Start seeds indoors to get a jump on spring

In Gardening by tonka_admin

Starting seeds indoors is a great way to get a jump on spring.  Seeds are relatively inexpensive and there is a vast array of unique varieties to choose from.  With a little extra effort early in the spring, you will reap great rewards later in the summer.

It is so rewarding to eat and taste fresh veggies right from the garden or to watch pollinators as they flock to your beds and borders for a taste of sweet nectar.

Tonkadale offers a wide variety of flower and vegetable seeds, as well as seed starting supplies to get you growing this spring.

For additional information, check out Starting Seeds Indoors by the University of Minnesota Extension Horticulture.

About seed starting

Seedling tomatoes

Photo by Dennis Brown

There are various guidelines for sowing seeds indoors depending on the varieties you choose.  Follow the directions on the seed packet for sowing and planting out dates. Usually these dates correspond with the last frost date in your area. In the Twin Cities/Metro Area, the last average frost date is May 15.

For example:

  • Sow crops like tomatoes and peppers indoors,
 6 weeks before the last average frost date.
  • Sow crops like cucumbers and squash indoors,
 4 weeks before the last average frost date.
  • Plant tomatoes, peppers, cucumbers and squash transplants outdoors 
when the soil is warm and the night time temperatures are consistently
above 45° F, about 2 weeks after the last average frost date.

Heirlooms vs. Hybrids

Hybrid seeds are commonly defined as seeds that are produced from cross-pollinating plants chosen for their superior genetic traits. Hybrids are bred to improve the characteristics of the resulting plants, such as better yield, greater uniformity, improved color, disease resistance, and so forth. Hybrid seed cannot be saved, as the seed from the first generation of hybrid plants does not reliably produce true copies.

The definition of the use of the word heirloom to describe plants is highly debated. A true heirloom is a cultivar that has been nurtured, selected, and handed down from one generation to another for many generations. There are also open-pollinated varieties that are bred and stabilized using classic breeding practices.  Many heirloom vegetables have kept their traits through many generations through open pollination.

 and soil

The sky is the limit when it comes to seed starting containers.  You can make your own out of toilet paper rolls, newspaper, plastic lettuce containers, yogurt cups, milk jugs, etc. Just check out your recycling bin.

Many types of containers are also available 
to purchase at Tonkadale:

  • Plastic pots and containers.
  • Rice-hull pots.
  • Biodegradable pots.

Make sure to use germination mix when starting seeds.  Germination mix is lighter that regular potting soil and provides good drainage and aeration.  Tonkadale recommends Espoma’s Organic Seed Starting Mix.

Drainage and airflow

To ensure success, make sure your pots and containers have adequate drainage. Good drainage and proper airflow promote healthy seedlings and prevent disease.


In general, bright light is required for seedling growth. There are a few crops, such as lettuce seeds, that also require light to germinate. Check your seed packet for germination light requirements.

Once the seeds have germinated, provide bright light close to the height of the seedling. This promotes strong, sturdy growth and limits stretching.


Seeds need warm soil temperatures to germinate.  65- 75° F is the general range. Again, check out your seed packets for detailed temperature information. Many seed-starting enthusiasts provide bottom heat when starting seeds. Others rely on the ambient heat from heaters and radiators.


Moisture and humidity are important to seed starting success.  When seeds are germinating, increased humidity is required. Cover containers with plastic wrap or a plastic cover to increase the humidity next to the soil.  As soon as the seed germinates, remove the plastic wrap. Water frequently to keep moisture levels high, but be careful not to flood out seeds and seedlings.


After the first true leaves develop, it is time to start fertilizing your seedlings. Use a half-strength liquid fertilizer regimen on a weekly basis.  Miracle Gro’s All Purpose Plant Food will work just fine.

Hardening off and transplanting

Before seedlings can be planted outdoors, they need to be hardened off, or acclimated to direct sunlight and fluctuating temperatures. It is best to do this over a three-day period by placing them in direct sunlight during the morning of the first day, then increasing their time outside by a few hours each day until they are vigorous enough to be transplanted.

Mixing special soil amendments with your seedling starts helps promote vigorous growth, proper nutrition, robust blooms and heavy yields.  These are some of our favorites:

Bone Meal – Great for vigorous blooms and sturdy stems.

Coop Poop – High is calcium (which is great for tomatoes), stimulates microbe activity, disease resistance and overall for soil health.

Wiggle Worm Earthworm Castings – Higher yields and increased growth.

How to grow onions

Onions can be purchased in sets and planted as soon as the soil warms, early April in Minnesota.  Onion sets are short day varieties and bulbs usually grow as large long day varieties.

Onions need full sun and prefer a well-drained soil with plenty of organic matter.

Plant the pointy side up, 1”-2” deep and 3”-4” apart.  Firm soil around the bulbs

Soak the soil thoroughly when watering, to a depth of at least 1 inch each week during the growing season.

Harvest onions when about half the tops are falling over and dry. Undercut and lift bulbs with a spading fork.

Visit for more detailed information.

How to grow potatoes

Purchase seed potatoes that are fresh and firm.  Seed potatoes can be planted as soil warms: early April in Minnesota.

Cut potato tubers into 2 oz. pieces.  Make sure there is at least one eye per piece.

Allow pieces to dry on newspaper overnight.

Prepare a deep and loose soil bed. Adding compost helps add needed nutrients to the soil.

Plant potato pieces 4 inches deep, eyes facing up, and cover with soil.

Space tuber pieces 12 inchese apart, rows 36 inches apart.

Hill the soil around plants as they grow.

Harvest by gently loosening the soil with a pitchfork – 7-8 weeks after planting for “new potatoes”, or when the foliage has dried out and fallen over for fully mature potatoes.

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