Category: Seed Collection

I usually think of understorey shrubs as tolerating shade. Growing slowly, producing small amounts of seed but being long lived. Not at all like colonising shrubs like karamu, koromiko or manuka, which need plenty of sunlight, grow quickly, produce huge amounts of seed, tolerate extreme weather but are short lived.

Each species of plant has arrived at a unique combination of strategies for growth reproduction and dispersal. Having unique strategies makes sure the species fits in with the other plants around avoiding direct competition.ou have to be quick to get the bright orange fruit before the birds.

Kawakawa is certainly unique, like other understorey species, kawakawa grows in deep shade, is intolerant of even light frosts but it produces huge quantities of succulent fruits, each having lots of seeds imbedded in them. When we first fenced out the neighbours cows from under our kanuka forest, it was kawakawa which took over the understorey. First a few shrubs established on the bare ground, then within a few years they started flowering in late winter with ripe fruit coming in December. Before long those few shrubs were parent to a mass of shrubs, each covered in either male or female inflorescences (Clusters of tiny flowers). Now, each winter the ground is carpeted with kawakawa seedlings, way to many to all mature but ready in case an opportunity arises.

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Every attribute a plant has comes at a cost and every weakness has a corresponding strength. The strong selective pressure in the jungle out there ensures this.

There are plenty of understorey shrubs which will cope well both with intermittent flooding and with drought.

Rangiora is not one of these.

Rangiora does not have strong roots. Waterlogged soil, even for short periods spell disaster just as much as dry periods do.

I have sometimes grown fantastic specimens but I have had plenty of disasters as well, with whole lines of seedlings dying unexpectedly so I have learned to be careful.

Despite this Rangiora is a common shrub throughout most the the north island and mild parts of the south island so it must have some real attributes.

It does.

Rangiora will grow really well and quite quickly even in quite deep shade. So long as the roots are well drained (aerated) and consistently moist.

The masses of tiny seeds, each with their own parachute or sail made up of fine filaments like dandelion seeds do, catch the wind, the occasional lucky ones finding that ideal ground where they will thrive.

Last month we discussed Porokaiwhiri which takes about a year for the quite big fruits to develop.

Rangiora take about a month from the flowers opening until the fluffy seeds start to blow away in the wind during November.

 So plant Rangiora in shady moist well drained places and it will grow spectacularly well.

In October, almost a year after the flowers on female trees have been pollinated, the clusters of drupes on the porokaiwhiri begin to turn orange. This is the sign that we need to get out and collect the seed.

If it is going to be sown soon and not stored, then green seeds might be just as profitable as the bright orange, ripe ones are. I have often found that seeds from green fruits germinate more quickly than those of ripe fruit.

If on the other hand you are collecting for a seed bank where the seed will be stored in long term cold storage, it is better to wait until the fruit ripens and the seed develops dormancy so that it stores well.

Porokaiwhiri seems to be less well known than it deserves. I know that it is not known as a timber tree and it doesn’t grow tall enough to reach up into the canopy of a forest so it doesn’t feature in the classification of forest. Despite this, porokaiwhiri is a really important part of a restored forest. All of the native bush in this area is regenerating after clearance for farms and timber milling some time in the past.

Well established bush has a lot of porokaiwhiri in the understorey. Younger, less established has more mahoe and other quick growing shrubs and small trees. So porokaiwhiri may be slower to establish but more persistent in established forest. This is a trait we are keen to exploit. Once we can get a few established the prolific seeding of porokaiwhiri will mean that the forest floor is carpeted with seedlings, the understorey is on the way to recovery and year-round food supply for native birds is so much more secure.

Collecting the seeds of our native trees is the best way that I have found to get to know those trees. I have been collecting seeds and propagating native plants for the past few decades. It has been a fascinating pastime and I have learned so much. Not just about the individual native trees, shrubs and other plants but how they fit together to make a forest or wetland. I plan to share those experiences so that others can apply the lessons I have learned and we will all be the richer for it.

There is no opening day of seed collection season. Any tree which produces seed when there is little else around has a monopoly on the birds for dispersing their seeds. Last month I began with lancewood / horoeka (Pseudopanax crassifolius) just because in late winter it is one of the few native trees with ripe fruit. This has been a fantastic year for fruit on lancewood. Last year I visited the same place and couldn’t tell which were male and which were female trees. There was no fruit on any of them. This year, trees were full of fruit and the native kereru pigeons were full as well, or at least making an honest attempt to be.

I found plenty of these unusual looking trees along the bush edge at the top of a farm on the lower slopes of Mount Pirongia. I often come across lancewood on dry ridges with shallow soil but also remarkably in wetlands as well. So, I guess lancewood really needs plenty of sunlight and isn’t too fussy about how rich the soil is. Lancewood grows across the whole country and to quite high altitudes so must be quite resistant to frost.