Asexual reproduction in plants is an important concept in plant biology and agriculture. Let's evaluate the given options to identify the correct statement:

1. It involves formation of gametes. - This statement is incorrect because asexual reproduction does not involve the formation of gametes. Instead, it involves a single parent reproducing without the fusion of gametes, creating clones of itself.
2. It occurs rapidly during unfavourable conditions. - This statement is incorrect. Asexual reproduction generally occurs when conditions are favorable. Under unfavorable conditions, plants may not have the energy resources to reproduce asexually.
3. It is found in both lower and higher plants. - This statement is correct. Asexual reproduction occurs in both lower plants like algae, mosses, and ferns, as well as in higher plants like angiosperms (flowering plants) and gymnosperms. This method of reproduction is widespread across different plant taxa.
4. It involves male and female flowers. - This statement is incorrect. Sexual reproduction involves male and female flowers whereas asexual reproduction does not involve any flowers or distinct sexual organs.

Conclusion: The correct statement is "It is found in both lower and higher plants.", as asexual reproduction is common across a wide variety of plant species, regardless of their complexity.

Therefore, the correct answer is: It is found in both lower and higher plants.