JRiepe Loc: Southern Illinois

18mm may not be wide enough for his needs on a crop sensor.

CHG_CANON Loc: the Windy City

Don't buy a single piece of additional equipment until seeking review and advice on your current images. Post unedited JPEGs being sure to store the image files.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

IMHO, this lens is a NIKON lens and the most affordable lens yet the sharpest lens you could ask for.
https://www.bhphotovideo.com/c/product/1341603-REG/nikon_20067_af_p_dx_nikkor_10_20mm.html

uhaas2009

Older lenses with aperture ring won’t auto focus. I don’t think the 5xxx doesn’t have the screw drive focus build in

camerapapi Loc: Miami, Fl.

"What is the best (affordable) wide angle zoom lens for a Nikon D5300 for nature photography."

If you are looking for an affordable lens for nature photography for your D5300 the 18-55 kit lens is very hard to beat. I use two Nikon lenses with my D7000, the 18-70 AF-S and the 18-200 VR. The 18-70 has been an exceptional performer for me. Last year the AF stopped working and the repair of the lens was more expensive than buying a used one. Ever since I use it in manual focus. The 18-200 VR has had some bad reviews but it also has worked beautifully for me and it will work like that for anyone that understands that the lens at the longests focal lengths, beyond 85mm, will be close or at maximum lens opening of f5.6. That means that an aperture like f8, which works beautifully below the mid range of the lens will not render the best performance at the longest focal lengths if the operator wants maximum sharpness and depth of field.

If 18mm is an acceptable focal length for your nature photography Nikon has several lenses starting at that focal length that are excellent performers.

MrBob Loc: lookout Mtn. NE Alabama

As others have Said, Tokina 11-16 2.8 is a WONDERFUL and affordable lens for APS-C bodies. I have had one on my Canon for over 10 years. Make sure on your Nikon you have later ver. which will auto focus. BELIEVE me, you cannot go wrong with this lens for the price...

ELNikkor

The Nikon 18-55 kit lens for that camera will give you excellent results. I never needed a wider or longer lens for landscapes with my D5100. It is very sharp, has great color, and focuses close. It is really a "bang-for-the-buck" lens! (If on occasion, you do want wider, just do panning and stitching.)

skipwv Loc: West Virginia

I love my Nikon 10-20mm. I don’t use it a lot, but it delivers nice, crisp shots when I need one.

RolandDieter

... or if f/2.8 is not fast enough for what you may shoot there is the Tokina 14-20 f/2.0 which is also very highly regarded

Architect1776 Loc: In my mind

Nikon 10-20mm reasonable and well made for your camera.

RolandDieter

Based on the replies you got, including my earlier one, your first decision is not which lens but what focal length. Decide on how wide you want/need to go and then pick a lens. At that point, the aperture you need should be added to the criterion. I got the Tokina 14-20 for the f/2 in low light interiors. Absent that need I would have bought the 11-16 f/2.8 ... although, if I shot Nikon I might prefer their 10-20 over the Tokina 11-16

ronpier Loc: Poland Ohio

I use my Tamron 17-50 f2.8. Great DX lens. No longer produced but available used.

starlifter Loc: Towson, MD

That 18-55 is hardly a wide angle, more like a 27-82 0n a cropped sensor camera.

Architect1776 Loc: In my mind

For decades 28mm was considered wide angle except for the well heeled who could afford the ultra wide 24mm.