Until this summer I had never grown Zinnias before, but after listening to a podcast about them and hearing how tough they were, how spectacular their flowers are, we decided to give them a shot at growing them and they were well worth it.
Zinnias were easy to sprout from seed, grew easily in the heat with no extra watering, handle the hot weather with ease and put on flowers that made me awe and enjoy. We recently had a weeklong heat wave with temperatures around the 40 degree Celsius and the Zinnias planted in the full sun handled the heat no problem and just continued to flower.
When to Grow Zinnias
Zinnias are a heat loving plant and love the summer heat. They can be grown from October through to April.
How to Grow Zinnias From Seed
Starting zinnias from seeds is very easy, they take around 4 to 14 days to germinate and germinate best when soil temperatures are between 20-25 degrees Celsius. Zinnias can be direct sown or sown into seedling trays. We planted ours into seedling trays in our greenhouse.
When to Transplant Zinnias
Zinnias are ready to be transplanted once they have their first true leaves, are about 5 to 10 cm tall. Watch the weather when transplanting your Zinnias that you’re not transplanting them straight into a hot weather.
After transplanting your Zinnias they will need regular watering. For the first 2-3 days we water twice a day, then we go to once a day for another 2-3 days. After 4-6 days we will change to watering every other day for a week. Then we stop the extra watering and allow our sprinklers to water them twice a week.
Where to Plant Your Zinnia Seedlings
Zinnias are recommended to be planted in full sun and have at least 6 hours of full sun a day. We have found that Zinnias still do well planted in part shade. A lot of the Zinnia varieties are a tall plant, so remember this as to the location that you plant them, as you may want them planted further back so you don’t block other shorter plants out.
Preparing the Soil Before Planting your Zinnias
When planting your Zinnias we like to add some compost, a small amount of blood and bone and organic slow release fertilser. Mix this well into the soil, then plant into this. Don’t forget to cover the soil with a good layer of mulch before giving the plant a deep watering.
How Long Does it Take for Zinnias to Flower
Zinnias take 80-90 days to flower.
How to Care for Zinnias
Zinnias love the summer heat, however they don’t like the soil drying out, so make sure plants are regularly watered and plants mulched well to insulate the soil. Zinnias benefit from a liquid fertilser feed.
Once Zinnias have started flowering, they will require the old flowers removed to encourage more flowering.
Depending on the variety of Zinnia it may need to be staked. You can do this by placing a small stake next to the zinnia and tie it to it.
Can I Save my Zinnias Seed?
Zinnias seed can be collected by allowing the flowers to dry on the plant. Once dried remove and place in a mesh bag to dry for another 2 or so weeks. Break apart flowers, collect seed and store in a cool dry place.
Common Pest and Diseases
So far, we have been lucky with growing our Zinnias, with no pests or diseases. But like most plants, Zinnias are susceptible to pest and diseases. Here is a list of the common pest and diseases and how to treat them.
Slugs and Snails
Slugs and Snails, what wont they eat? They are the biggest pest in our garden and in most gardens. Be on the lookout for slugs and snails especially after transplanting them. We recommend in the first few nights after transplanting them to go out and check on them for slugs and snails. Here is a in depth article on how to control slugs and snails.
Aphids
Aphids are a small sap sucking insect generally found on the underside of the leaves and new shoots. We recommend in squishing the aphids with your finger, you can also use a jet of water to blast them off. If you have multiple plants infested with them, you can also spray them with a horticultural oil.
Whitefly
These are a tiny whitefly which you will find on the underside of the leaves. Their numbers can multiply from a few into a complete infestation in just days. Here is how to control whitefly.
Spider mites
These are tiny little spiders which suck sap from the plants. It makes the leaves dry and wilt and causes the plant to look discoloured feeling like sandpaper. The spiders are not visible to the eye. We recommend in treating by spraying with horticultural oil or a wettable sulphur.
Downy mildew
This is a fungal disease which causes discolouration on the leaves, especially the undersides. To prevent water plant at the soil level or early in the morning and allow plants to have adequate spacing. Prune off diseased foliage and spray with a fungicide like eco fungicide.