Hello,

Thanks for your intriguing question. I can’t see what foreign substance you have encountered. In the photos it could even look like compost. 

Since we’re volunteers for DC, we don’t have a list of plant clinics in Silver Spring MD. However , heres a link for plant clinics in MD which may help you https://extension.umd.edu/resource/ask-master-gardener-plant-clinics-and-demonstration-gardens/

Let us know what you find out.

Lesley for UDC Master gardeners



Good morning, sorry to hear about your problems with identifying whatever substance you detect in your tree-box garden contents. The contents appear dry in the photo, is that what you see in person? Unfortunately, it is difficult to visually identify what is amiss by your photos.

Here are a few suggestions:

1. Soil Sample: UDC has a soil testing lab, samples can be brought in for testing. Recommend emailing to confirm open hours in summer, https://docs.udc.edu/eqtl/Fee%20Schedule%20updated%20on%20October%2011%202024.pdf. UDC is on the same block as the Van Ness Metro and has a for-fee parking lot. (Fees apply)

2. UMD no longer has a soil lab, but here is a link with information on testing and a list of soil labs for mailing in samples (fees apply): https://extension.umd.edu/resource/soil-testing-and-soil-testing-labs/

3. University of Maryland has a plant diagnostic lab, https://extension.umd.edu/programs/agriculture-food-systems/program-areas/fruit-vegetable-production/plant-diagnostic-laboratory/

The plant diagnostic lab serves Maryland residents, and may be able to detect what substance that is in question if it has been taken up by plants already in the tree-box. The preferred contact method is by email:

Lab email: <personal data hidden>

Lab phone: <personal data hidden>

Fax: <personal data hidden>

Physical Lab Address: 3171 Plant Sciences Building, 4291 Fieldhouse Drive, College Park, MD 20742

Hours: Monday-Friday, 9am - 5 pm

4. Master Gardeners, some volunteer at tables at farmers markets, for example, Share-a-Seed regularly has a table at the Mt. Pleasant Farmers Market on Saturdays, 11-1, let us know if you would like us to verify details.  Also, some work at nurseries! Please note that many plant nurseries today have outsourced their nursery operations and just buy plants wholesale to sell retail, priced to compete with big box stores, so they may no longer have as many plant experts on staff as when they grew their own plants. As an extension for UDC, we do not recommend one business over another, however, both specialty and smaller nurseries provide growing expertise, https://www.nutsfornatives.com/where-to-buy-native-plants

5. Phytoremediation. Lastly, plants are amazing and diverse, many can actually “clean up” contaminants and have the added benefit that they do no harm. Phytoremediation is a cost-effective and environmentally friendly technology using plants selected for the remediation of that specific site. For example, reportedly poplar trees planted at Aberdeen Proving Grounds have reduced the contaminant levels from weapons disposal by 85%. https://19january2017snapshot.epa.gov/sites/production/files/2015-04/documents/a_citizens_guide_to_phytoremediation.pdf

An alternative method involves fungi instead of plants. 

Of course, we would need to know most about the sun exposure etc. To assist in plant selection and process. Depending on the site, the process could be to fence the box with a low border fence to limit public access during phytoremediation.

Some plant possibilities could be native grasses interplanted with low growing sunflowers if the site is sunny or native ferns and sedges if it is shadier, but there are many options.

We could help with this, please provide photos showing the site from different angles and let us know where it falls in the shade, part-shade, part-sun, sun spectrum.

6. Additional gardening groups & highly resilient plants. Several organizations work with residents on sustainable gardening.
DCNatives is an all volunteer group https://dcnatives.org/ Volunteering with DC Natives is a great way to learn about what plants can grow where, raise garden skills to a near-pro level while meeting other DC gardeners.
Casey Trees has a garden consulting program. Understand that the initial assessment is free, https://caseytrees.org/get-involved/gardens/

And yes, this is a process, but there are lots of resources available along the way. Please keep us posted on what you decide and what you find out so we can continue to assist.

Many thanks,

KatieMacDC, Ask Extension volunteer team



Dear Earnestine,

Terribly sorry our efforts have been uphelpful.

I am happy to look up the location nearest your zip code. Addresses aren’t given to us, so if you could please give me your zip code?

Many thanks, 

KatieMacDC, just a fellow gardener & Ask extension volunteer team





Hi Earnestine,
Found two plant clinics locations in MD: Silver Spring Library on alternating Sundays, so advise calling ahead for address, details & whether this is an “on” week. 
Another would be Brookside Garden & I have their website:http://www.mc-mncppc.org/parks/brookside/contacts.shtm

Mt Pleasant Farmers Market & Van Ness Farmers Market have master gardener tables, too. Reach out if you would like help on finding contact info on those as well.

Please keep us posted!

Many thanks,

KatieMacDC, Ask extension volunteer team