Growing sweet corn in GreenSmart planters

Growing Sweet Corn in GreenSmart pots

Growing sweet corn is one of the most rewarding plants because the plants are very easy to grow and freshly picked sweet corn is amazing.

Just the thought of freshly cooked corn dripping with butter …..Here are some tips for growing sweet corn in a GreenSmart self watering planter. Modern sweet corn is derived from maize which has its origins 5000 years ago in Mexico.

Plant out doors in late spring – early summer in most NZ areas. A good guide is to start planting at the same time as when apple trees are flowering in your area.

Sweetcorn on a plate

Conditions for growing sweet corn

Prepare the planter with plenty of well rotted animal manure or compost. Boost the potting mix with plenty of organic fertiliser. Corn likes rich soil.You can start doing this several weeks ahead of planting. Growing sweet corn in containers requires ample nitrogen and moisture.

Wait until you have soil temperatures of about 16 deg C. Be sure to use fresh seed for best results each season. Soak the seeds overnight then plant the seeds about 2 cm deep and 10 cm apart. Plant deeper if the soil is warmer. Sprinkle water over the top of the seeds and fill the water reservoir. When the corn is about 10 cm high thin out the weaker plants (remove about half of the seedlings). You can also buy seedlings from your garden centre.

This year I am going to start some Honey & Pearl sweet corn seeds in mid September in my hot house, then I will shift the planter out doors when the weather is warmer and I start more seeds at the same time. You can continue successive plantings until Xmas.

Sweet corn likes full sun (at least six hours per day) and protection from too much wind. Position the planter against a north facing wall if you are in a windy area. The plants are wind pollinated, ie they have both male and female flowers on the same plant. In windless places you may need to shake the tops of the corn to spread the pollen from the tassels.

As the rapidly growing sweet corn plants get larger and the weather is hotter, the plants will drain the 12 litre water reservoir after about three days. It is worth mulching the soil surface to reduce water loss.



SEAWEED FERTILISERInclude plenty of animal manure with the potting mix. eg A few handfuls of sheep manure pellets, Yates Dynamic Lifter. When the growing sweet corn plants are 25-30 cm high, add more nitrogen rich fertiliser. Every few weeks add liquid seaweed or fish fertiliser into the water reservoir.


Keep birds away by covering the pot with light netting until the seedlings are established.Birds love to dig out your freshly planted corn seeds. Keep an eye out for signs of snails and slugs when the seedlings are first emerging.


Companion Plants – Three Sisters

The ‘three sisters’ of traditional North American gardens are maize, beans and pumpkin. The idea is to grow the three of them together so start the corn first, then inter-plant with beans or peas and pumpkin. Corn provides a frame for the beans to climb up and the beans or peas (legumes) fix nitrogen into the soil. Pumpkins provide shading to the roots of the legumes and corn.


Check the corn when the tassels start to dry out to a chocolate brown. The corn is ready to harvest when the kernel juice is milky in colour. Harvest the cobs by pulling them downwards and twisting to break off. The sucrose in corn starts to convert to starch right after harvest so you will have the sweetest corn if you cook it immediately after picking.

corn on the barbecue

In The Kitchen

Summertime, your own corn on the cob right off the bbq …. it doesn’t get better !!

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