Seed Starting 101

Seed Starting Tips Step by Step

Seeds are nothing short of magic!

You hold this seemingly inanimate object in your hand. Once you place it in soil, give it some water and light it GROWS! And it keeps growing, giving pollinators a purpose and habitat, sequestering carbon, building soil, and giving you food—plus providing its own seeds to continue the process.

Being part of this process ties us back into nature in a way that very few things can. And more of us are feeling that pull back to nature as gardening continues to grow as a hobby and passion across the globe.

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Why Start Seeds?

On a more practical level, an obvious benefit of growing a garden from seed is major cost savings. A packet of seeds is usually less than the cost of a single small potted vegetable or herb start. Add perpetual savings if you can save the seeds that grow from the plants as well. More about this in my article, Seed Saving Starts Now.  

Remember only open pollinated varieties are recommended for seed saving, as these are the only kinds that will grow back ‘true to type’. Many seeds sold are hybrids, meaning that they took certain traits from two different plants and combined them. Growing seeds saved from those hybrids will likely revert back to parts of their parent plants, sometimes with really funky outcomes!

Plant Diversity

There are thousands more varieties of seeds to choose from compared to the numbers of plants available to purchase already started in nurseries. I counted over 100 lettuce varieties in one seed catalog! This is similar to the differences in selection at the grocery store versus a Farmers Market…

Plus, you can choose seeds for fast maturing, cold tolerant, different colors (like carrots) and so many other traits. Not to mention that saved seeds become acclimated to the conditions they grow in. You can also play more with Companion Planting when you choose your own seeds.

How To Start Seeds

Timing

The golden rule of seed starting is to not start them too soon!

Seed packets give maturity dates—those will give you dates that you can harvest *from days after transplant*. Many companies suggest a number of days or weeks prior to average last frost date. For my growing zone (4b) the typical last frost date is generally around May 1–10, but this is changing due to climate chaos.

You can also start seeds a little earlier if you plan to transplant them out into the garden under cover. I usually pop up a simple low tunnel to protect my peppers and tomatoes. I make these simply by pounding some stakes (rebar) into the ground, and then sliding over some hollow PVC pipe, forming it into a half circle, then draping some sheet poly over that. Bricks and clips keep the plastic in place.

My basic seed starting schedule:

8–10 week prior seeds = beginning of February

6–8 weeks prior seeds = mid-February

4–6 weeks prior seeds = beginning of March

I grow in Minnesota, Zone 4b

Seed Planting Prep

Trays + Pots

Before you get planting you’ll want to sanitize whatever you’ll be using for seed starting by washing in hot, soapy water and scrubbing off dirt, then soaking in a bleach solution (if 8% bleach use one tablespoon per gallon of water) for a few hours. Rinse well and let air dry. This is important to avoid the fungal disease of damping off, which kills seedlings.

Soil Blocking

I love Soil Blocking so much I wrote a whole separate blog post about it! Read that article HERE !

Also, I give you THIS VIDEO clip of the OG Soil blocker and legendary organic Gardener, Eliot Coleman.

The standard for seed starting trays is the “1020” which is roughly 10” X 20”. I use a solid 1020 with a mesh 1020 nestled inside this for my soil blocks. I also have an assortment of older pots that I use to plant into, always with a solid 1020 tray underneath. I Absolutely swear by Bootstrap Farmer’s trays. They cost more up front but will literally never need to be replaced- so much stronger then the box store trays!

Seed Starting Mix

Start with a sterile seed starting mix. Do not use regular garden soil, or already used potting mix. There are quite a few good brands out there, I prefer Promix if I’m buying a pre bagged blend. But for when I do my main seed starting, I mix up my own, to be able to control the exact contents (yes, I am a bit of a control freak!) and to save money!

I buy compressed bricks of organic coco coir, like these, to make up about half of this mix. You’ll get roughly 2.5–3 gallons from one compressed brick after letting it expand for a few hours.

I’ve got a YouTube Video on my soil mix for starting seeds in trays. There are many ways to create a good seed starting mix. Here’s what I found works well for me. Here’s a link to my Amazon page if you’re interested in seeing all the products together.

