Plant that will spread again if I kill it every five years

Looking for suggestions...

I'm turning an overrun planting bed into a perennial herb/flower garden. My septic tank is an old, homemade system with huge openings covered by concrete slabs buried under about 12 inches of dirt - inside the bed. It works fine, but every five years or so I know I'm going to need to dig up the dirt to access the concrete slabs in order to have it pumped out. I don't mind the digging; however, it means I will inevitably dig up whatever is growing there, and myself and the septic folks will likely stomp on whatever is within a foot or so of it.

I'm looking for something that I can grow on this patch. It's around 5 foot by 3 foot, with 12 inches deep of soil. It needs to have shallow roots since I don't want it to try to grow into my tank. I want something though that if I kill it every five years, it'll regrow over that area within a few months to a year. But I don't want it to take over the whole bed (looking at you mint...), since I'll be growing lots of other plants. Preferably it would be edible or medicinal, but I guess I could go with something that isn't.

Grow zone is 8b. Lots of sun with a bit of dappled shade depending on the season.

We have the same situation. A septic pump that has to be replaced about once every 8 years or so. It is in grass. Over the years the grass grows back, but we lose dirt to erosion just about every time we dig it up. So the ground over the pump is sunken down several inches and quite uneven.

At another house we set a piece of culvert on end above the access to the tank, then put a lid on the culvert. That way we don't have to dig it all up every time the inlet to the tank gets plugged.

I wonder, strawberries have an effective life of only a few years. Maybe you could grow them there.

Plenty of options... will suggest strategies, since so many plants can fit into different schemes.

Flowers/plants with bulbs, tubers, or rhizomes that are easy to lift and transplant, which is often done in colder zones for overwintering anyways. You may be able to make divisions to increase/replenish your stock, or to sell/give away.
Plants for harvest that take more than one season to grow, especially medicinal roots such as echinacea.
Plants for seed, especially biennials?
Something such as garlic, potatoes, or Jerusalem artichokes that you could replant some after taking a harvest
Something spready (maybe not mint?) that your periodic digging out would serve to keep its advance in check. Walking onions?
Something that you can propagate by cuttings which you could do before digging out the mother plants, the cuttings might fare better without transplant shock that a larger plant torn from its roots might.
Container gardening, in dense clusters and possibly mulched in so that you might not even notice the pots. come time, you can just move the pots away and back again.

I like Kenneths suggest for flowering bulbs.  These usually will not have roots that cause damage.

Most folks don't recommend edible in the septic area.

Here are some threads that might be of interest to you or others:

Bryant said, Sweet Yellow, Crimson, Dutch White are great clovers to use in a feed plot or a pasture.

https://permies.com/t/69593/Ideas-septic-field#584328

https://permies.com/t/91761/Planting-drain-field

https://permies.com/t/221507/plants-septic-field

Jeremy VanGelder wrote: At another house we set a piece of culvert on end above the access to the tank, then put a lid on the culvert. That way we don't have to dig it all up every time the inlet to the tank gets plugged.

That's what I was hoping to do, but our tank is an old, homemade design. Sturdy as hell, but it's opening is four feet across. I can't find any culvert local that would fit that. Expense and weight were starting to get up there as well unfortunately...

I do like the suggestion about strawberries. I've been trying to decide where I'd put some, so that might work.

I am eager to plant both Jerusalem artichokes and walking onions. I'm curious - how quickly do they spread? Will they take over a patch that size within a season if there are plants surrounding it? Do those two plants grow well together? Like if I just wanted to plant one on each side or intersperse them?

I have zero experience with bulbs, though I have been wanting to get into them more. How delicate are they when being dug up? If I dig out the dirt 12 inches deep and just toss it back on a few days later (while the bulbs are dormant), will they reestablish themselves? Or do I need to go through it by hand searching for the bulbs and replanting them?

Anne Miller wrote: Most folks don't recommend edible in the septic area.

I was thinking about this. The bed is over our tank though - not the drain field. Our tank is really tall , so the roots would have to go probably 4-5 feet down to get into the effluent in the tank. I don't think I'm too worried about it as long as I'm not growing anything with roots that will go searching that far. If I start to notice a leak or smells or anything like that I would definitely stop harvesting immediately though.

I not rushing the decision right now since the area is still dug up. I'm pretty sure any of the recommendations would need to be planted while dormant anyways, so it'll probably just get mulched over until it cools down later this year. If anyone has more recommendations I'd love to hear them!

If saffron grows in your climate, that would be a lovely bulb (corm) to plant. Productive and pretty and benefits from being lifted an divided every few years.

They are autumn flowering so are out now in the southern hemisphere.

@chard irking, what did you end up planting in the bed over your septic tank?

A few days ago, I dug up the bed of saffron in the photo above.

There were hundreds of corms, kept the biggest ones to replant and am selling the rest as a fund raiser for our community garden.

Our water tank is fed from a stream that often runs dry so we have dug a bore but need funds to buy and install a pump and generator.

Megan Palmer wrote:@chard irking, what did you end up planting in the bed over your septic tank?

A few days ago, I dug up the bed of saffron in the photo above.

There were hundreds of corms, kept the biggest ones to replant and am selling the rest as a fund raiser for our community garden.

Our water tank is fed from a stream that often runs dry so we have dug a bore but need funds to buy and install a pump and generator.

Wow that's impressive! Life got busy so we ended up just leaving it covered in woodchips for a few months. Then we planted bulbs (daffodils and tulips if I remember correctly) back in the fall. I'm excited to see what we get this spring!