Tired of tiny, egg sized garden potatoes? Not having luck with grow bags or worse, potatoes from the garden beds are turning to mush? In this article we will share all of the best tips, tricks and organic practices to ensure you can grow big garden potatoes!
How to Grow Big Potatoes
Potatoes are members of the nightshade family and they are HUNGRY. They have nutrition needs similar to carrots, as opposed to other nightshade family members like tomatoes and peppers. Because of this it is easy to give them too much nitrogen and grow huge, gorgeous green plants that produce lots of marble sized potatoes. Let’s talk about how to remedy this!
Potatoes are Picky About Their Soil
Potatoes LOVE sandy soil that is made up of play sand and compost. They can do very well in pots if you grow them in a mix of compost and play sand. They like loamy, fluffy soil but need significant amounts of phosphorus (P) and potassium (K) to grow. Properly aged compost is rich in potassium and phosphorus and potatoes desperately need it!
Organic Fertilizer Needed
Many gardeners make the mistake of giving their potatoes Miracle Grow and then wonder why they have such small spuds? Potatoes are HUNGRY plants that need nutrition from above and below, typically in the form of organic foliar feeds and compost plus some organic fertilizers if you would like to use them. Good quality inputs is how you are going to grow big potatoes. Chemical fertilizers that may be good for tomatoes, like Miracle Grow, are not ideal for potatoes. Miracle Grow is going to produce stunning foliage with poor potato tubers.
My Favorite Potato Foliar Feed
I give my potatoes my favorite foliar feed mix at least once per week while the leaves are bright green and growing. Here is what I use:
In a 2 to 2.5 gallon watering can (I use Behrens) combine 1 Tablespoon Trident’s Pride Fish Foliar Feed, 1 Tablespoon Organic Liquid Kelp and 1 teaspoon Cal-Mag. Exact measurements are not needed – just eyeball it as your pour it into the bottom of an empty watering can then fill with water to mix the solutions. Use this as a foliar feed by deliberately watering the leaves of your plants in the morning. Plants will absorb the nutrients within 15 minutes. Works beautifully on all vegetable plants as well as onions, herbs, flowers, flowering shrubs and vines.
If you would like to qualify as 100% certified organic, opt for this organic Cal-Mag product.
While I love this foliar feed blend and I get medium sized potatoes using it as the only fertilizer, potatoes typically need just a little bit more help getting enough phosporus (P) and postassium (K) if you want a larger harvest of full-size spuds.
Additional Fertilizers
If you are growing in buckets, bags or pots, consider using one or more organic soil additives!
Bone meal (4-12-0) is often added to the soil potatoes are grown in to give a boost of phosphorus (P). Rock Phosphate (0-3-0) is another organic way to supplement phosphorus. Langbeinite, which is Sulfate of Potash Magnesia, also called Sul Po Mag (0-0-22) is used to boost potassium (K). (You can also use langbeinite around fruit trees that are not flowering much nor setting much fruit to get tons of flowers and set fruit!)
If you already have Bloom Booster types of fertilizers (0-15-16) or (10-30-20), these can give noticeable potato tuber results because of the high phosphorus (P) and potassium (K) content but they are usually not organic. Dr. Earth is organic if you’d like to try their 3-9-4 NPK blend but the organic Big Ass Carrots fertilizer (1-9-3) may perform better and is ideal if you’re also growing carrots.
Potatoes need both phosphorus (P- the center number), and potassium (K- the last number) to grow well.
Do NOT use Blood Meal (12-0-0), Feather Meal (12-0-0) or Urea (46-0-0) on potatoes. These all contain too much nitrogen and have no phosphorus or potassium.
Cool Temperatures Required
Potato plants absolutely will not produce tubers in the heat. Their leafy tops may grow beautifully but they need very cool soil temperatures in order to form potatoes. Research has shown that 71°F is pretty much ideal for planting/starting the potatoes and getting foliage to grow while 59° is the best temperature for tuber growth. The planting window during your growing season is vitally important and you need to look for a 90 day span in which your weather is between 50-80°F, where the soil temperature will be 45°F or warmer when planting. Being just a couple weeks too late can be the difference between a bumper crop or finding lackluster littles when you dig them up.
Not Too Much Water
Potatoes can be flooded and “drown” in too much water. My area’s late winter and early spring rains are so drenching that I do not water my potatoes. I grow them in jumbo plastic patio pots so the excess rain water can quickly drain. Growing in raised beds can also help. It is easy to give potatoes the little water they need by hand so opt for high and dry areas when planting your spuds. Potatoes that turn to mush in your garden beds most likely have experienced too much water in the root zone.
Selecting a Good Variety
Your local garden center and feed stores that sell seed potatoes in bulk can usually tell you which varieties do the best in your area. While it is fun to try different colored potatoes, consider growing the popular local variety to ensure you get a harvest of some type. Red potatoes have always performed the best for me. You may find that you need to buy seed potatoes early, as soon as they show up at the nursery or feed store, to get the variety you want. In my area the best sell out wildly fast.
Potato Grow Bag, Pot or Bucket?
If you live in a southern climate that tends to have wet, rainy winters, your potatoes are going to need to be in a bucket, bag, jumbo flower pot or raised trough bed of some sort so they get excellent drainage. (Afflinks)
I prefer using huge, 36 inch wide plastic flower pots that can handle planting 2-3 seed potatoes for a larger harvest from one container. 5 gallon buckets also work if you drill drain holes in the bottom and only plant one seed potato in each.
Your Potato Experience Wanted!
I hope this article has given you some great tips on how to grow big potatoes this coming season! If you have any additional tips or fertilizer blends that worked especially well, please share in the comments below!
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Hi, Tay. I just discovered your website in my search for tips to grow larger, organic potatoes. I don’t hill anymore because it was too much work and I don’t have the space. I’ve tried potato bags and, this year, built a potato tower using chicken wire and layers of straw and compost soil I bought. Unfortunately, to date, all my efforts have resulted in lots of small potatoes. So, after reading your article on this, I realize I need to provide correct nutrition, sandier/looser soil and, perhaps, plant fewer slips or whole potatoes to get the size I’d like.
My main question is this: you mentioned that the plants do better in cooler weather but you didn’t go into specific times of year. I live in CT not near the shoreline. Should I be planting in the early spring or in the fall? And I’d very much appreciate any other comments that would help my garden efforts be more successful. Thanks so much! Lorraine
Hi Lorraine!
Potatoes are tricky. There isn’t a correct time of year to plant them for the entire US. They can handle a very light frost, where temps barely reach 32°F for only a few hours but it does damage the leaves and usually kills back tender growth, which can stunt the tubers. The tubers need cool weather to form. It’s best if the potatoes grow in cool weather but are protected from frosts & freezes OR if they begin in warm weather but it cools off as the tubers develop. (Covering helps if there will be a freeze, I add incandescent Christmas lights for warmth under the sheet/cover if needed during an overnight cold snap.) You have to find a 3 month window for your area’s climate where you don’t get many/any freezes but the weather stays below 85°F. Potatoes seem to grow best between 50-80 degrees but they will bud in soil that is 45°F or warmer. Tubers form best around 59°F, which happens during the last 45 days of growth. Where I’m at near Houston, Texas I have to plant in late January or early February since we begin to hit 85°F 90 days later. Late winter is our ONLY Irish potato growing window. In other places potatoes can be grown all spring and all fall. Research has shown that 71°F is pretty much ideal for planting/starting the potatoes and getting foliage to grow while 59° is the best temperature for tuber growth. I hope this helps you identify the perfect growing season for your climate!