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Figuring out when to look for morels


vitog

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The earliest morels that I pick require a long day trip that uses a lot of expensive gasoline. So I don't want to drive out to the site until I'm pretty sure that there will be morels to pick. I keep a record of all of my natural morel finds and have been downloading relevant weather data into a database. I've been playing around with degree-day calculations for a number of years but this year decided to do a detailed analysis to see how useful degree-day data really is.

For this analysis I used the data from the 2 weather stations closest to the morel location. I had data for 5 years from 2006 to 2011 (didn't pick at that location in 2009), with a range of picking dates from April 4 to May 1. To make sure that I covered all bases, I added all of the degree-days from January 1 to the picking date, using base temperatures from -3 to +10 degrees C. In case you are not familiar with degree-days, the value for any particular day is simply the average temperature for the day minus the base temperature. Negative values are calculated as 0 degree-days.

After comparing the various totals for the 2 weather stations, I noticed that 1 year, 2006, had a value significantly higher than the other years. Examination of the weather data for that year showed that March, 2006 had much less rain than any of the other years, which explained why the degree-day total was high. I then removed the data for that year as not being representative, and the remaining years gave amazingly consistent results. For those years, the the average difference from the average value was 2% for the closest weather station and a bit over 5% for the other station. These were the best results, obtained by using base temperatures of -2 and -3 degrees, respectively.

To see if these good results could be improved, I then combined the data from the 2 weather stations by using weighted averages. I varied the weighting to optimize the results and found that I could get the average difference down to less than 1.5% by using a weighting of 3.6 to 1 (nearer station to farther station) and a base temperature of 0 C. This difference is equivalent to less than the degree-day value for a single day at that time of year. In other words, I should be able to predict the day for picking morels at this location, on average, within 1 day. I'm sure that this result is a bit too good to be true, since I only pick on weekends; and my picking dates should have an average error of at least 3 days. Regardless, it should be interesting to see if this year will substantiate my earlier results or not. I can already see that this will be a late year, unless the temperatures suddenly climb above normal for the next few weeks. At least we have plenty of rain.

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Interesting idea. I'll guess that degree-day calculations will be most useful when the analysis begins with the first day for which the ground is completely thawed, assuming one lives in an area where the ground freezes.

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Dave, I think that it doesn't matter if the ground is frozen or not, as long as it freezes fairly consistently. Some of the degree days above freezing will go towards thawing the ground rather than developing morel mycelia, but the totals should still be similar. If the depth of freezing varies drastically from year to year, I agree that it would be better to start when the ground thaws. We have a similar situation here at higher elevations, where the snowfall amount varies considerably from one year to the next. Some years take a lot more heating to melt the snow than others, and I can see more variation in the degree-day totals for one such location that I monitor.

Upsinker, thanks for the encouragement. My suspicion is that these calculations will work best where winters are consistently mild, such as the West Coast and the southern half of the eastern US. I'd love to hear about results from other areas. I had previously not found much on the Web about degree-day calculations; but, interestingly enough, I just found a reference to a study in a mycological publication that stated that morels started fruiting at a total of around 1000 DD F using a base temperature of 32 F. My own average figure is 549 DD C, which converts to 988 DD F; and I used the same base temperature. That same Web site also gave this Web address for a site that provides DD maps of the entire US up to yesterday's date: http://uspest.org/US/. Using those maps should make it fairly easy to determine the degree-days number for any location in the US.

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I examined that Website with the degree day maps and found that it is really useful. It takes all of the hard work out of determining how many degree days are required for morels at any place in the US. I visit my mother in Vancouver, WA fairly regularly; and naturally I'm always looking for mushrooms. In 2008 I found a few natural yellow morels on April 20; then, in 2009 I found them again in the same spot on May 2. That Website produces custom maps of most states for any day of the year, going back quite far, especially in western states. So I had it make maps for the 2 dates that I found the morels. Fortunately, both maps came up with the same degree day total: 1260 DD F, a good sign. This will allow me to time my next visit to Vancouver, WA so that I have a very good chance of finding some yellow morels. Yesterday's current map, for March 19, showed 840 DD F; so I still have to wait a while. Once the degree day total gets close to the magic 1260, it will be easy to determine how many more days I have to wait. All that needs to be done is to look at the long range forecast from AccuWeather or similar Website, take the average temperature for each day minus 32 F, and then add each day's degree day number to the current one, until the total is 1260. That will tell me when to schedule the visit. If I have to go earlier, I'll try to schedule the visit for when the degree day total is close to 1000 and look for black morels.

It would be interesting to hear from other members who keep track of find dates what degree day totals correspond to their finds.

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vitog - I can see how the data can help you time a trip to a known spot, as you've shown. However, we have so many microclimates out West that it seems like it would be difficult to pinpoint dates for general exploration. It would be nice to be able to take the degree day figures, then adjust for elevation and slope orientation to figure an ideal time to hunt unknown territory. Do you have any feel for how microclimates impact the overall degree days numbers?

