user87444: Premise:
I'm trying to determine a good way to architect getting data from 4 plant monitors to a single Arduino. For context, that Arduino will have a Wifi connection that will transmit the data from the plant monitors to a web server internally.
Setup
Where I'm struggling to make a decision is how to go about hooking the sensors up.  Here's my plant setup:

Materials
Tools I have at hand:

Many Arudino Micros
Arduino Unos
Arduino Mega
Raspberry Pi 4 B
4x Monk Makes Plant Monitors
Wiring stuff and power supplies, basic electronics prototyping collection.

Solutions?
I would like to place 4 monitors into different plants (doesn't matter which ones at the moment, if it does, I can specify).  What I've considered:

All 4 plant monitors directly wired to the Arduino Mega.  This requires a 1k resistor in line of the data pin, which I'm not sure I have a good solution for that without a breadboard.  Also, I wasn't sure if the length of data line would be a problem.
Each Plant Monitor is hooked up to an Arduino micro and then use the USB of the micro to the RPI.
Like #2 but use I2C to send data to Arduino Mega. I would need to supply power to these minis then.
There are some options without using Arduinos, but since is the Arduino SE, I'm happy to keep it with this.

I'm open to other options as well, as well as possibly needing to purchase/make another part to optimize the solution some.

user37622: The distances between the plants on the shelf are in general too long for TTL level communication and soon you may want to connect more sensors at plants elsewhere in the room or even in other rooms.
In my opinion the solution proposed by dandavis, using esp-01 with WiFi or esp-now is the most simple and universal solution. I see no problems with the implementation. The esp-01 is small and will play nice with the 3.3 V sensor. Maybe it can be even made battery powered and then there are no cables between plants.
If wired solution was required, I would recommend to use RS485 bus. With RS485 modules with AutoDirection control the sensors could be directly connected to the RS485 module without a MCU at every sensor.

87444: <h2>Premise:</h2>
<p>I'm trying to determine a good way to architect getting data from 4 plant monitors to a single Arduino. For context, that Arduino will have a Wifi connection that will transmit the data from the plant monitors to a web server internally.</p>
<h2>Setup</h2>
<p>Where I'm struggling to make a decision is how to go about hooking the sensors up.  Here's my plant setup:</p>
<p><img src="https://i.stack.imgur.com/FIweI.jpg" alt="Three tiered plant shelves with 11 plants." /></p>
<h2>Materials</h2>
<p>Tools I have at hand:</p>
<ul>
<li>Many Arudino Micros</li>
<li>Arduino Unos</li>
<li>Arduino Mega</li>
<li>Raspberry Pi 4 B</li>
<li>4x <a href="https://monkmakes.com/pmon" rel="nofollow noreferrer">Monk Makes Plant Monitors</a></li>
<li>Wiring stuff and power supplies, basic electronics prototyping collection.</li>
</ul>
<h2>Solutions?</h2>
<p>I would like to place 4 monitors into different plants (doesn't matter which ones at the moment, if it does, I can specify).  What I've considered:</p>
<ol>
<li>All 4 plant monitors directly wired to the Arduino Mega.  This requires a 1k resistor in line of the data pin, which I'm not sure I have a good solution for that without a breadboard.  Also, I wasn't sure if the length of data line would be a problem.</li>
<li>Each Plant Monitor is hooked up to an Arduino micro and then use the USB of the micro to the RPI.</li>
<li>Like #2 but use I2C to send data to Arduino Mega. I would need to supply power to these minis then.</li>
<li>There are some options without using Arduinos, but since is the Arduino SE, I'm happy to keep it with this.</li>
</ol>
<p>I'm open to other options as well, as well as possibly needing to purchase/make another part to optimize the solution some.</p>
 37622: <p>The distances between the plants on the shelf are in general too long for TTL level communication and soon you may want to connect more sensors at plants elsewhere in the room or even in other rooms.</p>
<p>In my opinion the solution proposed by dandavis, using esp-01 with WiFi or esp-now is the most simple and universal solution. I see no problems with the implementation. The esp-01 is small and will play nice with the 3.3 V sensor. Maybe it can be even made battery powered and then there are no cables between plants.</p>
<p>If wired solution was required, I would recommend to use RS485 bus. With RS485 modules with AutoDirection control the sensors could be directly connected to the RS485 module without a MCU at every sensor.</p>
