Garden dead zone

I have strange and persistent dead zone in my garden, and I'm hoping you all can help me figure it out. I have an urban front yard garden with raised beds and in ground plantings. There is a small area, roughly 4' x 8', where no plant can be happy. Part of this area is inside a raised bed and part is in ground. No matter what is planted--annual crops, perennials, cover crop, nitrogen fixers, etc, all will be stunted and sparse. Even weeds don't like it much. The thing is, plants don't necessarily die, they just don't grow. Seeds germinate poorly, and transplants stunt. Eventually they succumb to pests or bolt in their stunted state. I have a healthy lavender hedge that runs along the front edge of my property, and as it passes through this zone the lavender is stunted. Not sickly, not seemingly stressed, but they have spent over a year in the ground and have pushed out almost no new growth and no blooms. Next to them are lavenders 4 times their size, planted at the same time from the same plant stock.

I have no gophers, moles, voles, or ground squirrels.
I have double-dug and added lots of compost and organic matter to the raised bed, twice per year.
I mulch, and chop and drop from healthy areas of the beds
I have used fish emulsion, kelp, bat guano, vermicompost, bokashi, and other amendments.
I have tried to seed and transplant cover crop, to no avail.
Sunlight and water are consistent with the healthy beds.
There are no allopathic species around that I know of. There are 2 redwoods 20' away.

Anyone had this happen?

Kelley-
Innnnteresting. Well, there are a lot of tannins in redwood, but if the rest of your plants are doing alright, then that mayy not be the culprit. For some reason, when I read your post, it reminds me of the introduction to A Biodynamic Farm by Hugh Lovel, in which he is troubleshooting a dying tree with a much more experienced agriculturist. The elder shrugs aside all of Lovel's notions and points to a rotting fencepost some distance away, which he insists is harboring a malevolent fungal vector that is killing the tree. Is it possible that there was once a tree in the "dead zone," that might be rotting now and tying up N, in addition to harboring potential fungal pathogens? Could there be a buried electric or internet line near that spot? And do you remember what kind of weeds/plants were growing in the spot before you started working with it?

Maybe just some roots from those redwoods that happen to be closer to the surface in that spot and are taking up most of the water and nutrients. They can easily spread more than 20'.

Ben, there was once lawn covering the whole yard, but that was 7 or 8 years ago. When I tore up the lawn, built the raised beds and planted other things in ground, all areas grew consistently. This dead zone seems more like a decline over time. There are no buried lines in that area.

I've always suspected the redwoods play a part in this, but have nothing to back my suspicions. Their roots aggressively seek water and nutrients and colonize everywhere that is irrigated. This problem patch is closest to the drip line of the trees. I wonder, could there be exudates, tannins, or fungal strains that support redwoods but exclude other plant life? And, in just that small area?

Patrick, I'm convinced their roots can colonize a city block, maybe more.

A couple of things that come to mind.

Septic or sewer somewhere near the dead zone? Other city underground things like electric, gas, whatever else they do in the city poisoning the soil? Do you have a 'call before you dig' that you can double check that someone hasn't put some nasty pipe underground?

Another thought. We had a dead zone for about 4 years after someone had created a huge fire and sterilized the soil in one spot of the garden. It wasn't your normal yard waste fire. This was several meters wide and lasted for a few days. Burned very hot. Once we figured out why the dead zone was there, we mixed in some healthy soil, and the next year things started to grow much better.

How about some home PH testing of your soil from the healthy section and the dead zone. You can even make a very basic PH test from boiled purple cabbage water, I'm told.

As R Ranson said, pH testing would be a quick and easy option. If that doesn't turn up anything, you could send a soil sample in to one of the labs - though in such a small area I'm not sure the results would be reliable or worth the cost ($15 at the University of MA, not sure about others).

I suggest testing only because it's possible someone dumped something toxic there at some point (lead, other heavy metals, persistent herbicides, etc.), though that theory wouldn't really explain the slow decline you've had.

As a former Californian I can confirm that redwood roots can go a very, very long ways and wreak a lot of havoc - they regularly broke the sanitary sewer line in our yard growing up.

Kelley Burnham wrote:This problem patch is closest to the drip line of the trees. I wonder, could there be exudates, tannins, or fungal strains that support redwoods but exclude other plant life? And, in just that small area?

Yes. Yes, indeedy. The drip line you indicated is possibly an area of high concentration for the "feeder roots" of the redwood- they love to stay in shallow soil where oxygen is abundant, to capture as much N as possible from aerobic bacteria, dew runoff, etc. Is there standing water in the problem area at any time during the year, or is it maybe naturally moist soil? If your dead zone is the closest to the trees, it stands to reason that it would be "invaded" by redwood roots, and affected accordingly, before anywhere else. Also, conifer trees are the only plants that can be colonized by endo-mycorrhizae, which actually grow within root tissues, as opposed to ecto-mycorrhizae, which just colonizes the surface of roots. It is possible that the fungal dominance of the redwood mycorrhizae are outcompeting other microbes in the soil, keeping other plants from being able to thrive there? Here's the way my thought process is rolling here:
A. Redwoods and turfgrass co-exist for X number of years.
B. Turf gets pulled up, likely with a lot of topsoil still attached to it, and creates a new layer of oxygen-rich soil
C. Roots branch out, aggressively, and near where they touch the surface, their fungal cohabitants have a sort of root stronghold, from which to subjugate the bacterial natives of the now-dead-zone. Mwuhhuhahahahaha

Additionally, if you've been ammending the zone with fertilizers and compost, the redwoods may have now determined that this spot is sometimes rich in fertility, and have probably grown additional roots in this area in response. A way to test this theory is to dig into the spot and see if you come up with lots of smaller, woody, roots, covered in a good-smelling white web-like substance. If you find them here, then this could be your culprit, and the problem may end up being a systemic one- it could be that the redwood roots are branching out from their previous confines to invade the newly (relative to a redwood) worked ground that holds so much fertility.

Would you be able to post some pictures? I'm getting rambly, and without pictures, I'm basically just creating my own fantasy dead-zone in my head and giving it the properties that come along with such things, namely infinite possibility hehehe...

Radiation?

Have you tried planting anything drought tolerant in the space? I’ve got a dead zone in my yard caused by the combination of a hill, hackberry roots, and an odd combination of shade with sun at the hottest part of the day. I was able to fill the space with succulents, thornless prickly pear, butterfly bushes, and banana trees. You may want to try a drought tolerant plant in the space just to see if it could be a water related problem from the roots.

Thanks everyone for your replies. I will post pics in the next couple of days, and try to do a pH test.

Kyle, I have lavender planted, and it's just as stunted as the crops/annuals. If only the crops/annuals were affected I'd assume something, likely the redwood, is hogging nutrients and water, but lavender likes lean dry soil, so I that tells me there's more to it than that.

I have quite a love/hate relationship with the redwoods. The genius who planted them 30 or 40 years ago thought nothing of what was to come. They perpetually clog the roof gutters with their relentless litter, shed prodigious amounts of biomass year round (which would be great if it actually composted and played nicely with others) and were planted directly over the sewer lateral and too close to the overhead power lines, wreaking havoc with both. I cannot dig anywhere on my property without finding roots. If I leave a potted plant on the ground they will grow into the container. They are, of course, in my compost pile. Pretty admirable tenacity, but Jeez! On the other hand they provide fantastic shade in the summer, although too much in winter. Beautiful trees. They grew particularly deep green and healthy after finding their way into the sewer lateral. Sigh. I'd like to meet the guy who planted them...

Oops, was that a rant?