Potato Crop - Introduction
6 September 2023 – by Doug Weir – Mill Station Road – The Green Valley of West Sonoma County
Are you a suburban gardner who wants fresh, premium quality potatoes? Are you seeking the reward and satisfaction of growing potatoes yourself?
Do you want to choose the best potato varieties for your garden?
Ever wonder about the debate about using grocery potatoes as seed potatoes?
Want to replicate the potato crop drama from the movie, “The Martian?”
Keep reading to learn how to grow potatoes in garden plots, bags, towers and more. Also learn how much to water and fertilize your potato crop.
We won’t be discussing yams or sweet potatoes in this article, but they’ll get a separate write up on this blog shortly.
Which Variety of Potato is Best for Your Garden and Kitchen?
There are countless varieties of potatoes. Let’s begin by looking at early, mid and late harvest varieties. You may want to plant all three to stagger your harvest so you can enjoy a continuous yield of fresh potatoes throughout the growing season, without having to store the surplus in a root cellar except at the end of the growing season.
Early, Mid and Late Harvest Potato Varieties
Early harvest potatoes only produce a single cluster of tubers. Once the leafy part of the plant has flowered, gone to seed, and died back, it’s time to dig up the tubers.
Mid harvest potatoes, or “mids,” are similar to the early varieties, except that larger tubers can be harvested a bit later in the season. Like early varieties, they tend to produce a single cluster.
Late harvest potatoes are most amenable to the tower planting method. By this method, you continually stack more and more soil over the growing potato stems in order to stimulate the production of successive layers of tubers. The potato plant will continually add tubers to the as the growing stems are covered by soil.
We can also group potato varieties according to their starch content.
Low and High Starch Potato Varieties
Note: this is discussed in more detail on the cooksillustrated.com site.
Grow low starch varieties if you plan to cook potatoes in soups, stews and chowders. For these recipes, you want the potatoes to hold together, and not crumble apart. Low starch (high water) varieties can lose a lot of water during cooking without falling apart. The red wax type potatoes tend to be low starch varieties.
Don’t use low starch potatoes for french fries, English style chips, baked potatoes or roasted potatoes. The excess water in the potatoes will give you fries that are limp and soggy, while roasted potatoes will fail to form a crunchy crust.
Grow high starch varieties for french fries, baked, or roasted potatoes. Their high starch content prevents them from soaking up a lot of fat. The high starch content also works in combination with sugars and pectin in the potato. As they cook, the starch, sugars and pectin in the potato combine or gelatinize. This process draws moisture away from the outside of the potato to help form a crunchy shell on the outside.
What are New Potatoes?
New potatoes are freshly harvested. They’re dug up immediately after the potato plant has died off. They have the thinnest, most delicate skins. The key feature of new potatoes is that they have been dug up either before or immediately after the leafy green part of the potato plant has died off.
By contrast, potatoes that have been left in the dirt for a couple of weeks develop a thicker skin and can no longer be considered “new potatoes.” Even more distinct from “new potatoes” are potatoes that have been cellared or held dormant in storage for months. These will have the thickest skin of all.
What are the Best Potato Varieties for Boiling and Serving with Butter?
Jersey Royal potatoes are mini, bite-sized, new potatoes. You’ll see them in supermarkets early in the growing season in the UK. These are particularly good for serving freshly boiled with plenty of melted butter.
I’ll have much more to report on potato varieties in future revisions of this post.
Where Can I Get Seed Potatoes?
Can I Use Potatoes from the Grocery Store that have Sprouted in the Pantry?
Oftentimes, potatoes from the grocery store will sprout and go to seed in the cupboard. Why not plant those as seed potatoes?
I’ve had very good luck doing this. Mind you, the potatoes were originally “organic,” i.e. free of chemicals. So far, I’ve harvested an average of 3 and half pounds of lovely, delicious potatoes from each 5 gallon potato growing bag that I’ve seeded with a few grocery potatoes that had sprouted. The varieties I’ve harvested so far were from organic russet and red wax potatoes.
Why not use grocery potatoes? There are two main objections. First, they may harbor fungal potato diseases that may ruin your crop. Second, they may have been treated with growth inhibitors that will degrade their quality as a seed potato.
To work around these two objections, thoroughly inspect your sprouted grocery potatoes for discoloration or signs of rot. These signs may indicate an infection by either fungus or mold. Double check to ensure your sprouted potatoes are organic. Otherwise, you’ll need to rinse off the growth inhibitors, if that’s even possible.
You can also hedge your bets, as I did, by planting only a few grocery potatoes in each of your potato growing bags. That way, any potato disease will be confined to a single bag.
