Determinate potato (left), indeterminate potato (right). Ill.: http://www.supercoloring.com, montage: laidbackgardener.blog
Most serious gardeners know the difference between determinate and indeterminate tomatoes (Solanum lycopersicum). Determinate tomatoes are the shorter ones, the ones that don’t necessarily need staking. They grow to a certain height, then stop growing. They also produce most of their fruits all at once. Many early tomatoes are determinate.
Indeterminate tomatoes are the tall ones. Staking or caging is required and they keep growing taller and taller all season. They produce fruits over a long period and indeed, in tropical climates or heated greenhouses, produce continuously. They’re usually mid-season to late types.
So, that’s what you know. But did you know that potatoes (Solanum tuberosum), also come in determinate and indeterminate varieties and that this can influence how you grow them?
The difference is that this mostly happens underground.
Determinate potatoes produce a single layer of tubers just below the soil surface. They produce fewer tubers than indeterminate ones, but they tend to be earlier, even much earlier, most maturing in 55 to 70 days. In short season climates, only determinate potatoes may have time to produce full-size tubers good for storage. They also have shorter stems not given to flopping.
Plant determinate seed potatoes (small tubers) about 4 inches (10 cm) deep. There is no need to mound up soil at their base, but mulching can be of great help, ensuring that the tubers are not exposed to the sun. (Those touched by the sun will turn green and be inedible.)
The following varieties are among the more popular determinate potatoes:
- ‘Adirondack Blue’
- ‘Adirondack Red’
- ‘Dark Red Norland’
- ‘Dakota Pearl’
- ‘Gold Rush’
- ‘Irish Cobbler’
- ‘Purple Majesty’
- ‘Red Norland’
- ‘Red Pontiac’
- ‘Russian Banana’
- ‘Sierra Gold’
- ‘Sierra Rose’
- ‘Yukon Gold’
These potatoes are capable of producing tubers at multiple levels, so, although you plant them at the same depth as determinate potatoes (4 inches/10 cm), you will need to keep mounding soil, mulch, chopped leaves or straw up around the plant as the season progresses. This mounding will not only help support their tall, often floppy stems, but tubers will form in the increasingly high mounds, to a maximum of up to about 1 foot (30 cm) above the original level. They’re also the potatoes used in “potato towers” and “potato bags.”
Indeterminate potatoes produce more tubers than determinate potatoes, but need a longer growing season. Some are mid-season (70 to 90 days) varieties, but most are late varieties (90 to 110 days, even 135 days). Not all late varieties are adapted to short-season climates.
The following varieties are indeterminate, at least to a certain degree:
- ‘All Blue’ (‘Russian Blue’)
- ‘Canela Russet’
- ‘French Fingerling’
- ‘German Butterball’
- ‘Green Mountain’
- ‘Maris Piper’
- ‘Pink Fir Apple’
- ‘Red Cloud’
- ‘Red Maria’
- ‘Russet Burbank’
- ‘Russet Nugget’
- ‘Strawberry Paw’
Helpful Hint: No matter what type of potato you grow, you can tell the tubers are ready to harvest when the foliage begins to die back.
How to Tell?
Oddly, potato suppliers rarely seem to mention which type of potato—determinate or indeterminate—they sell. They tend to stick to the terms “early,” “mid-season” and “late” in their descriptions: helpful information, to be sure, but it doesn’t necessarily tell you which ones will produce tubers on mounded stems and which won’t. Mid-season varieties, for example can belong to either group.
Of course, you can find out if a potato is indeterminate or not by growing it! Determinate potatoes rarely grow very tall and are often early to bloom. However, if the plant’s stems just keep growing up and up, it’s indeterminate, a fact you can confirm by mounding the stems and checking to see if new tubers form in the added layer.
Still, knowing in advance which potatoes are determinate and indeterminate would really help gardeners, especially those who want to experiment with growing in towers and bags, so, potato suppliers, would it really be so hard for you to just add one more word to your descriptions: either determinate or indeterminate?
Thanks so much!