Growing tips

A bag of spuds

You can’t beat the taste of a new potato, fresh from the garden.

If your garden’s small, try growing your potatoes in a bag. You’ll need:

• a size-40 black plastic planter bag
• potting mix suitable for outdoor containers
• three seed-potatoes (Swift, Liseta and Rocket are early varieties that mature in 60-90 days).

Pre-sprout the potatoes by laying them in a warm well-lit spot indoors to encourage the eyes to grow. They’re ready to plant when shoots are 1-2cm long.

Roll the sides of the bag down until they’re about 20cm high. Half-fill with growing mix, place the potatoes on top and cover with mix.

When the shoots emerge and are 6-8cm high, roll up the sides and add more mix – but leave the tops of the shoots uncovered. As the plants grow, repeat the process until the bag is full.

Keep the bag in a well-lit but sheltered spot outdoors and water it regularly – planter bags dry out quickly in warm weather.

After 10-12 weeks cut a slit in the side of the bag and feel for the potatoes. If you’re careful you can harvest some and seal the slit again with waterproof tape.

You can also use this method to grow potatoes in old car tyres. Start with two tyres and add more tyres and soil or mix as the potatoes grow.

The trickle-down effect

We didn’t add fertilisers to the potting mixes because all but one contained “slow-release” fertilisers. These consist of granules that break down in moisture and release nutrients into the soil over a period of months.

These mixes claimed to provide enough nutrients for at least three months – some claimed up to six months’ supply. That’s plenty of time to raise a crop of radishes or lettuces.

But vegetables such as tomatoes, beans or capsicums need additional feeding with a liquid fertiliser or granules once the mix’s slow-release time is up.

Tui Vegetable Mix contained sheep pellets, blood and bone, and dolomite lime to boost plant growth. Although it didn’t contain slow-release fertiliser, there were no recommendations on the pack about adding extra fertiliser. 

More from consumer.org.nz

• Growing herbs
• Growing vegetables 

Report by Bev Frederikson