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There's nothing more tasty than home grown sweetcorn. If you have never tasted it fresh off the plant, you are missing out. There are many vegetables that grow better in wicking planters - let's take a look at corn to see how it goes with the constant water supply the wicking process provides.
Corn grows extremely well in wicking beds. Research shows that corn needs around an inch (2.5mm) of water per week, with the most critical supply 2 weeks before the silks form. A well drained, fertile soil is required - so self-watering beds are perfect to grow sweetcorn in the home garden, and can easily outperform corn grown in the ground
How to Prepare a Wicking Bed for Corn
The potting mix in the bed should be well rested ideally, and heavily mulched . Lots of organic material should be mixed in; well composted manures, worm casting, or whatever you have to hand.
A soil pH of 6-6.8 is ideal - there are many low cost pH meters available to measure this - it is well worth doing.
Prevent Corn from Falling Over in a Raised Bed
A well constructed wicking bed will contain a friable potting mix with good quality wicking additives. It will not usually contain very compactible soil, which helps keep the wicking process going.
However a tall, shallow rooted plant like Corn does require a fair amount of support, especially in windy areas. A good wicking mix can be a little too soft and spongy to give it the support it would have in an arid South American plain!
For that reason, we started planting our corn seeds in trenches about 100mm deep - pulling aside any mulch then parting the soil a little with the side of a plank and compacting where the seeds are to go . When the plants grow a little, the soil can be backfilled around them to help support the plants
How to Sow Corn in a Wicking Planter
Can I Plant Corn Kernels from Last Year?
One mistake we made a couple of years back was growing left over kernels from last years year's crop. However we had not chosen an heirloom variety, which meant the corn reverted to type - some strange South American variety that was very chewy and starchy!
Corn kernels can be sown the following year if they are taken from heirloom seeds. If you can select an heirloom variety you can keep a couple of cobs back to provide you with kernels to sow the following year.
How deep should I plant Corn in a Wicking Bed?
Soil temperature needs to be 15-30 Celsius (60-85 F) to allow germination - best not to plant if it's older than that. And of course, hotter days than that are easily tolerated in a wicking bed, since the constant evaporation of the water from below keeps things at a nice even temperature.
Corn kernels should be planted no more than 25mm deep (1 inch) if the temperature is on the colder side. However later in the season they can be planted deeper, which will give the plants even more support later one. We recommend sowing in a small trench and backfilling when the plants grow to provide additional support.
How Close Together Should Corn be Planted in a Wicking Bed?
We see a lot of spacing recommendations bordering on ridiculous - anything up to 30-60cm (2-3 feet) between plants. We have had great success planting around 30cm (1 foot) apart or even less in some cases.
If you are a farmer planting a whole field, yes you will want wide spacing. But for the average home gardener the plants do fine bunched up close - 30cm spacing or less. They even help support each other.
Check out the bumper crop in the video opposite planted extremely tightly in one of our early wicking beds in 2022.
Note that for pollination purposes it's important to plant them in a block rather than just a row. So more than two rows is preferable. More on that later.
Do I need to Water Corn in a Wicking Bed?
Since wicking beds water from below, the corn will be well serviced with water throughout it's life. However a good wicking bed will be filled to just above wicking level to give a dry surface in order to deter weeds, pests and disease.
It is recommended that the kernels be watered when first planted in a wicking bed, and kept moist until germination occurs, One great way to do this in a wicking planter is place a plank over each row of newly planted kernels after initial watering to stop the soil drying out, and increase the temperature.
Then simply check under the plank each day until you see the germinated seedling. At that point, remove the plank completely. At this point, the wicking bed will provide sufficient water below the surface to the roots that will have developed.
Seeds will germinate in under a week in most cases. If excess seeds were planted, they can now be pricked out to give the spacing required. Once the corn is 30cm (1 foot) high, backfill the trench they are planted in with the soil that was set aside. Pat it down well to give good support to the plant
Corn Pollination in a Raised Garden Bed
As mentioned previously, corn is best grown in multiple rows or blocks. This is because corn gets pollinated by breeze carrying the pollen from the tassel (on top of the plant) to the silk (on top of the cob). Each piece of silk is connected to a different kernel. For that kernel to develop, it needs it's silk strand to be pollinated.
Plants grown in rows rely on the wind blowing exactly down the row for the pollen on one plant to land on another plant's silk. However plants grown in blocks have a much better change of pollinating more fully as the wind can come from any direction and be effective.
Typical Pests Affecting Corn Grown in Wicking Beds
In Sydney where we are located the corn ear worm is the most common pest. This can be treated with a neem oil/detergent spray, however it is important this is not done during pollination as it could have an impact on the yield. Best done before pollination and after.
When to Pick Corn Grown in a Raised Bed
The first thing to look for is that the silks on each cob have gone completely brown.
Then on the largest cob, peel back the very top until you see kernels. If they are not yet yellow, they are not ready. Beware - some varieties have dappled white and yellow kernels so check a few.
Pick a yellow kernel and squeeze out the juice. If it is clear, give it another day or two. If milky, it is ready and should be picked immediately.
As soon as corn is picked, it starts to lose it's sweetness, so try cooking one that day and comparing to a store bought variety - you will be amazed at the sweetness!
Companion Planting Corn in Wicking Beds
We have had success companion planting with beans - they like to grow up the plants. We've also tried with eggplant planted first to establish, then maturing whilst the corn goes through it's faster cycle, before finally taking over once the corn is gone.
Another experiment was planting sweet potato slips under the corn and eggplant to give a final crop of sweet potato.
Wicking Beds are Ideal for Corn!
The combination of a good constant water supply, and low nutrition runoff that a wicking bed provides makes them great for growing Corn. Every year we get a bumper crop and are always pleasantly surprised.
