Cork Oak Acorns

[leatherback]

Heya All,

I happened to jave a quick break from life in the very south of spain and catch some sun..

On one of the reaodsides we spotted cork oak trees and I jumped out to search for acorns. One frustrated wife and half an hour later I have. few handsfull of cork oak acorned. Sitting in the fridge till I decide what to do.

Urge is to just plant them, put them outside (protected against rodents) and see what happens. If many germinate (I read to expect 10% success!?) I will clip the main root as soon as possible to reduce later trouble.

Maybe someone has experience and better suggestions?

 

[Wulfskaar]

I only have experience with oaks in California, along the coast where it doesn't normally get to freezing temperatures. I also have Mesa oak and southern live oaks, all from warmer areas of the USA. I think cork oaks are similar (someone please correct me if I'm wrong).

I plant mine about an inch or so deep, on their side. They germinate in potting soil and bonsai soil, so I don't think the soil matters much. They sprout above the surface in 2-6 weeks usually. I get nearly 100% germination rates on all the different types I've tried (6 or 7 species).

I worry that an oak tree that thrives in southern Spain may not react well to super cold freezing temperature. If I'm right on that, I would keep them in the fridge until early spring and sow then.

If you have a handful, you may as well put some in the ground now and keep some for spring.

As for the taproot, I have had 0% success when I trim roots or repot them. 100% have died shortly after.

I'll be very interested to see what you can do!

On the flip side, I grabbed a handful of acorns I found in a colder area of the USA (Missouri) and will see if I can keep those alive here in southern California.

 

[leatherback]

Thx. It seems that they can stand down to -5c, so this will be interesting.

Cutting the taproot I have done on q robur with great effect. So that is also curious that for you it has not worked.

Indeed, I have enought to do some comparison. Plant some now, keep them protected, plant some now outside, keep some in the fridge till late feb.

 

[Maiden69]

Thx. It seems that they can stand down to -5c, so this will be interesting.

Cutting the taproot I have done on q robur with great effect. So that is also curious that for you it has not worked.

Indeed, I have enought to do some comparison. Plant some now, keep them protected, plant some now outside, keep some in the fridge till late feb.

I potted up a few 1 year seedlings this past spring. Their tap root is STUPID large in comparison with other trees I have worked with. The 3 pre-bonsai I bought had tap roots almost as thick if not larger than the trunk above the surface. I my opinion this is a species that you have to be on top of it and probably repot yearly until you reach a refinement stage. The largest one died on a cold spell, roots probably froze so I would provide some sort of shelter once you get close to below freezing.

 

[LuZiKui]

I'm with @Wulfskaar , I started somewhere around 200-300 acorns when I was in SoCal between 2 different years, about 2/3 coast live oak and 1/3 cork oak. The germination rate was almost too high, lol. Might not have been 100% germination rate but dang near close enough. We did have the benefit in Southern Cal of having a very Mediterranean climate. I would plant them in the fall right after I collected them and would leave them outside for the winter. Our winters rarely got below 40 F (5 C) though.

I like the idea of splitting them and trying both to see what happens. As far as transplanting them, I started my first batch using trays like this:

The RootMaker System | ROOTMAKER

RootMakers® are designed to create fibrous, non-circling root systems for easy transplantation.

rootmaker.com

I had no issues with tap roots and was able to transplant them all pretty easily into different containers and do a little bit of root work on them. Sort of out of laziness and cheapness, I planted the majority in boxes like the pictures attached. I never did get a chance to see what the roots looked like in these boxes. They would escape out the bottom and I'd prune them from time to time, but I'm sure the rest of the roots were kind of a mess.

Good luck with your project!

 

[Gabler]

I potted up a few 1 year seedlings this past spring. Their tap root is STUPID large in comparison with other trees I have worked with. The 3 pre-bonsai I bought had tap roots almost as thick if not larger than the trunk above the surface.

That's pretty normal for all of the oak species I've grown. In the first year, the tap root is usually twice as thick in diameter as the stem above the soil line. If you pull them up, they're like little carrots.

