Conversation with AI about edible plant recommendations on a septic drainfield [long]

I have started chatting with AI about various permaculture / land regeneration topics. This convo is about planting over a drainfield.
I would LOVE to hear more experienced gardeners' opinion on how well AI did with this topic!
I am also posting for the interest of others who might be AI-curious...

Caveat/background -- ours is a not a standard drainfield (as you will see if you read the following conversation). We are in NW New Mexico on the Colorado Plateau and our drainfield is downstream of a vermifilter septic tank, so the water should theoretically be very clean. Also, the pipes are shallower and smaller than a typical septic trench. We have those pipes running full length along the west side of the 3'x43' trench, and on the east side we have four infiltration buckets (like shown in Brad Lancaster's rainwater harvesting books and in Greywater Oasis designs) which are more of a bulk water version (pipe dumps into 5-gallon bucket which is perforated to flow into the trench). Our trench is 3' deep with a tad bit of gravel at the very bottom to please the state, and then filled with woody matter (big branches down to wood chips) and, finally, topped with 6-9" of dirt.

Here is the convo with the AI bot. It is long, but I left most of it in for the sake of those curious about how AI interacts. If you want to skip over for the main content, you can scan down to see my questions and just read the sections of interest to you. (my voice is in bold italics):

edible plants good for drainfield planting zone 6

While landscaping a septic drain field is encouraged to prevent erosion, planting edible crops directly over it is generally not recommended by university extension offices and septic professionals. The primary risks include microbial contamination from pathogens like E. coli and damage to septic pipes from root intrusion.

If you choose to plant edibles in Zone 6, focus on shallow-rooted perennials or annuals where the harvestable part is well above the soil surface and can be cooked before consumption.

Recommended Edible Plants (Zone 6)
These plants are often cited as safer options because they have shallow, non-aggressive roots or harvestable parts held high off the ground.

Blueberries (Vaccinium spp.): These have shallow, fibrous roots and are both salt and moisture tolerant, making them suitable for the perimeter or even over some fields if the soil is kept acidic.

Lavender (Lavandula angustifolia): A shallow-rooted perennial that thrives in the well-drained conditions of a functioning drain field.
Violets (Viola spp.): These edible flowers act as a good groundcover and are listed as safe for septic areas due to their shallow roots.
Bee Balm (Monarda spp.): Noted for being salt and moisture tolerant with non-invasive root systems.
Trellised Fruiting Crops: If you must plant vegetables, choose those that can be grown on a trellis to keep the fruit off the ground, such as tomatoes, peppers, and pole beans.
Thyme (Thymus species): An edible groundcover that is shallow-rooted and helps with erosion control without interfering with pipes.

Plants to Absolutely Avoid

Avoid any plant that is water-hungry or has deep, aggressive roots that could clog or break the septic lines.
Root Vegetables: Carrots, potatoes, onions, and beets should never be grown over a drain field as they grow directly in potentially contaminated soil.
Leafy Greens: Lettuce and spinach can be contaminated by soil splashing onto the leaves during rain.
Deep-Rooted Trees: Avoid water-seeking trees like willows, maples, poplars, and elms, which can send roots hundreds of feet to find the moisture in your septic lines.
Woody Shrubs: Most large shrubs have root systems that can reach and damage the gravel layer or pipes.

Best Practices for Safety
Harvesting and Preparation: Never eat anything from the drain field raw; thorough cooking can help kill many pathogens. Always wash produce from these areas thoroughly.
Avoid Raised Beds: Do not build raised beds directly over the drain field, as the weight can compact the soil and the extra soil can inhibit the evaporation of moisture necessary for the system to function.
Minimize Disturbance: Avoid rototilling or deep digging, which can damage the filter fabric or pipes just a few inches below the surface.

which edible drainfield plants are good in neutral or slightly alkaline soil (say 6-8 pH) and a bonus if they support pollinators
Finding plants that balance septic safety, Zone 6 winters, and alkaline soil can be a bit of a puzzle, but there are several excellent candidates. Since your soil is neutral to slightly alkaline (𝑝𝐻 6.0–8.0), you'll want to avoid acid-loving plants like blueberries and instead focus on these resilient options:
[nice summary table I cut out due to formatting, but info repeated below]