In any case, it will be an experiment. I recommend that you try it for fun. Meanwhile, I also recommend that you plant seed potatoes from commercial garden suppliers.
Commercial Seed Potato Varieties
When you buy seed potatoes from a seed catalog, garden supply shop, or plant nursery, you’ll be able to choose from countless varieties of potatoes to suit your taste and harvest preferences. You’ll also minimize the risk of potato disease, and eliminate the possibility of growth inhibitors.
Fertilizer and Soil Preparation for Your Potato Crop
Before planting your crop, fertilize and prepare the soil.
Use the fertilizer that is rich in both potassium and phosphorus, but relatively poor in nitrogen. This will encourage tubers to grow rather than triggering the potato plant to “bolt” or divert all of its energy into growing greenery above ground.
Enrich the soil with two to three times as much potassium and phosphorus as nitrogen.
Ensure that your soil is rich in organic material that allows water to drain and air to circulate amongst the growing potato tubers.
Loose, friable soil, such as volcanic soil or sandy loam will be far better for your crop than clay. If your garden soil is rich in clay, then you need to augment it with lots of sand, compost and soil modifiers such as perlite and vermiculite to keep the soil loose and friable while preventing it from compacting into a dried clay hardpan.
Planting Seed Potatoes
You can maximize your planting by cutting the seed potatoes into sections, with each section having at least two eyes or sprouts. Watch for this trick in the movie, “The Martian.”
Before planting, allow the cut sections to dry for a couple of days to form a callus over the cuts to boost their resistance to mold or fungus.
Alternatively, you can simply plant whole seed potatoes. That’s what I did.
Plant the sections or whole seed potatoes about one hand width or one hand length deep, i.e. much deeper than you would normally plant seeds, about 4” to 6”.
You may choose to plant your seed potatoes as a row crop. In that case, plant one every 6” to 8” in raised rows or ridges of soil. Plant the rows about 2 feet apart, with enough space between rows to walk along and dig up dirt to pile onto the rows.
If you’re planting late harvest varieties, then continually build up the rows of soil to cover the potato sprouts by an additional 4” to 6” of dirt as they emerge from the surface.
Alternatively, you can plant your seed potatoes in fabric potato bags or large garden pots that hold 20 gallons or more of dirt. Potato towers are another option if you’re growing late harvest potatoes.
For early and mid harvest varieties, plant the seed potatoes in filled bags or pots right from the get go.
For late harvest varieties, don’t completely fill your containers before planting. Instead, only fill them 6” to 8” deep and then plant the seed potatoes.
That way, you can continually bury the emerging sprouts with another 4” to 6” of dirt.
Continue to let the sprouts emerge and add another 4” to 6” until the pot, bag or potato tower is completely filled.
For row planted potatoes, continue until the row is 12” to 18” high.
Again, late harvest varieties will continue to produce new tubers as you build up the soil around the growing stems, while early and mid harvest varieties yield only a single cluster of tubers.
How Much to Water Your Potato Crop
After planting, you’ll need to water your crop with about 12” to 16” of water for the entire season. That works out to between 7 and 10 gallons of water per square foot of crop, roughly for each potato plant. Spread this out over the entire growing season of roughly 3 months, watering every other day or so. In other words, 10 gallons per plant divided by 45 waterings works out to about one liter, or one quart, of water per plant, every other day.
For row crops and potatoes grown in bags or towers, the risk of watering too much is pretty low. But you always risk over-watering plants grown in a pot or other container that can’t drain the soil freely. So take a close look at the moisture level of the soil in your pots to make sure it’s not saturated.
Of course, if you notice your plants beginning to wilt while still full and green, then give them extra water.
How Can You Tell When the Potatoes are Ready to Harvest
The first sign telling that harvest time is approaching is flowering.
If you miss noticing the flowers, look for small fruit on the plants that look like small, green tomatoes.
Soon after these appear, the plant will begin to wilt and turn brown. Now you can harvest new potatoes.
If you’re not planning to harvest new potatoes, then cut off the tops of the potato plants one or two weeks before harvesting. The skins of the tubers still underground will harden and thicken. This makes it easier to store the potatoes. In other words, it extends their shelf life.
Crop Rotation for Potatoes
It’s best to rotate your potato crop with other crops because the potatoes are susceptible to soil borne diseases. The best practice is to only grow potatoes in a specific location every 3rd to 4th year.
Happy potato harvests! Stay tuned for updates and reports on our 2023 potato crop. Share your own potato stories in the comments. Also use the comments to ask questions or share your potato growing know-how.