Indoor Seeding Success Without A Greenhouse
Indoor Seeding Success: How I Grow Thousands of Seedlings Without a Greenhouse
We built the big, beautiful greenhouse.
I had the same vision you probably do: a lush winter house full of baby plants, condensation on the plastic, trays everywhere, me out there being a “real” flower farmer.
But I never moved forward to use it for starting my own seedlings. I use it to grow in the dirt and produce flowers for early-season harvests. Instead…
I’ve been starting thousands of baby plants indoors for years, in a simple closed system… and it works beautifully. When I had the chance to move to my greenhouse, I didn’t. I stayed with my warm and cozy indoor system.
If you’re a northern grower (or just don’t have a greenhouse), this is very good news.
You Don’t Need a Greenhouse to Grow Serious Flowers
When people picture “real” flower farmers and cut flower growers, they almost always picture the greenhouse.
But you don’t actually need one to:
Start hundreds or thousands of plants
Grow any time of year
Keep things simple, clean, and manageable
You just need:
A bit of indoor space (garage, basement, spare room, studio, even a bedroom wall)
A vertical rack with lights
Trays without drainage holes
Clear domes
A simple seeding workflow
That’s it. No fancy structures. No huge energy bill.
And for those of us in colder climates? Growing indoors through winter is not just convenient — it’s often the smarter, more efficient choice.
My Indoor Setup (That You Can Copy with What You Have)
Over the years, I’ve set this system up in:
Our basement
My husband’s shop
My studio
And you could absolutely do this in a garage or an extra room.
Start by asking:
“What little patch of space do I already have that I could dedicate to seeding?”
You don’t need a dedicated “seed room.” You just need a station.
Here’s my current version in simple terms.
1. The Soil + Tray Station
I like having a table or counter where I can:
Set a tray down
Fill it with soil or soil blocks
Seed it
Top it with vermiculite
Mist and label
Move it to the rack
A few key details:
I use trays with no drainage holes because this is a closed system.
We don’t want water dripping onto lights, floors, or into places it shouldn’t go.
I do not buy the cheap, flimsy trays anymore (ask me how I know 😅).
Go for a decent grade of plastic that doesn’t crack every time you look at it.
You can use:
Standard plug trays (128s, 200s, etc.)
Or soil blocks (more on that in a minute)
Once a tray is filled and seeded, I sprinkle the top with vermiculite, give it a light mist (just enough to settle things, not flood it), and spray with a bit of peroxide solution as part of my damping-off prevention.
Then the magic happens on the rack.
The Rack That Does Double Duty: Lights + Germination Chamber
This is my favorite part, because it’s so simple.
I use a shelving rack that’s roughly:
18"–24" wide
4 feet long
With 5 shelves
Each shelf has a light suspended on chains so I can raise and lower it.
Here’s how it works:
Newly seeded trays are placed on top of the lights, not underneath them.
That top area becomes a germination chamber.
The lights below provide gentle bottom heat, which many seeds love.
I cover the trays with clear domes.
This holds in moisture and warmth.
It keeps everything neat and contained — no water spraying all over your room.
Once the seeds pop and you see green?
The trays move down under the lights on the shelves.
Now they get strong, consistent light and grow into sturdy little plants.
That’s the whole “fancy system.”
No heat mats required (though you can use them if you want).
No climate-controlled greenhouse.
Just one rack doing two jobs: germination and growing on.
PRO TIP: Your light strength needs to be balanced with the air temperature of the environment to prevent leggy plants. If the room becomes too warm and your lights aren't strong enough, your plants will become leggy and spindly. Keep your room a bit on the cool side.
How Many Plants Can You Actually Grow Indoors?
This is where people’s jaws usually drop.
Let’s talk numbers for a minute.
On a standard 2' x 4' rack with five shelves, you can fit approximately four trays per shelf. That gives you:
20 trays total (4 trays x 5 shelves)
Now it depends on the size of the cells (or soil blocks), but here are some realistic scenarios:
75 seedlings per tray → about 1,500 plants
100 seedlings per tray → about 2,000 plants
200 seedlings per tray → about 4,000 plants
300 small soil-block seedlings per tray → up to 6,000 plants
All of that in roughly 8 square feet of floor space.
