Do it.

Natur 2 [nur Sg.] Gesamtheit der Tiere, Pflanzen, Gesteine, Gewässer, unberührte Landschaft; draußen in der freien N.; in die N. hinauswandern http://www.wissen.de/wde/generator/wissen/ser...

Natur 2. [Gesamtheit der] Pflanzen, Tiere, Gewässer u. Gesteine als Teil der Erdoberfläche od. eines bestimmten Gebietes [das nicht od. nur wenig von Menschen besiedelt od. umgestaltet ist]: die unberührte, unverfälschte, blühende, liebliche, erwachende, wilde N.; durch die Industrieanlagen wurde die N. verunstaltet, verschandelt; ein Stück einsame N. suchen; in die freie N. (ins Freie) hinauswandern; diese Pflanzen gedeihen nur in freier N. (wild wachsend, lebend); antike Tempel werden in die N. (Landschaft) gestellt (Bild. Kunst III, 29);
© 2000 Dudenverlag

the open air a place outside rather than in a building
He likes to cook in the open air. http://www.oxfordadvancedlearnersdictionary.c...

the open air outdoors
in the open air The dancing was outside, in the open air.
Jane wanted to rush to the door and get out into the open air.http://www.ldoceonline.com/dictionary/open_1
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Reiterferien in Österreich - reiten in der Naturhttp://zeitreisen.zeit.de/ratgeber/oesterreic...

Simple pleasures – a walk in the countryside, the discovery of local wildlife and, above all, time together as a family http://www.guardian.co.uk/national-trust-time...

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Unabhängig davon, ob ein Gärtner nun die Natur schützen, die Lebensmittelindustrie boykottieren oder einfach vom Büroalltag entspannen will, tut er bei der Gartenarbeit nebenbei etwas für seine Gesundheit: Wer sich in der Natur aufhält, hat bessere Laune und einen niedrigeren Blutdruck.http://www.zeit.de/zeit-wissen/2011/s2/Natur-...

Another early success is an organic market gardening scheme, run by Mind in Solihull. "People are eating the healthy fruit and vegetables, getting physical activity out in the open air, and doing something constructive.http://www.guardian.co.uk/society/2007/oct/31...

Capturing the Beauty of Nature by Working in the Open Airhttp://query.nytimes.com/gst/fullpage.html?re...

Is there another more popular way of saying "in the countryside" in AE? Most NY Times articles featuring it seem to be about the UK, Australia, anywhere but the US.

"In die Natur" literally means "into the countryside", describing movement. In English you'd talk about going for a walk in the countryside, so "in the countryside" would work for Germans looking up "in die Natur". However, for English people looking up "in the countryside", "in die Natur" will not work if they mean "I have a house in the countryside".

The fact that the German side will say "in die (Akk.) Natur" will help anyone who knows about grammar, but for people who don't know as much, how about adding this extra entry "in der Natur" to make it more obvious that there's a difference?

(Leo also has Erholung in der freien Natur - recreation in the open air.)

Is there another more popular way of saying "in the countryside" in AE? Most NY Times articles featuring it seem to be about the UK, Australia, anywhere but the US.

Americans would call it the great outdoors.

Siehe Wörterbuch: the great outdoors

country
http://www.merriam-webster.com/dictionary/country
noun
Definition of COUNTRY
1 : an indefinite usually extended expanse of land : region
4 : rural as distinguished from urban areas

* He moved to the north country to fish and hunt.
* We went camping in the hill country.
* They drove through miles of open country.
* She lives out in the country.
* They prefer the country to the city.

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coun·try
http://dictionary.reference.com/browse/country
–noun
5. rural districts, including farmland, parkland, and other sparsely populated areas, as opposed to cities or towns: Many city dwellers like to spend their vacations in the country.
6. any considerable territory demarcated by topographical conditions, by a distinctive population, etc.: mountainous country; the Amish country of Pennsylvania.
7. a tract of land considered apart from any geographical or political limits; region; district.

"Great outdoors" works, but I find it a bit too...cheesy? inflated? for normal use. I would be inclined to mark that [hum.]. But that might just be me.

"Countryside" didn't bother me when I first read it, but since you asked, CM2DD, I might be more likely to just say "country."
I spent the weekend:
-out in the country.
-hiking in the country
-going out to the country.

I read this idiom at dictionary.com: "go to the country, British . to dissolve a Parliament that has cast a majority vote disagreeing with the prime minister and cabinet and to call for the election of a new house of Commons. Also, appeal to the country."

In light of this idiom, perhaps in GB you don't use "country" to mean "countryside"? I don't have any evidence that's its chiefly US, though.

For me 'countryside' is more typical in contexts where it means the landscape or the appearance of the landscape, seen as a view, like a picture:

The whole countryside was green after the rain.

But in the context of getting out into nature:

They used to drive out in the country on Sunday afternoons.
She has a house in the country.
a walk in the country

I don't think I would use 'countryside' for any of those.

I could also support 'the open/fresh air,' and 'outdoors,' but I agree with Strawberry that 'the great outdoors' is humorous or clichéd.

>>Landschaft, die fast nicht von Menschen verändert wurde

Is that citation from a particular published dictionary? Commercial sites like thefreedictionary are not themselves very serious sources.

If 'die Natur' always has that implication, you might need something like 'unspoiled nature,' 'pristine/undisturbed natural area(s),' or just 'the woods,' 'the prairie,' etc., though 'wilderness' is probably too far. There's some discussion somewhere in the archive about wilderness/nature preserves/reserves etc. In any case, just 'the country' is liable to be mainly fields, pastures, and farmhouses, which is far from untouched by humans, even if it's not the city.

This makes me think of the Schubert song 'Im Grünen,' which also doesn't translate very easily 1:1.

- Lernen in der freien Natur-was gibt es schöneres
- Mitten in der freien Natur und doch mit einer Top-Infrastruktur
- Outdoor in Schweden - Aktivitäten in freier Natur


Google Books:
- In freier Natur: spannende Tiergeschichten aus aller Welt
- Im Studio oder in freier Natur Nicht jeder ambitionierte Amateurfotograf verfügt über ein komplett eingerichtetes Fotostudio.
- Bei günstigen Umweltbedingungen in freier Natur oder sekundär in menschlichen Wohnungen steigt andererseits die Artdensität sehr schnell und überraschend hoch, so daß es zu Invasionen kommt, besonders bei den Skorpionen Tityus ...


LEO:
the great outdoors --- die freie Natur

Ich wuerde der "Natur" noch ein "frei" spendieren, da dies die meiner Ansicht nach die haeufigste Verwendung ist. Persoenlich kann ich die Verwendung von "outdoors" im Englischen hierzu bestaetigen.

open air/fresh air - Natur wuerde ich eher nicht unterstuetzen. Die Verwendungen sind meiner Meinung nach anders. "Dining in the open air" kann auf der Terasse sein, was dann nicht in der Natur waere.