Random thought
The stone from plucked from the bottom of the wadi and used by David to kill Goliath is still out there, somewhere in the Valley of Elah. It may be entombed in concrete or in a road-bed...but it is probably still be out there.
While I have never read of it occurring, I assumed that hundreds of crusaders were sold "the stone that killed Goliath" by enterprising locals. Those crusaders carted off stones and random bones by the bushel-basket to take back home and to be displayed as Holy Relics. There have been mystery stories published that used the market for Medieval Relics as a backdrop.
Rain
The inch of rain that was promised has been down-graded to 0.25 inches. I will be lugging more water today.
Fertilizer and trees
Winter hardiness is a factor in northern climates. That would be USDA Zone 5 and lower. I am right on the edge between 5 and 6.
Bud on the tree that are richly endowed with carbohydrates (various types of sugar) are cold-hardy. Buds that are poorly endowed with carbohydrates are NOT cold-hardy.
It is usually not an issue of the leaves not photosynthesizing enough carbs although that can happen if insects or a wandering moose eat the leaves or if the tree is defoliated by disease. It is more often a consequence of how trees budget where the carbs go.
Developing seeds and fruit get first dibs on carbs. That is one reason why letting your tree over-bear is bad for the tree.
Actively growing shoots get second dibs.
Last on the list are roots and buds.
In a perfect world, the tree would get a dose of nutrients and water early in the season. That would quickly fill the canopy with enough leaves to capture all of the sunlight that hits the tree. Additionally, it would be enough nutrients (primarily nitrogen) to hit the management's targets for shoot-extension.
After the shoots had extended to the desired length, the nutrients would be shifted from high N to low-N and high-K to encourage the formation of a terminal bud on the shoot. The growing tips would no longer be "sinks" for carbohydrates and they could start accumulating in the buds. Additionally, the higher carb level helps the buds to "decide" to be fruiting buds rather than vegetative buds.
Since I don't have the power to instantly switch-off the nitrogen levels in the soil, that means I need to lead-the-duck and stop applying nitrogen before I want the shoots to stop growing. My best guess is that August 1 should be that date. That is when the supplemental water I am giving the newest trees should stop being supplemented with 300 PPM of nitrogen. I will use the last of the water I have premixed today and then will just water with simple well water.
The trees should coast through August and have set terminal buds by Labor Day. At least, that is the plan.
Hydroponics and organic fertilizers
Growers who use hydroponics do have almost absolute control over the nutrients available to their plants. I don't know of any hydroponics orchards but trees on sand (like stabilized dunes) are pretty darned close.
The downside of hydroponics is that if you screw up there is no forgiveness. If you don't put it in the irrigation water, Mother Nature isn't going to help you out.
Organic growers have a different problem. Most organic fertilizers like composted manure have a long, slow release. The traditional wisdom is to apply your compost early in the spring but then to not add any more. It isn't that a flush of growth is bad in July. The problem is that a flush of growth at the end of August can be catastrophic.
Plum pollination
Plums can present a lot of issues with pollination.
For one thing, there are two very different types of plums and they don't cross-pollinate.
European plums are hexaploids (six sets of chromosomes) and will not pollinate Japanese or wild American type plums.
Within the European plums there is a range of bloom times with the earliest ones having little overlap with the latest ones.
Some European plums are at least partially self-fertile. Identifying and finding them is where the internet can be your friend.
The Japanese type plums are diploid (two sets of chromosomes). Burbank created the modern Japanese plum by crossing it with other species of diploid plums. Neils Hansen and breeders in the upper mid-west and in Canada crossed Japanese plums with the American plum and the Canadian Black plum to create hybrids that can resist the winter cold.
That ended up creating a dogs-breakfast of genetics all swept into one pile.
Unfortunately, most of the hardy hybrids (Waneta, Superior, Toka, Underwood) produce flowers that are not attractive to bees AND have very little viable pollen. HOWEVER, wild plums in the mid-west and Canada (P. americana and P. nigra) have large amounts of viable pollen. The challenge is getting the bees to fly the distance between the wild trees/bushes and the hybrid trees in your orchard; remember, bees are not attracted to the hybrid blossoms.
The textbook answer, if they are not already growing in the fence-row beside you orchard, is to plant a wild tree in your orchard or use them for rootstock and to allow one root-sucker to grown into a mini-tree large enough to produce blossoms. Problem solved.
A more labor intensive solution is to graft a branch from a wild tree into each hybrid tree. A word of caution is in order here. It is a near certainty that you will prune out that odd looking branch unless you mark it in some permanent and visually arresting way.
