Hardiness Zone: 6a
Betty from Slate Hill, NY
There are several factors that can affect tuber growth. The first is harvesting too early. Most potatoes take between 90 and 120 days to fully mature. Once they reach full size, the foliage naturally turns brown and starts to die back. You can harvest them before they mature, but you're going to get smaller potatoes.
Plants usually reach a height of 12 inches and then they go through an enlargement period. During this time, the soil needs to be kept moist (not wet) in order for the potatoes to reach their full size. Over watering can adversely affect their growth.
Another factor that affect their growth is planting non-organic seed using potatoes purchased from the grocery store. These potatoes are often treated with chemicals that inhibit sprouting so they may not grow properly.
In regards to using cow manure for fertilizer, it will work okay as long as it's well rotted. If you use fresh manure, make sure you work it into the soil at least 3 weeks before planting.
WE have never dug our potatoes until the plants dry up or the talk of a frost it in the air. We have not planted any in some time , but that worked for us. Also it can be the soil you are planting them in too. clay not good, cow manure or not. Hope this is a help.
For more potatoes... Keep the leaves covered in dirt all but about 6" and you will get tons of potatos and huge ones too! We do that here in Wa. State and have tons of them. We missed some last year durring harvest time and have almost as many "volunteer" potatoes as the ones we planted.
I am not an expert but it sounds like you are digging them up too soon.
We plant ours on St Patty's Day and dig up in late fall.
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