What to Sow in Spring for your Cut Flower Garden
Cut Flower seeds held by small scale flower farmer ready to sow in spring.
August (if you are in the Southern Hemisphere) marks the exact midway point between the Winter Solstice and Spring Equinox. You will notice the first stirrings of Spring as the daylight levels have increased to a total of 10 hours a day, triggering growth in many buds, bulbs and other plants.
It is now that we consider starting our seeds for summer - but beware temperatures are still freezing for many and last frost dates still must be considered prior to sowing tender annuals. While some temperate regions will be able to transplant sooner, with little to no risk of frost. Others will have to wait until warmer days of Spring to get started.
The main thing to consider when sowing seeds for summer is the HARDINESS OF THE FLOWER + the time it takes from SOWING TO TRANSPLANT.
Taking the seed to transplant dates into consideration is the key to success at this time of year.
Frost Dates & Maturity Rates
Most people aim for Labour Weekend as the ‘safe zone’ for planting out tender annuals, as the risk of frost has passed. However, in reality every region is different. Some may experience little to no frost and can start transplanting into the garden in September while some can still experience frosts well in November.
Because of this it is essential that you take records of your regions first and last frost dates every year and this will help you to know your ‘safe zone’ for transplanting tender annual varieties.
In zone 9b, we generally can start planting tender annuals in October as risk of frost has passed. But because the soil is still cold, there are certain flowers I will not bother transplanting until November or even early December as they are fast growing, thrive in better warm conditions and will sulk if it is a particularly wet or chilly Spring.
Here is a list of all the Hardy and Tender annual flowers you can sow in the month of August with seed to transplant dates included.
Achillea seedling ready to transplant into garden in Spring.
Hardy Annual Flowers
These flowers can be planted out before your last frost date because they are hardy. Sowing dates should be timed depending on whatever your preference is for planting, i.e. when a crop is harvested and the space becomes available.
If you sowed a crop of Hardy Annuals in Autumn, expect these to flower from September - November depending on your location. Therefore a succession crop of hardy annuals may be timed to be planted out in October for harvesting in December.
By the end of Spring you may find (depending on your region) you will need to stop sowing hardy annuals until Late Summer / Early Autumn as they need some cool to really flourish.
4 weeks from seed to transplant
Cornflower
Agrostemma
Persian Cress
Calendula
Honeywort
Nigella
6 weeks from seed to transplant
Strawflower
Stock
Statice
Matricaria
Scabiosa
Mignonette
Ammi
Sweet Peas
Buplureum
Dill
Orlaya
Rudbeckia
9 weeks from seed to transplant
Snapdragon
Phlox (germination can be slow and sporadic)
Larkspur (germination can be slow and sporadic)
Poppies (Icelandic, Breadseed, Shirley)
Tender Annual Flowers
These flowers CANNOT be planted outside before your last frost date because they are tender. Sowing dates should be timed depending on your last frost date.
You can continue to sow tender annual flowers throughout the Spring and even into Summer. These are called succession sowings and will give you prolonger harvests right into the autumn time.
4 weeks from seed to transplant
Zinnia (doesn’t like cold soil, best to aim for transplant in November when it really warms (could be earlier if you are in Auckland / far North regions).
Sunflowers (half-hardy)
Marigold
6-8 weeks from seed to transplant
Cosmos
Gomphrena
Rat’s Tail Statice (half-hardy)
Celosia
Amaranthus
Didiscus
Orach
China Aster
9 weeks from seed to transplant
Dahlia (with pinching)
I know that many new gardeners can be overwhelmed by what seeds to sow and when so I have created this free Spring seed sowing calendar for download.
This calendar includes the seed sowing dates for all tender annual & hardy annual cut flowers that I intend to grow in my garden this spring and are based on a transplant date of Labour Weekend, (October 26th) relevant to zone 9b, 10a & 10b Plant Hardiness Zone.
Please bear in mind, last frost dates may differ if you are outside these zones. If you are new to gardening or are unsure of your last frost dates - I would recommend finding a neighbour or local gardening account to follow that will help guide you in your cut flower journey.
Cut Flower seeds following germination.
There is nothing worse than tenderly raising seeds only to leave them too long in the pots to become root bound before you can transplant into the garden. I’ve experienced this frustrating feeling before, thriving seedlings becoming shocked and stunted by sowing too early then getting caught out by late frosts and cold temperatures.
Hopefully this calendar will give you a good starting point as it outlines that sow dates that I use for my own small scale cut flower farm. If you’re interested in learning or reading more about my seasonal flower Bloom Buckets and what services I offer then check out these relevant articles:
