Seeking chestnut orchard groundcover seed sources and ideas

Seeking shade- and acid-soil-tolerant, very-low-growing and nitrogen-fixing groundcovers for chestnut orchard floors.

Ideally these would be low-growing enough that Autumn's fallen chestnuts could be harvested from atop them, with little mowing needed.

I've found seed of 'Empire' Birdsfoot Trefoil; Lotus corniculatus cv. 'Empire', 'Microclover' White Clover; Trifolium repens cv 'Pirouette'; Mahala Mat; Ceanothus prostratus; and Miniature Lupin; Lupinus bicolor.

I seek Black Medic; Medicago lupulina; Forest Clover; Trifolium breweri and Brewer's Lupin; Lupinus breweri, as well as Prostrate White Clover; Trifolium repens subsp. prostratum.

Seed source and other cultivar suggestions are welcome.

Brian
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I'm not sure I know of anything that fits all of those criteria, but one thing you do see a lot in temperate deciduous woodlands are bulbs, like bluebells and wild alliums. They take advantage of the early spring sun before the trees are fully leafed out, do their thing, and then go dormant when it gets shady. They're not nitrogen fixers but all that decaying foliage must contribute a bit right around the time the trees can use it.

Tom Wahl of Red Fern says in this video https://www.youtube.com/watch?v=PAf1lUrqSq4 that typical pasture mixes of grasses and such compete with his chinese chestnuts too much, so he finds that planting lower-vigor grasses and such that compete through persistence, not vigor, works better, and saves mowing, as they need less mowing to leave a clean, low surface that his PYO pickers can harvest chestnuts off of.

I've been searching out acid-soil-tolerant nitrogen-fixing low- and slow-growing groundcovers to complement chestnuts.

Prospects include:
Ceanothus prostratus Mahala Mat - seed is doubly-dormant from plant; needs both cold- and heat-treatment, reportedly. Reportedly found in high and thus winter-cold, well-watered areas of the coast range of the West coast.

Lupinus brewerii Brewer's Lupin: A low-growing lupin adapted to acid soils.

Lupinus bicolor Miniature Lupin: I have these growing in chestnut seedling's pots, for future grandcover use.

Trifolium brewerii Forest Clover: low-growing and shade tolerant, I believe.

Trifolium repens White Clover cv. 'Microclover': Low-growing, acid-soil tolerance uncertain.

Lotus corniculatus Birdsfoot Trefoil cv. 'Plena'/Pleniflorus'/'Empire' These are prostrate or nearly so.

Medicago lupulina Black Medic cv. 'George' I have not yet found a seed source for this University of Montana-bred release.

What has worked for you?

ive found if you make the trees fight with the grass and weeds it makes them stronger. I didn't even irrigate or mow after planting more than 400 trees until about the 6th year after planting 1 year old seedlings. some trees disappeared, eaten by deer, and other unknown reasons but they bulk of them are still there and most look excellent. 11 years on now, two years ago I had a handful of nuts, last year about 15 -20 lbs after letting the wildlife eat what they wanted for at least the first week after they began to ripen. this year some trees are 4 to 5' taller and looking forward to nut harvest. for me it is becoming a way to a sustainable future with a completely organic crop that gets bigger and bigger every year that only requires mowing around the trees before the nuts begin to mature.
a word of caution is once trees begin to produce nuts you need to remove every single nut from the orchard to prevent chestnut weevil infestation.

also another note on growing chestnuts. DO NOT plant chestnut trees where you would have any livestock except maybe birds. sheep, goats, cattle and horses CANNOT be in area with chestnuts. better check with a vet if your animals would be safe if they tried to eat chestnut.

bruce Fine wrote:also another note on growing chestnuts. DO NOT plant chestnut trees where you would have any livestock except maybe birds. sheep, goats, cattle and horses CANNOT be in area with chestnuts. better check with a vet if your animals would be safe if they tried to eat chestnut.

My cow cleaned up most of my chestnut (Chinese) harvest before I could get to them.  Didn’t seem to bother her any, but it wasn’t that much off of two 15 year old trees.  Might be different with higher volume off of more mature trees.  Pigs really enjoy them as well.

The low-vigor groundcover approach makes a lot of sense for harvest. Anything too vigorous just becomes another thing to manage. I've seen comfrey used in fruit tree guilds but it can get out of hand fast — the persistence-not-vigor principle is a good way to think about it.

bruce Fine wrote:also another note on growing chestnuts. DO NOT plant chestnut trees where you would have any livestock except maybe birds. sheep, goats, cattle and horses CANNOT be in area with chestnuts. better check with a vet if your animals would be safe if they tried to eat chestnut.

Bruce, at Badgersett research farm, horses were grazed under 15-20 foot tall chestnut to mow down the weeds and such, with no harm to the horses or trees. Also, sheep grazed under mature chestnuts in Leverett, Massachusetts year-after-year, with no harm done, at the farm of a friend. These are not horse chestnut; they are Castanea species.

