Sweet Potato Heat Units to determine harvest?

[taffy341]

I've read that you can add daily 'Heat Units' to determine when to harvest Sweet Potatoes.

The article read for a 90 day harvest it takes approximately 1200 Heat Units. I may have misunderstood if the accumulated Heat Units (1200) applied only to 90 days, etc. Is this just for a 90 day maturity harvest or do the number of Heat Units (1200) apply to all Sweet Potatoes?

To calculate the day's Heat Unit:
1 - Add the day's high & low temperatures
2 - Divide by '2' the sum total of the day's temperatures
3 - Subtract '55' from the division answer
That will give the day's Heat Units

Example: High '95' plus Low '75' equals '170'
'170' divided by two (2) equals '85'
'55' subtracted from '85' equals '30'
'30' HEAT UNITS for that day

1. Has anyone used this Heat Unit method to determine approximately when to harvest (90 days) Sweet Potatoes???
   
2. I would like to try this method and I'm adding Heat Units. However, the Heat Units I'm adding will reach 1200 Heat Units before 90 days.
   

I planted 'Wilma's Sweet Potato slips back on June 10, 2012. This week I will plant three (3) more varieties.
Orange Oak Leaf (semi-bush), Amish Red (bush) & Cordner Red (bush).

All advice, suggestions & information will be appreciated as this is the first time I've planted Sweet Potatoes (raised bed garden).

[kellysgarden]

I played around with heat units last year as it applied to tomatoes of different varieties. As I understand it, it is "ACCUMULATED heat units," or the time it takes TOTAL to accumulate the 1200 heat units. In some climates, this may take 70 days, other climates it may take 90 days, or in other climates might take 110 days, depending upon weather and temperatures. So, I don't think the 90 days you referenced has anything to do with how long it takes your sweet potatoes to ACCUMULATE a total of 1200 heat units. If you get 1200 heat units before the 90 days, then I would guess you should go by the 1200 heat unit date, not the 90 day calendar date.

My opinion only. I don't know anything about sweet potatoes.

[sharon in missouri]

It is my understanding you use 55 degrees for cold season crops and 65 degrees for warm season crops.Using 65 will change your heat units. Sweet potato is a warm season crop. We usually harvest ours here in Missouri after the very first light frost.

[kellysgarden]

In greenhouse production, there is a different base temperature for every different type of flower. At least they are grouped into different groupings. 50 is the base temperature for tomatoes. But, I have no idea about sweet potatoes.

[taffy341]

Thanks for your information and thoughts. The article I read was written by Linda Drowns of Sandhill Preservation Center. My Sweet Potato slips came from Sandhill.

As of today, the Heat Units for the Wilma's Sweet Potato slips is 1262 Heat Units useing the '-55' (planted slips June 10, 2012).

QUESTION:
Will the Sweet Potatoes continue to grow as long as not harvested and if so, will it affect the quality of the Sweet Potatoes??