Hawaii Morel Mushroom Forecast
The federal synthesis puts morels on the forested slopes of Hawaiian volcanoes, with a citation, so Hawaii gets a page rated on its own soil reading rather than on a mainland spring. The reading below is the soil temperature at two inches near Waimea, summed the way the published predictor does and shown against the 410 degree day threshold.
Is the Hawaii soil ready this week?
Soil temperature at 6 cm for Waimea, which is 2.4 inches and the depth the threshold is measured at, with every degree above freezing added up over the last 20 days and the rain of the last 30 days counted behind it. Open a day for every factor and its points.
Waimea
Reading the soil temperature for Waimea, HI.
Read your own Hawaii woods
A ZIP code gets the same seven days for your own coordinate rather than for Waimea. Aspect and elevation move the start inside Hawaii by weeks, so a reading a county away is a different week from a reading on your hillside.
What sets the timing in Hawaii
On the volcanic slopes the reading itself is the whole answer: the soil degree day count above, against the same 410, on the slope you are standing on. Elevation does the work latitude does on the mainland, and the published order for that is below.
The state window
minus 55 well outside it, plus 3 in the opening fortnight
Each state window steps north at the published rate of about 100 miles a week. The live soil reading outranks it inside the window.
The sources behind it
“The morel season generally begins in the south and progresses 100 miles or more north per week.”
May is Morel Month in Michigan (Extension Bulletin E-2755) The rate the national map is drawn at. A land-grant extension bulletin, and it matches the Forest Service synthesis independently.
“Lonik (2002) reported that in the Eastern United States, the morel season moves south to north at about 100 miles per week.”
Ecology and Management of Morels Harvested From the Forests of Western North America The same rate in a federal report, attributed to a popular book. Two sources agreeing on 100 miles a week is why the state windows step the way they do. It is a latitude rate, from the Gulf to the northern tier.
“In any one location, the season can last from several weeks to several months depending on rainfall, humidity, topography, and the morel species.”
Ecology and Management of Morels Harvested From the Forests of Western North America Why each state window here is a band with a middle rather than a date, and why the live reading outranks the band on any given weekend.
Elevation and aspect
Shown, not scored
Low ground and south faces first, then higher and north-facing. Follow the season uphill and around to the north faces as the weeks go on.
The sources behind it
“In areas that have hilly or mountainous topography, morels will fruit first at low elevation or on south-facing slopes that warm up early, then at higher elevations and on north-facing slopes that warm up later (Low 1995).”
Ecology and Management of Morels Harvested From the Forests of Western North America Elevation and aspect in one federal sentence. Low ground and south faces first, then the high ground and the north faces, which is the order to walk a hillside in as the season climbs it.
“Morels frequently occur in moist microhabitats and the morel season progresses upwards in elevation as summer weather warms (Miller 2003).”
Ecology and Management of Morels Harvested From the Forests of Western North America The interior West pattern, independent of the Sierra statement, and it pairs the climb with the moist pockets that hold on after the open ground quits.
“Fruiting generally starts in early March at about 4,000 feet in the northern Sierras and about 5,000 feet in the southern Sierras, and increases in elevation as spring progresses.”
Ecology and Management of Morels Harvested From the Forests of Western North America The one quantified elevation band in the government literature: a start month, a start elevation, and a thousand feet of latitude adjustment inside one state.
“Because this region lies in the rain shadow of the Cascade Range to the west, the mesic coniferous forest habitat that morels inhabit is found at fairly high elevations ranging from 2,500 to 7,000 feet.”
Ecology and Management of Morels Harvested From the Forests of Western North America Why the northern Rockies pages point high rather than low: in the rain shadow the habitat itself sits at 2,500 to 7,000 feet.
“In some cases, such as in Nevada and Utah, morel habitat occurs as isolated islands near or on mountain peaks.”
Ecology and Management of Morels Harvested From the Forests of Western North America In the Great Basin the habitat is an archipelago, so the state reading means less than the range reading and the pages say which ranges.
The Hawaii ground that comes on first
Upland forest on the volcanic slopes, where elevation sets the season and the soil reading says what the ground is doing now. The host trees worth walking here are koa and ohia forest, introduced hardwood, and the published work on hosts is specific about why: a dying elm or an old orchard is a tree in trouble, and the fruiting follows the trouble.
Lilac, mayapple, apple bloom
Shown, not scored
Lilac leaf out is a measured national index, and the early shrubs leafing out around you are a sign the spring morels follow is under way.
The sources behind it
“The First Leaf Index is based on the leaf out of lilacs and honeysuckles, which are among the first plants to show their leaves in the spring. This Index is associated with the first leafing of early-spring shrubs and other plants.”
Status of Spring: the First Leaf and First Bloom Indices Lilac leaf out is a measured national index, so the lilac is worth watching. When the early shrubs leaf out around you, the spring that morels follow is under way, and the soil reading says how far along it is.
