Growing Potatoes - Determinate vs. Indeterminate Varieties
Updated: Sep 22
Whether you have been growing potatoes for years or are a beginner gardener I have tips to help you get the best yield possible out of your potato crop and to grow your confidence as a knowledgeable potato gardener.
The Best Soil to Grow Potatoes In
The first think you want to take a look at is your soil. Potatoes prefer slightly acidic soil with a pH between 5.5 - 6.5. You may want to pick up a soil testing kit. These can often be found at hardware stores that carry gardening supplies. If you are like me and have highly alkaline soil (mine is a pH of around 8.5 - 9) you may want to do some amending prior to planting. Mixing organic matter such as compost, mulch or peat moss into your existing soil are some easy ways to begin adjusting soil pH and improve soil quality. The best time to start this is in the fall but if you are beginning in the spring it is not too late and can make a big difference in your potato production.
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You may also have soil with a high clay content which will hinder your potato growth and yield. Adding in organic matter will go a long way to creating a nice loose soil with good drainage. Sand, as a soil amendment for clay, is controversial. It is difficult to add enough to actually make a difference and another problem with sand is that there is no nutritional benefit to it. Some believe adding sand to clay soil creates a concrete type mixture but there in little to no strong scientific evidence supporting of this. For these reasons adding organic matter is a much better option.
If you chose to add wood ash to your compost or garden, do so with caution as it can cause scabby potatoes.
Another thing worth mentioning is that too much fresh compost may work against you when it comes to potatoes. Compost is high in nitrogen. High nitrogen levels can send too much nutrients to the tops of the potatoes causing it to grow beautiful leaves and spending little time growing the tubers underneath. For this reason don't add compost after planting.
Types of Potatoes - Determinate or Indeterminate
One thing many of you may not know is that not all potatoes grow up the stem creating all those vertical layers in the potato bag or large container that you may have seen pictures or videos of. With this idea you add soil to your container throughout the growing season. And did you know that hilling your potatoes may not actually be necessary?
There are two main types of potatoes, determinate and indeterminate. What is the difference you ask? Let me explain.
Determinate potatoes are fast growing (this is why they are the more common variety for our growing zone) and their tubers grow in only one layer. This is why hilling them does not impact your yield. You do not want the growing potatoes exposed to sunlight as this will turn them green. Adding mulch or hilling them once, although not altering the yield, will ensure they don't end up green. Determinate potatoes also produce earlier than the indeterminate varieties - a big plus for those gardening in the cooler zones.
Determinate (Early and Mid-Season) Varieties include:
If you are hoping to try growing multiple vertical layers of potatoes you will want to make sure you are buying the correct variety. They normally take 110 to 135 days to produce. If you are planning to do a big pot or bag of potatoes try planing them early in the season and plan for as late as possible harvest. Don't do like I did and spend the summer adding layers to your large container, only to empty it in the fall and feel much disappointment and very underwhelmed! Am I the only one or have any of you tried this with a big fail?
Indeterminate (Late Season) Varieties
All-Blue (Russian Blue)
There is no way of physically telling these two different types apart and oddly, potato suppliers do not always seem to label them "determinate" or "indeterminate but "early", "mid" or "late season".
Once you have chosen your seed potatoes and are ready to plant you need to prepare them. Look through and any potato that has more that 3 eyes (the "dimples" or small growths on the potato) you will want to cut into sections.
Leave 2 to 3 eyes and as much potato possible on each cut piece. This takes guess work but don't worry too much about it. A few extra or missing eyes or a little more or less potato will most likely grow just as well as the others. If there are less than 4 eyes plant the potato whole. Dig a hole approximately 4 to 6 inches deep and drop potato in with eyes facing up (again, if some are facing down no biggie, they will find their way up). Keep plants 12 - 24 inches apart.
If you have potatoes from last season or ones with large shoots, you can simply break them off and they will regrow, or if they are not too long to cover with soil, plant them as they are. Don't be concerned if the potato is a little soft, it will still likely grow. If you see mould that is a time to toss it. Many people wonder if you can plant store bought potatoes. I have done so successfully. Just make sure they are locally grown (Canadian on my part) and be aware that they may have been treated with a growth inhibitor and can carry disease.
When to Harvest Potatoes
Potatoes are ready to be harvested around two weeks after the tops have turned brown and died. Harvest what you want to eat. It may be beneficial to wait and harvest the remaining closer to winter. They will be fine in the ground for weeks after the tops have died as long as the soil is not overly wet. Leaving them in the garden keeps them fresher for a longer period. When harvesting do not wash! Washing will cause them to go bad sooner. It is best to harvest when the soil is dry, as less of it will stick to the potatoes this way. Allow the dirt on potatoes to fully dry by laying them out in a dark, well ventilated place for up to a week. Set apart any potatoes that are cut or nicked to use sooner rather than later as these will go bad first. I like to pack mine in wood shavings. Other options are layers of newspaper or sand. Try to keep potatoes from touching. If some are it is not a big deal but if one begins to rot it will rot any other potatoes that are touching it. Store your potatoes in a cool dark place. Potatoes with thicker skins will keep longer than the thinner skin varieties.