Soil testing availability

Hey all. Just finished the Understanding Soil live stream, and I immediately starting searching for soil labs. I found that my county does free testing of up to 5 samples (Seattle, King). $20 for each sample thereafter. One thing I do not know is how long the program lasts…if it will last until the spring so I can send some of my used soil.

King County WA Soil Testing

Samples are sent to A and L Western Laboratories in Portland, OR to test for Nitrogen, Phosphate, Potassium, Magnesium, Calcium, Sodium, Sulfur, Organic Matter, pH, and Cation Exchange Capacity. The laboratory will analyze your soils and provide recommendations specific to your plant needs.

Hopefully there are other programs out there wherever you’re located!


Why would you need this? Basic components pumice, lava, perhaps akadama or floor dry work just fine without this. Most fertilizers make up for any lack in soil unless having an exotic tree like Azalea or such that uses kanuma or acidic substrate. I’ve never worried about this in over 60 years and other than killing an azalea have had no problem. Didn’t know I needed acid fertilizer.

There are very few studies on bonsai soils and it’s effects on plants in a small container. What if 1:1:1 mix isn’t the end-all of all bonsai soil for all trees/plants/shrubs…in all areas of the US? If we used the same water supply

I’d like to do more than keep my trees alive. I think there is so much we don’t know. Sure 1:1:1 works, I’m not trying to prove that wrong or right. But, understanding why it works can help progress my bonsai care even further.

I agree that it’s a good thing to start really thinking about all these things. I’ve just recently started researching my water (first step on the soil science journey) and realizing that it sits around 7.5 - 8 pH (although thankfully rather soft). It’s good to know this because now I know to fix it with a siphon system or some other way to add a little acidity to the pot.

Also, it seems like a lot of municipalities shoot for a 7.5-8.5 pH as it is safer for pipes to be slightly alkaline.