Native plants in general are not difficult to grow from seed but there are always a few exceptions that are easier from cuttings. Hebe and Griselinia are two examples. Cuttings are also good if its likely you can't get seed at the right time or if there is a chance of hybridising between species growing closer together, Pseudopanax and Pittosporum for example.
Eco-sourcing
Wellington City Council follows an eco-sourcing policy in their approach to restoration which I whole heartedly embrace. It means collecting seed from wild local populations to plant back into the local environment. The reason is simple, over evolutionary time the local plants have adapted to the local environment, they have through natural selection, accumulated genes that increase their chances of survival in the Wellington area. The aim is to capture as much of that adaptive potential as possible. So when I'm out seed collecting I want to be as sure as possible that the seed I'm collecting is from original wild populations. This is not always easy in a highly modified urban environment ! Enthusiasts have been planting their favourites around the place for hundreds of years so just deciding it looks pretty old is not really good enough. So it is a case of assessing the most likely areas, the most unmodified and the more isolated naturally regenerating areas.
Collection
You need a permit to collect seed from council or DOC land so make sure you find out who looks after the land and apply for a collection permit. Wellington City Council will need you to be a registered community group with an MOU with the council.
The rule of thumb for when to collect is "Is it ready to disperse?" . In the case of fleshy fruits, the birds gorging themselves might be the dead give away but generally the fruits will be softer, turning to brighter bird attracting colours, and falling off the stems easily. For dry seeds that disperse in the wind, do they fly off the seed heads when you shake them ? Rolling a seed head between your palms is a good test, if the seeds fall out easily they're likely to be ripe. If you want to get more technical you'll need a very sharp knife to check if the endosperm inside the seed is nice and white and chalky but in general, whether its a grass or a fleshy fruit, if the seeds are hard and have a pale brown instead of pale green colour to the seed coat they're usually good to go. There are a few exceptions to this rule but I'll mention that in the details with specific plants.
Processing
Process your seeds as soon as possible after collection. The worst thing you can do is collect your seeds in a plastic bag and then leave them in there, so once you get your seeds back to your nursery put them in an open container if you're not going to process them immediately because believe it or not they do need to breathe ! If you're a long way or a long time out collecting use a cloth bag.
Some seeds need processing to break their natural dormancy mechanisms. Dormancy exists to make sure the seed germinates in the best place, i.e. a good distance from the parent plant, and under the best conditions for successful growth. The most common types of dormancy are physical and physiological. Physical dormancy can be caused by a very thick or woody seed coat that won't take in water to start the germination process until the seed coat has weathered and broken down. Physiological is an internal state that can be regulated by germination inhibitors in the fruit or the need for an over wintering period. For dry fruits this physiological change can come about through thorough drying as would happen sitting on a seed head for a period of time in summer.
So to deal with those two main dormancy types wash the flesh off and either sow fresh, or follow a suggested pre germination treatment. For dry seeds like grasses leave them on the stem to fully dry, I usually put them in a very warm dry place in a paper bag for two to three days then rub them off the stem, a sieve is good for this.
Storage
If you're going to store your seeds make sure they are dry, dry, dry, not just dry (!), then store them in paper bags, in an air tight container in the fridge (preferably a fridge that is not constantly opened). If you don't have that option then dry, cool, dark and air tight is the next best thing. My approach is - if it doesn't have a long shelf life don't risk it, either sow it straight away or Cold Moist Stratify for sowing at a later date. Grasses, rushes, sedges in general store pretty well and are easy to get lots of but if you're collecting fruits that birds and lizards also like, please don't risk it, just collect what you plan to sow.
