Does caffeine inhibit germination?

Hi.  A couple of years ago, I started a hybrid hugelkultur/raised garden bed.  Unfortunately, I didn't have any rotten wood, so I used a mix of green & dry wood.  Last year, I tried planting peppers and beans on it, and they didn't do well.  The beans were doing OK for a while, but then they just started turning yellow.  I think that they weren't getting enough nitrogen.  As it's breaking down, the wood must be using up a lot of it.  So this year, I've struck up a relationship with a local coffee shop and have been picking up their coffee grounds.  I've been spreading these mostly on my hugelbeds, and trying to mix some of it into the soil. I also got my hands on some fireplace ashes and have mixed those in as well.   I've sewn a variety of greens & herbs and transplanted a few squash & melon plants into this bed.  I sewed the greens 2-3 weeks ago and have been keeping the soil moist, yet only a few of the greens & herbs seem to be growing, mostly mizuna and cress.  
I did some research, and somewhere on the net, I read that coffee grounds are a great weed suppressant because caffeine inhibits seed germination.  Has anyone found this to be the case?  If so, I'll need to either buy some seedlings or start them elsewhere and transplant them into the beds...  

never heard that one, also grounds should be seriously depleted in the caffeine department (that is what we use the hot water to extract) so I'm guessing that is not the issue. How much have you added roughly?

Thanks, that's encouraging.  The amount of coffee grounds varies quite a bit, but I don't think that any area got much more than a 3/4 inch, certainly less than that in some areas.  

Here's a link to the article I read which got me wondering:  https://www.theguardian.com/lifeandstyle/2016/oct/23/coffee-grounds-are-not-good-for-plants-its-a-myth

I'm hoping you're right about the caffeine depletion.  But I'd think that some of those other seeds would be sprouting by now.  

Do you know the ph of your garden bed?  Many plants struggle in alkaline soils.  We don't use our ashes in our garden here because they would make already alkaline conditions worse.

Of course,  some plants dislike acidic soil and then wood ashes may be ideal.

Do you know the ph of your garden bed?  Many plants struggle in alkaline soils.  We don't use our ashes in our garden here because they would make already alkaline conditions worse.  

You ask a good question, one I've never had reason to consider, because everything was growing pretty well-- until I started experimenting with hugelkultur.  

I've done some research, and saw that you can test ph with a probe or with litmus paper.  Are both methods pretty reliable?  I'm assuming that litmus paper must be more affordable.

Litmus papers work just fine for testing soil pH, take a sample of the soil and put it in a quart sized jar, add non chlorinated water to fill and stir or shake for about a minute, let the soil settle out before trying to take the pH by dipping the litmus paper.
If you have distilled water, that is the best for doing this test, if not, no worries, just use tap water that has sat out for a day or two in an open container.


Lighting is important when you are comparing the test paper to the color chart, you want even light and no glare for an accurate reading.

Pen type testers are the step up from litmus paper and then you get into the Probe types where the good units cost about 250 US and Up, both pen types and Probe units need calibration solution and distilled water to be able to use them correctly.  

Redhawk

Thanks, Bryant!  I've added litmus paper to the shopping list.

I'm curious if other people have been adding lots of coffee grounds to their gardens with our without issue.  I just got access to all the grounds from a coffee shop so I'm about to start mulching with them in my garden...

I've been using spent coffee grounds in all my gardens, to condition straw bales which grow our tomatoes and squash and all over the yard along with heaping them on ant mounds that are where I can't let them live since 1973, never had any issues with spent coffee grounds.
When I was raising show roses I used spent coffee grounds mixed with cotton seed meal as the main amendment to those rose beds, I never didn't win first place in 9 years of rosarian shows.
I also built an in the ground fishing worm bed for a friend in which we used 90 lbs. of spent coffee grounds dug into the top 8 inches of the soil.
He had so many worms in that worm bed that he was able to sell 100 boxes of worms every month for at least two years, then he moved away and the new neighbor used that same spot to grow a massive amount of vegetables.

Your coffee ground find is a true windfall.

Redhawk

Awesome, thanks Bryant!  They say they'll fill a 5 gallon bucket every 2-3 days and they keep the filters out of the bucket.  Should be some good stuff...

And for the OP's benefit, I'd trust Dr. Bryant Redhawk's professional and personal experience over James Wong (Guardian garden columnist and ethnobotanist) any day.  The article sounded scary and made me worry but it was probably intended that way to get more clicks.

Mike Jay wrote:Awesome, thanks Bryant!  They say they'll fill a 5 gallon bucket every 2-3 days and they keep the filters out of the bucket.  Should be some good stuff...

That is outstading! what a great thing for your gardens.  

If you should find problems with ants, fresh coffee grounds poured over the mound and surrounding area then watered for around 1 hour will get rid of them, the acid in the fresh brewed coffee (cold water works great) kills the ant colony.