Giving plants enough space
If you rolled up in a ball on a sofa you would be a little like a tiny plant inside a seed. A plant is made from two main parts, the root and the shoot. Imagine that you were going to be like a tiny plant that had sprouted from a seed. What would you have to do? First of all you would have to decide that your feet and legs were going to be the root and that your body, arms and head were going to be the flower. Next, you would have to move them like a tiny sprouting plant. To do this you would have to stick out your feet and then stretch out your legs. You could then put your legs down the side of the sofa like a root growing down into the soil. Once the root had formed you would then raise your head and body until you were sitting up and then stretch out your hands to form the leaves.

Now imagine trying to mime the action of a sprouting seed if there were three other friends on the sofa trying to do the same thing. It would not take long before legs or roots and bodies or shoots became tangled up. It is just the same with real sprouting seeds. If they sprout too close to each other their roots and shoots get in each other's way. You may not think that this is important but in fact it is very important indeed and can affect the survival of the plants.

When a root sprouts from a seed it grows downwards and sends out branches on all sides. At the tips of all the growing roots are clusters of tiny white hairs. They suck up water and nourishment from the soil. Inside the roots the water and nourishment passes along tiny pipes. Shortly after the root has grown from the seed the shoot emerges and pushes its way though the soil to the ground surface. Once it has arrived there, it sends out leaves to catch the sunlight and make food. If the seedling is alone it has enough space for its roots to draw in all the water and nourishment the plant needs. It also has enough space to spread out its leaves and collect all the sunlight that the leaves need. But if the seedling is in a crowd problems soon begin.

The roots of each seedling grow to the same depth in the soil. They send out side roots, which tangle up with the side roots of neighbouring seedlings. All the roots have root hairs drawing water and nourishment out of the same piece of soil. There is not enough for all of them to grow well. At the same time that the roots are struggling to find water and nourishment the shoots are growing up and sending out their leaves. It does not take long before some leaves are growing over the top of other leaves and putting them in the shade. When this happens the leaves in the shade cannot get enough light to make enough food to grow healthily.

Imagine being a seedling in a group. You cannot take all the water and nourishment you need and you cannot absorb all the light you need. It is not long before you grow more slowly than some of the seedlings around you. When this happens you are in bigger trouble because the other seedlings are producing larger roots and leaves. This means you have even less water, nourishment and light so you have even less chance of surviving. If you were sown in the wild you would have no chance of survival but if you were sown in a seed tray there is still a chance you might grow into a plant.

Gardeners often sow seeds close together in a seed tray then, when the seedlings have started to grow, they separate them and put them in individual pots. When this happens some of the smaller seedlings that were being crowded out by the larger ones are given a second chance to grow. These small plants, now free from the leaves and roots of the larger plants, grow healthily once more.

How can wild plants stop their seedlings growing close together?
They can spread their seeds in a variety of ways. Some plants, such as the sycamore, use the wind to disperse its seeds. Each seed is enclosed in a winged fruit. When the seed falls, the wing catches the wind and the seeds are blown away from each other. Some plants, such as the elderberry, have fruits which are eaten by animals. The seeds pass through the animals unharmed. Some plants have fruits which stick to animals, and the seeds may be carried for many kilometres until the fruit drops off. Wherever the seed lands it is often far from others of its kind and it has enough space to grow healthily.

If you sow seeds too close together how can you separate them?
You can do this by preparing a second seed tray of compost and making holes in it with a pencil. Each hole is for one seedling. You may then use a plastic plant label to act as a little spade carefully and slowly to lift a clump of seedlings out of the first tray. Put the clump on some paper and hold the seedlings by their seed leaves while you separate their roots with a pencil. When the seedlings are separated, place each one in a hole in the second seed tray.

Should you get hold of the seedling stems while you separate them?
No. The stems damage very easily. It is better to get hold of the seed leaves.

Can the seedlings in the second tray be planted quite close together?
No. They need enough space to grow healthily but if they are too close together they may suffer from a disease called damping off. This is caused by a mould, which makes the base of the seedling turn brown then kills the seedling. If the seedlings are planted too close together the disease can spread quickly from one plant to another.

When the seedlings grow too large from a seed tray can they be separated again?
Yes, they can. You may need to use a spoon to separate them this time. You still need to treat the plants with care. You may wish to plant them in pots or in a flowerbed. If they are planted in a flowerbed make sure that they will have enough space around them to reach full size.

Does a farmer plant seeds at the correct distance apart in a field?
Yes. A seed drill is used. This device has a wheel, which releases a seed after the wheel has moved a short distance across the field. As the drill is moved along it drops seeds at a distance apart, which will let them grow healthily. A number of seed drills are set up behind a tractor so many rows of seeds can be sown at the same time. The seed drills are set up so that the rows are wide enough apart for the seeds to grow healthily.

When was the seed drill invented?
It was invented by Jethro Tull in 1701.

How did people spread seed before the seed drill was invented?
The seed sower carried a basket of seed and walked at a steady pace across a field. As the sower walked across the field he or she reached into the basket and flung out a handful of seed at regular intervals. If this was done carefully the seeds would be spread evenly over the ground and the crops would have enough space to grow healthily.

How do different wild plants manage to grow close to each other?
They may have roots that grow at different depths. This allows the different plants to take water and nourishment from different levels in the soil. The shape and arrangement of the leaves will be different. This will stop each one completely shading the other so both can receive enough light for their needs.