Selecting seed and growing your own transplants to harvest can be one of the most rewarding feelings in gardening. When you sprout a seed and grow it all the way to harvest, you’re empowered in knowing the major steps to growing your own food!
In this article we’ll go over the steps required to turn a seed, some soil, and a container into a living, breathing organism- a vegetable transplant!
1. Choose your seed. The first step in growing transplants is to select what kind of transplant you want to grow!
Find an accurate local planting calendar; you can find them online or at local plant nurseries. A planting calendar shows what seeds should be started depending on the season. Our planting calendar for the Tucson region can be found here.
If you plan on keeping your plant indoors its entire life, you can skip the planting calendar.
Pro-tip: Here’s a list of seeds that don’t do very well as transplants. These plants grow best when they are seeded directly into the ground. Carrot, parsnip, turnip, radish, peas, and beans
If you plan to collect seeds from your plants when they mature, you’ll want to buy seed that has been open-pollinated. These seeds have been carefully bred to give offspring that will resemble the parent plants.
If you don’t plan to collect seed and just want the most uniform, predictable crops on the market, look for hybrid seeds, a.k.a. “F1 seeds”. Seed collected from hybrid plants can give wildly variant offspring or even be sterile.
Choose a variety. Plant breeders have put a lot of time and energy into giving us varieties of plants that can do very well in our individual environment. Growing in containers? Growing in an extremely hot or cold environment? Have a plant disease that you just can’t beat? There’s seeds that can fit all of these needs. Find seed suppliers and other information in our seed resources here.
2. Choose your soil. Your transplant’s soil is it’s home for up to 8 weeks, so be sure to give it everything it’ll need.
Your soil should be fine, uniform, and aerated (fluffy). You can purchase a soil mix, just make sure it doesn’t have large chunks of wood or rock that could hinder the seed’s growth.
Your soil should also have some slow-release nutrients available. Good, finished compost or vermicompost is always our recommendation. We like to buy organic soil and mix ⅔ soil with ⅓ compost when filling containers.
Don’t try to save money by mixing in native dirt to your soil mix; it’s too heavy and will cause too much compaction, leading to seeds that can’t breathe.
3. Choose your container(s). If you’re using the right soil, most vegetable transplants will be perfectly happy in a 2”x2”x2” container.
If you’re new to growing transplants, we recommend using 606 trays. These trays are similar in size to most 6-packs you get at local nurseries, so reduce and reuse if you can!
Once you get good at growing transplants, you can experiment with smaller trays such as a 72 cell tray.
Using a larger container won’t hurt anything... other than your wallet. Using pots that are 4 or 5 times the recommended size leads to a much larger soil bill, not to mention the extra space that is required to grow the same amount of transplants. The only added benefit of using a larger container is that you won’t need to up-pot your long-lived transplants like tomatoes and peppers.
4. Sow your seeds.
Spread out and mix your soil well; this prevents any uneven distribution of materials. When you are mixing, moisten the soil to the consistency of a well-wrung out sponge.
Fill your containers with soil.
‘Drop’ the containers from about 6” to remove any large air pockets.
Create a ½” divot in the center of each container.
Drop a seed in each divot.
Pro-tip: Seeds in the allium family (onions, scallions, leeks, etc.) can be multi-sown, meaning you can put 10-15 seeds in a single cell and transplant them individually once they’re mature.
Pro-tip: Beets, bok choi, basil, parsley, and spinach can be multi-sown, meaning to place 2-3 seeds/container and they can be happily transplanted into the ground without ever needing to thin them down to one plant.
Mark each container with some kind of deviation so you can tell what each tray is and the date sown.
Finish filling the containers with soil.
Water the containers with a gentle spray of water 2-3 times to ensure it’s wet enough. If the soil starts puddling, stop watering and give it time to soak up the water.
Place your containers in an area that has the seed’s desired germination temperature. https://www.thriveandgrowgardens.com/seedresources
Keep the soil moist, but don’t overwater.
5. Caring for your newly emerged transplant.
When the seeds have emerged, it’s very important that they get enough light, water, and are in their desired temperature range.
Light: If you’re growing indoors under grow lights, be sure to run the lights for 12-16 hrs/day.
For best results, get lights that have a Kelvin value between 4100-6000K and a lumen between 2000-3000.
Water: Keep the soil the same moisture as a well wrung-out sponge. Not too wet, not too dry.
Pro-tip: Don’t use extremely cold water on the transplants as it can slow their growth. Lukewarm water is best.
Temperature: The seeds will grow best if they stay in the same temperature range as you sprouted them in.
6. Planting
Your transplants are ready to plant when they are your desired size and have white, lightly circling roots and green, full leaves. Don’t wait until the leaves begin to turn yellow or the roots are heavily circling.
b. Before planting, harden-off your transplants for 3-5 days by placing their container outside for increased time each day. (Ex: day 1: 2 hr; day 2: 4 hr; etc.)
c. For a guide on how to properly transplant, check out this article: https://www.thriveandgrowgardens.com/post/5-step-guide-for-proper-transplanting