Seed Starting Indoors


Herbs, vegetables, annuals, perennials and wildflowers can all be grown from seed in your own home.  It’s a very satisfying and economical late winter past time.  It is also a great family activity that triggers a sense of wonder in children.  The diversity of nature is particularly evident in this process because different seed varieties require different amounts of time to germinate and grow before taking them outdoors to plant in the garden.  Some even need special pre-treatment before sowing like chilling, nicking the seed coat with a sharp knife, or soaking overnight.  Read the back of each seed package carefully to learn its’ particular preferences.

We often need to give plants a critical head start by germinating and growing seedlings in the warm indoors in early spring. When it warms up outdoors in late spring, we can plant sturdy, well-established seedlings to bear fruit or flowers before cold weather sets in.  Favorites like tomatoes and peppers are both plants that need a long warm growing period to set and ripen a good crop. Except in the most tropical areas, all U.S. summers are too short for them to complete their fruiting cycles before summer’s end if started directly in the ground, since seeds won’t germinate until frosts have ended and weather warms up.  Another reason to start your own seeds is the ability to grow some of your favorite varieties that may not be available as plants in your area.  There are many heirloom varieties that fall into this category.

It's critical to follow the timing instructions on the seed packet when to start your seeds indoors.  If you start too early they’ll become tall, leggy, and root bound before they can be planted in the garden.  Other seeds if started too late will have a lot of catching up to do in the garden.  Remember that most perennials started from seed shouldn’t be expected to bloom until their second year.

One of the easiest ways to start seeds is to use a mini-greenhouse or seed starting kit that consists of a drainage tray, plastic cell pack inserts, and a clear humidity dome.  Some even have a capillary mat that absorbs water from below to act as a self-watering mechanism.  Jiffy pellets can also be used to plant seeds. Jiffy Peat Pellets that are soaked in water until they have expanded to seven times their size.  Each Jiffy pellet becomes a small growing sack with peat soil large enough for sowing two to three seeds.  Jiffy pellets, individual peat pots, & biodegradable peat cell packs can be planted directly into the garden in spring, preventing any root disturbance.  

Choose a soil specifically designed for seed germination. These soils are very light, allowing fragile young roots to grow easily.  They also allow for easy air penetration and are sterilized to eliminate insects and disease.  Don’t use topsoil, triple mix, or houseplant soil.  The first two aren’t sterilized and the latter is too heavy a mixture.  When you’re ready to start your seeds, it’s a good idea to slit open the top of the bag of soil, add some water, and let it stand overnight.  Fill your plastic or peat cell packs or pots with the pre-moistened soil and spread two or three seeds over the surface of each compartment or pot.  Lightly cover the seeds with more soil or, if specified on the package, leave the seeds exposed to direct light.  Set your cell packs or pots into a drainage tray.  The mini-greenhouse has a plastic cover that can be put over the drainage tray.  Don’t snap it onto this tray.  Rather, leave a small gap for air circulation.  This is left on until the plants touch the cover, then it’s permanently removed.

At a temperature of about 60 to 75 degrees F, most seeds will germinate in a few weeks.  For most annuals and vegetables, a temperature of 72 degrees F is just about perfect for germination. Many perennials can tolerate a slightly lower temperature. The best seed germination results when consistent bottom heat is applied.   Seedling heat mats are especially designed for this purpose. This gentle warmth warms the soil to promote the quickest and most consistent germination.

Keep your seeds under natural bright light or lamps that are kept 15 cm (6 inches) above your seed flats.  Be sure to identify what’s sown in each flat by writing on seedling labels with a permanent marker.  You’ll need several labels if there’s more than one variety in a flat.

Don’t allow your seedlings to dry out.  Water them from a mister bottle when the soil surface is dry.  Watering with a watering can gives too forceful a spray and will probably dislodge the seedlings and the soil.

To plant young seedlings outdoors, you need to “harden” them off to ensure they can withstand fluctuating temperatures and wind.  A week ahead of the time scheduled weekend, place the trays outside in light shade for a few hours each day, bringing them back in at night.  Each day move them into a bit more light until they’re finally in full sun.  If you put the flats in direct sun, the foliage burns and the leaves will have to be plucked off.  Some seedlings can tolerate frost and can be planted earlier than May 15 (Zone 6 frost free date).  These seedlings will have the earlier transplanting date on the seed package.