Zinnia

Zinnia elegans

These cut flowers come in bold colours from midsummer to the first frost. The more you cut, the more they flower. Zinnias love heat and sun and they struggle in cold, wet weather. They don't like their roots being disturbed, so sow them where they will flower or in small pots.

Looking after it

Water: Zinnias need normal watering. In dry spells, water deeply at the base of the plant, because wet leaves bring mildew. Check plants in pots every day in summer. Feeding: They need little food. Ordinary soil with some compost is enough and too much feed gives soft growth. In pots, give a liquid feed every two weeks once flowering starts.

Cutting and after flowering

Cut a flower when it's fully open and the stem is stiff just below the head. A simple test: shake it and the stem shouldn't bend. Cut low down, just above a pair of leaves. Snip off the faded flowers on the rest so new buds keep coming. Cut zinnias last about a week in a vase. Give them fresh water every couple of days.

What can go wrong

Powdery mildew. A white, dusty coat appears on the leaves in late summer. Water the soil rather than the leaves, leave space for air and remove the worst leaves. Varieties that resist mildew help too.
Leaf spots. In wet weather, brown or dark spots with a pale edge appear on the leaves. Remove spotted leaves and water at the base. Clear the plants away at the end of the season.
Slugs and snails. They eat seedlings overnight. Protect them at night or raise them in small pots, then plant them out once they're sturdy.

Growing facts: RHS, UC ANR and seed-company sowing guides. Zinnia care: RHS. pH: University of Florida IFAS extension.