From: 'The Reference Manual of Woody Plant Propagation - From Seed to Tissue Culture' Second Edition: Dirr and Heuser, JR. (2006)

Betula nigra
SEED: Matures in spring, shed at theis time, and will germinate without any pretreatment.

CUTTINGS: becoming more popular since the advent of 'Heritage'. June-July, 1000 strength (PPM IBA-Solution), peat:perlite, mist good rooting. Cuttings are best left undisturbed and handled when growht ensues in spring. Can be rooted in fall before leaf drop. Overwinter cuttings in flats until following spring.

Terminal and sub-terminal (basal) cuttings, 6" long, lower leaves removed, wound, peat:sand, mist, 70F bottom heat, greenhouse. Cuttings were taken from a 13-year-old tree in late July (Chicago). Ninety percent rooting of basal cuttings with 2% Benlate-talc without hormone after 6 weeks. Terminal cuttings rooted 60% with the same treatment. Basal cuttings broke bud and grew while most terminal cuttings did not. In all cases, terminal cuttings ttreated with auxin rooted better than basal cuttings treated with auxin [The Plant Propagator 23(2):a5-7 (1997)]

River birch responds to extended photoperiod and cuttings that were rooted in June (Georgia), fertilized with 18-6-12 Osmocote and place under interrupted night lighting (10 pm to 2 amA) continued to grow. In fact, the growth was so fast and structurally weak that the plants assumed a weeping posture.

Here's what you want to do basically. I root cuttings in June/July etc-

build a box or use tupperware flats with tops with at least 6" of depth and then cover the flats. Spray with a fungicide about once every two weeks. Use your 1000 strength hormone. Stick the cuttings, cover your box and keep it in shade or under a large tree so that the sun intensity is always very minimal. Dappled light but never direct light is fine....very good.

Here's a few photos of Dawn Redwood cuttings (from a special tree) - othewise I'd of simply grown them from seed.

Cuttings taken and kept in shade (in my basement) in water:
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I prefer a very deep box. My root-systems can travel over ~18". The box has multiple layers of hardware cloth at the bottom for drainage and to hold the soil in. You see that I propped the box up on a couple 2x4's:
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50/50 perlite/peat
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Cuttings were stuck. I use a pencil to make holes prior to sticking and so should anyone else.
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These are the tools and hardware and wood furring strips I'll be using along with screws, you must use screws:
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White poly - use a lightweight clear poly otherwise - you see the furring strips are in place - label the plants and add a date and mark your home calendar as to when you should be applying your fungicides and as to when the cuttings should be starting to root. A simple tug done lightly will let you know if they are rooting:
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Strips are now screwed to the box and the date is on as well as the plant material in the box is clearly written there as well:
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After this photo, I draped multiple layers of shade cloth over the chamber.

My cuttings were not disturbed and they now rest in my hoophouse for the winter. If you have no hoophouse, then find other means of protection.

Take care,

Dax
p.s. the next one to possilby two years the cuttings must be kept in dappled light, under a shade structure or in more shade then sun. 3hours of afternoon sun is ok but that's all. Otherwise treat them as rhododendrons for example - up against the east side of your home.

I grow these from seed all the time and give away.
I would be happy to send you seedlings or seed come spring, just pay postage.
The seed germnates in about seven days just spread on soil and kept moist.
They grow like weeds!!

Grancru
jtcrane@aol.com

Awesome info gardener365.

grancru, I wasn't aware that they seed. Looks like seed is easier. I'll let you know.

Thank you so much to both of you! :)

River Birch seed pods begin to swell in the spring, dry and fall over a couple weeks. To be honest they make a mess and germinate all to easily.

Seeds should be available for harvest in the near future.