Starting Seeds

Growing plants from seed allows you to grow a wider range of varieties, and often at a significant savings over purchasing more matured plants. It is also fun & satisfying!

Here are a few guidelines for starting seeds:

You will need a clean, well-drained medium for germinating your seeds. Seed starter blends are actually soil-less and are usually made up of perlite or vermiculite and peat moss.

Perhaps the most convenient way to start seeds is in a specially designed seeding tray, but you can use a wide range of containers as long as they have adequate drainage. If re-using a container it is important to thoroughly clean and sterilize it first.

The general rule of thumb is to plant seeds two to three times as deep as they are wide. When in doubt, err on the shallow side – planting your seeds too deep will inhibit germination. Some seeds need light to germinate so should not be covered by soil at all. Planting depth information is usually included on the seed packet.
Seeds need to be warm to germinate – most like temperatures between 65 &75 degrees Fahrenheit. If you do not have a warm spot in your house you can purchase warming germination mats to put under your seeding flats. Supplemental heat only needs to be provided until the seeds sprout. After that, the lights they are growing under should provide adequate heat.
Even a South facing window usually will not provide enough light to start seedlings. Full spectrum lights should be hung as close to the seedlings as possible, about 2”-3” above. Raise the lights as the seedlings grow to maintain this same distance. Once the seeds germinate the lights should be kept on 16 hours a day and off 8 hours a day. The easiest way to achieve this is to hook your lights up to a timer.
Keep moisture levels high for germination by covering your seed tray with a clear plastic top to lock in moisture. Once seeds germinate remove the plastic cover. Check your plants every day. Soil should be kept moist but never wet. Spraying with a mist bottle is a good way to water young seedlings.
Make sure to label your seeds! We usually simply mount the seed packet on a small stake at the top of each section of seeds.
starting seeds flower vegetable seed seedling container johnson's gardens cedarburg garden center
starting seeds flower vegetable seed terrarium hot house greenhouse johnson's gardens cedarburg garden center

Starting Seeds – Flowers

PlantWhen to sow seeds indoorsNotesBest sown outdoors
Ageratum6-8 weeks before last spring frostdo not cover seed (need light to germinate)
Amaranth6-8 weeks before last spring frost
Bachelor ButtonDirect Seed in May-can tolerate light frost
CalendulaDirect Seed in May-can tolerate light frost
Castor Bean6-8 weeks before last spring frostsoak seed before sowingSeed outdoors after last spring frost
Celosia4-6 weeks before last spring frost
Cleome6-8 weeks before last spring frostDirect Seed in May-can tolerate light frost
Coleus6-8 weeks before last spring frost
Cosmos4-6 weeks before last spring frostSeed outdoors after last spring frost
Gomphrena6-8 weeks before last spring frost
Hyacinth Bean VineSeed outdoors after last spring frost
Impatiens6-8 weeks before last spring frostdo not cover seed (need light to germinate)
Marigold4-6 weeks before last spring frostDirect Seed after last spring frost
Morning Glorysoak seed before sowingSeed outdoors after last spring frost
NasturtiumSeed outdoors after last spring frost
Nicotiana6-8 weeks before last spring frost
Nigella6-8 weeks before last spring frostDirect Seed in May-cold tolerant
Petunia8-10 weeks before last spring frostTiny seed (mix w/ sand)/do not cover (need light)
Poppy (annual)Seed outdoors after last spring frost
Salvia6-8 weeks before last spring frost
Snapdragon6-8 weeks before last spring frostTiny seed (mix w/ sand)/do not cover (need light)Direct Seed in May-cold tolerant
Sunflower4-6 weeks before last spring frostDirect Seed after last spring frost
Sweet AlyssumSeed outdoors after last spring frost
Sweet Pea (annual)soak seed before sowingSeed outdoors after last spring frost
Tithonia6-8 weeks before last spring frost
ZinniaSeed outdoors after last spring frost
starting seeds flower vegetable seed growing greenhouse johnson's gardens cedarburg garden center

Starting Seeds – Vegetables

PlantWhen to sow seeds indoorsWhen to sow outdoors
BeansJune
BeetsJune
BroccoliMarch/AprilMay
Brussel SproutsAprilMay
CabbageMarch/AprilMay
CarrotsMay
CauliflowerMarch/AprilMay
CornJune
CucumberJune
EggplantMarch/AprilJune
Garlic (bulbs)October-December
KaleMay
LettuceMay-August
MelonsMay
OnionsFebruary-AprilMay
PeasMay-July
PepperAprilMay
Potatoes (tubers)April-May
PumpkinAprilJune
RadishMay-August
SpinachAprilMay-August
Squash (Summer)June
Swiss ChardAprilMay-June
TomatoAprilN/A
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