The kowhai, our national flower, welcomes spring with a burst of bright yellow flowers, rivaling the pinks of Japanese cherries.
Tuis and wood pigeons love the flowers.
Small tree with graceful weeping leaves.
The tree has a distinct juvenile stage, where it looks more like shrub than a tree.
||Spring, Summer, Autumn.
In areas with very harsh Winters, it is best to sow in Spring to give the seedlings enough time to grow before the cold weather sets in.
||In containers for transplanting later.
||Germination rate is approximately 85%. Seed takes approximately 4 weeks to germinate.
Kowhai seeds retain viability even if stored for several years.
Growing from Seed
The secret to successful germination is to know and understand the seed coat.
This is a thick water impermeable skin that covers the whole seed.
The skin protects the seed and allows it to remain viable for many years, and helps the seed float in water for a long time.
The seed only germinates when bacteria and fungi in the soil has decomposed the skin allowing water to soak into the seed.
This process normally takes many years.
Use a pair of pliers to hold the seed
and nick with a knife.
To speed up germination, the seed coat needs to be broken (scarified).
An easy way to do this is to hold the seed with a pair of long nose pliers and use a sharp knife to nick a small hole in the skin, preferably on one of the flat sides of the seed as this minimises the chance of damage to the embryo.
Fold one kitchen towel twice, place the seeds between the folds and lay the towel flat on a saucer.
Wet the towel, but not so much that it is submerged in water.
After 24 hours the seeds should have doubled in size.
You should also see a yellow dye leached into the towel.
Caution - this dye is poisonous.
Nick seeds that have not doubled in size and place back in the kitchen towel for a further 24 hours.
The soaked seeds would have doubled in size and
leached out a yellow dye (germination inhibitors).
The next step is optional but it increases the success rate and speeds up germination.
Gently peel the now soften skin from the seed, taking extreme care not to damage the seed.
The skin contains germination inhibitors (the yellow dye) and this needs to be leached before the seed can germinate.
Sow the seeds into containers with moist seed raising mix at a depth of not more than ½cm.
Place a sheet of glass over the container to keep the moisture up.
You may want to cover the seeds with newspaper to keep off the light but it is not necessary.
Keep moist, but not soaking wet.
Like a moist sponge - moist to the touch but not dripping.
Be patient. Kowhai seeds take some time to germinate.
Protect from slugs and snails.
One slug will easily wipe out all your seedlings.
Prick the plants out when they have 3-4 leaves and plant in a 5cm tube.
Seedlings are initially quite slow growing and it may take a couple of months before you are able to prick them out.
I prefer to fill the bottom half of the container with potting mix that contains some 3 month slow release fertilizer (eg Osmocote).
This way, the seeds will germinate in seed raising mix, but the seedling will send its roots down into the potting mix to extract nutrients necessary for its growth.
If you don't do this, you will need to feed the seedlings.
Care for Seedlings
Grow your seedling in a semi-shaded spot until it is around 12cm tall, then pot on to a 100cm pot.
Gradually introduce to more light.
Water well when grown in a container.
Protect from slugs and snails.
As your seedling grows, progressively pot on to larger containers as required.
After 12-18 months, the seedling is ready to go into the ground.
The best time to plant is Autumn - because the winter rains help the plant establish itself.
Kowhai grows in most soils but when young needs to be kept moist.
The kowhai moth larvae can be a problem in late Summer or Autumn - quite capable to stripping all the leaves from the plant.
A pyrethrum spray should be sufficient to get rid of this pest.
Water well until the tree is established.
For S. microphylla, the plant has a very long juvenile stage where it will grow like a shrub.
To speed up its transition to the adult phase, train one leader up a stake.
Progressively remove lateral branches from the bottom 1/3 of the plant.
Keep traning until the small tree is around 2m tall.
For S. fulvida and S. tetraptera, it also pays to train as per S. microphylla, but you remove the laterals from bottom ½ instead.
S. fulvida lacks the distinctive juvenile phase and is relatively quicker growing.