Urban Farming: Indoor Starter Plants From Seed

Introduction: Urban Farming: Indoor Starter Plants From Seed

Starter plants are grown indoors when the weather outside is too cold. They can also give you a head start on turning over your garden. When you have plants in the garden that are a few weeks away from harvesting, it is a great idea to start planning what will take their place and get new plants started indoors. This will keep your garden more productive and reduce the time between your harvests.

Growing plants from seed is pretty easy. But, growing really healthy starter plants from seed indoors requires some additional assistance. Seedlings need water, soil, warmth and light to grow well. Living in an urban setting, we rarely have a window that provides direct sunlight all day long. In the northern hemisphere, the south facing windows will get the most sun. My south facing windows are blocked half of the day by my neighbors house. My east and west facing windows get sun for about half a day. When I started seeds indoors, they started well, but then grew long, skinny and bent over. When this happens, they aren't very robust and take longer to take hold in the garden. For a long time, I was reluctant to try grow lights or heating mats, because of the extra cost. But both of these have made a big difference in germination and growing healthy starter plants. I put together this instructable to help anyone who suffered from this same problem. Take the plunge and do it. Although there is additional cost, you will be much better off in the long-term, and your gardening experience will improve.


  • Plant Growing Tray: 20" x 10"
  • 6-Cell Seed Starting Tray (8 per growing tray). Make sure these have holes on the bottom to drain. I re-use the trays I get when buying nursery starts.
  • Planting Mix: remove any large pieces.
  • Pencil
  • Seeds
  • Heating Mat for 20" x 10" tray
  • Grow Light: I use the Hydro Farm 2' Jump Start System. It claims to be twice as efficient with 20% more light intensity than standard grow lights. It has worked well for making my starters more robust.
  • Timer: analog, grounded (3 prong)
  • Spray Bottle


  1. Fill the 6-cell trays with planting mix. Do not push down and compact the planting mix in the cells. If it is too loose, you can gently shake the tray or drop it from an inch or two above the ground. This will compact the soil slightly without compacting it too much. Place the tray into the growing tray. I like to use the 6-cell containers since 8 of them will fit into one plant growing tray and they can be shifted around as needed when the plants start growing.
  2. Make small holes in each cell based on the seed you are planting. I use a blunt pencil tip to do this. Any small stick can work. Generally, the depth of the holes should be 1-2 times the size of the seed. I will usually plant 2-3 seeds per cell. You can always thin out and keep the strongest plants. Cover and water. I use a spray bottle to water initially. If the planting mix is a little dry, then it will not absorb a lot of water quickly. Using a spray bottle lets the moisture sink in. I also water by directly pouring a liter of water into the tray and letting the water soak up from the bottom.
  3. Place the heating mat in your desired sunny location. I place a piece of foam under the heating pad since I don't want to waste energy heating my tabletop.
  4. Place grow lights over the tray. It is recommended to adjust the height so it is 2-4" above the trays/plants. I use an analog, grounded timer to turn the light off and on. It is set to run 14 hours a day from 6am to 8pm. If you desire, you can set the light to be off when you get strong sunlight. The grow light will help the seedlings grow naturally and not become long and stringy.
  5. Once the seeds have germinated and grown their first leaves, you no longer need the heating mat. If your growing area is really cold, your plants my benefit from having the heating mat on for a longer period of time.
  6. Water and adjust the height of the grow light as needed, keeping it 2-4 inches above the plants. One growing tray needs about 1/2-1 liter of water per day. Once the starters reach transplant size, they can be moved into the garden. You want the plants to be around the size that you find at the nursery. If they are too small and fragile, you may damage the plant when you are pulling it out of the cell. The soil won't hold together and the roots will be damaged. Typically, when roots start to grow out the bottom of the cells, they are more well-formed in the cells and make for easier transplanting.

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    3 Discussions


    11 months ago on Introduction

    This is great! May I reblog this on our website? Thanks!

    Penolopy Bulnick
    Penolopy Bulnick

    4 years ago

    Looks like a great little garden. What all are you growing?

    TLP Shop Lab
    TLP Shop Lab

    Reply 4 years ago

    Thank you for your interest. The main picture has in the middle tray: cucumbers (front right), beans (front left), Squash (middle right) and Snow Peas (back). The tray on the right has some succulents that we are trying to propagate. In the second to last photo, we have Curly Leaf Kale, Romansco Broccoli, Tong Ho (Asian vegetable), Lettuce and Shallots. They are all getting ready to go into the garden!