Starting Seeds Indoors

Starting seeds indoors is relatively easy, and it’s (past) time to start thinking about your spring planting in the Southwest.

Starting Out Starting Seeds

You will need a well lit space and some way of keeping your seeds and tender young plants protected from household pets and other slings and arrows of misfortune.


Necessary Supplies 

Sterile seed-starting soil mix
Seedling trays with clear plastic covers – either purchased or repurposed

Optional Supplies 

Grow lights
Heat mat

You can purchase kits that have seedling flats and covers that fit, or get creative with clear boxes from salads or even cut open 2 liter soda bottles covered with plastic wrap.  The top of the refridgerator makes a dandy “heat mat.”

Windows can be too bright and drying for baby seeds – and cold too if they are single paned.

Many seeds in one tray. You will transplant to individual pots later.

Plant Your Seeds

Fill the tray with pre-moistened seed-starting mix, not potting soil. This lightweight mix is sterile and specially formulated to encourage easy, problem-free germination. Plant the seeds according to instructions, and water the seeds in the soil, taking care not to wash them away. You don’t have to use a heat mat, but using one will result in faster germination and growth.


Keep the seed trays covered with plastic until they sprout, then hang grow lights 2 inches above the heads of the seedlings. As the plants grow, move the lights up so that they are no more than 2 inches above the plants.

Outdoors the birds would eat this for breakfast and hunt for more. This is one reason to start everything indoors.

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Give them enough but not too much to drink. Keep the seedling mix moist, but not soggy. Damping off (which looks like rotting or wilting of new seedlings) is a problem when seeds stay too wet and cold while germinating. When plants have three sets of true leaves, you can transplant to a 4-inch pot.

True leaves are different than the “seed leaves” that first emerge.


When you pot your tiny seedlings into the next size pot – skip the whole peat pot thing. I have never found those to work here. Likewise the paper pots so beloved of permaculture. Our air has LOW humidity and these products do not decay in a timely fashion and will stunt your plants growth.


Planting Transplants Outdoors

Once they are hardened off (see below) you can plant your plants in the garden. Plant so that the soil line of the hole and the soil line of the transplant are exactly the same. Do not plant deeper (unless they are very vigorous tomato seedlings – a special case.)

Hardening Off – Before Planting Out

Vegetable transplants grown inside will need to be hardened off before they’re planted outside. Even if you buy plants that were sitting outside at a garden center, it’s a good idea to harden them off before planting. For all you know, the plants were taken from the greenhouse, loaded on a truck, and brought to the garden center on the same day you bought them.

Harden off your young plants on a protected porch.
How to Harden Off Transplants
1. Place plants in a sheltered location such as a porch or patio for the day, and bring them in at night. Do this for three or four days.
2. Next, leave them outside all day and night in the protected location. Do this for about a week. Don't forget to water while you're doing this!
3. Finally, move the plants from the sheltered location to a more exposed location (next to the garden). Leave them there for three or four days.
4. Plant your plants in the garden early in the day, when they have ample time in sunlight to recover from the inevitable damage to their roots. If you have a cloudy day to plant in, even better.

Need Some Garden Help?

May I recommend my book?  The Southwest Fruit & Vegetable Guide offers not just growing guides but some of the latest varieties – including ones specifically for raised beed and container growing. Price is what you would pay on Amazon – only when you buy from me you get a signed copy!soule-books-buy

From the review:

In this updated 2nd edition of Southwest Fruit & Vegetable Gardening, you’ll find much-needed advice and practical tips on growing an edible garden, no matter which part of the southwestern US you call home.

Growing in the Southwest isn’t easy. It’s either too hot or too cold and often very dry. The region hosts a range of soils and climate conditions that can be difficult for a gardener to navigate. That’s why this region-specific garden guide is a must-have for every Southwestern gardener!

Botanist Jacqueline Soule simplifies the ins and outs of gardening in the Southwest and serves as your guide to success. Regardless of whether you’re tending an in-ground plot, a small container garden, or a series of raised beds, Southwest Fruit & Vegetable Gardening is an invaluable resource.”

Profits from the sale of this book go to the Horticulture Therapy non-profit Tierra del Sol Institute.

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