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How to Start and Care for Seedlings

Are you eager to start gardening? Here at Gertens, we have some tips on how to start and care for seedlings indoors, so you can start your vegetable, herb and flower crops before spring arrives. Follow these helpful guidelines for seeding success!


Seeding Supplies


Choose small individual containers that allow you to plant single seeds.  These come in many forms, such as plastic and compressed peat. Jiffy and Hydrofarm, as well as others, have designed seeding trays and flats just for this purpose.  The larger containers, 3-4” size, are used later as the small seedlings grow and need to be up-planted.  Since some of these containers can be re-used, be sure to disinfect with a mild bleach solution to prevent disease.


When planting seeds, it is very important to use a seed starter.  Seed starters are sterile, lightweight, and specially formulated for young roots.  Hoffman and Fafard Seed Starters are available in many sizes.


Adding a thin layer of vermiculite as a top layer just after seeding will provide easy emergence for the young shoots.  Be sure to use a coarse grade for best results.


Gertens carries a vast selection of top quality seeds, such as Lake Valley and Botanical Interest.  Be sure to read labels, they contain information on variety characteristics and maturity dates.  Refer to guides- some seeds need to be directly sown in the garden- where as others can be started indoors.

Humidity Domes

After seeding, the tray should be covered with a humidity dome.  This clear dome allows light to pass through while trapping heat and moisture inside for quick germination.  Gertens has available several choices; High Domes, Jiffy Easy Grow Greenhouse or Jiffy Professional Greenhouse as well as those included in the seeding kits from Jiffy.

Heat Mats

Applying heat to the bottom of a flat as the seeds germinate will increase your success and ensure a healthy root system.  Hydrofarm and Jump Start Heat Mats come in many sizes to suit your seeding needs.

Let's Get Sowing

Timing of the Crop

Following the recommendations on the seed packets will help determine when the seeds should be started.

Prepare the Tray

Open the seed starter mix and add a bit of water to moisten slightly.  Fill the cell tray to the top and press down very lightly- add more mix if necessary.


Jiffy Tomato Greenhouse

Plant one seed per cell.  The depth can be determined by reading the seed packet.  If older seed is being used- test germination and it may be necessary to plant more than one seed per cell. Coarse grade vermiculite then can be lightly layered over the seed.


Mark with labels.


Using a mist bottle will allow you to water to fully moisten without dislodging seeds.  Mist as needed to keep moist. Open the humidity dome often to let in fresh air.  As the seedlings grow, a fine nozzle watering can works well.

Growing Lights

While you may have success starting seed with natural sunlight, grow lights- such as those from Hydrofarm, will help develop a healthy, stocky plant.  Our Jump Start Grow Light Systems are an easy way to set up your seeding project.  More advanced lighting systems are available.


Once your seedlings have developed 4-5 sets of leaves, you will need to fertilize them.  A good choice would be Gertens Flower and Vegetable Fertilizer at ¼ the strength.


After sowing, the seed tray can be lightly watered using a plant mister to prevent dislodging the small seeds and seedlings. Once the plants have developed, a water can from Haws has the perfect watering nozzle for young seedlings.

Plant Markers

Labeling your seed trays is important.  Luster Leaf has a great selection of plant marking tags and permanent marking pens.

The Final Touches

humidity dome
Humidity Domes are great to help with moisture retention while starting your seeds.

Cover the flat with the humidity dome.  This can be removed once all seedlings are germinated.  Add a heat mat.  Grow lights can be used once the seedlings are germinated and the dome is off.  Hang the lights above the seedlings, and as the plants grow, raise the lights.


Once the seedlings outgrow their cells it is time to up-plant them into the larger 3-4” containers.  Potting soil can now be used.  We recommend Promix or Hoffman's All Purpose Soil.

Hardening Off

Young seedlings need to slowly acclimate to the outdoor conditions such as sunlight, wind, and cooler air temperatures.  This can be done by slowly introducing the sun and outdoor air.  Acclimation can take about two weeks before it is safe to plant your tender crops in the garden.