Corn and beans seem to prefer being sown directly in the soil as long as the ground isn’t too wet and the soil temperatures are comfortably above 12ᵒC for the corn and 18ᵒC for the beans. That being said they do just fine when they get a cosy start in a warm sunny spot indoors.
For the most part, summer vegetables begin life indoors. Some amongst thousands of others on the bench of a climate-controlled commercial greenhouse and others as a handful of seedlings being nurtured into life on a sunny kitchen windowsill. Either way, they will have to go through a few steps to make sure they adjusted well to life on the outside.
If you are growing from seed at home, the first stage is generally germinating the seed in a low nutrient seed raising mix. Seeds have no need for nutrient rich soils because they have everything they need to get started. If the soil is too rich, it can harm the tender young roots. Once the seedling develops its true leaves, the situation changes and the plant begins to seek out nutrients. You can compare this to weaning a young baby from milk to solids, a slow and gentle process.
The first transplant should be made shortly after the true leaves come out, these are the ones that are recognisable as the shape the plant will have all its life. The first set of leaves are seed leaves and are often more a reflection of the seed. Gently prise the delicate tiny plant from the soil taking care not to damage the roots. It is best to hold it by the leaves as these are replaceable and holding it by the stem can cause irreparable long-term damage. Carefully pop it into a prepared hole in a small container full of a fine potting mix at the same level in the soil that it came from. Gently firm the soil around it and give it a good watering to settle it in. A seaweed tonic can help reduce transplant shock and can promote healthy root growth. Make sure to label it well since it is easy to forget which plant is which.
If all goes well, the plant will appreciate and thrive in the new environment quickly growing to fill the space. Before you know it, roots will appear and soon enough they will attempt to burst out of the bottom, this is a good sign that it is time to transplant again. Returning to the “weaning a small child” analogy, now you can introduce more complex solids. Use a normal potting mix with its lumps and bumps and maybe mix in some compost to introduce some of the micro organisms they are likely to meet in the garden. They aren’t as fragile at this stage, but you still need to be gentle and, as before, it is still important to avoid touching the stem.
For most plants, is it important for them to be planted in the new soil at the same level they were in the pot they just came from. The cell structure above ground is different from the cell structure below ground and so plunging the stem too deep can cause the cells who prefer to be above ground to rot. There are, of course, exceptions to everything. Tomatoes, for example, can be buried deeply. You can remove the first and even second set of leaves, bury them up to their necks and they will love it. New roots will even grow from the stems. You are also encouraged to bury potato plants as they grow up to a height of 30 cm and they don’t seem to mind at all! In fact, they prefer it.