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Starting seeds / seed starting medium options

Updated: Jun 9, 2023

Our process and setup to starting seeds. We are in a shorter growing zone so a lot of what we grow during the summer gets started early inside.

We follow the same process every year, but if we learn something beneficial or we get curious to try something new, we implement that into the structure. Our setup and process for starting seeds is a simple one. We try to find the most efficient and affordable way to start seeds, without compromising the health of the seeds or seedlings. Sometimes this can be a little bit of a balancing act, but we hope you can learn from some of our mistakes when we started back in 2018.

Seeds starting doesn't need to be difficult or complicated, It should be fun and exciting to learn about soil requirements, temperature requirements, fertilizer requirements, germination times, etc.

Seed start soil options

Seed start mix can be expensive, especially if you are planning to grow a lot of different seed starts. Many of the commercially available seed starts mixes contain Sphagnum Peat Moss. Sphagnum peat moss is a non-renewable resource, making it an expensive commodity. Mixes containing sphagnum are so expensive for this reason. In addition, not all seeds are created equally, some plants prefer alkaline soil. Mixes with sphagnum peat moss are more acidic. Even if lime is added to adjust the PH, this is another ingredient that increases the price for the consumer.

Other options include reusing or repurposing soil from the prior year, coco coir, or standard potting mix.

Repurpose outdoor soil / potting mix

On occasion, we get questions about repurposing outdoor soil or reusing potting mix from the prior season. This can be done, but with caveats. Soil from outdoors can harbor several harmful elements that can be detrimental to the health of your new seedlings. These include soil-born fungi, diseases, eggs from bugs and pests, etc. We had run into some folks who had volunteer seeds from prior years sprouted with the seeds they purchased and planted. For this reason, we always encourage folks to use a new medium each season.

If soil is used outdoors, it can be sterilized by either boiling water and pouring it into the soil, or allowing it to cool. You also have the option of microwaving or putting your soil in the oven and heating it hot enough to where it dispatches any living organisms within. We tried this method last year, but we found our re-purposed soil wasn't staying moist and drying out quickly. This led to us having to restart several seeds using a new medium.

Potting mix is also an excellent option although it can be expensive. The benefit is that all the nutrients your seedlings will need as they mature are already in the soil. The potting mix should provide adequate nutrition until they are ready to transplant.

Coco Coir is our option of choice for several reasons. We will lay out the benefits (and some small cons) of coco coir. We will also show you the process of how we prepare ours.

Find what works best for you. Research to see what seeds need damper soil, which needs alkaline vs acidic soil, and see if the time it takes to repurpose soil is worth spending a little extra money towards a new medium for the new growing season.

Coco Coir

We absolutely love coco coir. Coco coir comes in small convenient starter pellets or in large blocks that need to be rehydrated. We purchased 2 large blocks of organic coco coir from Amazon for about $20.30 each. Once rehydrated, each block expands to 18 gallons of mix. This came out to about $1.13 per gallon, which is much more affordable than seed start mix or potting mix, and it's fresh for this season. Coco coir maintains moisture easily which prevents seeds from drying out between waterings, it is almost neutral ( almost a 50/50 balance of acidic vs alkaline) so most seeds can start without issue. The endosperm in each seed provides adequate nutrition for each plant to grow its first true leaf, similar to how the egg white in an egg feeds the chick until it hatches. In addition to being close to neutral, as your seedlings grow and show their first "true leaf" you can customize your fertilizers to add to the soil to create a more acidic or alkaline environment.

These are images of the preparation of coco coir. We place a brick in a large garden wagon outside our door. We fill the wagon with some water from the hose and put the brick of coco coir inside. We wait a few minutes for the coco coir to absorb some of the water. We slowly add more water and stir the coco coir in until the right consistency is achieved. As you can see, the brick of coco coir makes a significantly larger amount of mix compared to a bag of seed start mix.

Our indoor seed start setup

Indoor setups don't have to cost a lot of money. We use 4 utility racks we purchased from Walmart. We also purchased several affordable shop lights and attached them to the utility racks.

Be mindful when purchasing your shop lights. They need to be strong enough to "mimic" the sun's bright light. You will need to watch for two details, the number for the Lumens, and the number for the kelvins. Lumens are the unit of measure to how bright the light is, Kelvins are the units that measure the color of the light. We learned a great deal from Gary Prichard of the Rusted Garden Homestead. His recommendations are light with a Lumen level of 5000 or more, and a Kelvin level of 4100-6500. The Walmart brand "Hyper Tough" met these requirements and with his suggestion, we were met with great success.

We also purchased two wall timers. These allow the shop lights to turn on and off, similar to how the sun will rise or fall. We aim to keep our lights on for 12 hours, then off for 12 hours. This allows the seedlings to rest and get used to their own circadian rhythm as they will be planted outside in the future. You want to mimic nature as much as possible.

In addition, we have spray bottles prefilled with neem oil to fight potential pests and fungus, and a bottle of water with a little hydrogen peroxide to keep the soil sterile and to help oxygenate the plants. We also have a heavily diluted fertilizer to spray the soil once the seedlings have developed their first true leaves. Lastly, we have a spray bottle with just water to keep the top of the soil damp so the seedlings don't dry out.

Our seed library

I used to work at Michaels and they frequently have their colorful photo boxes on sale. I have to admit, the quality isn't the best, and the plastic is a bit flimsy, but they are perfect for seed storage. We have one dedicated case for pumpkins and winter squash, we have another case for everything else. When the growing season arrives, we put everything in order of when to start indoors for our growing zone (5a,5b). A good rule of thumb for us is everything starts to get transplanted after mother's day. We may change this as we have had surprise winter storms hit right after we put everything outside. Last year we had to put everything back inside and cover everything up that wasn't a container (see our blog about the late winter storm during spring). Colorado weather is always unpredictable but we make due.

Final thoughts on starting seeds indoors

Always be mindful of when to start your seeds. For example, pumpkins grow very quickly. We start ours 2 weeks prior to going outdoors. Planting these any earlier and they would go root bound in their starting containers and may not make it to transplant time. Tomatoes and chilis take a long time to grow. If we started these in April or May, the frost would kill them before they had a chance to fruit.

Always do the math to see when your last frost date is and do the math backward to see when to start your seeds. We also use Smart Gardner software to let us know when to plant what for our zone. You can also check the farmer's almanac to see when your frost dates are. We provide a link and more information in our "more" section of the main menu.

What are some of the things you have learned, or what would you suggest when starting seeds indoors?

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