Knocked-down marijuana plants need to be picked up, supported, and tied up to keep it steady. First, you need to make all the preparations. Place the support stakes in the ground and have a rope or some tape on hand. Then, lift the plant into position gently and hold it in place while it's being tied up.
Generally, three or four stakes positioned around the plant or stem will provide much greater support than just one stake tied to the stem. With only one stake, the marijuana plant will experience more stress at the stem which can occasionally result in stem breakage. You should also water the plant if its fall was a result of a dry windstorm or other phenomenon.
If the roots were ripped from the soil, cover them with more of your preferred planting medium and gently pack it in around. All roots should be covered by a thick layer of soil so that they don't get exposed to the air. Water the plants using products like Super-Thrive or a B-12 rooting compound. Also, try using humid acid to help with any strain or breakage in the root system. Download my free marijuana grow bible to learn more tips and tricks for growing marijuana.
On some occasions, it is not practical to raise the plant to an upright position because the stem and branches are too damaged. Even so, the plant's branches should at least be raised off the ground using sawhorses or shipping pallets. They could also be supported with some plastic netting.
After the plant dries out and stabilizes (this usually takes only a few days), you can take a gentle water spray to them to clean off all the dirt. Try to do this on a relatively warm, sunny day early enough to ensure that the plant will dry by the time night rolls around. Do not do this on cool or cloudy days because the moisture allows for unsightly mold growth. Put a rug underneath the plant to keep debris and mud from bothering the buds.
If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.