Trace Dominques, from DNews, explains why it is hard to have plants on Mars even though the tests we did here, on Earth, were surprisingly good. While there is 2% water int he soil, the conditions are not quite ideal for plants to grow on Mars.
Plants need more than soil and water to grow, they also need nutrients, nitrogen, minerals that you might not find on Mars, some bacterium or other living organisms in the soil to break down matter and aerate it.
You will also discover that the gravity is lower on Mars and that also the temperatures drop drastically overnight. Also the Sun is a lot farther away and the plants might not be able to survive in such conditions.
But, there is a but, you first need to try this on Mars to really know what it will be.
If you build some greenhouses on Mars, maybe you’ll be able to have some nice crops. With a couple of genetically engineered plants you could even have forests in there. It could be pretty incredible to see Mars in about 200 years.