Detailed Profiles
1. Bee Balm (Monarda didyma or M. fistulosa)
Bee Balm is a powerhouse for Zone 6. It thrives in neutral to slightly alkaline soil and is famous for attracting hummingbirds and specialized bees.
Safety: It has shallow, creeping rhizomes that won't dive deep enough to puncture pipes.
Edibility: The leaves and flowers make a spicy, Earl Grey-like tea.
2. Anise Hyssop (Agastache foeniculum)
This is one of the best "honey plants" in existence. It prefers well-drained soil and handles a higher 𝑝𝐻 quite well.
Safety: It has a non-aggressive root system.
Edibility: The leaves and purple flower spikes have a distinct licorice/anise flavor, great for salads or teas.
3. Lavender (Lavandula angustifolia)
Lavender loves the "high and dry" conditions of a septic mound and thrives in 𝑝𝐻 levels up to 8.0.
Safety: While it is a small shrub, its roots are relatively shallow and prefer the aerobic (oxygen-rich) top layers of soil.
Edibility: Use the buds for shortbread, syrups, or calming teas.
4. Creeping Thyme (Thymus serpyllum)
If you want a "stepable" groundcover that functions as a lawn replacement over your drain field, this is it.
Safety: The roots are incredibly shallow (only a few inches).
Edibility: While mostly used as an ornamental, it is edible, though smaller-leaved than upright culinary thyme.
5. Sweet Goldenrod (Solidago odora)
Unlike some aggressive field goldenrods, this variety is clump-forming and behaves well. It handles neutral to alkaline soils easily.
Safety: Fibrous roots that stay in the top layer of soil.
Edibility: The leaves have a faint anise scent and make a wonderful tea (it was actually used as a tea substitute during the Boston Tea Party).

Important Considerations for Zone 6
Salt Tolerance: Septic effluent can be salty due to water softeners or detergents. Both Lavender and Bee Balm have moderate salt tolerance, making them more likely to survive if your system has a heavy load.
Moisture Levels: The center of a drain field is often wetter than the edges. Plant the Lavender and Thyme on the higher, drier slopes of the mound, and the Bee Balm or Anise Hyssop near the slightly moister areas.
Would you like me to help you design a "planting map" to show where to place the moisture-loving vs. drought-tolerant plants across the field?

so are violets and wild strawberry too acid-loving
Actually, no! Both Violets and Wild Strawberries are surprisingly adaptable and would be excellent choices for your neutral-to-alkaline Zone 6 drain field.
Here is how they stack up for your specific soil 𝑝𝐻 (6.0 to 8.0):
1. Wild Strawberry (Fragaria virginiana)
While garden strawberries (the big ones from the store) often prefer slightly acidic soil, our native Wild Strawberry is much tougher.
pH Tolerance: It thrives in a wide range, from 5.0 to 7.5+. It is frequently found in limestone-heavy areas with alkaline soil.
Root System: Very shallow. They spread via "runners" (stolons) along the surface, making them one of the safest plants for septic pipes.
Pollinator Value: They provide an essential early-spring nectar source for small native bees.
Edibility: The berries are tiny but have a flavor ten times more intense than store-bought varieties.
2. Common Blue Violet (Viola sororia)
Violets are the "utility players" of the edible landscape. They are nearly impossible to kill and aren't picky about soil.
pH Tolerance: They are very comfortable in the 6.0 to 7.8 range. They actually tend to pop up as "weeds" in alkaline lawns.
Root System: They have short, thick rhizomes and shallow fibrous roots. They won't interfere with your lines.
Pollinator Value: They are the host plant for Fritillary butterflies (the caterpillars eat the leaves).
Edibility: Both the leaves and the flowers are edible. The flowers are great in salads or candied, and the leaves are high in Vitamin A and C (though they can be a bit mucilaginous/okra-like).

Comparison for Your Drain Field
[this was a nice summary table that I can't replicate here due to formatting]]

Why they work well together:
If you plant these two together, they create a "living mulch." The violets will handle the slightly wetter spots directly over the lines, while the strawberries will colonize the drier, sunnier slopes of the drain field. This prevents erosion and keeps the soil from getting too hot, which helps the septic bacteria do their job.
Safety Reminder: Because these are low-growing "ground-huggers," they are at higher risk for "splash-back" contamination from the soil. Always wash these thoroughly and consider using them in teas or cooked preparations rather than eating them raw right off the ground.