“The USA-NPN generates daily Accumulated Growing Degree Day (AGDD) maps using a January 1 start date and two base temperatures, 32°F and 50°F.”
Accumulated Growing Degree Day maps Read this before comparing anything. The national maps accumulate from January 1. Mihail’s threshold is a rolling twenty day sum. Same base temperature, completely different magnitudes, so the 410 here is never checked against a published AGDD map.
“Growing degrees days are defined as the number of degrees the average daily temperature exceeds a base temperature, or the temperature below which the organism will remain in dormancy.”
Accumulated Growing Degree Day maps The definition the forecast computes, word for word as the page prints it.
Host trees
Shown, not scored
Dying elm, living white ash, just dead cottonwood, sycamore, tulip poplar, old apple. Where to walk, which is a different question from when.
The sources behind it
“Found especially under dying elms and living white ashes and cottonwoods; also under tulip poplars, oaks, and hickories.”
Yellow Morel (Common Morel), Morchella esculentoides A state agency on the hosts, and note the asymmetry it asserts: elms dying, ashes and cottonwoods living. That distinction is worth more than the species list.
“Weber (1988) reported morels in Michigan as associated with oak-hickory or beech-maple forests, or under sycamore, elm, ash, cottonwood, and apple trees.”
Ecology and Management of Morels Harvested From the Forests of Western North America Forest types as well as single trees, which is the scale a reader can actually see from the road.
“Kuo (2005) listed morels in the Eastern United States as associated with ash, elm, and tulip trees, and often found in old apple orchards.”
Ecology and Management of Morels Harvested From the Forests of Western North America The old apple orchard, with a citation behind it instead of folklore.
“Thompson (1994) found morels with senescent or dying apple trees, just-dead cottonwoods, and especially elms.”
Ecology and Management of Morels Harvested From the Forests of Western North America Tree health, and how narrow the window is: just dead, not long dead. Which is exactly why this is a timing product.
“Massive crops of yellow morels at the bases of dying elms (Thompson 1994, Weber 1988) and extensive fruiting of natural black morels in insect-killed forest (Pilz and others 2004) are two examples.”
Ecology and Management of Morels Harvested From the Forests of Western North America Two different disturbances feeding two different species. A dying elm for yellow morels, an insect-killed stand for black ones.
“Volk and others (1997) theorized that such mass fruiting represents a last-ditch effort to reproduce when the morel’s food source disappears.”
Ecology and Management of Morels Harvested From the Forests of Western North America Why a dead or dying host matters at all, in one sentence: the fungus is leaving, and it fruits on the way out.
“Morchella esculenta – common morel, yellow morel. May. Various habitats including under dead elms and in old apple orchards.”
Common Wild Edible Fungi in Illinois A species, a month and two habitats on one extension line. The same handout gives the black morel as April to May under dead elms and living ash, so inside one state the black morel runs a few weeks ahead of the yellow.
“it fruits in spring, likes recent burn sites, likes a mixed conifer forest as well as cottonwoods, fruits mostly on the east side of the Cascade Crest, and starts low and moves higher in elevation as the season progresses.”
Spore Prints 501: morels of eastern Washington The whole eastern Washington pattern in one clause: spring, burns, mixed conifer and cottonwood, east side, low to high.
The sentences behind that, in full
“Morels can be found throughout the United States if you look in the right habitats, such as the forested slopes of Hawaiian volcanoes (Hemmes and Desjardin 2002).”
Ecology and Management of Morels Harvested From the Forests of Western North America The Forest Service puts morels on the forested slopes of Hawaiian volcanoes, with a citation, which is why Hawaii has a page rated on its live soil reading rather than on a mainland spring window.
“Morels can be harvested 6 to 8 months a year if harvesters are willing to travel extensively.”
Ecology and Management of Morels Harvested From the Forests of Western North America The national season is far longer than any one place, which is the whole reason a per-state window beats a national one.
What moves the Hawaii score, and by how much
The soil degree day count sets the base and everything else adjusts or caps it. The forecast hub carries all twelve factors with every source, including the rain, the moisture, the host trees, the burns and the plants worth watching.
Soil degree days
sets the base, 8 to 80
Daily mean soil temperature above 32 F summed over the trailing 20 days, read at 6 cm, against the published threshold of 410.
The sources behind it
“The best predictor of first yellow morel appearance was the accumulated average soil temperature above freezing (32 °F) over the preceding twenty days. However, first yellow morel appearance seems to be delayed beyond the prediction when winters have been especially warm.”
Predicting the Spring Morel Season The whole model rests here. Not a single soil reading on one afternoon: the sum of daily mean soil temperature above freezing over the preceding twenty days, measured at two inches. The published threshold for that sum is 410 degree days Fahrenheit.
“Winter chilling, as well as spring soil warming, are both important in determining the when we will first see early spring morels.”