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If you have the picking date for a particular spot, regardless of its microclimate, simply look up the degree day total for that date and general location on the map. The value that you read should apply to similar microclimates for any year, assuming that soil moisture is comparable. If you do this for a number of sites with different microclimates, you should soon get a feel for what numbers apply to south facing slopes versus flat versus north slopes. My numbers are for pretty average (flat) locations. I haven't found a nice, early spot on a south slope.

My plan is to nail down the earliest spots and then go to later spots based on the sequence worked out from previous picking dates. I've organized my morel database by calculating the average difference in picking dates between each location and the earliest one(s). That way I know what locations to check out each weekend after the first find. The database indicates that the date sequence is pretty regular.

For new locations, I would use the average degree day value or even a slightly higher value. You might be a bit late for the first morels, but that is better than being too early; you will certainly find more morels that way. Then next year you can adjust your timing. The maps automatically adjust for elevation differences, except where the terrain is steep.

I see that low elevation parts of southeastern WA, like around Kennewick, have already reached around 800 degree days F; so it shouldn't be long before the blacks are popping up there. I think Spokane will take quite a bit longer.

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Thanks vitog. Good info. I've never looked for morels in the lower elevation areas in Eastern WA. They're so bone-dry, it's almost desert. There must be enough moisture for morels in places but I've just never looked. I've seen reports of people finding morels in grape vinyards in other parts of the country, so maybe here too, but I'd worry about agricultural chemicals. I have a friend with a little vinyard down by Lind I could probably poke around in in a couple of weeks.

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EasternWA, for dry areas it's probably best to check out rainfall amounts during the last few weeks before the morels' ETA. A good source for that is the monthly forecast charts from AccuWeather. Just click on the month forecast for the nearest town and then select the chart version rather than the calendar version. However, I can't say what the minimum rainfall requirement might be. On the coast we rarely have to worry about too little rain during spring.

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  • 1 month later...

We where in the Priest River ID. area this week and the conditions are looking good for the start of morels.

I always go up to the Priest Lake area in the Fall but have never gone up for Spring mushrooms, since I usually do ok for morels closer to home. But Priest is so beautiful. I may go up there next weekend and stay in the cabin of one of my wife's friends. I have no idea where to look but maybe I'll check with the Forest Service and look for controlled burns or thinning operations.

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EasternWA, to give you an idea of the degree-day requirements for the earliest morels, I found one Black on a burned south facing slope when the DDF count had reached 775 at a nearby weather station. This was in a small burn with some cover remaining; so I would expect some burn morels to start popping when the DDF is even less.

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EasternWA, to give you an idea of the degree-day requirements for the earliest morels, I found one Black on a burned south facing slope when the DDF count had reached 775 at a nearby weather station. This was in a small burn with some cover remaining; so I would expect some burn morels to start popping when the DDF is even less.

I've found a smattering of blacks the last couple weeks. It's time to get more serious over the next month. I didn't see much in the way of 2011 fires when I checked geomac, so I'll need to find controlled burns or freshly logged areas if I want to get good quantities. Otherwise, it's hunting for the elusive "natural," which sometimes seems to be a lot of work for small rewards. We'll also check a 2 year old burn where we had moderate success last year. I've had decent luck with 2 year old burns in the past and this one seemed like it should have been great.

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Here in southwestern BC we also had a lousy fire season last year - no decent sized fires within a daytrip distance of Vancouver. I agree that finding "naturals" is much harder than finding burn morels. However, a decent natural morel site will keep producing year after year. The site that I used for the degree-day calculations discussed in the first post has been procucing every year since I originally found it in 2006. This year the morels popped up at that location right on schedule. That characteristic of natural morels allow you to catalog their locations and keep increasing production every year, as long as you find a few new sites every year. My database contains 156 locations that produced 1084 morels last year. It won't be much longer before I won't have enough time on weekends to visit all of the sites; so I will have to be selective about which locations to visit. That will be an easy decision; I will simply omit some of the sites that only produce a few morels or are located farther from the road. The best location produced 58 morels over 3 weekends last year, and it is so close to the road that I have to watch where I park because I might run over morels on the way. That same location has produced 38 morels from 2 visits this year; so it is pretty consistent.

I have to admit that it is possible to pick 1000 morels in one day in a good burn, but in the 7 years starting in 2006 only 3 have produced any burn morels; so that brings the average yield from burns down considerably. I like the consistency of natural morels, as well as the challenge of finding them.

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I do like searching for naturals, since I normally combine a nice hike with some prospecting. That way, finding morels is a bonus rather than the only purpose. Last weekend, I checked out an area that's new to me but looked promising on google maps. We didn't find a thing but had an enjoyable walk. Went back to a known spot nearby and found 8. I do need a better inventory of locations that produce naturals. I was so sure an area I was checking last year would produce but all I found was 2. I still think I can find morels there but the area is infested with mosquitoes and hobo camps, so I'll probably turn my attention elsewhere.

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  • 5 years later...

