How To Make and Use a Storage Tote Greenhouse For Seed Starting

Since I’m not a person who is into organizing things (I’ve just accepted it at this point), I’ve never gotten too excited about storage totes…that is, until I learned I could use them to start my spring garden seedlings outside.

Turns out, you can make a mini greenhouse out of a clear plastic tote, and it works like a charm. Since you keep the tote outside, it frees up space in your indoor growing area for pickier seedlings that need consistent heat. I don’t know about y’all, but my garden plans are always bigger than my seed-starting room can handle. Naturally, I now have six totes dedicated to seedlings, with definite plans to make more.

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Using Tote Greenhouses as a Winter-Sowing Alternative

The storage tote “greenhouse” idea came from my first attempt at winter sowing a while back. Winter sowing is a no-fuss strategy often used to start seeds that need a period of cold or freezing weather to sprout, like many of our native wildflowers. It also works well for leafy greens, annual flowers, and other cold-hardy vegetables and herbs.

To winter sow, you plant seeds around mid-winter in clear or translucent upcycled containers. The most popular method is to use plastic milk or water jugs with the top halves cut off to create a ventilated lid. Once your seeds are planted, you place your winter sowing containers out in the elements and wait for them to germinate naturally when temperatures rise.

The containers protect the seeds from birds, scavengers, and rain/snow while providing a greenhouse effect to give them a head start. In a perfect world, you’ll have seedlings ready to divide and transplant at spring planting time.

Winter sowing is a smart strategy if you live somewhere with reliably cold weather during winter months. Here in north Georgia (zone 7), we’re prone to rollercoaster temperatures, especially during the last two-thirds of the season. I quickly found out it only takes a few warmer days in a row to wake things up way too early in those little greenhouse jugs.

So, yes, my first winter sowing experiment became minor chaos. I sowed my jugs at the end of January, and the seeds were sprouting all over the place after a warm spell a couple weeks later. That was several months before most of those seedlings could be planted in the ground, which was…not ideal. But the whole situation gave me the idea of using the plastic container method for spring, instead.

Nowadays, I use “greenhouse” totes for all kinds of seedlings I used to grow in my seedling room. I start them around the same time I would do so indoors, maybe a tad earlier if there’s cold weather in the forecast. The only thing I truly winter-sow are onions (which I’ll mention further down).

Why Totes, and How Do They Work?

Here’s why I use totes instead of milk jugs or other smaller containers:

The totes provide the same greenhouse effect and frost protection as traditional winter sowing jugs. But they have enough room for individual containers like solo cups, which means I don’t need to untangle and re-pot a bunch of seedlings packed into one jug. This is better for plants that don’t like having their roots disturbed, like dill and cilantro.

The totes are also less hassle to carry than a dozen jugs if I need to move the seedlings- such as into the shade on an unusually hot day, or onto the deck when a gnarly thunderstorm is rolling in. And, since they’re bigger, they don’t overheat as quickly when we get our afternoon temperature jumps. Forget to open up your milk jug planters when it’s suddenly 60F and blazing sun, and those little seedlings are toast.

If you live somewhere the weather won’t cooperate with traditional winter sowing (I’d say for Zone 7 and up, it’s a gamble), the greenhouse totes make the perfect alternative. You can also use them for things that aren’t usually winter-sown, such as squash and melons.

On top of saving lots of space, they’ll save you some time, too. You don’t need to do much in the way of hardening off for seedlings grown this way, since they’ll be exposed to outside conditions from the beginning.

Making The Greenhouse

All you need is a clear tote (or totes), a drill, and some pea gravel.

It’s important to find a tote that has clear sides and a clear lid. Some clear totes have solid lids, which block out too much sunlight. Get a tote that’s big enough you can fit plenty of small pots in it, but not so big it becomes hard for you to carry. Keep in mind the gravel and seedlings inside will add up to some weight.

Also, you don’t really need heavy duty totes for this. I got the cheapest ones in the size I wanted, which costed me about $15/tote. They’ll still last a while, since they’re only out in the sun and weather for a short time each year.