Pre Germination treatments
Cold Moist Stratification (CMS): To mimic the wintering period seeds experience in nature (and to deal with any seed bourne pests or diseases) seeds can be placed in moist peat (3 - 4 parts peat to 1 part seeds) in the fridge (below 6 degrees celcius) in a plastic bag wrapped tightly to keep the moisture in for about a month. Some seeds seem to benefit from longer periods but a lot of the evidence for stratification times is anecdotal and the considerable variation of other factors influencing germination make this quite difficult to measure rigorously so a month is a good standard time. I sometimes stretch this time period out if I don't need more stock of a certain plant until later in the year or reduce it if there is a bit of a hurry. One of the main reasons for CMS is to even out the germination which is particularly useful for large scale production. Bear in mind though that most seed will germinate without this but may take a bit longer or be more uneven.
Warm Moist Stratification: This is a good one to use prior to a period of CMS to encourage the breakdown of seeds with thick woody seed coats like many of our large emergent or hardwood trees, miro, hinau and matai are examples of these and can take many years to germinate. Prepare as for CMS but place in a warm spot above 15 degress C.
Hot Water Scarification: Seeds with very tough shiny seed coats like those of legumes (kowhai, kaka beak, Carmichaelia - native broom) germinate considerably faster after scarification. For the toughest ones like kowhai I usually rough them up between two very coarse sheets of sandpaper first to speed it up even more. Put boiling water in a container and let it cool down just a bit, 70 - 90 degree range (for softer seeds make it more like 50 - 70 degrees) then soak the seeds for about 24 hours before sowing.
Seed raising medium and sowing
Many popular ready made seed raising mix you can buy at garden stores usually contain a lot of peat. A good seed raising mix consists of peat and pumice sand, both of which are available at garden supply stores so you're better off to mix these two together for a more suitable mix or find the ones that have a good amount of pumice sand in them. A thin layer of pea metal in the bottom of the seed tray is good for drainage and then your mix on top. Ideally you want the mix deep enough to let the roots get going a bit before they get to the bottom and start taking off on a right angle once they hit whatever surface is underneath or alternately, growing on into the soil beneath and need to be wrenched out before pricking out, so about 5cm deep is a good amount. Sprinkle on the seed and try not to make it too thick because if you get a good strike rate you end up with overcrowded seedlings that are more prone to damping off and will grow long and leggy making them weak and bit a bit harder to prick out. A good guide for how deep to bury your seed is ; the size of the seed times two, so if the seed is 5mm then cover it with 10mm of mix. A lot of the seed I sow is tiny so I don't put any mix on it at all. Then another thin layer of pea metal is good for a number of reasons; it stays dry on top so liverwort can't get going as easily; birds are less inclined to scratch around in it, it keeps the moisture in and it deters sciarid fly
Eco-sourcing
Wellington City Council follows an eco-sourcing policy in their approach to restoration which I whole heartedly embrace. It means collecting seed from wild local populations to plant back into the local environment. The reason is simple, over evolutionary time the local plants have adapted to the local environment, they have through natural selection, accumulated genes that increase their chances of survival in the Wellington area. The aim is to capture as much of that adaptive potential as possible. So when I'm out seed collecting I want to be as sure as possible that the seed I'm collecting is from original wild populations. This is not always easy in a highly modified urban environment ! Enthusiasts have been planting their favourites around the place for hundreds of years so just deciding it looks pretty old is not really good enough. So it is a case of assessing the most likely areas, the most unmodified and the more isolated naturally regenerating areas.
Collection
You need a permit to collect seed from council or DOC land so make sure you find out who looks after the land and apply for a collection permit. Wellington City Council will need you to be a registered community group with an MOU with the council.
The rule of thumb for when to collect is "Is it ready to disperse?" . In the case of fleshy fruits, the birds gorging themselves might be the dead give away but generally the fruits will be softer, turning to brighter bird attracting colours, and falling off the stems easily. For dry seeds that disperse in the wind, do they fly off the seed heads when you shake them ? Rolling a seed head between your palms is a good test, if the seeds fall out easily they're likely to be ripe. If you want to get more technical you'll need a very sharp knife to check if the endosperm inside the seed is nice and white and chalky but in general, whether its a grass or a fleshy fruit, if the seeds are hard and have a pale brown instead of pale green colour to the seed coat they're usually good to go. There are a few exceptions to this rule but I'll mention that in the details with specific plants.