some of our septic pipes are perforated 2" pipes about 6-9" below the surface. Does that change any of your calculus?
Yes, that changes the "safety margin" significantly. Standard modern drain fields usually have pipes
18 to 36 inches deep. Having pipes only 6 to 9 inches below the surface is considered a "shallow trench" system or may be the result of soil erosion over time.
This depth is very shallow, meaning the root zone and the effluent zone are the same space.
Revised Strategy for Shallow Pipes
With pipes at 6–9", you must shift your priority from "what can grow there" to "what will not clog the holes." Even "safe" plants can become a risk when the pipe is that close to the surface.
1. The "Fine-Root" Rule
At this depth, you must avoid anything with woody roots or thick, fleshy rhizomes.
Lavender is now a risk: Even though it’s shallow-rooted, lavender develops woody, structural roots as it ages. At 6", those roots could easily find a perforation and expand inside it.
Stick to Fibrous Roots: You want plants with hair-like root systems that are easily pushed aside by water pressure or that don't have the "strength" to break into a pipe.
2. Best "Ultra-Shallow" Edibles
These three are your safest bets because their root systems are primarily "adventitious" (surface-level):
Wild Strawberry: This is now your #1 choice. The roots rarely go deeper than 4–6 inches, and the plant spreads via surface runners. It stays almost entirely above your pipe line.
Violets: Still a strong candidate. Their roots are dense but fine. However, keep an eye on them; they are hardy, but their "clumping" nature is safer than a deep-taproot plant.
Chives (Allium schoenoprasum): These have very shallow bulbs and fine, hair-like roots. They are excellent pollinators (bees love the purple globes) and thrive in neutral-to-alkaline soil.
3. The "Annual" Advantage
Because your pipes are so high, perennials (which grow larger root masses every year) are riskier than annuals.
Consider planting Sweet Alyssum (edible flowers, smells like honey, massive pollinator magnet). Its roots are tiny and die off every winter, meaning they never have the chance to "choke" a pipe.

Critical Warnings for 6-9" Depth
No "Drought-Tolerant" Specialists: In a shallow system, a plant that is too good at finding water (like certain Mediterranean herbs) will find those 6" deep perforations immediately during a dry spell.
Pathogen Risk is Higher: Because the "filter" (the soil between the pipe and the surface) is only 6 inches thick, the risk of pathogens reaching your strawberries or violets via capillary action or heavy rain is much higher than a standard system.
Action: I strongly recommend cooking anything harvested from this specific area (e.g., making violet jelly or strawberry jam) rather than eating them raw.
Soil Compaction: With pipes this shallow, never walk on the area when the soil is wet. You could literally crush or shift the 2" pipes just by standing over them.
What about "No-Mow" Grasses?
Since your pipes are so vulnerable, the safest thing for the system is often a mix of native fine fescues. However, if you want the "Edible/Pollinator" mix, the Wild Strawberry/Violet/Chive trio is the safest biological "carpet" you can lay over such shallow lines.

our water is tertiary treated and should be 99% pathogen-free but we will know that within a few months because we will be testing it
That is a game-changer! Knowing you are working with tertiary treated effluent(effectively "recycled water") significantly lowers the biological risk profile. If your testing confirms the low pathogen counts, you are essentially running a sub-surface irrigation system rather than a "waste disposal" site.
However, the physical risk to those shallow 2" pipes remains. Here is how we adjust the plan for a clean-water, shallow-pipe system in Zone 6:
The "Tertiary-Safe" Plant List
Since you don't have to worry as much about pathogens, you can focus on plants that love the consistent "fertigation" (fertilizer + irrigation) provided by the treated water, while still respecting the 6–9" pipe depth.
Chives & Garlic Chives:
Why: They thrive in 𝑝𝐻 6–8 and are pollinator magnets when they bloom.
Root Check: Their roots are very fine and "bulbous-shallow," posing almost zero threat to your pipes.
Roman Chamomile (Chamaemelum nobile):
Why: It creates a low-growing, apple-scented carpet that handles neutral soil well.
Root Check: Very shallow.
Edible/Pollinator: The flowers make a relaxing tea and attract hoverflies (beneficial predators).
Nasturtiums (Annual):
Why: Since they are annuals, they reset their root systems every year, preventing "root-choke" in your shallow pipes.
Edible/Pollinator: The flowers and leaves are peppery and delicious. Bees love the nectar.
Wild Strawberry & Violets: Still the "Gold Standard" for this setup. They will be incredibly lush with tertiary treated water.
Managing the Shallow Pipes (6-9")
Even with clean water, the 2" diameter of your pipes is small. They can clog more easily than standard 4" lines.
Avoid "Thirsty" Perennials: Even if pathogens aren't an issue, a plant like Mint or Lemon Balm will sense that tertiary water and send a "mat" of roots into those 2" pipes, potentially backing up your system in a single season.
The pH Factor: Tertiary treatment can sometimes slightly raise the 𝑝𝐻 of the effluent depending on the treatment method. Your choice of neutral-to-alkaline plants is even more important now, as the soil may drift toward 7.5 or 8.0 over time.
Observation is Key: Since the pipes are so shallow, keep an eye out for "lush spots." If one patch of strawberries is three times larger than the rest, it might mean a root has found a perforation and is "drinking straight from the tap."

