By: Garden4Dinner

I don’t know about you, but I want a vacation and seedlings. Vacationing in a warm place when it is still cold at home is so nice. I don’t normally go on vacation, but this year I did. My goal was to have my plants “take care” of themselves while I was gone for 9 days. I love not having to water as often all of the time, not just while on vacation. I wanted to have an inexpensive and easy way to do this and this is what I came up with.

Most of my plants are in a dormant phase and require little amounts of water because of the winter, so I wasn’t worried about them. My seeds and seedlings really need their moisture though.

I started off by making a chart and keeping track of how often I was watering all of my plants. I started this 2 weeks before leaving for vacation. The length of my vacation will be 9 days, so I needed my self-watering to last that long. Before my self-watering seedling tray, I couldn’t wait 9 days between watering. Now I can wait over 2 weeks.

I purchased a Burpee Self-Watering Greenhouse Kit for my very first indoor seedlings several years ago, which is great at self-watering. It uses a fabric type watering mat and capillary action to wick the water up from the reservoir in the tray and up to the base of the plants. The Burpee trays are too expensive for me this year because I want 20 – 10”x20” trays. There is no way I am paying about $31 per greenhouse tray kit for all of my seedlings. Since I need more than just a few trays, this solution will save me a lot of money. My version also has a larger reservoir which holds more water. The cost of this project is $6.90 per tray for 9 self-watering tray systems.

The basic list of materials:

  • A Self-Watering Capillary Mat
  • 2 Plant Growing Trays – 20″ x 10″
  • An Exacto knife
  • Fabric scissors (Any nice new pair of scissors are excellent for cutting fabric. Cutting paper will dull the scissors and make cutting fabric difficult.)
  • A small amount of untreated wood (I used 1 ¼” x 1 ½” x 12”)
  • A way to cut the wood into pieces (saw?)
  • A ruler

diy self-watering seedling trayA picture of some of the materials

  1. Cut the self-watering mat into a 9 ½” by 24” rectangle.

diy self-watering seedling trayThe self-watering mat cut to 9 ½” by 24”

  1. Take one of the trays and the Exacto knife. Cut on both of the short edges of the tray as shown in the images below.

diy self-watering seedling trayCutting the short edge of one of the trays

diy self-watering seedling trayWhat one of the short edges of the tray looks like after it is cut

  1. On that same tray that was just cut, add holes with an Exacto knife (if there aren’t any already) to allow water to drip through the tray. This will prevent too much standing water. I made 24 holes total in my tray, evenly spaced along the bottom. When I did this, I discovered that if I could see through the hole, it was big enough for water to drip out.

diy self-watering seedling trayThe Exacto knife cutting a hole in the bottom of the tray

diy self-watering seedling trayI can see through one of the cut holes.

  1. Next, I tested to be sure the holes I created allowed water to drip through. I held my tray under the kitchen faucet and observed the bottom of the tray to make sure drips were coming down from the holes. Some water did drip out of where I cut the edges also, no big deal.
  1. Place the cut rectangle of self-watering mat on the tray and feed the mat through the edges that were cut.

diy self-watering seedling trayThe self-watering mat going through the newly cut edge of the tray

  1. Cut the wood into 6 blocks about 2” x 1 ¼” x 1 ½”. This isn’t an exact dimension. The important part is to make them the same height and make sure they are large enough to hold up a tray, but not too large to displace too much water.
  1. Distribute the 6 blocks evenly close to the edges onto the tray that has not been cut. This tray will be used for holding the water. The blocks should be placed to be 1 ½” high. This should hold the top tray up 1 ½”, so that the top tray still fits down in the bottom tray a little bit. If you purchase different trays than I did, make sure they are a little shorter than the height of the tray edges.

diy self-watering seedling trayWater reservoir tray with the wooden blocks

  1. Place the water reservoir tray under the tray with the self-watering mat. Feed the watering mat into the watering tray on the edges.

diy self-watering seedling trayHolding up the top tray to show the self-watering mat folds down into the watering tray

  1. There will be some extra slack in the self-watering mat. I generally let it fold up a little on the edges.

diy self-watering seedling trayA view from the top of the trays showing some slack in the self-watering mat

  1. Water the mat. Make sure it is all wet.
  1. Place the pots into the tray. I use peat pots which absorb the water well from the self-watering mat. I assume that using soil blocks or peat pellets would work well also. I am not sure how well it would work with plastic pots.

diy self-watering seedling trayThe completed self-watering tray with seedling pots

  1. There is a gap between the two trays. This makes it easy to add more water into the lower tray using a watering can. I fill it until it almost touches the bottom of the top tray.

If I am just starting seeds, I cover the top with some sort of plastic, like a plastic dome. This will make sure the moisture is held in enough for the seeds to start. Once the seeds start to germinate the plastic can be taken off.

I was able to self-water my plants for over 2 weeks without having to do anything! I had no problems with watering while on vacation!

Materials: (I assume some of the basic supplies like a saw to cut the wood, a ruler, scissors, and an Exacto knife are already available.)


  • 15 minutes – Once I had all of the supplies it was quick and easy to make.

Total cost: $44.83 (to make 5 self-watering kits and have left over self-watering mat)
Total time:
15 minutes

Do you use something for self-watering? What do you use? If you make this, I would be interested to hear how it works for you!

[Image Credit: ©2017 Garden4Dinner]