花 and 草: observing flowers and grass
Separate plant names from their blooming or growing states.
Flowers blooming
花 (はな) means flower. 「花が咲きました」 says flowers bloomed.
「花を花瓶に飾りました」 means arranging flowers in a vase. This differs from growing the plants.
Where grass grows
草 (くさ) means grass or herbaceous plants. 「庭に草が生えています」 says grass is growing in the garden.
「草を抜きました」 means pulling grass or weeds. Depending on context 草 can mean weeds, but it does not always classify plants as harmful.
Classification and a part's state
Grass-like plants can also flower, so 花 and 草 are not wholly exclusive plant categories. 花 may identify the flower as a plant part.
「花はまだ咲いていませんが、葉は出ています」 says flowers have not yet opened but leaves have emerged. It does not deny growth of the whole plant.
Does 「花はまだ咲いていません」 mean the plant has no leaves either?
Show the answer and why
Not necessarily. The sentence only negates flowering.