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How to Grow Zinnias

How to Grow Zinnias

Zinnias. Like the late summer lollipops of the garden - these statement flowers on strong stems are a must-have in your cut flower patch. They come in the brightest, bright colours but I am a big fan of the paler more neutral tones so they can play a supporting role amongst my flamboyant Cosmos and Dahlias.

Here's the low-down on growing them well.

Think sun. Think water. Lots of both.


You can sow these under cover no sooner than 6 weeks before your last frost date but I would recommend as late into the Spring as you can stand it and even into May and June if you can be patient enough - for the reasons shared below.

If you go the under cover route, sow onto the surface of the compost into a module tray (to minimise root disturbance) and cover lightly. Prick out when first two true leaves appear into 9cm pots and Keep these things away from frost - they are half-hardy annuals and curl up and give up the ghost at the slightest whiff of cold. If you have minus temperatures predicted, make sure they have a lid or fleece to protect them if they're inside an unheated greenhouse.

Apparently Zinnias absolutely hate root disturbance so direct sowing is the official preferred way to go about things here - in which case direct sow onto soil from last frost date through to the end of July and thin to final spacing when a few cm tall.

I am a disaster-zone personally with direct sowing so break all the rules and start mine all under cover but have at it if that's your thing.


Plant seedlings into garden after last frost. Click here to find your last frost date.

Pinch when about 20cm high to create bushier plants.

May require staking - I support mine with a simple netting structure.

Potential Problems

They are susceptible to both downy mildew and botrytis - mine experienced both last year - so definitely sow way more than you will finally need to flower and keep some in reserve.

To minimise this happening, always respect their final planting distance (22cm apart) and try to water them at the base of the plant instead of overhead watering.

Here's what I did that helped though - sprayed them with milk. Make up a solution with one part milk, three parts water and spray all your Zinnia's weekly BEFORE they experience the problem if you can - but if you're a little lazy like me, you'll only remember as soon as you see the first sign of that dreaded white mould start to appear. Preventative action is always preferred....yeah yeah we know....but you can still save them if you start a weekly spray as soon as you see it coming.


Final Spacing: 22cm

Pinch: Yes when 20cm tall

Position: Full or partial sun

Height: 75cm


Harvest: Flowers June - October.

When harvesting, cut at the base of the stem and remove all the leaves before conditioning. If you're not giving every flower you have, make sure to deadhead to encourage more flowers.

Be light-handed. Because they have hollow stems below the flower  head, they are prone to snapping in your hands as you pick or arrange.

You can give handfuls of these all on their own to create your jam jar posies or bunches or mix them up with the Rudbeckia, Dill, Strawflowers, Cosmos, Dahlias Roses and Daucus Carota  - Here are a few simple ways I used them last summer.






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Everything you need to create your own cut flower patch - even if you've never done it before.

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