Over the past 6 months, I’ve been having a go at growing a Sturt Desert Pea (Swainsona formosa) plant from seed, with some minor success. I thought I’d put together an amateur report on what I did and what the results were. I’m based in Southern Sydney, near the Royal National Park in a spot that tends to more humid given proximity to bush and river.
I ordered a packet of seed from The Seed Collection, and they came with the instructions to soak the seeds in water overnight before planting. I also read a piece by Greg Kirby in the Winter 2023 (Vol 32 no 255) about his far more in depth and scientific knowledge of this plant and his growing methods.
Germination
I tried both soaking seeds and also nicking a tiny notch from the seeds (recommended by Greg Kirby). Unfortunately, in my haphazard approach, I didn’t note which of these produced better results.. a more formal experiment for next year! I prepared a large bowl shaped pot with drainage holes with a mix of native garden potting mix and river sand and just popped some seeds in, not really expecting any success. I also put a terracotta watering spike into the pot, because I knew I needed to try and keep the humidity down and I didn’t want to have to water the potting media. Lo and behold I did have a seedling emerge. I then put a few more seeds into cardboard roll tubes and got one that germinated but I unfortunately knocked the seedling and it turned up it’s leaves. So I just had the one plant to focus on. The pot was sitting on a raised base, in a protected spot on a north facing terrace.
Plant development
It only took a week before the proper leaves started to emerge. After 3 weeks it was starting to show little branches and I thought I just might have a chance to keep it going! I was worried about the sulphur crested cockatoos in my area as they tend to investigate anything new and novel, and I knew I would be in tears if I found they had plucked my new ‘baby’ out of it’s pot. Harry Loots once recommended wire baskets to protect seedlings, so I purchased some baskets from kmart and they were perfect to sit upside down on the pot, secured with some small bamboo stakes.
As the sun started to drop lower in the sky, the pot was getting less direct sun, and the rain really started to ramp up. I noticed the plant was slowing down it’s growth. I also noticed aphids on the new growth. So I moved the pot under the eaves of the house, sat it higher on top of another pot (in anticipation of the plant getting large and needing to trail down) and next to a stone wall- to try and reduce the humidity, improve airflow and sunlight. I also added a layer of river sand as mulch around the base of the plant to try and stop any rot and got a small paint brush to start brushing the aphids off every day. Because this was next to my front door, it was a VIP spot I could have a look at it easily every day. After I made these changes, the plant pushed out a bunch of new tiny growth around the main stem so it seemed much happier.
Flowers!
At about 8 weeks since the cotyledons emerged, I noticed some strange new leaves at the end of some of the stems and my breath caught. Was it possible this was buds? I googled and didn’t find any pictures of what the buds looked like, but it seemed likely. It took about 2-3 weeks for these to confirm they were buds and to see the flowers starting to show. At this point, I had noticed some of the leaves starting to yellow. I added a full layer of river sand mulch and also ramped up the watering via the terracotta spike- I had let the plant get quite dry. With all the rain we’d had in Sydney I’d assumed it was getting a little but tucked under the eaves and with the river sand it was thirsty. I also had to fashion a new cage for the plant before it started to open the flowers, as it had outgrown the basket. So it got a large chicken wire enclosure. Not the prettiest but I knew my inquistive bird neighbours would be straight in there, given a chance.
By about 4 weeks after the buds had first started to form the flowers were emerging. Firstly as a drop shaped bud and I couldn’t work out how they would turn into what we know as the iconic flower, but as they opened they sort of popped out and up. The distinctive black middle spot also started quite pale and darkened as the flowers aged. I felt very fortunate to be able to observe this happening day by day.
The flowers lasted about 1month on the plant before they started to show their age. There were some other clusters of buds that never opened and the plant seemed to be struggling with further dying off of leaves. Now I get to watch the seed pods emerge, and I’ll have to try and figure out how to collect the seed.
The plant itself only got to perhaps 35cm tall and 50cm wide. I’m not sure whether this is because the conditions weren’t ideal, or just the particular seeds I had. This was ok though, because protecting the plant if it’d grown large would have been difficult. It would look great trailing down my north facing brick wall but then I’d still want to protect from the cockies..
It’s been a fascinating experiment and I’m already thinking about what I’ll do when I have another go next season. I doubt this particular plant will survive, I’m expecting they are annuals especially given the rain and cold we’ve had in Sydney, but I’ll let it do it’s thing and see.. you never know!
What would I do differently?
1)Keep better records of what germination methods work better, nicking, soaking or both.
2)Sow the seeds earlier. This year I don’t think I started until early 2024 (maybe late Jan?) I’ll start some late in 2024 to hopefully get the plants to grow bigger before the weather cools into Autumn.
3)I’ve read that because they are actually thirsty plants a self-watering pot can be good, so I will try one of those as well. I also got a piece of terracotta pipe in preparation and will also try one in there, sitting in a garden bed, although that will be tricky to protect from the cockies. They have deep tap roots so apparently terracotta pipe can be a good vessel for them.