First, you need to drill some holes in your tote(s) for airflow. I like to make several clusters of vent holes on all four sides. Make sure you have a buffer like some thick cardboard beneath the tote if you’re working on a surface you don’t want to damage (like your floor or deck). What size bit you use doesn’t matter a whole lot, as long as it’s not teeny tiny narrow- I think I used a 5/8 for mine.

When you drill the holes, try to put them in the same place on each opposite side so air can flow through easily. Don’t worry if the plastic cracks in a few places- it won’t matter. You’ll also want to put some holes in the bottom of the tote for drainage. The best place is in the corners, since they’re the lowest points.

I avoid adding holes to the lid because they funnel rainwater into hard streams that can dislodge the seeds/seedlings (something I learned in the first go-round). For that reason, it’s better to hand-water the tote seedlings.

Finally, the bottom of the tote needs a thin layer of pea gravel so the seedling containers drain properly. You can use any kind of gravel you have on hand, as long as it’s small enough for the containers to sit level on it. I just recommend using rock of some kind, not wood or bark chips, since those may attract mold and bugs.

Another option is to use a seedling tray with holes in it. However, the tray option wasn’t space-efficient for me- I could only fit one 10 by 20 tray per tote with quite a bit of room left over.

At this point, the mini greenhouse is ready for occupants.

Containers and Soil

When choosing your planting containers, opt for something a little bigger than you’d use for indoor seedlings. 2-inch seedling cells will dry out too fast from the sun and warmth in the tote. My go-to is solo cups or 4-inch pots.

For the same reason, I don’t recommend a seed starting mix by itself for the greenhouse seedlings. Those mixes are really quick to dry out, which you don’t want for this. I like to blend 50% seed starting mix with 50% potting mix for better water retention (all potting mix works fine, too, as long as it’s not an overly heavy mix). Make sure to get an all-natural potting mix option. Those that aren’t might contain synthetic fertilizers that can burn young seedlings.

What Can You Grow Inside the Tote?

When using the tote greenhouse to start seedlings in the spring, you’ll have a wider range of possibilities than you’d get with traditional winter sowing. But what you can reasonably grow in it depends on the spring temperatures in your area and the ideal sowing dates for what you want to plant. Here’s a list of good candidates:

Brassicas, such as:
- Cabbage
- Broccoli
- Kale
- Cauliflower
- Collards
- Mustard Greens
- Brussels Sprouts

Greens, such as:
- Spinach
- Swiss Chard
- Lettuce
- Bok Choy

Cold-hardy herbs, such as:
- Dill
- Cilantro
- Parsley
- Mint
- Fennel
- Chamomile

The above crops are great for actual winter sowing, since they’re so cold tolerant, but spring planting may be a safer bet if your climate has random warmups in the winter. A few sunny days with highs nearing 50 F is more than enough to wake up these kinds of seeds. You don’t want them to sprout the first week of February if you can’t plant them out until late April.

For other herbs and annual flowers that aren’t typically winter sown, using the tote method for spring planting works best once snowy/dreary weather has mostly passed and nighttime lows have moderated to 30F or higher. At this point, anything that isn’t too picky about consistent temperatures will do well outdoors in the tote, including:

Herbs, such as:
- Thyme
- Sage
- Rosemary
- Basil
- Oregano

Annual flowers, such as:
- Marigold
- Calendula
- Nasturtium
- Cosmos
- Aster
- Sweet Alyssum
- Snapdragon
- Mexican Sunflower
- Borage
- Zinnia
- Impatiens
- Petunia

Later in the spring, I’ve had good turnouts using the totes for squash, cucumbers, and melons as well. They grow rapidly, so it’s a great way to get them to transplant size and hardened off in one go. But these guys require a bit more babying, so they’ll need to be brought inside for the night with temps much lower than 45F. A cold night probably won’t kill them, but they don’t like it, and it might affect their growth.