Processing
Process your seeds as soon as possible after collection. The worst thing you can do is collect your seeds in a plastic bag and then leave them in there, so once you get your seeds back to your nursery put them in an open container if you're not going to process them immediately because believe it or not they do need to breathe ! If you're a long way or a long time out collecting use a cloth bag.
Some seeds need processing to break their natural dormancy mechanisms. Dormancy exists to make sure the seed germinates in the best place, i.e. a good distance from the parent plant, and under the best conditions for successful growth. The most common types of dormancy are physical and physiological. Physical dormancy can be caused by a very thick or woody seed coat that won't take in water to start the germination process until the seed coat has weathered and broken down. Physiological is an internal state that can be regulated by germination inhibitors in the fruit or the need for an over wintering period. For dry fruits this physiological change can come about through thorough drying as would happen sitting on a seed head for a period of time in summer.
So to deal with those two main dormancy types wash the flesh off and either sow fresh, or follow a suggested pre germination treatment. For dry seeds like grasses leave them on the stem to fully dry, I usually put them in a very warm dry place in a paper bag for two to three days then rub them off the stem, a sieve is good for this.
Storage
If you're going to store your seeds make sure they are dry, dry, dry, not just dry (!), then store them in paper bags, in an air tight container in the fridge (preferably a fridge that is not constantly opened). If you don't have that option then dry, cool, dark and air tight is the next best thing. My approach is - if it doesn't have a long shelf life don't risk it, either sow it straight away or Cold Moist Stratify for sowing at a later date. Grasses, rushes, sedges in general store pretty well and are easy to get lots of but if you're collecting fruits that birds and lizards also like, please don't risk it, just collect what you plan to sow.
Pre Germination treatments
Cold Moist Stratification (CMS): To mimic the wintering period seeds experience in nature (and to deal with any seed bourne pests or diseases) seeds can be placed in moist peat (3 - 4 parts peat to 1 part seeds) in the fridge (below 6 degrees celcius) in a plastic bag wrapped tightly to keep the moisture in for about a month. Some seeds seem to benefit from longer periods but a lot of the evidence for stratification times is anecdotal and the considerable variation of other factors influencing germination make this quite difficult to measure rigorously so a month is a good standard time. I sometimes stretch this time period out if I don't need more stock of a certain plant until later in the year or reduce it if there is a bit of a hurry. One of the main reasons for CMS is to even out the germination which is particularly useful for large scale production. Bear in mind though that most seed will germinate without this but may take a bit longer or be more uneven.
Warm Moist Stratification: This is a good one to use prior to a period of CMS to encourage the breakdown of seeds with thick woody seed coats like many of our large emergent or hardwood trees, miro, hinau and matai are examples of these and can take many years to germinate. Prepare as for CMS but place in a warm spot above 15 degress C.
Hot Water Scarification: Seeds with very tough shiny seed coats like those of legumes (kowhai, kaka beak, Carmichaelia - native broom) germinate considerably faster after scarification. For the toughest ones like kowhai I usually rough them up between two very coarse sheets of sandpaper first to speed it up even more. Put boiling water in a container and let it cool down just a bit, 70 - 90 degree range (for softer seeds make it more like 50 - 70 degrees) then soak the seeds for about 24 hours before sowing.
