JSFiddle - React, Tailwind, and code Playground

HTML

<table>
	<tr>
		<td>
			<select class="plantSize" name="size_4">
				<option value=".5">.5 feet</option>
				<option value="1">1 foot</option>
				<option value="2">2 feet</option>
				<option value="10">10 feet</option>
			</select>
		</td>
		<td>Row 1</td> 
		<td>
			<input type="submit" name="Submit" value="Calculate" />
			<span class="recalcwarning" id="reCalc"></span>
		</td>
	</tr> 
	<tr>
		<td>
			<select class="plantSize" name="size_4">
				<option value=".5">.5 feet</option>
				<option value="1">1 foot</option>
				<option value="2">2 feet</option>
				<option value="10">10 feet</option>
			</select>
		</td>
		<td>Row 2</td> 
		<td>
			<input type="submit" name="Submit" value="Calculate" />
			<span class="recalcwarning" id="reCalc"></span>
		</td>
	</tr> 
	<tr>
		<td>
			<select class="plantSize" name="size_4">
				<option value=".5">.5 feet</option>
				<option value="1">1 foot</option>
				<option value="2">2 feet</option>
				<option value="10">10 feet</option>
			</select>
		</td>
		<td>Row 3</td> 
		<td>
			<input type="submit" name="Submit" value="Calculate" />
			<span class="recalcwarning" id="reCalc"></span>
		</td>
	</tr> 
</table>

JavaScript

$(document).ready(function() { 
    $(".plantSize").click(function() { 
        var span = $(this).closest("tr").find("span.recalcwarning"); 
        span.css({ color:"red" }).html("Click button to update after making changes.").width(400); 
    });
});