A Note on your upcoming Testing
When you get your results in a few months, look specifically for:
Fecal Coliform/E. coli counts: This confirms the "edible" safety.
Total Dissolved Solids (TDS) / Salts: If these are high, your Lavender and Strawberry will be fine, but Violets might struggle with leaf-burn.
Nitrogen Levels: Tertiary water is often high in Nitrogen. This is why I recommend leafy or flowering herbs rather than fruiting plants—the extra nitrogen will give you tons of leaves and flowers, but sometimes "boring" fruit.
Next Step Recommendation
Since you’ll have test results in a few months, would you like me to help you draft a "Wait and See" planting schedule? We could plan for a "temporary" annual cover (like Crimson Clover) for this spring that improves the soil while you wait for the lab results, before committing to the permanent perennials.

ok
Since you are waiting on water quality tests and dealing with very shallow 2" pipes, a staged approach is the smartest way to protect your infrastructure while building a pollinator-friendly edible landscape.
Phase 1: The "Test Run" (This Spring)
While you wait for your lab results, plant shallow-rooted annuals. These provide immediate pollinator food and edible harvests but won't "clog" your 2" pipes if you decide to change the layout later.
Crimson Clover (Annual): A fantastic "placeholder." It fixes nitrogen, loves 𝑝𝐻 6–8, and has extremely fine roots. It is a favorite for honeybees.
Edibility: Flowers can be dried for tea or used fresh in salads.
Sweet Alyssum: This acts as a living mulch. It’s a "magnet" for parasitic wasps and hoverflies (which eat garden pests).
Edibility: The tiny flowers have a mild, honey-like flavor.
Pot Marigold (Calendula): Extremely easy to grow in alkaline soil.
Edibility: Petals are "poor man’s saffron" and great for skin salves or salads.
Phase 2: The "Permanent Carpet" (Post-Testing)
Once your tests confirm the water is safe, you can transition to your perennials. With 6–9" depth, think of this as a "Low-Profile Meadow."
The "Ground Layer": Intermix Wild Strawberry and Blue Violets. They will knit together to prevent erosion over your shallow pipes.
The "Vertical Accents": Spot-plant Chives and Anise Hyssop. These grow in clumps, making it easy to monitor if their roots are getting too aggressive (you’ll see the clump over-expand).
The "Drainage Edge": If the perimeter of your field stays a bit drier, that is where you put your Lavender or Thyme. Keeping them at the edge keeps their woodier roots further from the primary perforations.
Maintenance Checklist for 2" Shallow Pipes
Avoid "Heavy" Mulch: Don't pile 4 inches of wood chips over the field; it can trap too much moisture and "suffocate" the aerobic bacteria in a shallow system. Use a thin layer of straw or just let the "living mulch" (strawberries/violets) do the work.
No Rototilling: With pipes at 6", a tiller will destroy your system. Always hand-plantusing a small trowel.
Check the "Green-Up": If you see a specific 2-foot section of your garden growing twice as fast as the rest, it’s a sign that the pipe below might be slightly clogged or leaking more in that spot.
Would you like a specific list of "pollinator-friendly annuals" that can be direct-seeded right now while you wait for those lab results?

