✉ hello@onemoregarden.com
One of my absolute favorite cut flowers to grow each year is the zinnia. Not only do they happily survive in a vase for ten days to a fortnight – and dry beautifully, if that is your sort of thing – but their abundant flowers in bright colors make your garden look cheerful all summer. Knowing exactly when to plant zinnia seeds is the secret to buckets full of bouquets. This is how you do it.
Do zinnias come back every year?
Answer: It depends entirely on your climate. When we talk about zinnias for the cutting garden, we are usually referring to Zinnia elegans, an annual zinnia. This means the plant crams its entire life cycle – from germination to seed production – into a single growing season.
Being native to Mexico, zinnias are true sun-worshipers. In cooler climates, you must face the chore of sowing them anew each year. However, if you live in a warmer climate without frost in winter, they may well self-seed, meaning your zinnias come back every year without you having to lift a finger. Are zinnias perennials? Decidedly not, but they certainly know how to put on a recurring show if the weather plays along.
How to sow zinnias
Personally, I always start my zinnias indoors around mid-April. I plant the zinnia seeds shallowly in a modular seed-tray. I usually use a mix of universal potting soil with perlite and coco coir. I put the tray in a heated propagator under grow lights for the seeds to germinate and transplant them when they have their first true leaves.
Outside, the spring air in April or early May is still far too chilly for their liking (especially at night). Besides, slugs view the tender young seedlings as a delicacy. As soon as the plants look sturdy enough, I harden them off outside. Once the threat of frost has safely passed, they can be planted out into their final positions.
How long does it take zinnias to bloom from seed?
If you are the impatient sort (like me), you are in luck. Most zinnias do not dawdle. Once you figure out how to plant zinnia seeds properly, they generally need about 60 to 75 days (2 to 2.5 months) to show their first flowers. That’s a remarkably quick return on investment – assuming you manage to keep the slugs at bay. Zinnia types with larger flowers might need a bit more time to join the show.
Pinching zinnias and taking cuttings
My latest little experiment involves pinching zinnias out as soon as they have produced two or three sets of true leaves, and immediately using the snipped tops to make zinnia cuttings. This clever trick forces the parent plant to branch out and produce far more flowers, while simultaneously handing you a batch of extra plants entirely for free.
I’ve tried and tested this method as well with snapdragons, and it works great! It’s a good way of succession planting, so you won’t run out of cut flowers in the summer.
Caring for your zinnias
Zinnias require remarkably little fuss. It is a wise move to work some organic fertilizer granules into the soil before planting to give them a decent start. As soon as the flower buds begin to form, you can treat them to an extra feed high in potassium (tomato food does the job) to stimulate an abundance of flowers.
When it comes to moisture, zinnias are pretty drought-tolerant, so there is rarely a need to water zinnia plants constantly. On my heavy clay soil, I tend to water them only immediately after planting out. After that, they are left to fend for themselves.
Regular deadheading
The one thing you absolutely must do is pick the flowers regularly. This forces the plant to keep pushing out fresh, flowering shoots. By cutting them for the vase, you prevent the plant from setting seed – which is crucial, as seed production signals to the plant that its life’s mission is complete and it can happily die. Regular harvesting ensures you can cut zinnia bouquets from midsummer right through to the autumn.
Location: zinnias love full sun (and some elbow room)
As I said earlier, Zinnia elegans hails from Mexico and is a real sun-lover. Plant zinnias in full sun and give each specimen plenty of space – about 30 cm (1 foot) apart. Crowd them, and you could be inviting powdery mildew into the garden. Especially during a wet summer, tight spacing means the foliage never dries out properly, giving fungal spores the perfect climate to strike.
Zinnias for wildlife
On a brighter note, the nectar-rich zinnia flowers are much loved by pollinators, making zinnias for butterflies an absolute must if you want to invite a bit of wildlife into your plot.
Oh, and should you worry about your furry companions, you can rest easy: zinnias are not toxic to cats or dogs, so you can enjoy their dazzling display entirely worry-free.
