how to plant, grow & care for zinnias
complete growing guide
Zinnias are fantastic for their daisy-like shapes in vibrant colours from summer all the way through to October or the first frost. They are as lovely in a vase as they are growing in the garden. There are some excellent compact varieties that look great at the front of a border, lining a cutting bed, or to fill a pot, and there are also zinnias that reach 1m (3ft) tall. Plant them en masse, or mix with other flowers such as cosmos, for wonderful layers of intense colour. Reliable, long-flowering and brilliant for picking, it’s hard to fault zinnias. Find the varieties you love in our range of zinnia seeds and seedlings.
details
- Common name: Zinnia
- Latin name: Zinnia
- Type: Half-hardy Annual
- Height: 30cm (12in) to 1m (3ft)
- TLC rating: Easy
- Aspect: Full Sun
- Planting position: Borders, Containers
- Suitable for pots: Yes
- Good for pollinators: Yes, the single flowered varieties
- Good for cut flowers: Yes
calendar
how to grow zinnias
where to grow zinnias
Soil type: Fertile, well-drained soil is best.
Aspect & position: Zinnias love sunshine and a sunny border is ideal.
when to plant zinnias
Zinnias don't like root disturbance, so direct sow the seeds in May-June, as soon as the nights are warm. However, they can be planted in gutters or Jiffy pellets undercover in April or May and then planted out once all risk of frost has passed.
how to plant zinnias
sowing zinnia seeds
Zinnias famously hate root disturbance, so it is best to sow directly into freely drained soil with a fine tilth. Do this in May or June, but not before the nights are warm enough to sit outside in the evening. If the evening temperatures are chilly enough to have you reaching for the blankets to eat supper in the garden, then it’s still too cold. If you live in a part of the country where supper outside is a once-every-five-years experience, then your zinnias should be planted in a greenhouse or polytunnel.
Pick a sunny position and sow two or three seeds 5cm (2in) apart, with each cluster about 30cm (12in) apart. When the seedlings emerge, thin them out so you end up with one plant every 12in (30cm) or so. Pinch out the tips to encourage branching.
Zinnia plants are best supported by individual stakes. If they’re being grown in a veg or cutting garden for picking, use pea or jute netting – stretch the net horizontally over your young plants and between bamboo or hazel canes to support it. The zinnias will grow up and through the grid and are lightly supported. New leaves and growth will soon cover the netting.
It’s worth taking the time to stake them properly as they benefit greatly from growing straight early on. If they collapse, they’ll never grow or flower as well as when vertically supported.
sowing zinnia seeds undercover
You can also sow zinnia into modules in April or May undercover.
Because zinnias hate root disturbance, I use coir Jiffy pellets, that way you minimise handling. You can also sow them into lengths of guttering so that the seedlings can slide straight out into their planting hole.
Place them on a sunny windowsill or on a heated propagator.
Sown in modules or in gutterpipes, there’s no pricking out and the seedling can be planted straight out when still small with only a pair or two of true leaves. Do this when the nights are warm enough to sit outside (usually June).
Plant the seedlings in a sunny position into fertile, freely drained soil. Pinch out the tips as you plant them to encourage branching.
Stake each plant individually to encourage them to grow straight and tall and to flower well.
growing zinnias in a pot
Zinnia seedlings you’ve bought or grown yourself can be planted into containers in late May or June, as soon as the nights are warm (earlier if you keep the containers under glass for a few weeks). Wait until the seedlings have 2-3 sets of true leaves before planting.
Some zinnia varieties are more compact than others, so choose your pot size accordingly. Fill it with peat-free, free-draining compost. For a pot around 35cm (1ft) in diameter, plant a maximum of 3 seedlings, but this will really depend on the variety you have, so check the individual variety instructions.
Water well and feed with a liquid fertiliser approximately 4-6 weeks after planting, which is about the time the fertiliser in the compost is depleted.
how to care for zinnias
watering
Zinnias are thirsty plants. Give them a good dousing at the roots once a week during dry periods. Pay particular attention to zinnias in pots and notice when the compost starts to dry out, this may be daily during hot weather.
fertilising
Feed zinnias through summer with a liquid feed, especially if they are in containers. Do this approximately 4-6 weeks after planting, which is about the time the fertiliser in the compost is depleted.
staking
Plants are best supported by individual stakes. If they’re being grown in a veg or cutting garden for picking, use pea or jute netting – stretch the net horizontally over young plants and between bamboo or hazel canes to support it. The zinnias will grow up and through the grid and are lightly supported. New leaves and growth will soon cover the netting.
