Sorghums are generally inbreeding plants, which means they are self fertile, self pollinating and do not readily cross, although some crossing can occur. You can bag the flowers with squares of frost cloth or something similar tied loosely over the heads before the flowers open. You must leave room for the heads to get bigger.
Zea mays (corn) does cross readily. In areas where thousands of acres of corn are being grown and the pollen clouds are moving around high with the wind, there would need to be long distances between the varieties to keep them pure. However, we’ve found that it’s relatively easy in our gardens to keep the seed pure in quite small areas where attention is paid to planting in blocks rather than long rows, staggering planting times so the flowering is staggered, keeping a few metres between different cultivars, planting tall things such as sunflowers or climbing beans between blocks and collecting seed only from the middle of each block. Watch for bees however as some years the bees seem to actively harvest the pollen and this may cause cross pollination issues.
Rye is self fertile and does not cross with other varieties of rye, however all other grains do cross to some extent with other members of the same species. They are mostly wind pollinated so isolation distances will be determined by terrain, areas being grown, wind etc. Use common sense and see how you go. Staggering planting is very effective with grains as well.
If you wish to save corn seed that will be strong for the long haul, you need to plant large blocks of around 200-500 plants. Save the best 100 cobs from the field – tag them at the eating stage, so they are left to dry on the plants. It is critical that you plant your seed corn in blocks rather than rows to ensure good pollination (see diagram 5). For sorghum you need only one plant, but preferably 16-32 plants to save seed from. We recommend with all other grain that you save seed from blocks of more than 500 plants.
When To Plant: The best seed will be from plants that have had the whole growing season to fully mature. Plant when the seed packet or catalogue tells you is the best time to plant that particular cultivar.
Rogueing: It is best to do your first rogueing with all grains, as you notice differences in the way the plants grow, or the colours in the leaves. If you see plants that stand way above the others or way below you need to decide if you would choose this variability or not. It may be a sign that the seed is crossed, or just a diverse population you could be keen to maintain.
Corn requires constant viligance to keep a line strong and pure. It varies a lot on colour, height, how much it tillers etc., and I always rogue to ensure I have an even looking strong patch. The next stage where you can rogue corn is at the sweetcorn or green stage. Selecting and marking only the best corn cobs for seed before picking the rest for eating is critical. I usually tie brightly coloured pieces of cloth on the largest and best looking cobs. If you are growing blocks of more than one cultivar then be sure to harvest or mark your seed cobs from the middle of the patch.
The third point at which you can rogue is when you harvest the seed heads/cobs. You can then go through all the seed cobs and choose the 50-100 best cobs. These cobs will contain genetic diversity from the entire population they have come from, but may still vary a lot so choose the best 60-80 of them for your own special seed.
For corn the forth possibility for rogueing is when you remove the kernels from the cobs. I take a machete or heavy chopper and chop off both ends of every cob, to ensure I only collect the biggest and best kernels in the middle of each cob. Once you have the kernels from the middles of your best cobs all mixed up, you can then take out of that seed, the amount you actually need. Corn ‘runs out’ very fast if you do not follow all these steps every year. Genetic strength is absolutely critical with corn, making it difficult tomaintain seedlines in small home gardens!
Support/Protection: Corn needs no support or protection except from birds and rats in some cases; common sense is applicable here. Other grains may need support if they are being grown in BioIntensive beds. We put stakes around the outside of beds and tie string around to make a tight fence so the grain doesn’t fall over. Most grains will need bird netting placed over the grain as explained on page 5 to avoid losing your crop.
Harvest: Leave corn and other grains to dry on their stems as long as possible. If necessary harvest before fully ripe and place in greenhouse to finish drying. Maturing grain was traditionally stooked, harvested and left in the field for a few days/weeks to mature before threshing. When picking corn leave the husks on the cob until it’s very dry then you can remove the husks to finish drying the cobs. There are different ways the corn cobs can be managed. Some people leave the corn in the field until it is very dry, then simply pull off the outside sheaths covering the grain and then throw into a corn crib. The other way I’ve done it is to leave the cobs on the plants as long as possible, keep an eye on rat and bird damage, and then throw the cobs, after pulling off the sheaves, onto the wire rack in the greenhouse to fully dry.
Threshing/Processing: Most grains are very easy to thresh simply by placing when dry and hard, onto a tarp on the ground and dancing on them or using a flail to beat them. Once the corn seeds are really dry, you can put the cobs through the shucker and store the grain in a polypail. Leaving the seed on the cobs helps to keep the weevils out, as was traditionally done. Check out storage below if you plan on keeping your own seed.
Selection: For most small grain seeds you can use the selection instructions on page 7. For corn there is a little more to it. You have to keep your best 100 cobs separate to the rest of your cobs. Take off the husks (shuck them), then choose the best 70 looking of those cobs. Next organise yourself so that you have a good chopping board and a machete or chopper, and chop off both ends of each cob. If you look carefully you will see that on each cob the kernels in the middle are uniform; at each end they vary in size and shape. We cut these varying, usually small and unusual shaped kernels off so that they are not in the seed corn. The chickens get those kernels! The remaining cobs with all the kernels on them can then go through your corn shucker or you can remove the seed by hand and mix it. The mixing ensures you have genetic strength to keep that line strong.
Storage: For those of us growing corn in large enough quantities to make porridge, and use for chook food, bread etc., corn cribs (as our ancestors used to have) will probably be the easiest way to store it.
Seed Life Expectancy: Sorghum and sweetcorn will retain 50% germination for 4 years under cool, dry, dark conditions; popcorn, flour corn and dent corn will remain viable for far longer.