How to start a whole garden in one tray

Thank you to Park Seed for partnering with me on this post. As always, all words, thoughts and seed choices are my own.

The hardest part of growing plants from seed is keeping the amount I grow in check. I can’t be alone in this. It can be so tempting to plant just a few more, or the whole pack of seeds. But that kind of volume can take the fun out of growing from seed when it becomes overwhelming. 

And plenty of people, including maybe even future me, want to grow a few plants from seed without piles of gear. 

And it’s not hard, as long as you have a plan, a system and a little restraint.

WHERE TO GROW

A nice, self-contained seed-starting kit is a joy to have when you’ll be making the most of a small amount of growing space. Park Seed’s Bio-Dome is a mini greenhouse growing system that is well suited to growing a variety of plants from seed.

I’m using Park’s Original Bio Dome with 40 cells, which is suitable for all but the biggest and fastest growing seeds. It has a footprint of about 15 inches long by 9.25 inches wide, which makes it small enough to sit on a table in a window. Made of sturdy, hard plastic, the bottom tray and humidity dome should last for years.

A styrofoam insert holds bio sponges, a growing medium that springs to life after a quick soaking to fill each cell. Everything other than the bio sponges is reusable and refills are available.

WHAT TO GROW

If you’re planning to mix and match a variety of seeds—and you should because how many of us need 40 of one plant–you have to look for some similar characteristics among plants.

Ideally they will all need to be started around the same amount of time before the last frost. Most seed packets offer a range of a couple weeks in which to start seeds, so aim to have all the varieties fall within that range. 

Seeds need different temperatures for germination. Look for varieties that all germinate at about the same temperature.

It’s a bonus, but not strictly necessary, if you can also find seeds that germinate in about the same amount of time.

I grew a variety of seeds, including ‘Daisy Wheel Lemon’ marigold, ‘Big Blue’ Salvia, two types of Ageratum, Rudbeckia ‘Sahara’ and even a lone Tithonia seed I found in a packet. I could have grown several other varieties, but I wanted quite a few marigolds to tuck in around the vegetable garden as well as to help fill holes in the rest of the garden.

DEVELOP A SYSTEM

When you’re planting several varieties of seeds in the same tray good labeling is key. I start from the back of the tray (which could be the long or short side depending on your approach) and label from there, so the label sits at the back of a run of cells. When I start a new variety, a label goes in the cell that is farthest back.

PLANT AWAY

Bio sponges have a small hole for larger seed but small seeds that are meant to be sown on the surface can just be pressed into the top. There’s no need to add anything else.

Watering seedlings from the bottom is always a good idea but it’s the only way to water with the Bio Dome. Just keep a quarter-inch or a bit more water in the bottom of the tray and allow the bio sponges to absorb it.

HEAT AND LIGHT

If you’re growing seeds that need bottom heat, set the Bio Dome on a heat mat or another warm surface. Keep the humidity dome vents closed until seeds start germinating and then you can open them as needed.

Once seeds germinate, they will need light. A very bright window might work if you have very clean windows and very strong light. A grow light is a much better option, and with a small system like this an inexpensive clip-on grown light can do the job of supplementing natural light if you don’t have a large grow-light system.

GROWING ON

Different varieties will grow at different rates so you’ll have to offer some individual attention as they grow. With some dilute fertilizer applications, seedlings should be happy in the Bio Dome for some time as the roots will reach down in the system, not circle around.

When they outgrow their cells, pop them out (there’s a finger-sized hole at the bottom of each cell) and pot them up in larger pots to grow on before you harden them off and plant them outside. Fortunately you can do this without disturbing other cells so you can pick and choose which need to move on, an important factor when you’re planting multiple varieties.

OTHER CONSIDERATIONS

Odds are that you’ll want to grow several varieties of plants with different needs. If you can divide them into two groups by starting time, you can get away with just two systems for all your seedlings.

You may even be able to replant the first Bio Dome with another set of seeds, perhaps those that should be started four weeks before your last frost, assuming some of the plants you started in the first round have moved on to larger pots. The system comes with an extra dozen or so bio sponges but more are available separately.

Every year I wonder why I started so many plants from seed, far more than I could ever use in my own garden, and I think it’s because I feel the need to fill a tray. Starting only what I really need in a simple setup is very appealing. Maybe this old dog can learn a new trick.