Gardening: How to prepare and care for a potato crop

The agria potato has a long oval shape with yellow flesh that is perfect for roasting, chips and wedges, writes Gareth Carter.

Gareth Carter is the general manager of Springvale Garden Centre in Whanganui.

OPINION

I was recently talking with my father-in-law (a great vegetable gardener) about potatoes and he shared with me long-forgotten New Zealand history about potato growing and an event called Spud Monday.

Spud Monday was observed each year as a special holiday on the first Monday of August. It was to commemorate the plight of the first European settlers who came so near to starvation they dug up their seed potatoes, already planted, to use as food. The eyes of the potatoes were replanted to provide the next crop. Spud Monday was a unique Nelson holiday that lasted until about World War II, according to the Nelson Historical Society Journal. All shops, businesses and schools closed for the day. It became a tradition for hundreds of people to walk the Dun Mountain Track on Spud Monday.

Thankfully, food supply in New Zealand is a lot more secure than what the early settlers experienced. Despite the passage of time, the planting seasons remain true. New-season seed potatoes have arrived in stores and now is the time to choose the varieties you want, take them home and allow them to grow sprouts ready for planting in early August. Once they have been mounded a few times, we will be past the time for late frosts.

It is important to select a good spot for them to grow because potatoes need a sunny (at least five hours a day) position where they will not be competing for moisture. They also benefit from being in a sheltered area that does not receive strong winds.

Next, the soil needs to be “well worked” — this means it has been dug over to a depth of 25-30cm. This will allow the potatoes to grow and multiply. If the soil is very heavy and clay-like, creating raised beds to ensure good drainage will be beneficial. If, on the other hand, the soil is very light or sandy, the addition of organic matter such as compost or sheep pellets will be beneficial because they not only add nutrients, but will help hold moisture for longer.

Potatoes are a tuber that forms on part of the stem that is under ground. By “mounding up” soil around the stem as the plants grow, you will increase the amount of stem underground and the yield from each potato plant.

Like many plants, there are a number of potato varieties available. The way to choose which to plant is to know when you want them to mature and how you like to eat your potatoes. Have a look in store and check out the varieties. Three favourite varieties are agria, heather and jersey benne. Agria is an early main cropper and has a long oval shape with yellow flesh that is perfect for roasting, chips and wedges. Heather is a main-crop potato that is oval and has a distinctive purple skin with white flesh — it’s great for boiling, roasting and casseroles. Jersey benne is an early variety with a kidney or oval shape whose white skin and flesh are excellent for mashing or boiling.

If you do not have enough space in your garden for a row or two of potatoes, you can grow them quite successfully in containers, large plastic bags or a bucket (say 35 litre), using a good-quality mix such as Ican Premium Potting Mix or Tui Vegetable Mix. Make sure there are plenty of drainage holes. Place tubers in the potting mix near the bottom of the container, covering them by about 50mm. As the sprouts grow, keep adding the potting or vegetable mix until it is up to the brim of the container, add a dressing of Ican Potato Food each time the potting/vegetable mix is added or some Tui Novatec every two months. Harvest when the tubers are ready.

The often-asked question is “do I need seed potatoes or can I plant a few potatoes left in the bottom of the pantry that I purchased from the supermarket?” The answer is to purchase “certified seed potatoes”. This means the seed has been assessed by an authority called Potatoes NZ. This certification ensures the seed is free from viruses, which can significantly reduce the yield.

Here is an easy seven-step process for delicious home-grown spuds. Ensure you select varieties that suit how you like to eat your potatoes because some varieties will roast well, while others are excellent in potato salads.

Step 1: Site selection, taking into account the factors previously discussed (sun, moisture and wind).

Step 2: Purchase certified seed potatoes, spread out in a warm-light location and leave to grow sprouts (about three weeks).

Step 3: Prepare the soil for planting. Remove any weeds from the area and dig over the soil to 25-30cm deep, working the soil to a fine texture. Spread both Potato Food and Garden Lime over the soil and mix well so that none will come into direct contact with the potato tubers when they are planted. Add gypsum to the garden if the soil is clay and raise the bed to improve drainage if required. If the soil is very light, the addition of compost or sheep pellets will improve moisture retention.

Step 4: Plant seed potatoes about 10cm deep, 35-45cm apart and in rows about 75cm apart. This gives a good amount of space to later mound up soil around each plant.

Step 5: Check weekly. When shoots have emerged and are reaching 20cm high, it is time to start mounding. Mound up the soil, almost completely covering plants, and continue to check regularly. Once they have grown another 20cm, mound them up again. Having so much of the stem covered will ensure a decent crop as tubers form up the buried stems. Sprinkle the soil around the plants with Potato Food each time before you mound up the soil. By covering the stems of the plants with soil you are also providing protection from any late frosts. Any tops remaining should be covered with frost cloth if a frost looks likely.

Step 6: Pest control and care. The potato/tomato psyllid has become a problem throughout New Zealand. The symptoms often don’t show up until it is too late because the insects can be seen only under the microscope. However, it is easily controlled using Yates Mavrik or Yates Success on crops growing from November to April. If you like to avoid using sprays, I suggest planting sooner rather than later, because the insect problem becomes more prevalent as summer progresses (December onwards). By starting your potato crop now, they will probably be ready for harvest before needing treatment for psyllid.

Step 7: Harvest. You know your potatoes are ready for harvest when the plants flower. There are a few varieties (such as rocket) that do not flower, so in this situation it can be useful to mark on the calendar when they would be due. Generally, early varieties will be ready to harvest about three months from planting, while four months for late and main crop varieties is more suitable. The later and main-crop varieties are usually better for storing.

For more gardening information go to www.springvalegardencentre.co.nz