Seed raising medium and sowing
Many popular ready made seed raising mix you can buy at garden stores usually contain a lot of peat. A good seed raising mix consists of peat and pumice sand, both of which are available at garden supply stores so you're better off to mix these two together for a more suitable mix or find the ones that have a good amount of pumice sand in them. A thin layer of pea metal in the bottom of the seed tray is good for drainage and then your mix on top. Ideally you want the mix deep enough to let the roots get going a bit before they get to the bottom and start taking off on a right angle once they hit whatever surface is underneath or alternately, growing on into the soil beneath and need to be wrenched out before pricking out, so about 5cm deep is a good amount. Sprinkle on the seed and try not to make it too thick because if you get a good strike rate you end up with overcrowded seedlings that are more prone to damping off and will grow long and leggy making them weak and bit a bit harder to prick out. A good guide for how deep to bury your seed is ; the size of the seed times two, so if the seed is 5mm then cover it with 10mm of mix. A lot of the seed I sow is tiny so I don't put any mix on it at all. Then another thin layer of pea metal is good for a number of reasons; it stays dry on top so liverwort can't get going as easily; birds are less inclined to scratch around in it, it keeps the moisture in and it deters sciarid fly
Germination times
Germination times can vary considerably depending on when the seeds were sown and climatic conditions, hence the sometimes broad range indicated in my blog notes for different species. Germination rates will also vary depending on how old the seed is, old seed that has been stored usually takes a bit longer and may need to be stratified to kick it into gear where otherwise it might have germinated easily if sown fresh.
Germination times can vary considerably depending on when the seeds were sown and climatic conditions, hence the sometimes broad range indicated in my blog notes for different species. Germination rates will also vary depending on how old the seed is, old seed that has been stored usually takes a bit longer and may need to be stratified to kick it into gear where otherwise it might have germinated easily if sown fresh.
Cuttings
The medium used for seed is just as suitable for cuttings though extra coarse sand or pumice sand can be beneficial. The same environmental conditions are also fine though humidity is important in the early stage until roots are produced. The mix must be kept moist particularly until they have produced roots and then they can be treated as any other seedling. When the plant is flowering it's putting its sugars into making flowers rather than roots so cuttings are generally more successful when the plant is not flowering. Autumn is the traditional time because there is some 'semi-hard wood' which means the new growth has firmed up but is still fresh as opposed to spring when you have lush soft growth from last seasons harder wood. However the easiest plants will perform from cuttings taken almost anytime of year.
In general the best cuttings are from well watered, young, healthy plants. Select stems about 7 - 10 cm long that have nodes close together and cut directly under a node. Snips must be very sharp to make clean cuts and expose the lower nodes to encourage root growth (a blade can be useful for exposing the nodes without tearing them). Remove the lower two thirds of the leaves and any very soft floppy growth from the growing tip and set them in the cutting tray. Use a dibber (stick wider that the cutting stem) to make a hole in the mix first so you don't tear the clean cuts you've made. Halving the remaining leaves is not necessary unless they are very big but it's always beneficial to leave smaller, new leaves in tact. Rooting hormones and heated benches may speed up the rooting process but they won't make cuttings root that otherwise wouldn't. Success is based more on the freshness of the cuttings, the age of the source plant and the sharpness of your tools.
If you're just doing a few, placing them around the edge of a plastic plant pot is a good option. Nearer the edge means they will get warmer which encourages root growth.
Most important tip !: Keep the cuttings cool and moist at all times from the point of collecting them.
Plants that are easy from cuttings but not so from seed include Olearia, Brachyglottis, Hebe, Griselinia, Melicytus crassifolius.
Below middle: Exposed node below an non exposed node.
The medium used for seed is just as suitable for cuttings though extra coarse sand or pumice sand can be beneficial. The same environmental conditions are also fine though humidity is important in the early stage until roots are produced. The mix must be kept moist particularly until they have produced roots and then they can be treated as any other seedling. When the plant is flowering it's putting its sugars into making flowers rather than roots so cuttings are generally more successful when the plant is not flowering. Autumn is the traditional time because there is some 'semi-hard wood' which means the new growth has firmed up but is still fresh as opposed to spring when you have lush soft growth from last seasons harder wood. However the easiest plants will perform from cuttings taken almost anytime of year.