It’s worth taking the time to stake them properly as they benefit greatly from growing straight early on. If they collapse, they’ll never grow or flower as well as when vertically supported.
deadheading
Deadhead or pick zinnias regularly to ensure they go on flowering and looking beautiful into autumn. Cut the stem above a set of growing leaves.
propagating
Zinnias are half-hardy annuals and best sown from seed each year. Collected seeds may not come true if they are a hybrid variety, but they should still produce attractive flowers. To harvest seed, wait for the flowerhead to fade and dry and when the seeds have ripened, gently cut it off. Over a piece of paper, knock the flowerhead to release the seeds. Discard any petals and leave the seeds to dry for a few days before storing them in a labelled paper bag for next year.
overwintering
Zinnias will continue flowering until the first frosts, but then as annuals, they die.
seasonal checklist
spring
- In mid- to late-spring, sow zinnia seeds undercover.
summer
- In early summer, sow zinnia seeds directly outside.
- Plant seedlings in containers and borders.
- Feed plants with a liquid fertiliser.
autumn
- Continue to deadhead zinnias to encourage flowering until the first frosts.
winter
- Plan which zinnia seeds you’d like to sow and get ready for the following spring.
pests, diseases & common issues
botrytis
Zinnias have a tendency to botrytis, a fungus which affects plants under stress. Symptoms include shrivelled leaves and fluffy grey mould. Zinnias are especially susceptible during damp and cool weather so it is important to ensure good air circulation around plants and tidy up any dead or dying leaves and plant material. Avoid overhead watering as this tends to spread the fungal spores; water the soil around the base of the plants.
what is eating my zinnia leaves?
Zinnias are generally pest-free, but you may find earwigs or slugs having a nibble, particularly when the plants are young. Protect them from slugs with copper bands, and try to tolerate earwigs if you can, as they are useful in keeping numbers of aphids down.
why are my zinnia leaves turning white?
Powdery mildew is the probable cause – it’s a type of fungus that creates a powdery white coating on foliage. Make sure the plants are in a sunny position, water once a week and clear up any dead leaves beneath them to encourage good air circulation.
why are my zinnia seedlings leggy?
If you’ve sown your seeds undercover on a windowsill indoors, they may not be getting a sufficient amount of direct light. This will lead to a weaker plant, so move them to a position where they will get lots of sunshine. Don’t sow them too early as light levels won’t be high enough to produce healthy plants. Pinch them out once they have 3 pairs of true leaves to encourage branching.
why are my zinnia leaves curling up and turning brown?
Check the underside of the leaves and also the stems for aphids. And look for symptoms of botrytis.
frequently asked questions
are zinnias perennial?
No, zinnias are half-hardy annuals and need to be sown from seed each year.
can zinnia seeds be saved?
Yes, you can save zinnia seeds, but collected seeds may not come true if they are a hybrid variety. Wait for the flowerhead to fade and dry and when the seeds have ripened, gently cut it off. Over a piece of paper, knock the flowerhead to release the seeds. Discard any petals and leave the seeds to dry before storing them in a labelled paper bag for next year.
how tall do zinnias grow?
There are compact varieties as well as very tall zinnias, the range could be anything from 30cm (12in) to 1m (3ft).
do zinnias self seed?
Yes, zinnias can self seed but might not come true to the parent plant and seedlings won’t overwinter outside in the UK.
are zinnias edible?
Yes, zinnias are edible if grown organically, but they are bitter. The petals bring vibrant decorative colour to cakes.
are zinnias poisonous to dogs and cats?
No, zinnias are not toxic to pets.
are zinnias and dahlias the same?
Zinnias and dahlias share some characteristics and they are both members of the Asteraceae family, but they are not the same.
will zinnias grow in shade?
Zinnias love the sunshine, so plant them in full sun.
will zinnias grow in pots?
Yes, zinnias will grow in pots, and there are some compact varieties that look fantastic all summer long.
how to cut & arrange zinnias
Zinnias have hollow stems below the flower and weak necks which can bruise and break off all too easily – this can make zinnias tricky to lace into a hand-tied bunch and is one of the reasons you often see them arranged just on their own. They are brilliant cut flowers though, and coloured glass or bright ceramic jugs are a good match for them. With most zinnias, you’ll get at least a week in a vase if they’re kept cool. They last best on a short stem.
Get more inspiration for displaying your flowers with our flower arranging videos:
