A compact coco coir brick does not look like the beginning of a vegetable garden. Add water, give it time and the material loosens into a fibrous growing medium that can fill a surprising amount of tray space. In Tuesday Seeds 155, Uriah Israel walks through that transformation, then combines the hydrated coir with perlite and sows spinach in reused nursery trays. His DIY seed starting mix uses two main ingredients, but the demonstration also highlights the habits around them: preparing equipment, managing moisture, leaving room for air and paying attention to the seed. The work is approachable. Each stage gives a gardener something useful to observe before moving on.
Begin With Clean Equipment
Uriah starts with a washed bucket and returns to the same point when preparing his trays: young plants deserve a clean beginning. Reused plastic trays can serve another season when they remain sound and drain properly. Remove old roots, debris and growing medium, wash thoroughly, then disinfect using an appropriate product and its directions. Rinsing alone does not establish sterility. University of Minnesota Extension recommends disinfecting previously used containers to reduce disease carried over from earlier plants. Treat the mixing bucket, tools and work surface with the same care.
Understand The Two Ingredients
Coco coir is the fibrous material derived from coconut husks; horticultural products are often compressed for storage and transport. Perlite is the lightweight white material commonly visible in container mixes. They serve complementary purposes. Oklahoma State University Extension identifies coir as a moisture-retaining ingredient and perlite as a component that improves aeration and drainage. Together, they help create a porous growing medium, meaning one with spaces that allow water and air to move around roots. Garden soil behaves differently in a shallow container: it can become dense and may carry weed seeds or plant pathogens. Fresh materials intended for container growing make the starting conditions easier to manage.
Hydrate The Coir Before Measuring It
The compressed brick needs time to absorb water before it can be mixed evenly. Uriah places his coir in a bucket, adds warm water and later returns to show how readily the expanded material breaks apart. Follow the hydration directions on your own package rather than treating one recorded water amount as a universal recipe. Brick sizes and products vary. Break apart the softened sections, check for dry cores and distribute moisture throughout the batch. University of Maine Extension recommends uniformly moist growing media without oversaturation. The finished material should be loose and damp, with any excess free water drained before the next step.
Mix Coir And Perlite Evenly
Once the coir has expanded, Uriah adds roughly an equal part of perlite and works the ingredients together. For a repeatable version of his demonstration, measure one scoop of hydrated, loosened coir and one scoop of perlite using the same container. This gives a one-to-one blend by volume; measuring the dry compressed brick against loose perlite would produce a different mixture. Distribute the white particles throughout the brown fibers instead of leaving layers or pockets. Treat this as Uriah’s demonstrated starting point, rather than a universal formula for every crop. Extension recipes vary because containers, watering practices and growing conditions change what a mix needs to do.
Fill Cells Without Packing Them Hard
A loose mixture can lose its useful structure if it is pressed heavily into the tray. Uriah spreads the prepared medium across his cells and emphasizes keeping it able to breathe. Work enough mix into every pocket to avoid large empty spaces, then settle it lightly so each cell offers consistent contact for the seed. University of Maryland Extension recommends moistening growing media before filling containers and firming it lightly. Check drainage openings before setting the cells into a support tray. The goal is an evenly prepared seedbed that holds moisture while letting surplus water escape, rather than a tightly packed block or a tray sitting permanently in water.
Use Spinach Instructions For Spinach Seeds
Bloomsdale and Giant Noble spinach are the varieties named in the episode. Uriah uses a small skewer to make planting holes and places two seeds in each cell, explaining that an extra seed offers another chance if one fails to emerge. If both emerge, thin the cell to one healthy seedling. For depth, read the seed packet rather than judging solely by how small a seed looks. Utah State University Extension recommends planting spinach seed about one-half inch deep. Cover gently and water without displacing the seed. Label each variety and record the sowing date so later observations remain connected to the correct tray.
Balance Moisture, Oxygen And Temperature
Uriah emphasizes warmth and moisture, both important parts of starting seeds. Oxygen also matters, and light requirements vary with the species, as Montana State University Extension explains. A constantly saturated tray can deprive the developing roots of air. Match temperature to the crop as well: spinach is a cool-season vegetable, and Utah State University notes that temperatures above 80°F reduce its germination. Warm water used to expand coir is a preparation step, not a reason to keep spinach trays hot. Maintain appropriate moisture, provide suitable light after emergence and watch the actual growing conditions instead of assuming more heat or water will help.
Plan Beyond The First Sprout
A seed carries stored reserves that support early germination, which explains Uriah’s decision to begin without fertilizer amendments. As growth continues, a plain coir-and-perlite blend needs a nutrition plan. University of Minnesota Extension advises feeding seedlings in soilless media as true leaves develop, using an appropriately diluted fertilizer. Follow a product’s directions for seedlings and account for any nutrients already included in your materials. Keep feeding and transplanting in the plan as young plants grow beyond the germination stage.
Choose The Right Route Into The Garden
Spinach can be grown from seed or transplants, so trays are one option rather than a requirement. Direct sowing may fit your garden just as well. If you choose Uriah’s tray method, monitor development and avoid leaving young plants crowded in small cells. His discussion of a roughly 45- to 50-day harvest window is an expectation for the crop, not a guaranteed finish date; variety, weather and growing conditions affect the result. Texas A&M AgriLife Extension identifies spinach among crops suited to cooler growing seasons in Texas. Use a local planting calendar and the variety’s packet directions to connect the seed-starting project with a realistic place and time to plant.
Keep The Resourceful Habit
One of the strongest lessons in the episode appears when Uriah picks up nursery trays he already owns. Reusing suitable equipment turns an ordinary purchase into a resource for the next planting, and he connects that practice with the ingenuity of earlier generations. Keep a small record of what you use, how the mix behaves and which seeds emerge. A missed germination or uneven tray can become information for the next attempt when the conditions are recorded. Watch Tuesday Seeds 155 for the full coir-to-tray demonstration, and follow @blackfarmerscbo for more practical conversations about growing food, using resources thoughtfully and building confidence one planting at a time.
