How We Start Tomatoes, Peppers, Eggplants & Herbs in the Greenhouse (A Step-by-Step Guide)

Each spring we start our warm-season crops in the greenhouse so they’re sturdy and ready for May planting. Right now we have baby tomatoes, peppers, eggplants, and herbs growing on, plus flowers that will become Mother’s Day baskets.

Below is the process we follow and what we watch for along the way.

1) Timing: start for your planting window

We plan backward from our target outdoor planting time in May. The goal is a transplant that’s healthy and well-rooted—not overgrown. If seedlings sit too long in small cells, they can get stressed and slow down after transplanting.

2) Potting Mix & Containers: set roots up for success

We use a light, well-draining seed-starting mix so roots get both moisture and air. Good drainage matters as much as watering. We start in smaller cells, then “pot up” as plants outgrow them so they keep building roots instead of getting cramped.

3) Warmth: steady temperatures for even growth

Warm-season crops like consistent warmth. We keep the greenhouse warm enough for steady growth, and we avoid big swings when we can. Cool nights can slow peppers and eggplants in particular, so we pay close attention to them.

4) Light & Spacing: prevent tall, weak seedlings

Strong light and enough space between plants helps keep stems thick and growth compact. When seedlings are crowded, they stretch. As they grow, we space trays out so leaves aren’t stacked on top of each other.

5) Watering: a simple rule we follow

We water thoroughly, then let the mix dry slightly before watering again. Constantly wet soil can lead to weak roots and disease issues. We also try to water earlier in the day so foliage dries out.

6) Feeding: gentle, consistent nutrition

Once seedlings are established, we feed lightly and regularly rather than giving a heavy dose all at once. The goal is steady growth and good color, not fast, soft growth.

7) Potting Up: when and why we do it

If roots are filling the cell, plants are drying out too quickly, or growth stalls, it’s time to pot up. Moving to a larger pot gives roots room and helps plants keep building strength before they go outside.

8) Hardening Off: the step that makes or breaks transplants

Before planting, we gradually introduce plants to outdoor conditions like sun, wind, and cooler nights. We start with short periods outside in a protected spot and increase time each day. This reduces transplant shock and sunscald.

9) What “ready to plant” looks like :

For us, a good transplant is:

- deep green, healthy leaves

- a sturdy stem (not stretched)

- a well-rooted plug that holds together

- actively growing, but not root-bound

We’ll keep sharing greenhouse updates as we get closer to May planting, and we’ll post details on our Mother’s Day hanging baskets as they’re ready.