Or does it just keep the tubers from greening, plus keep them a bit cooler?
It seems like there’s an age old debate on this. Some people say that as you mound the potatoes, the tubers will actually set up the stem
to the final soil line, whereas other people insist that the tubers set where they set, but the mounding and mulching keeps them from turning green, as well as keeps them from getting too hot.
When I was a kid plenty of potatoes were raised here under straw or hay and they never used any dirt at all. Once the potato vines died they pulled the hay back. It got real snakey around there when We started pulling back that hay. Thankfully none of them encountered were poisonous but I would recommend caution. Wet soppy hay and moist muddy soil in July is at a premium and snakes love it! Voles nest in hay and eat potatoes, those voles are most snakes food. In those days we called voles field mice. Several types of rodents, Rats included and other undesirable creatures are attracted to a patch like that here.
Simple answer, hilling does not increase yield with any variety of potato grown today. It is entirely for protecting the spuds from greening and to some extent from varmints intent on getting a free meal.
More complex answer, the potatoes we grow set stolons at the plant crown just above where the plant grew from the potato that was planted. The crown portion of the stem is about 3 inches long and all of the stolons emerge from that region of the stem.
There are some wild species of potato that can set stolons further up the stem. When you read about mounding up the stems to produce more spuds, the reference is to these varieties.
True, but also temperature control:
Temperature: Tuber development declines as soil temperature rises above 20 ºC (68 ºF) and practically stops above 30 ºC (86 ºF). The number of tubers per plant is higher at low soil temperatures, while bigger but fewer tubers are set at higher temperatures. Harvesting when tuber pulp temperature exceeds 18 ºC or soil temperature is greater than 20 ºC (68 ºF) increases the risk of microbial rots, especially in damaged tubers.
Several factors can shift the balance between vine and tuber growth, and one of these is temperature. For the Russet Burbank cultivar, for example, the optimum soil temperature for tuber growth is about 61°F (16°C), while the optimum air temperature for vine growth is about 77°F (25°C). However, with a full leaf canopy shading the soil, it’s possible to have 77°F air temperatures at the same time as 61°F soil temperatures. High soil temperatures will delay tuber growth. A thick layer of mulch may decrease soil temperatures by 10 degrees. Tuber initiation is strongly influenced by air temperature and day length. Short days induce tuberization. Under long days, tuberization occurs if the night air temperature is well below 68 degrees F. (20 ºC). The temperature-sensitive parts for tuberization are the tops not the stolons. This explains why we have less tubers set per plant when day temperatures are over 90 degrees F., and night temperatures are in the high 60′s by mid-May, when our day length is approaching 14 hours. It is known that for every one degree F. above the optimum air temperature for tuberization, the yield of potatoes can be lower by about 4%.
– Joey Williamson, Clemson Cooperative Extension.
I actually used the trench method, and then when they got tall enough I filled in the trench. Which means tubers will be developing between about four and 8 inches below ground for the most part.
They look pretty good!!
The Desiree plants are setting flower buds.
This is correct, but some varieties, like Red Pontiac, grow that stolons very long, and they going upward, to the soil level. The stolons also branch, ones they reach just bellow soil level, they set. But if you keep adding materials, they will branch and grow upward again, and set more. For some reason they grow up more willingly than far from the plant. This is my own experience, just describing what I see every year.
Here’s mine after mounding up the other day. There’s fencing around the planter bed so that none of the tubers will be stolon by the dog.
potatoes are the cash crop here. they plant them 6in. down on flat ground once the plant is 6in. they disk the soil 12in.high on either side. when done the row is about 15in wide at the base. even then you see quite a lot of green ones coming on the harvesters when dug.