🌿Seed Starting Mix🌿
6 parts coconut coir (or peat moss)
2 parts compost or 1-2 parts worm castings
2 parts perlite
1/4 cup blood meal
< 1/4 cup bone meal
< 1/4 cup Azomite (aka rock dust)

soak coconut coir for at 2+ hours prior to mixing, wet more after mixing

Germination

Heat mats

In general, seeds germinate better a little warmer than we keep our northern climate homes in winter. However, there is wide variation here, as I start pea seeds outside in 45F soil. But in general, you’ll get a higher germination rate and quicker germination with the use of a heat mat. Most seed packets or a quick online search will tell you the exact best temperature for germination. These heat mats are plug in units that sit under a regular 1020 tray.

Cover Them Up

After watering seeds in you’ll want to keep them warm and damp. The simplest way to do this is to cover the top of the soil. We’ve all seen the clear plastic domes, to help keep in the humidity. These work well—as long as they are removed as soon as you see green popping up! Keeping the soil and emerging seedlings covered too long invites molds, which are a seedling’s worst enemy.

Grow Lights

There are so many options out there for indoor grow lights. You can get a regular fluorescent ‘shop light’ and do well by your seedlings. But there are some specific benefits to different kinds of light that mimic natural sunlight more—or focus on parts of the spectrum that plants need most. This is a deep subject, and if you’re interested in more info, this podcast on Joe Gardener’s site where he talks with Leslie Halleck covers it really well.  For me, I use these T5 LED Grow Lights and I’m really happy with my results.

Watering

Just like watering plants in the garden, you’re going to want to water the soil not the leaves. And since we’ve got them in trays, we can actually water from below. This will help water more evenly and more fully, hence less often which is also better for root development. You also decrease the ‘splash up’ and most of the chance for fungal and mold (damping off) problems. There are systems you can set up for this, but I still prefer to lift an edge and hand water—it gives me a chance to check on the individual plants better as well. You are going to want to let the top layer of soil dry out a bit, and keep in mind many more seedlings suffer from being over watered than drying out!

This will get your seedlings off to a good start, but the most important step is simply paying attention. Truly, this is the part that brings gardeners the most joy—tending to their babies, watching closely and responding quickly.

Tips for Growing Big + Strong

• When fertilizing seedlings, use a diluted (50%) form of organic fertilizer.

• Pinching off will help some seedlings (like flowers and peppers) grow stronger and produce better crops. Pinching off at the flower bud will keep the plant’s energy going into growing leaves and roots.

• If your seedlings get pests (like aphids) try spraying them off with the  ‘stream’ setting on a water bottle. If needed, you can mix up a simple organic pest spray: in a 1 Qt spray bottle, mix in 1 cup Olive Oil, 1 Tbsp Castile Soap, and then fill with water.

Finally, it will be time to bring them out into the garden…

Hardening Off  

This is an essential part of growing healthy plants, and one of my favorite seed starting tips. You’ll need to slowly acclimate your seedlings to the full power of sunlight, wind, and changing temperatures. This process is called hardening off. You’ll want to find a partially sunny spot, maybe up against a wall and not open to wind gusts. You start with bringing the plants out for 15–30 minutes the first day, and increase 30–60 minutes per day for a week. Only then will they be ready to live outside and be transplanted out into their forever home. Not giving them enough time to acclimate can give them ‘sun scald’ and set the plant’s growth back by days or weeks. This happens to me with some plant almost every year—so a little sun scald is just part of the garden game.

Transplanting

You should plan on transplanting once soil is warm enough for the crop—and as this varies greatly, refer back to the seed packet. Both soil and air temps need to be warm enough so I transplant my earliest plants under cover. Tomatoes, peppers, and other heat-loving plants will especially appreciate the warmer soil and air—plus protection against those dropping overnight temperatures.

A big part of gardening is watching what is happening and reacting to nature—so be patient with nature and yourself!

On a more philosophical level, starting from seed brings you closer to nature. Growing a bean vine with hundred of beans from a single seed is nothing short of magical. I hope you get to experience that magic too.

What was your favorite seed starting tip?

Can’t wait to Dig In!
Michelle