How I grow Potatoes in Tasmania.
(Note this is just how I do it, there are many great growers who have their way)
Potato (Solanum tuberosum) is in my opinion the most important food plant in my garden. Who doesn’t like spuds on the dinner plate. There is a reason the spud spread quickly around the world to form a major component of many cuisines. Plus the good ol spud is so versatile.
Potatoes are relatively inexpensive to purchase. A bag of certified pink eyes from Mitre 10 is around $6 from memory and last season that one bag produced 30kg of fresh flavourful organic spuds. Homegrown spuds are so much tastier than the shop bought ones, plus I have heard some commercial crops have been sprayed with glyphosate prior to mechanical harvesting!
In Tasmania outside, seed potatoes can be planted when the soil can be worked, after the last chance of frost. However pink eyes can go in a little earlier (mid August in my garden). The bulk of the other varieties I put in mid September to Mid October (Up to date, Kennebec, Dutch Cream etc). I find this timing has produced the biggest yields given the temperatures at that time of year, however I sometimes put some in after x-mas for an April ish harvest (I also plant some in grow bags in the hothouse to go through winter). Later plantings seem to yield lower largely due to less favourable weather.
The soil temperature should be at least 10 degrees Celsius so if your concerned your early, use a soil temp probe. Time to full maturity can range anywhere from 90 to 120 days, depending on the variety. Pink eyes put in late August are nearing harvest by x-mas (hence the first x-mas day spuds on the plate).
How to Plant
Many dig a big trench, plant and back-fill. I did this for years and dreaded the spud planting day given my soils. These days I am generally a no dig gardener so I simply dig a small hole to place the spud in so it is below the soil the height of the spud. Once the spuds leaves break the surface, I add compost on top and have excellent success doing it this way. Charles Dowding shows the method I use at this link
If you want to use the trench method, dig a trench 6 inches deep, place spuds about 25cm to 30cm apart then cover a few inches. Once the leaves break through, add more soil in the trench (helps keep soil loose for developing tubers.
Notes on success:
- To extend your potato growing season, choose an early variety as well as a late-season variety. (ie: pink eye / kipfler and kennebec).
- Buy certified disease-free seed potatoes. Attempting to plant potatoes purchased from the grocery store is a gamble. Besides the disease problem, potatoes are often treated with a growth inhibitor to keep them from sprouting.
Avoid planting potatoes where tomatoes or eggplant were grown the year before.
Buy your spuds as early as May when the stores receive the new season certified spuds. Then I place them in egg cartons in my studio and by planting time they have a head start and have sprouted short strong stems.
Plant in full sun to encourage top growth, which will support the growth of the roots – at least six hours per day. Frost will damage the leaves, so when pink eyes are up if you see a frost forecast in September onward, put a sheet over the plants, buckets, anything to prevent frost damage. However, if they do get a bit of light frost damage, it won’t stop the harvest. I have had some damage in previous years and good harvests. Severe frosts will set them back so cover. Hopefully by October we are good to go in the majority of places below say 300m.
Potatoes prefer soil with an acidic pH between 5.0 and 6.0. Potatoes grown in soils with a high pH (alkaline) seem prone to scab (rough spots on the potato). Potatoes don’t require rich soil, so if you have a good amount of organic matter in the soil and the pH is neutral to acidic, the potatoes should be happy. The soil needs to be loose and well-draining. If you have soil that is heavy in clay, you will need to prepare it down to the depth where the potato tubers will grow (The charles Dowding method in the link above would be useful on clay as you can lay cardboard down, compost on top and grow)
I add Complete Organic Fertiliser (Steve Solomons recipe) at planting and every 4 weeks. Every two or three weeks (or when I remember) I water with Seasol and Powerfeed.
I plant a spud with 2 to 3 eyes so I cut the spud up to allow for this. I then plant straight after cutting. Never have I had a problem with this.
Potato plants rely on a steady water supply. This is one of the key points to large yields from my years of growing spuds. Water them deeply at least twice a week unless we have had plenty of rain (ramp your watering up when leaves are up, plants are growing and rain is scarce). They are sensitive to drought conditions, especially when they flower, as that is the peak time for forming the potato tubers. So, when it is dry and warm water them often and stick your finger into the soil to ensure the water is getting down.
I find that once flower form, this is the pivotal moment to promise not to let the plants struggle for moisture. Water well and once the leaves start to turn from lush to looking withered, I back right off.
It is around November I add more compost around the spuds. This helps ensure the forming spuds are not seeing the light of day thus turning green. In the south for large loads of compost I recommend the organic compost at the South Hobart tip or Cherries Tasmania. After that Barwick at Mornington is ok. I can’t make any recommendations up north. The best obviously is homegrown but producing enough for many is difficult.
Potatoes should not be planted until the soil temperature is at least 5 degrees C, and preferably 10 C. Potato tubers grow best when the soil temperature is 15 to 22 degrees C (which is around November to December thus planting in Aug to early October is ideal), and stop growing when the soil hits 26 C (January in Tasmania but depends on the season. Sometimes the soils rarely get to this temperature outside of those occasional hot days). Mulching around the plant, such as with a thick layer of straw, can keep the soil cooler if this is of concern, not really an issue in Tasmania.
I add homemade compost if I feel there is a need but once flowering starts I stop adding compost (sometimes they just don’t flower).
Once you see the plants no longer look lovely and lush green, it is a sign the spuds are nearing harvest. Pull back a bit of soil and look. I harvest a few for dinner at this time.
Expect to wait four months for potatoes to reach their full size. The entire crop is ready to harvest once the tops of the plants die off. I even harvest when the plants show signs they are well are truly done but leaves are not completely dead. Harvest one plant if you are unsure. You can leave the potatoes in the ground for a few weeks longer, as long as the ground is not wet as this impacts their storability.
I harvest on a warm sunny day, I leave the spuds on a hessian bag for a couple of hours to dry more. Then they go in the hessian bag and into my pantry which is dry and dark.
Growing the varieties available for purchase over the years is the only way to learn what you like and don’t.
Commonly grown ones in Tasmania include
- Dutch Cream: creamy yellow flesh perfect for boiling or mashing. Not bad roasting either
- King Edward: close to my favourite. An English variety I use for baking, mash, chips and roasting. Great all rounder (but only my opinion).
- Pink Eye: Popular early spud for potato salads and boiling. Ok for baking but shines in a creamy potato salad. Early maturing
- Kennebec: US variety similar in versatility to Dutch Cream with white flesh
- Up to Date: Scottish variety I grow and use like Kennebec.
- Kipfler: interesting cigar shape. Only grown this a few times and not for a few years. Excellent in a potato bake and quicker to grow than some others.
- Nicola: a great spud as is so buttery and boils well like Pink Eye but also good in mash.
There are others available on the market but these are some of the more commonly found ones. Each year I like to add a new one to the potato growing list.
I do about 20 grow bags a year. Spuds can take up some space in the veggie patch, so I find grow bags handy to keep beds open to other veg. I fill each bag up with a mix of compost, manures, some peat moss and perlite (water retention). Organic Rooster Booster is useful. I plant the spud close to the bottom of the bag, fill up to almost the top and that is it. Keeping the bags moist is the key.
Best of luck with the coming spud growing season.