ok
To accommodate your shallow 2-inch pipes buried just 6–9 inches deep, the best strategy while you wait for test results is to use annual pollinators. These plants provide edible flowers and nectar for bees but have shorter-lived, less aggressive roots that die back each winter, preventing them from "choking" your small-diameter pipes.
Best Annual Pollinators for Zone 6 (Alkaline Soil) These can be direct-seeded in early spring once the soil is workable:
Sweet Alyssum (Lobularia maritima):
Edibility: Tiny flowers have a mild, honey-like taste—great for garnishing. Whitwam Organics
Benefits: A massive magnet for honeybees and hoverflies. It grows only 3–9" tall and has a very shallow, fine root system. Gardenia.net
Calendula / Pot Marigold (Calendula officinalis):
Edibility: The peppery petals are edible and can be used in salads or dried for teas. NWF.org
Benefits: Thrives in 𝑝𝐻 up to 8.0 and is a notorious "bee magnet." It remains compact, which limits root depth. Gulley Greenhouse
Borage (Borago officinalis):
Edibility: Both blue star-shaped flowers and young leaves have a crisp cucumber flavor. Northern Gardener
Benefits: One of the best nectar-producing plants for honeybees. While it has a taproot, it is an annual and will decompose at the end of the season, preventing permanent pipe intrusion. NPSOT
Crimson Clover (Trifolium incarnatum):
Edibility: Flowers are edible and can be made into tea. Adaptive Seeds
Benefits: It fixes nitrogen to improve your soil while you wait for tests. It produces vibrant red spikes that are high-quality bee forage. USDA Plants
Bachelor’s Buttons (Centaurea cyanus):
Edibility: The colorful petals are edible and often used in baking. Longwood Gardens
Benefits: Very hardy for Zone 6 and attracts butterflies and goldfinches. UMN Extension
Seeding Guidelines for Shallow Pipes
Broadcast Seeding: Avoid digging deep to protect the 6" deep pipes. Lightly rake the surface of the soil, scatter the seeds, and press them down for contact.
Avoid Walkway Compaction: Since your 2" pipes are so close to the surface, stepping on them can cause damage or misalignment. Place stepping stones outsidethe pipe lines to access the garden.
Moisture Check: Shallow pipes release effluent closer to the surface. If you see a spot where the annuals are "yellowing," the soil might be too saturated; if they are extra lush, they have hit the "nutrient jackpot."

thanks for this.
You're very welcome! It sounds like you have a solid plan to balance your tertiary treatment benefits with the unique physical needs of those shallow 2-inch pipes.
By starting with pollinator-friendly annuals like Crimson Clover and Alyssum while you wait for your water tests, you're protecting your infrastructure while immediately helping the local bees. Once you confirm your pH and pathogen levels, your "living mulch" of wild strawberries and violets will make for a beautiful, functional landscape.
Good luck with the water testing, and feel free to reach back out if the lab results change your planting strategy!

oh I did have another question -- do the annuals you mention above self-seed, or will they be gone when I switch to perennials
Great question! Most of the annuals we discussed are prolific self-seeders. In the gardening world, we often call them "reseeding annuals"—they die with the frost, but they "plan ahead" by dropping hundreds of seeds for next year.
Here is how they behave so you can manage the transition:
The "Volunteer" Squad (Will likely come back)
Sweet Alyssum & Bachelor’s Buttons: These are the champions of self-seeding. If you let the flowers go to seed, you will likely see "volunteers" popping up next spring.
Borage: Often called "the plant that seeds for a lifetime." Once you have one borage plant, you usually have borage forever unless you pull the babies.
Calendula: Very reliable re-seeder. The seeds are large and "C-shaped"; they fall right where the plant grew.
The "One-and-Done" Squad
Crimson Clover: While it can self-seed, it usually requires a specific cycle and isn't quite as aggressive as the others. Most people re-sow it if they want it back.

How to "Switch" to Perennials
When your lab results come back and you are ready to put in your Wild Strawberries and Violets, you have two choices for the annuals:
The Integration: Just plant your perennials right in the gaps. The annuals (like Alyssum) will act as a "nurse crop," shading the ground while the strawberries get established.
The Clean Slate: If you don't want the annuals back, simply deadhead them (cut the flowers off before they turn into brown seed heads) or pull the plants in late autumn. Since the roots are fine and shallow, pulling them won't disturb your 6-inch deep pipes.
Bonus Tip: If you see "volunteers" popping up where you don't want them, they are very easy to hoe or pull out because their roots stay so close to the surface.

...and BTW the AI conversation is, in general, very nicely formatted and easy to read and to skim, unlike the quote in the forum post... lost all of the formatting except what I forced in.