I know i'm a few YEARS late to this discussion- if anyone involved is still around though, I would LOVE to hear more about this, any updates on how your yields using this method have been since 2012? I'm really curious about this method, it speaks to a quandary that unites history and meteorology- the attraction of analyzing data predictively vs. the impossibly infinite magnitude of the variables involved. So if any of you Hari Seldon's have gotten this working, even as a general indicator rather than an exact one, that's really really cool, I can't wait to hear more.

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Hi Brendan.  I still use the method I described in the original post every year to determine when to search different areas where I collect natural morels; and it works very well, at least where I live, out west.  Dry weather will have an impact on the starting date, especially later in the season.  Here in southwestern BC, west of the Cascade Mountains, rain is usually reliable, at least until the end of April.  So early morel growth is largely determined by degree-days, but later populations may be delayed or shut down if rain doesn't arrive when it's needed.

In eastern North America rain is less predictable; so the degree-day calculations will probably only provide the earliest starting date, which will have to be adjusted in accordance with the availability of soil moisture.  Temperatures are also more variable in the east, and a late freeze could have an adverse affect on morel fruiting.  It may be that degree-day calculations are not as useful in eastern North America, but I have seen reports of such methods being successfully applied in Michigan and Minnesota.

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  • 7 months later...

For degree-day calculations I use base 32 degrees F, as described in the first post.  I've done the same calculations with other bases but found that 32 F worked best.  I'm not sure what you mean by single sine, but it vaguely reminds me of something I saw in the US degree-day Web site.  I don't use that site any more because my mother passed away a few years ago; so, I only look for morels in Canada.

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Hi vitog,

Please go to: http://uspest.org/cgi-bin/glinks35.pl

On the top right there are all sorts of settings that yield very different results.
There seem to be many different ways to calculate Degree Days.
I have no way which one is more accurate, but I want to look into your 1000 DD suggestion.
On a now broken/abandoned website they use 365 Degree Days. That's likely a very different way to calculate.

So if you remember any calculation settings, please share!
Do you use a similar site for Cananda? 
What calculation method did you use when you counted 'manually'?

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Hi Hoosier.

I tried your link and only got an Internal Server Error.  I used the link shown in my March 19, 2012 post, and then clicked on the Degree-Day Mapping Calculator link in the paragraph below the maps.  That link,  http://uspest.org/wea/mapmkrdoc.html  ,  has all of the settings for generating the map.  These are the settings that I think should work: thresholds, lower: 32 F, upper: 130 F; calc type: Single Sine should be OK (My method is the simple average.); start date: Jan 1; end date: (as required); data from: Current Year; Region & Subregion: (as reqd - smaller area will require less computer time); Mapsize: (depends on screen size, huge for mine); Image Type: jpg; Legend: heat ramp; Resolution: original; Network Selection: all networks; Overlay: none.

I just tried it for NW Washington state, and it worked just fine; although the legend was shown in an awkward manner.  I'm not aware of a similar site for Canada.

I use MS Access 2016 for my calculations.  It's set up for copying and pasting into the database the daily weather data from the two weather stations nearest the mushroom location.  The database then calculates the simple average degree-days from Jan1 to the selected date.  In order to forecast degree-days to a future date, I enter forecast or average temperatures for dates after the current date.

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Thanks for the info/link!
I was using this link: http://uspest.org/GL/ddmaps.html
Much less to configure than on your link.

But I'm missing one option.
Generate a map from your link.
Click on a town/weather station.
There you see "Thresholds lower 50F". Changing that option to 32F (this is not the base 32 option!) gives me a different number of degree days.
I want to come as close to your 1000 DD advise, so I need the correct settings.

The maps generated from your link are different, the shaded one looks really  nice, and above helpful. I'm at a spot where 3 or 4 colors touch. So at a glance I can see the hottest location which would be great for picking an early spring location.
But... I don't know that map uses "Thresholds lower 50F"

 

 

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I tried your link, and it showed several different maps for the whole Great Lakes Central USA region.  I tried the uppermost map (32 F lower threshold).  It shows that all of Indiana is above 2000 DD, and the only area near 1000 DD is north of Lake Michigan.  I also looked at Indiana using my link, and it generated a similar map.  I see that clicking on that map brings up some different settings.  That is because the default selection just below the map is for the click to generate a query.  You can avoid that by selecting the zoom in button and then click on the map location that you are interested in.

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I've been reading about some experiments predicting when the Morels grow.
One experiment took 15 years. Using soil temperatures is much more accurate than air temperatures.
The problem is that soil temps are far less availble than air temps.

You seem to have good success with air temps. Is your climate very stable?
My reasoning is that if the air temp is stable the soil temp is stable to and follows the air temp with a certain delay.
Some states, like Michigan, have very stable Degree Days. They climb in a very predicatable way.
Not so in Indiana, temps are all over the place.
That likely makes using air temps not a very good option.

I've found a website that has soil temps. Also historical, but they need to be looked up one by one. There is no option to show a list of any sort. Do you know of a more usable soil temp site?

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