Sweetcorn features commonly in many edible gardens in summer around the world, whether in the northern or southern hemisphere. Children usually love sweetcorn. Corn is usually yellow, but it also comes in a variety of other colours such as red, orange, purple, blue, white and black. If you want to eat coloured corn, you’ll probably have to grow your own as it can’t be found in supermarkets, at least not in New Zealand.
Corn is rich in many nutrients, including protein, carbohydrates and fibre. It also contains many vitamins and minerals. I probably shouldn’t grow and eat a lot of corn myself as a diabetic, as it does contain a lot of carbohydrates compared to other vegetables. To put things into perspective, let’s consider how corn would fit into a diabetic diet. There are 25 g of carbohydrates in one medium fresh cob of corn or per cup of tinned corn kernels. Ideally, diabetics should aim to have between 30-50 grams of carbohydrates per meal three times daily. So you can see that the carbohydrate content is quite high in relation to my body’s needs. Not everyone would agree with me about how much carbohydrate I should be consuming as a diabetic. Remember that everyone’s bodies process sugar differently and you need to learn what works for you through trial and error. Mum and I both find that we’re able to control Type 2 diabetes naturally without recourse to any medication such as insulin or metformin by structuring our diet around the 30-50g of carbohydrate per meal rule. This is really all thanks to mum who is a retired nurse and has a very good understanding of health and the human body. Remember that as a matter of overall health, we all need some carbohydrate in our diet, whether we have diabetes or not. In my personal opinion, it’s best to opt for carbohydrates in moderation which are found naturally in fresh vegetables such as potatoes, sweet potatoes, parsnips and corn. They keep your blood sugar level rather than highly processed packet foods which are filled with sugar and will cause your blood sugar levels to spike dangerously.
Corn can be consumed in a variety of ways. My favourite way to eat sweetcorn is freshly boiled or microwaved, served with some butter, salt and pepper. Simply delicious! Sweetcorn is extremely versatile and can be used in other dishes such as salads, fritters, frittata, stir fries and curries.
You can expect to pay an average of $1 per cob in supermarkets in New Zealand during the summer when sweetcorn is in season. Homegrown sweetcorn tastes so much fresher, sweeter and nicer than store bought cobs. I can’t believe I’m writing a growing guide to corn, because I’ve never had much luck with growing it in the garden in the past. Problems I have encountered include:
o Low germination rates
o Poor pollination of kernels (ie gaps on the cob)
o Very small cobs
o Corn not maturing in time before it becomes cool again
I should also say that I didn’t originally plan to grow corn this season due to space limitations. The reason space became available is because my parsnip seeds (sourced from a different company for whom I’m not a brand ambassador) failed to germinate.
Given my previous bad track record with growing corn, it’s necessary for me to bring an expert on board for some advice. I decided that the best person qualified for the job is no one else but John McCullough, the owner of Egmont Seeds, New Zealand’s largest seed supplier for both commercial growers and home gardeners. We have gotten to know each other well over the years and I am proud to be a brand ambassador for Egmont Seeds. John is of the view that sweetcorn is very easy to grow and that any failure is sure to be due to cultural issues. With his help, I have managed to put together some advice which will hopefully help gardeners to grow corn successfully this season, including myself.
To view a short clip about John and learn more about his company Egmont Seeds, please click here.
When to sow
According to John, sowing corn seeds too early is by far the biggest reason for failure. Corn needs warm conditions in order to grow well. In the Auckland region, start sowing corn from mid to late October. On the other hand, you don’t want to leave it too late otherwise you run the risk that your corn won’t mature in time before the cool weather sets in again. To be on the safe side, it’s a good idea to sow corn by early December at the latest.
To soak or not to soak?
There are two broad schools of thought on this issue. Some gardeners prefer to soak hard-coated seeds prior to sowing them, including corn, in order to aid germination. Other examples of seeds that gardeners might soak include edible sweet peas, snow peas, ornamental sweet peas, beans and okra. John’s view is that there is no need to soak the seeds and that doing so may cause them to “drown”. Because I’ve had such bad luck with growing corn in the past, I’m going to do a bit of both with each of the varieties I’m trialling and hope for the best.
Sowing corn directly from seed v transplanting seedlings raised in punnets
Opinion is divided on this issue. As with the question of whether or not to soak seeds prior to sowing, there are two schools of thought. John’s advice is to sow corn directly where you want to grow it. He believes there is very little advantage in sowing corn early in punnets because the stress of transplanting will quickly undo any small advantage gained by sowing corn a few weeks early. Sowing directly leaves corn seeds vulnerable to rot, as well as being scratched up and eaten by mice and birds. Therefore, try to protect them if you can. It’s for this reason that I became attracted to the idea of sowing corn in punnets for transplanting later on. In the past, I’ve found that corn seed sowed direct to the ground simply failed to germinate. The seed was fresh, leading me to conclude that it either might have rotted or was consumed by mice or birds. As with the issue of whether to soak seeds prior to sowing or not, I’m also going to both sow corn directly and transplant my own seedlings raised in punnets to see which works best.