Predicting the Spring Morel Season Soil warming is necessary and not sufficient. The same paper publishes four thresholds, 510 and 660 degree days for air over twenty and thirty days and 410 and 520 for soil, which is why a soil reading is preferred here and an air reading is the fallback.
The 40 degree floor
caps the day at 14
A seven day mean soil temperature under 40 F holds the day at Dormant however the degree days read.
The sources behind it
“Eastern Washington morels, the subject of this article, need at least a consistent ground and air temperature of +40ºF to start fruiting. The timing of the fruiting varies from year to year, sometimes starting as early as March and in other years as late as mid May.”
Spore Prints 501: morels of eastern Washington A floor, in a mycological society bulletin, and the spread of start dates around it. Below a consistent 40 degrees the forecast does not rate a day above Dormant however the degree days read.
Rain events over 10 mm
minus 9 to plus 8
Counted over the trailing 30 days. It moves how many, never when: the timing is the temperature.
The sources behind it
“Fruiting onset was inversely correlated with spring air and soil temperatures, whereas abundance was positively correlated with rain events (>10mm) during the 30 d preceding fruiting.”
Spatial and temporal patterns of morel fruiting This is the sentence that splits the model in two. Temperature sets the date. Rain sets how many. So rain counts here as events over 10 mm in the trailing thirty days, and it moves the yield, never the timing.
“For instance, during the years 2001 to 2005 in north-central Missouri, the first day of morel fruiting reliably fell between the 104th and 110th days of the calendar year (mid-April) and total seasonal production was closely correlated with the number of rainfall events of greater than 10 mm during the next 2 weeks”
Ecology and Management of Morels Harvested From the Forests of Western North America The same 10 mm event threshold from the other direction, and a striking stability in the start date: five straight years inside a six day window in one place. The Forest Service carries this as a personal communication from a five year single location record, which is where its weight stops.
Soil moisture
minus 11 to 0
Volumetric water at 3 to 9 cm. The direction of the effect is contested in the literature, so it only ever takes points away at the dry and the saturated ends.
The sources behind it
“Such rainfall not only hydrates the morel mycelium that is nourishing the growing fruiting body, but likely also maintains high humidity levels near the soil surface so the growing morel does not dry out and shrivel.”
Ecology and Management of Morels Harvested From the Forests of Western North America Why moisture matters twice: in the ground for the mycelium, and in the air at ankle height for the fruiting body that is already up.
“Thompson (1994) claimed that soil moisture is only important for morel fruiting after the soil has warmed, whereas Goldway and others (2000) suggested that slowly drying soil stimulates morel fruiting.”
Ecology and Management of Morels Harvested From the Forests of Western North America The direction of the soil moisture effect is contested in the literature, which is the reason moisture here only ever takes points away at the dry and the saturated ends and never adds any.
“Morel spores germinate readily without any special requirements other than moisture (Hervey and others 1978, Schmidt 1983, Volk and others 1997, Weber 1988).”
Ecology and Management of Morels Harvested From the Forests of Western North America Four independent citations behind one claim, which is as settled as this literature gets.
A true morel is hollow from cap to base
One cut lengthwise settles it. A true morel is pitted like a honeycomb and opens into a single hollow chamber the whole way down. A false morel is reddish, wrinkled or brainlike rather than pitted, and its stalk is dense or chambered rather than open. Three sentences from the Missouri Department of Conservation, which states it without hedging:
“All Missouri true morels are completely hollow inside.”
Big Red False Morel, Gyromitra caroliniana The cut test, stated without qualification by a state agency. One cut lengthwise, one single open chamber from cap to base.
“Lookalikes: The poisonous or potentially toxic false morels (Gyromitra caroliniana and G. brunnea) are reddish and have wrinkled, lobed, or brain-shaped caps and dense (not hollow) stalks.”
Yellow Morel (Common Morel), Morchella esculentoides The contrast in one sentence from the same agency: wrinkled, lobed or brain shaped against pitted, and dense against hollow.
“For these reasons, we cannot recommend eating any false morel mushrooms.”
Big Red False Morel, Gyromitra caroliniana A state agency recommendation, in its own words, which is the strongest form this claim takes anywhere.
The full set, including what the toxin is, what cooking does and does not do to it, and the second cut test for Verpa, is on the forecast hub. Cook true morels before eating them. Mushrooms are named as a special forest product in the federal programme, so a permit question on a national forest belongs to that forest’s district office.
Hawaii morel questions
More for Hawaii foragers
Morel forecasts in other states
The rating forecasts whether the soil has reached the published threshold, which tells you when to go; the walking finds the mushrooms. Soil temperature, soil moisture and rainfall come from the Open-Meteo model for the coordinate shown, and the 410 degree day threshold, the 40 F floor and the hundred miles a week are each quoted from their source on the morel mushroom forecast.