What NOT to Plant in the Totes

Here are some things that shouldn’t be spring planted in the greenhouse totes:

-Heat-loving plants that don’t tolerate chilly nights, such as tomatoes, peppers, and eggplant

These seeds will either have very low germination or won’t sprout at all without consistently warm soil. Any seedlings that do sprout will grow poorly. While I’ve heard of other people successfully growing them “makeshift greenhouse” style, I don’t like to risk it. Mine always get to start indoors where I can keep the temperature stable.

-Onions, shallots, and chives

These make the list because they take a long time to grow, and they need to be transplanted at least a few weeks before the last frost. If you’re sowing them in spring once the days are getting warmer, you’re starting too late! They need at least 10 weeks to reach transplanting size. For me, that means winter-sowing in at the start of February. In this case, I actually want them to sprout at that time.

I start my onion seeds with the classic milk jug method, so I don’t have to worry about them for a while. Then, I remove the jug lids and put them in one of my totes with other seedlings once the warmer afternoons set in.

For most things, I don’t do the jug method because of the extra potting-up and disturbance it requires. But onion seedlings can stay in the jugs until it’s time for them to go in the garden, and they really don’t mind having their roots roughed up a little.

Though they’re very cold-tolerant, you might consider starting onions or shallots indoors, if you’re still getting regular arctic weather at the time you need to sow them. Think daytime highs below freezing and nights in the teens or single digits.

-Any seeds that need cold stratification, like native wildflowers

Native flowers that require a period of cold to sprout, like milkweed, black eyed susans, and purple coneflower, shouldn’t be planted directly in the tote in the spring. These should either be sown in winter when possible or cold-stratified some other way (like your freezer) before planting. As long as they’re properly cold-stratified beforehand, they should grow well in the greenhouse tote.

Maintenance: How to Keep the Tote Seedlings Happy

Here are some tips for raising healthy seedlings in your greenhouse tote(s):

Cold Protection- The totes provide a good amount of frost protection on their own. But if it gets really cold, you might need to take extra steps, especially for seedlings that are less cold tolerant. If below-freezing temperatures are forecast, I usually throw a blanket over the totes for extra warmth. I’ll also bring more sensitive seedlings like basil and annual flowers into the living room overnight if a hard freeze is expected.

Tip: Keep more sensitive seedlings separated in different totes from the cold-hardy ones such as greens and brassicas. That way, you can cover or bring in only the totes that need it during a late cold snap.

Ventilation- Make sure your greenhouse totes don’t get too hot inside on warm days. You’ll be surprised at how much they’ll heat up, even when it feels cold outside. Once the sun is out and the temperature is creeping above 40F, the seedlings will enjoy some extra airflow. I use a small board or stick to prop the lid open an inch or two, then weight it with a rock to keep the wind (and the cat) from knocking it off. Once it warms up above 55F, I remove the lids completely until evening.

Critter Protection- Speaking of the cat, I recommend using some old screen or other breathable barrier to cover the totes when the lids are off. That way, your seedlings are safe from outdoor pets or other possible marauders you might have around, such as squirrels, chickens, and birds.

Watering- I’ve found that seedlings grown in the greenhouse totes will need a little more watering than traditionally winter-sown seedlings, especially on warmer days. It’s good practice to check on them whenever you go to open or close the lids and give some water if the soil is dry. Get a watering can with a long, narrow spout and you can make short work of it without removing the pots from the tote.

I’m also known to leave the lids off my totes during a nice spring shower, since something about rain makes plants green up and glow. That being said, you’ll want to make sure they’re covered during a torrential downpour or heavy thunderstorm.

Acclimating to Wind and Sun– While the tote seedlings don’t need nearly as much acclimating as indoor-raised seedlings, remember they’ve been shielded from blustery wind and direct sunlight inside the tote. It’s wise to introduce those conditions gradually, just to be safe. I put mine in a sheltered area with some filtered shade, the first couple times I take the lids completely off.

That’s pretty much all there is to it. When it comes time to transplant, your seedlings will already be hardened off and ready to go. All you have to do is carry the totes over to the garden and get to work. In lieu of having a real greenhouse, which isn’t practical for all of us, this simple little project is the best way to expand your seed-starting operation as much as you want to.