In general the best cuttings are from well watered, young, healthy plants. Select stems about 7 - 10 cm long that have nodes close together and cut directly under a node. Snips must be very sharp to make clean cuts and expose the lower nodes to encourage root growth (a blade can be useful for exposing the nodes without tearing them). Remove the lower two thirds of the leaves and any very soft floppy growth from the growing tip and set them in the cutting tray. Use a dibber (stick wider that the cutting stem) to make a hole in the mix first so you don't tear the clean cuts you've made. Halving the remaining leaves is not necessary unless they are very big but it's always beneficial to leave smaller, new leaves in tact. Rooting hormones and heated benches may speed up the rooting process but they won't make cuttings root that otherwise wouldn't. Success is based more on the freshness of the cuttings, the age of the source plant and the sharpness of your tools.
If you're just doing a few, placing them around the edge of a plastic plant pot is a good option. Nearer the edge means they will get warmer which encourages root growth.
Most important tip !: Keep the cuttings cool and moist at all times from the point of collecting them.
Plants that are easy from cuttings but not so from seed include Olearia, Brachyglottis, Hebe, Griselinia, Melicytus crassifolius.
Below middle: Exposed node below an non exposed node.
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Pricking out
This is when you transfer your seedling from the seed tray to a small pot. Don't go to a big pot or your seedling will be too wet and cold and will take forever to get going, that is if its not lost to damping off. Most nurseries use 5 - 7cm tubes or root trainers. Gently loosen underneath the seedling with a small pointed stick and lift it out holding the leaves or stem, don't handle the roots. Hold it over your pot in the middle and fill in with potting mix so that the stem is coming out of the mix at the same point it was in the seed tray. Tap the pot on the bench to settle the mix and water in, you don't need to press it down, it has tiny roots that are easily damaged and you want them to have a free root run.
Like germination times, pricking out times will also vary based on season and weather conditions but growth rates after germination will also be greatly influenced by whether there are nutrients in your seed raising mix. Some propagators top dress their seed tray with a medium release fertilizer once the seedlings have germinated which will reduce the time between germination and pricking out considerably. It will also create a softer seedling, more prone to attack by fungus and for restoration, the aim is to produce tough little individuals so fertilizing is really not needed. If the seedlings are left to sit in the seed tray for a very long time they will eventually run out of steam so when you see them start to really yellow or lose leaves you can give them a liquid seaweed fertiliser to tide them over till pricking out time.
Once tubed up, give them a stint in a cool shaded place to adjust to their new potted environment and once the roots start to establish (a few weeks to a month is a good guide) move them into a lighter spot to harden up. The idea is to get them used to the type of environment they will end up in. Placing them on something like a metal mesh surface will "air prune" the roots so they don't grow into the ground.
This is when you transfer your seedling from the seed tray to a small pot. Don't go to a big pot or your seedling will be too wet and cold and will take forever to get going, that is if its not lost to damping off. Most nurseries use 5 - 7cm tubes or root trainers. Gently loosen underneath the seedling with a small pointed stick and lift it out holding the leaves or stem, don't handle the roots. Hold it over your pot in the middle and fill in with potting mix so that the stem is coming out of the mix at the same point it was in the seed tray. Tap the pot on the bench to settle the mix and water in, you don't need to press it down, it has tiny roots that are easily damaged and you want them to have a free root run.
Like germination times, pricking out times will also vary based on season and weather conditions but growth rates after germination will also be greatly influenced by whether there are nutrients in your seed raising mix. Some propagators top dress their seed tray with a medium release fertilizer once the seedlings have germinated which will reduce the time between germination and pricking out considerably. It will also create a softer seedling, more prone to attack by fungus and for restoration, the aim is to produce tough little individuals so fertilizing is really not needed. If the seedlings are left to sit in the seed tray for a very long time they will eventually run out of steam so when you see them start to really yellow or lose leaves you can give them a liquid seaweed fertiliser to tide them over till pricking out time.
Once tubed up, give them a stint in a cool shaded place to adjust to their new potted environment and once the roots start to establish (a few weeks to a month is a good guide) move them into a lighter spot to harden up. The idea is to get them used to the type of environment they will end up in. Placing them on something like a metal mesh surface will "air prune" the roots so they don't grow into the ground.
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For more information on propagation visit New Zealand Tree Seeds http://www.nzseeds.co.nz/propagation-information/propagation-information