Why we cannot plant plant seeds in the Venus and mars

Unavailability of water and harsh weather conditions....

Because there is no soil on Venus and Mars.The nature of planet Venus is acidic so, the life is impossible on these planets.Plants need fertile soil and small microorganisms to grow but the life is impossible on these planets then how will the plants and microorganism survive with acidic and harmful environment

We cannot plant plants on venus and mars because the soil presented there is not appropiate for plants. There is no moisture in it. The plants will die if they are planted.
 

MARS 
 Mars has a lot of carbon dioxide in its atmosphere. It also gets a lot of sunlight. On Earth, plants use carbon dioxide and sunlight for photosynthesis.
VENUS
lMost plants can't survive in wet, acidic soil because it lacks adequate nutrients. ButVenus flytraps aren't "most plants"! They have adapted to living in this poor soil, obtaining most of the nutrients they need from the insects and other small animals they capture

Because the soil of those planets are not fertile enough to plant any plant