Easy Redwood Seed Germination

by Dan Levin

Growing Coast Redwood trees (Sequoia Sempervirens) from seed has long been considered "tricky" or hard.  This is due in large part to the inherently low germination rate of these seeds (most seeds that you collect in the wild or buy from a store do not have a viable embryo in them at all, and so will never germinate no matter what you do!), and in part because they do require some moderately special handling in order to successfully germinate them.

But with the right technique, it is not hard at all to grow your own Redwood tree, and if you start with the best seed available, like our premium seed, it is downright easy.

So the first thing that is important to understand is that if you collect your own seeds, or buy them from most vendors, you are going to get a very large percentage of "seeds" that are not viable.  If you look at the picture on the left, you can see that they vary considerably in size and shape - and that lots of them are really nothing more than slivers of seed shell or seed shells full of tanin.  Compare that to the picture on the right, which is a picture of machine upgraded premium seed from our inventory.  Note the much more uniform size and shape, and that the premium seeds are much larger on average.  If you collect your own seed, or buy non-upgraded seed, you should expect a germination rate of around 5-10% under ideal circumstances.  Machine upgraded premium seed, whether purchased from us or from another source, should have a germination rate (or "germ rate" as they say in the biz) of close to 50%.

 

 

For a more direct comparison, here is one picture with non-viable "seeds" on the left and two viable seeds on the upper right.

The second thing is that while you can sow redwood seeds right out of the bag or off the ground, you will have a very low germination rate if you do not pre-treat them.  Redwoods drop their seeds in the early winter, and those seeds spend their first few months on the ground waiting for good weather to grow in.  They need certain weather and day length related signals in order to break dormancy.  If we sow seeds without any pre-treatment, and especially if we sow them indoors, they will not do well.

Redwood seeds need what is called "cold moist stratification" before they will germinate well.  That means that we need to reproduce that period of cold, wet winter when the seeds are on the ground but before the weather is warm enough and the days longs enough for the seedlings to thrive.  Doing that is easy - I will give you the theory and then specific instructions.

The theory is that you want to put your seeds into a moist (but not wet), environment, and then keep them cool but not freezing for about a month.  The details don't matter too much, but your refrigerator is a good temperature.  So put your seeds into a container with something to keep them a bit moist, and leave them in the fridge for a month.

If you are a "ok, just give me the details" kind of person, here you go!

Place your seeds, up to a teaspoon (which will be about 300 seeds for premium ones, and more like 450-600 raw non-upgraded seeds) into a tupperware or other water tight storage container.  Add 1 cup of fine vermiculite, and 3 tablespoons of water.  Mix well with a spoon.  Seal, and place in the fridge for 20-30 days.  Every week or so, open the container, mix the seeds around so that they get some fresh air, and add a teaspoon of water to account for evaporation (yes, I know the container is sealed, but it isn't completely air tight).  At the end of 20-30 days, you have fooled the seeds into thinking that they have been on the forest floor through winter, and you are ready to sow them!

 <INSERT PIC OF CONTAINER HERE>

Ok, one trick down.  Now the second and third and fourth all at once!

Trick 2, the soil that you sow the seeds into and the sowing technique.  You want to sow these seeds into a very well drained but still nutrient rich soil that is slightly acidic.  You can use any commercial soil mix that meets these criteria, and is fairly finely grained.  Or you can mix your own.  You don't want big clumps or sticks or ground bark or stuff like that.

If you want specifics, here is what we use.

 

Here you can see - clockwise from the bottom left - coir, potting soil, Pro-Mix, pearlite with fertilizer sprinkled on top.  The Pro-Mix is peat moss based, and so is acidic.  It contains a natural anti-fungal, which is great because Redwood seedlings are prone to fungal infection.  The coconut coir helps to hold some water in the soil, which is otherwise very quick draining.  When mixed, you should have a light, fluffy mixture.  You then need to add just enough water so that your soil will clump a little when you grab a handful, but no more than that.

Ok, now pack your soil fairly firmly into your seedling container.  We like deep flats, but you can use whatever container you want.  It must be very well draining, so big holes in the bottom.  And it should be deep, at least 4" unless you plan to transplant the seedlings very early on.

Sprinkle your seeds, vermiculite and all, onto the top of the soil, as evenly as you  can.  Use the palms of your hands to pat the seeds down so that they are in good solid contact with the soil.  Then sprinkle a very light layer of soil over them.  We use one large handful to cover the seeds in a 16" x 16" flat.  You want the cover layer to be no more than 1/4" thick at the most.  Then cover that with another thin layer of pearlite, again, no more than 1/4" at the most.  Then lightly water everything in with a small watering can with a shower nozzle.  One quick pass over the entire surface of the flat with the watering can, no more.

Now on to secrets three and four.  Light, and heat.

Redwood seeds need sunlight to germinate.  You can use artificial light if you want, we do, but it needs to be bright.  We use LED grow lights suspended about 3' above the seed flats.  Give your seeds 12 hours of light a day, using a timer.  Or if you prefer, you can put your flats outside in the full sun.

And it needs to be warm.  Redwood seeds germinate best at 68-70 degrees F, or 20-21 degrees C.  We use artificial heaters that run about 8 hours each day, and we let the temperature fall at night into the high 50's or low 60's - whatever happens naturally.

Use a soil moisture meter to keep track of watering needs, or just water quickly over the entire surface of the flat every second or third day with your watering can.  You want the seeds to stay moist but not wet.  Too much water is bad.  Dry is also bad.

Your seeds will germinate in between 2 and 4 weeks.  Under ideal circumstances, our premium seeds germinate in 14 days reliably.

This is what success looks like:

That is about a 6" square area of a flat that had one teaspoon of our premium seed sown into it.  These guys are three days post germination, and way too crowded to be left like that, many will need to be transplanted pretty soon.

For another excellent view on all of this, please read the Turtle Island Restoration Project page on growing Redwood trees.  We learned a great deal from them.

We will talk about next steps in another blog post.

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