Eight. Square. Feet.
You could put that along a wall in:
A garage
A basement
A spare room
Even a bedroom, if you don’t mind sleeping next to baby snapdragons.
For a northern grower, this is gold. You’re not battling the weather. You’re not paying to heat a big structure. You’re quietly growing a whole season of flowers in a tidy corner of your home.
Soil Blocks vs. Cell Trays (Both Work!)
You can absolutely do this with regular plug trays:
128s, 200s, etc.
Easy to handle
Great for most flower crops
But if you love soil blocking:
You can fit a lot of blocks on a single tray
You still use the same domes and the same rack system
You just adjust how many blocks you make so they still fit under the domes
A couple of tips if you’re soil blocking indoors:
Don’t cram so many blocks in that they touch the dome immediately when they sprout.
Remember, you still need space to move them under lights once they emerge.
Either way, the principle is the same:
Keep it contained, provide bottom heat, give it light, and grow vertically to save space.
Avoiding Common Indoor Seed-Starting Problems
A few “learned the hard way” notes for you:
Don’t: Use plastic wrap sitting right on the soil
If you stretch plastic wrap directly over your trays and it lies on the soil or seedlings as they emerge, you’re creating a perfect environment for:
Damping off
Mold
Sad, spindly seedlings
Instead, use clear domes with a bit of headroom. You want moisture and warmth, but also a little air.
Do: Start with Moist Soil,
My goal is NOT to need to water the seedlings until they have sprouted. On this system, a great many of your seedlings will sprout within just a couple of days. It’s wild!!
I sowed on Monday and sowed again on Thursday. On Thursday, I will be pulling many baby plants that have sprouted under lights and have room to add more seeded trays from my Thursday work to the lights.
You only need a light mist after seeding and vermiculite.
Remember: this is a closed system. You’re not relying on the hose and drainage — you’re relying on initial moisture + domes to create that sweet little microclimate.
Do: Think in Trays, Not Just Plants
As a business-minded grower, you’re not just starting “some seeds.”
You’re thinking:
How many trays do I need for this crop?
How many plants per tray?
How many successions can I realistically manage on this rack?
That’s where the indoor system really shines — you can plan, test, and scale without adding more buildings… just light racks ( I have three)
Why Indoor Growing Is a Huge Win for Northern Growers
If you’re up north (like me), starting seeds in winter, in a greenhouse, can be expensive…. Especially when you are a small grower.
But with this indoor setup, winter becomes:
Planning season
Seeding season
Here’s what you gain:
Year-round control — You can start seeds when you want to, not when the weather says you’re allowed.
Low overhead: No heating a big greenhouse through snowstorms.
Any quantity you want: From a few hundred plants for a small beginner garden to several thousand for markets and subscriptions.
Grow what you want, whenever you want : You are now equipped to expand your cutting garden and grow a beautiful variety of plants. You are not limited, and you’ll save loads of money. You can practice seeding, germination, and timing in a controlled environment.
And remember my bigger philosophy:
You don’t need acres of land or a huge greenhouse to build a profitable flower business.
You need a well-planned system that fits your life.
Indoor seeding is one of those systems.
Bringing It All Together
So no, I’m not trudging out to a cold greenhouse in December and January, flipping on expensive heaters, and pretending I enjoy it.
I’ve got:
A simple 2' x 4' rack
Five shelves
Lights on chains
Sturdy no-hole trays
Clear domes
And a little seeding station with soil, vermiculite, and seeds
And from that small footprint, I can grow thousands of baby plants that will eventually become bouquets, bunches, and income.
You can do this too — in your basement, shop, spare room, or garage.
Want Help Turning Those Seedlings into a Profitable Garden Plan?
Starting indoors is just one piece of the bigger puzzle:
What to grow
How to time your plantings
How to keep blooms coming all season
How to sell what you grow with confidence
If you’re ready to start growing your own seeds and take my online course (that is like being with me here on my farm, learning), this is your next step:
👉 Indoor Seeding Success Course for Cut Flower Growers | From Start to Field