Notwithstanding, they tolerate the near complete removal of that tap root, provided there are a few lateral roots. They just won't have extra energy reserves until they can replace the tap root with thicker lateral roots.

Just be aware that nothing above the root collar is capable of producing roots, and nothing below the root collar will produce buds. It is close to impossible to take cuttings from an oak. You need tissue from both above and below the root collar.

 

[Wulfskaar]

I'm definitely doing something wrong when repotting, but you guys give me a little hope. I'll pick a couple this winter and try to repot.

 

[Maiden69]

That's pretty normal for all of the oak species I've grown. In the first year, the tap root is usually twice as thick in diameter as the stem above the soil line. If you pull them up, they're like little carrots.

On bigger ones as well.

This is one of the tap roots that were on my oak that died this past spring.




Bottom of the tree

 

[PaulH]

I've had close to 100% germination with cork oaks. I plant them on their sides in potting soil in shallow, +-2" deep, flats. The shallow depth seems to keep the tap root from elongating. Our winter temps seldom get below the mid twenties and they grow well. I move them into 4" pots the following spring and into my grow beds the next spring.

 

[Shibui]

I also get very good germination from fresh acorns of all types. Note they must be fresh. Viability drops quickly with dry storage. In nature the acorns fall and are quickly covered by leaves or buried by critters so they stay damp until germination.
I've noted that many acorns send out a root then sit and wait until the time is right to send up the top shoot.
I've trialled different root reductions at different stages and find that removing the root as it is emerging is the most effective. At that stage there's no stem alive ground and they are still living off the cotyledons in the acorn so have plenty of resources available to replace roots.

 

[leatherback]

Note they must be fresh. Viability drops quickly with dry storage. In

Agreed, my experience with my local oaks too. Which is why I picked the ones that had recently dropped and were fully shiny. As a good bonsaika, I always carry ziplocks in my suitcase and stored them with a few drops of water in the fridage during the travels where possible.

 

[Wulfskaar]

I also get very good germination from fresh acorns of all types. Note they must be fresh. Viability drops quickly with dry storage. In nature the acorns fall and are quickly covered by leaves or buried by critters so they stay damp until germination.
I've noted that many acorns send out a root then sit and wait until the time is right to send up the top shoot.
I've trialled different root reductions at different stages and find that removing the root as it is emerging is the most effective. At that stage there's no stem alive ground and they are still living off the cotyledons in the acorn so have plenty of resources available to replace roots.

I'm wondering exactly how this is done. I normally just pop the acorns in some soil and let nature do it's thing.

Are you germinating before planting, or do you dig them up?

When ready to "remove" the root, how much do you cut off?

 

[Shibui]

Are you germinating before planting, or do you dig them up?

When ready to "remove" the root, how much do you cut off?

I often pack acorns in a plastic bag or pot with some damp soil or leaves then check the bag every week until I can see some roots emerging. Then pick out any with roots showing, clip the root and plant it in an individual pot to grow on. Sometimes I have layered acorns in a single pot - some soil, a layer of acorns, more soil, another layer of acorns, etc until the pot is full. Need to check regularly to find when the roots are coming. If left too long that's a real mess.

Initially I would pick out acorns with an inch or 2 of root and just cut the tip off the root but that still leaves a reasonably long section from roots to first branch so I tried cutting the roots in half. That worked too. I had a few where the entire root broke off close to the acorn. I planted those, not expecting them to grow but those grew lots of laterals from the broken end too so I don't think it matters how much you cut or how much you leave, provided you do it when the roots are first emerging.

 

[leatherback]

, not expecting them to grow but those grew lots of laterals from the broken end too so I don't think it matters how much you cut or how much you leave, provided you do it when the roots are first

yup, what i saw with my local oaks too. The acorn has so much energy stored that it can afford to loose the first root pretty much completely

 

[Shibui]

The acorn has so much energy stored

Some big trees manage to grow from quite small seeds. When you remember that an acorn is really a seed that's a pretty big food reservoir to get started with so plenty of backup supplies until the seedling needs to rely on photosynthesis and making its own food. And cork oaks produce some of the largest acorns (seeds) that I've seen in the oak family.