Sowing corn directly from seed
Make sure that the soil is well drained in the area you are planning on growing corn. Add compost, sheep pellets and some general garden fertiliser. Dig into the soil and rake the area so that it is nice and level. John’s advice is to sow corn at a depth of 15-20 mm maximum. Space the seeds 15 cm apart. If spaced too closely, the result is smaller cobs of corn.
If you’re planning to grow corn from seed, you’ll find that they come in an impressive array of colours. Traditionally, corn is yellow as mentioned above. There are quite a few different varieties on the market in New Zealand. Thanks to Egmont’s generosity, this season I’m growing Florida Staysweet F1, Super Sweet Lumina Bicolour F1, Supersweet NZ Hybrid F1 and Tender Yellow F1 Hybrid. As we live on a suburban section, space is very limited. I was very lucky that John selected these four varieties for me as Egmont Seeds have an extremely extensive selection and I couldn’t decide which varieties to grow. There are other varieties on the market as well. You could also try growing Bicolour Honey N Pearl, Bicolour Xtra Tender Stellar, Early Marika, Super Sweet NZ Yellow and Xtra Tender Yellow F1 Hybrid, all of which are part of the Egmont Seeds range.
To order seeds from the very extensive Egmont Seeds range, visit http://www.egmontseeds.co.nz/.
According to John, corn seeds will last for many years so you don’t have to sow them all at once. Store them safely in your seed collection for sowing in future seasons.
Growing corn from transplanted seedlings raised in punnets
Corn can be started from seed indoors in October or even earlier if you live in a more temperate zone and have a hot house to protect them from the cold. Corn seeds need warmth in order to germinate. I germinated seeds in punnets filled with seed raising mix from Gardn Gro. I like Gardn Gro’s seed raising mix as it is very fine in texture, enabling seeds to push through the mixture easily as they rise to the surface. I placed the punnets inside plastic incubators which you can purchase from garden centres. I then placed the incubators on a heat pad indoors and sprayed plants with water once daily or twice if the seed raising mixture was very dry. If you don’t have a heat pad you can also use your hot water cupboard which will also provide seedlings with a warm environment so they can germinate successfully.
How to care for corn seedlings
For new gardeners, those who don’t wish to start their corn seedlings from seed or if you’ve simply left it too late, plants are available for sale in nurseries from September onwards. Palmers stock a great range of corn seedlings. Awapuni also sell high quality, large grade corn seedlings delivered direct to your door. If you order 7 or more bundles of seedlings, delivery is free.
I plan to sell a variety of different corn seedlings in my own boutique nursery later in the season. Keep an eye out for details in my newsletter, on Neighbourly and my Facebook page as to when they become available. During October and November, I will also circulate updated lists of available stock in my plant nursery to subscribers of my free weekly gardening newsletter. To be added to my mailing list and receive these notifications, please email me at firstname.lastname@example.org.
I’ll probably be selling seedlings a bit later than stores because I’m merely a home gardener, germinating and caring for seedlings in our patio at home without the help of the horticultural technology that you would expect to find in a commercial operation. Without a hot house, I simply don’t have a head start on the season like large-scale nurseries. To compensate for this, I do try and offer seedling varieties which are unusual and can’t be found in garden centres or online retailers. This is a good thing as it enables me to collaborate with other businesses in the industry and promote their brands. You can achieve a lot by working with other people in the same field (no pun intended), as opposed to simply trying to compete with them. To read my further thoughts on this issue, please click here.
Whoever you decide to buy plants from, take care to keep seedlings undercover until early October as corn is frost sensitive. The weather can be temperamental in spring and the nights are often still quite cool. From then on, start “hardening them off”. This is the process of exposing plants to the outdoors incrementally, for example, for two hours in the middle of the day for the first week, increasing to four hours per day for the next week. Continue to bring the plants indoors at night. By the third week of October, it should be safe to leave plants outdoors overnight.
How to care for corn plants
Be sure to water plants every day, preferably early in the morning or in the evening. In November and December, plants are in their most active growing phase. Liquid feed corn weekly to encourage the growth of healthy leaves and the formation of fruit after pollination. Sweet corn usually grows to a height of around 150 cm.
Pollination of corn
As with all grasses, corn is pollinated by the wind. John’s advice is to sow seeds in a block formation rather than in rows. Sown in a single row, corn will be pollinated poorly with only scattered kernels on the cob. He believes that it is best to sow four short rows in an area that gets good wind movement, rather than one long row.
John also attributes poor pollination to caterpillars who will eat the tassels later in the summer, preventing the pollen from reaching the cob. This will again result in scattered kernels only.
Harvesting your corn
It can take what seems like forever for your first sweetcorn to be ready for picking but be patient! It depends on the variety, but normally it takes around 100 days for sweetcorn to mature. You will know that corn is ready to be picked when the silks on the ends of the corn become dry and brown. Normally each plant will produce only one cob of corn.
Got a glut of corn that you can’t get through all at once? Corn can be stored in the fridge for up to 2 weeks prior to consumption, or you can give some away to family, friends and neighbours.
I will report back later in the season regarding the progress of my sweetcorn growing trial.