked below. Here is a link that might be useful: Will these fruits cross-polinate - same gensus/different continen

Mason bees are worth a try Greg. In my area I found out I am on a migratory flight path of several bird species, all of which stay for a few days then go. Warblers of all sorts make their way to the boreal forest in early spring. For myself, having a large pine next door made the difference because fruit trees next to pine are ideal resting spots for the Tennessee Warbler. Without these small birds I would have no plums as it is usually raining with gusty winds at blossom time. If I had to rely on warm sunny conditions favourable to bees I would wait every third of fourth year. My advice, plan for the bees but talk to the local birders of what passes through your area in spring.