Bruce, also, one can kill chestnut weevils in-shell without killing/cooking the nuts by holding the nuts in 120 degree Fahrenheit water for 20 minutes. If one holds them in that 120F water for 40 minutes, it discourages brown rot of the kernel, I understand.

Brian
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ChatGPT AI on prostrate lupins for usda zones 4-6 and 1-1.5 m precip/year:

"1. Lupinus nanus (Sky Lupine): A low-growing, prostrate species native to California, it spreads along the ground and reaches only about 6-18 inches in height. This species typically thrives in open, sunny areas and blooms with blue and purple flowers.

   USDA Zones: 4-6
   Height: 6-18 inches (prostrate to low-growing)
   Precipitation: Thrives in areas with moderate rainfall and good drainage.
   Habitat: Common in open, sunny meadows and grasslands.

2. Lupinus perennis (Wild Lupine)

Lupinus perennis ssp. perennis var. occidentalis, commonly referred to as the Western Wild Lupine, typically grows to a height of around 12-24 inches (30-60 cm). It is considered a low-growing or spreading form of lupine, with a sprawling habit compared to its upright relatives.

This variety thrives in sandy or well-drained soils and is commonly found in dry, open areas, including meadows, prairies, and sandy soils near coasts. Its height can vary depending on growing conditions, but it generally stays relatively short compared to other lupine species.


   USDA Zones: 3-7
   Height: 12-24 inches (prostrate or sprawling in some varieties, like var. occidentalis)
   Precipitation: Tolerates moderate rainfall, especially in sandy or well-drained soils.
   Habitat: Prefers dry, sandy soils, often in open woodlands and prairies.
Lupinus argenteus (Silvery Lupine)

   USDA Zones: 4-7
   Height: 6-24 inches (can have a prostrate form depending on environmental conditions)
   Precipitation: Tolerates 1-1.5 meters of precipitation, often found in subalpine and mountainous regions.
   Habitat: Rocky soils and open slopes.

4. Lupinus arcticus (Arctic Lupine)

   USDA Zones: 2-6
   Height: 6-18 inches (can grow prostrate in harsh environments)
   Precipitation: Adapted to areas with variable moisture, including higher precipitation zones.
   Habitat: Subalpine, tundra, and boreal forests.

5. Lupinus lepidus (Prairie Lupine)

   USDA Zones: 4-7
   Height: 4-16 inches (prostrate and mat-forming in some conditions)
   Precipitation: Thrives in dry to moderately moist soils, often found in meadows and open forests.
   Habitat: Tolerant of poor soils and rocky outcrops.

These species tend to thrive in cooler climates and areas with moderate precipitation, making them good candidates for USDA zones 4-6 with the specified precipitation range. You might find certain regional or subspecies variations that further suit specific local conditions.

Lupinus polyphyllus (Bigleaf Lupine)

   USDA Zones: 4-7
   Height: While this species typically grows taller, some varieties or environmental conditions can lead to lower, more sprawling growth.
   Precipitation: Tolerant of higher moisture, commonly found in moist meadows and along stream banks.
   Habitat: Prefers moist, well-drained soils but can adapt to various conditions.

7. Lupinus nootkatensis (Nootka Lupine)

   USDA Zones: 4-6
   Height: Can grow from 12-24 inches with a sprawling form in tough environments.
   Precipitation: Common in areas with high rainfall, including coastal regions.
   Habitat: Found in moist soils, often near water sources, but can tolerate poor soil conditions.

8. Lupinus breweri (Brewer's Lupine)

   USDA Zones: 4-6
   Height: 4-10 inches (very low-growing, mat-forming lupine)
   Precipitation: Adapted to moderately moist to dry conditions.
   Habitat: Common in rocky or sandy soils in alpine and subalpine meadows.

9. Lupinus albifrons (Silver Bush Lupine)

   USDA Zones: 4-7
   Height: Typically low-growing and spreading, around 12-24 inches.
   Precipitation: Well-suited to moderate rainfall but prefers well-drained soils.
   Habitat: Found in dry, open habitats but can tolerate seasonal moisture.

These species have a range of adaptations for both precipitation and USDA zone tolerance, making them suitable for landscapes that experience cool to moderate climates with decent rainfall. Adaptation can vary within these species depending on local conditions and specific subspecies. For best results, it's a good idea to test local strains or check with native plant nurseries to ensure the right fit."

Sometimes I ask Alexa simple planting questions and plant knowledge questions, most of the time she's right haha.  But for more complex questions I still ask here or I ask other people who are in my in-person life who are more knowledgeable than I.

the information I have about having sheep, goats, horses and cattle in area where chestnuts are grown comes from a vet with decades of experience with farm animals.
I was warned that the spiny spurs that enclose the nuts can be a serious problem for animals if eaten.