Disavantages of asexual reproduction are

There are many advantages as well as disadvantages of asexual reproduction.

1) Only one trait of the parent plant is passed on so there is no diversity
2) Because the same genes are passed on, the same weakness is also passed on. Thus, the species may be prone to extinction
3) Furthermore, due to the fact that each plant will have the same characteristics, the plant won't be able to adapt some environments

Hope it helped :)