Blueberries is what is the leading contender in my mind at the moment. However, 4 is pretty low on the scale for most plants. The coniferous forest makes/loves it though. Just wondering what else might be a good candidates for a food forest in the 4-5 ph range.
the one soil test we did with a cheap kit said our soil is 4 I think. My husband did the test in a master gardener class with distilled water and with an instructor showing how to do it to be the most accurate and even though it was a cheap kit everything growing native here does make and like very acidic soil so that number is probably pretty accurate.
we have wild huckleberries everyplace. they seem to thrive in this soil. I have a bed with naturalized wild arugula that is really impressive. wild strawberries cover my property. okinawa spinach and longevity spinach seem to do well along with a lot of leafy greens
the places we sheet mulched with a layer of oyster shells (saved from eating oysters) and other shells and then lots of compost certainly seem to do the best. we have kale naturalized over in that spot now along with a lot of other plants which include artichokes, cardoons and asparagus is growing below that bed in an area that is probably pretty acidic although it is doing ok. the asparagus I stuck in random places all over the place after I ran out of room in my asparagus bed seem to be doing better and some of those are just stuck in pure native acidic soil.
I just keep tossing in seeds and plants and a lot grows. some seeds never germinate at all I think from the acid levels. adding compost helps the most. sometimes i add lime or rock dust if I think of it. I am a pretty lazy gardener but my garden keeps doing better and better despite my lazy attitude and the high acid content of the soil in a forest that has a lot of bishop pine trees and a thick layer of pine needles covering the ground.
pomegranate trees that have native alkaline soil seem to be happy here with acidic soil
mulberry is growing ok
banana plants not as great the ones in planters are doing the best this could be that they get more fertilizer though or be related to coldness since the planter ones are against the house
all flower bulbs i plant seem to do ok
all alluims seem to be fine here, we have potato onions, walking onions, shallots, maybe 5 types of garlic. i have yet to harvest any but the tops look happy and healthy and they are all over the place stuck in the acidic soil
I am in the process of an experiment that tests the theory that soil acidity can be remediated through plantings of tolerant subspecies.
So far the results are showing that most plants can remediate soil acidity in a small sphere around the root system, the difference appears at this time to be sufficient for growth to occur.
More time is needed to get definitive data for determination of quantitative results of amount of alkalinity released by root systems.
So far it is looking like the theory may be correct in that plants which need certain soil alkalinities to thrive can, over time, remediate soils surrounding the root system to a pH that can be tolerated or even preferred by the plant.
Indications are promising at this time.
Fig trees seem to be very adaptable to differing pH conditions as long as soil makeup contains certain nutrients so the plant can manufacture secretions that effectively condition the surrounding soil pH to more desirable levels.
It is probable that many plants have the ability to perform similarly.
How about woodland plants that are native to the west coast of North America? There are a lot of native berries that grow in conifer forests, of various levels of deliciousness to humans: thimbleberry, salal, evergreen huckleberry, red huckleberry...
One of the best wild forage foods of acidic conifer forests is mushrooms. There's just not many available commercially that grow on conifer wood.
Here in Richmond, Virginia, I garden in soil that wants to be 4.0. The soil name is Lenoir, poor for crops, reacting strongly in water to acid. Every time it rains my soil acidifies, so I know this issue.
In addition to avid soil testing, adding limestone and sometimes hot lime, I use wood ashes whenever I can get them. (a lady offered me 6 5 gallon pails last week!)
If test calls for one pound of limestone, I use 2 pounds of ashes.
Your local agricultural school may have suggestions about wood ash from regional trees and regional soils.
Attached is a paper from the University of Georgia that was very helpful to me.