But first....what's a cold-frame?
This transparent roofed enclosure allows light in while preventing heat escape, mostly at night.
The top of a cold-frame is usually made of materials like glass, plexiglass or greenhouse plastic. The Juwel version from Exaco Trading uses a high-quality and lightweight polycarbonate material.
Sides of many cold-frames are made of lumber which is sturdy enough to hold up the roof. But I appreciate how Juwel used the same material, the polycarbonate for the sides, too.
Such innovation allows light in from all angles encouraging active growth. Sheer genius so to speak! It also makes the cold-frame much lighter than lumber would be.
Rarely are cold-frames heated. Their plant-protecting power derives from solar energy stored in the transparent structure.
Still...the Biostar 1000 cold-frame "feels" like a mini-greenhouse. Kind of like your car on a sunny, spring day. It gets super warm inside and you have to crack a window to vent yourself!
Most cold-frames don't have fans or bottoms either. Just quality soil that you can sow directly in.
Your options include:
1.) Sowing your seeds directly in the cold-frame and leaving them there for the long haul. (Probably cool-season crops like lettuce and kale would work best. Maybe a few herbs.) It might get too hot in the cold frame for summer crops even when fully ventilated.
2.) You can sow directly in the soil of a cold-frame and transplant into your garden beds when the last frost date has past.
3.) You can plant in grower flats and can leave them in the cold-frame until you are ready to transplant (as long as the temps don't dip below freezing.)
And if you plan on sowing seedlings in the cold-frame, I would recommend layering the bottom with seed starting soil/seed starting mix to encourage germination.
4 reasons you NEED a cold-frame!
1.) Give seedlings an early start
Besides, those grower flats clearly do not fit on a windowsill. I'm forced to house them on my sunny dining room table. So much for having guests over!
This results in lower germination rates and rather anemic looking plants.
Enter: the cold-frame.
Seeds sown in a cold-frame are less likely to go through transplant shock than ones grown exclusively indoors as the seeds will be better acclimated from the get-go.
Seedlings aren't going from indoor conditions to outdoor conditions with the flick of a switch. They are used to natural light in the transparent cold-frame.
But since seedlings are more susceptible to extreme weather conditions than mature plants, I know to keep a sharp eye on the degree of sunlight, moisture, temperature, and wind my plants are getting.
Some radishes, too, because they grow so dang quickly almost instant results which are fun for kids. No doubt I'll throw in some onions, shallots and kohirabi because I love them all!
My Biostar 1000 cold-frame was in place a solid two weeks before sowing any seeds to help warm up that soil for germination.
But I never want the interior to get too warm which is why proper ventilation is so critical.
The sliding top panes of the Biostar 1000 are incredible, not only for the ease in which they open and close, but also the fine screen underneath keeping bugs and slugs out!
And I will plant a few grower flats (I'm addicted to seed planting...what can I say?) So I saved some room in the Biostar 1000 for these flats specially.
All in all, I'm getting a 2-6 week headstart on seed planting using the Biostar 1000 cold-frame. Thrilling!
2.) Hardening off young seedings
When plants are moved from a warm and sheltered location (greenhouse or indoors) into the garden, they must be gradually acclimated to the fluctuations in sunlight, temperature, moisture and wind/rain exposure.
Our weather in Western New York is so volatile, that each year I find myself carrying plants in and out for countless weeks to "harden" them.
Seriously, I was making ten trips in and out of the house lugging trays of plants to my patio each day. What a pain. And mess. I nearly would drop whole flats going in and out the door.
With a cold-frame, the same hardening can occur in a 5-7 day period just by opening and closing the vents.
The grower flats can remain right in the cold-frame as long as temps don't dip below 35 degrees F. No need to carry them in and out anymore.
The key to trouble-free hardening is to watch the extended weather forecast and plan accordingly.
For my warm-season plants like eggplant and peppers, I like to wait until the temperatures have stabilized to start. At least when we are in striking distance of our last frost date. But this is usually the second or third week of May for us!
This is why I'm planting many of my cool-season crops directly in the cold-frame and many of my warm-season crops in grower flats.
And just so I can stagger my crops ensuring I get a constant supply of the essentials....lettuce, spinach and kale, I'll likely do at least one grower flat of cool-season crops, too. In time, I'll transplant them into my raised beds.
I'll vent the Biostar cold-frame during the warmest part of the day, and gradually increase that length of time the frame is left open each day as I harden off my plants.
If it's a sunny day, I'll vent my frame when the temps hit about 40 degrees F.
It's also vital to keep the soil moist, the soil does dry out more quickly in a cold-frame than outside.
As the plants that have been moved to the cold-frame adjust to more direct sunlight their foliage should thicken and darken in color.
New growth with multiple sets of true leaves is an excellent sign that my plants are doing well and can be transplanted to my raised bed gardens!
3.) Extending the season past frost
Frost is so sad! It's a killer for sure. Sometimes, it comes without any warning and poof, your plants are toast.
Depending on my planting mood, I may start a few favorite picking flowers mid-summer in the cold-frame (such as zinnia's) and be able to harvest flowers come fall without the threat of frost.
Another option. At just over 15 pounds the Biostar 1000 is super light, Tom and I may very well move it over the last of my lettuce and kale so we can continue to enjoy the harvest into late October and early November.
4.) Overwintering dormant plants
I live in zone 5A/5B, so the best I can hope for is gentle dormancy for my hardier plants. And definitely not tropical plants. A cold-frame is not a greenhouse where plants can grow lushly in winter.
Can I level with you? I don't have the room for every plant that I'd like to save in my house. No room at the inn. Sorry.
I will send a few favorite plants to a gentle dormancy this winter and (fingers crossed) they will be ready to resume new growth come spring.
In late fall, you'll see hundreds of hanging baskets and pots tossed in the garbage as there's nothing else to do with them. They'll just die if left outside in our harsh climate.
Now I wouldn't try to overwinter petunias here, I'm not that crazy. But germaniums? Let's give it a whirl!
The plan is to pack the cold-frame tightly with as many pots as I can squeeze in by mid-November. Then I'll add leaves/mulch in between the pots to aid insulation and tighten up any air gaps.
I don't want to encourage active growth so I won't water these plants a ton, but will keep the soil moderately moist. And of course if you overwater the plants could rot.
Since dramatic temperature fluctuations can harm dormant plants, I'll be mindful to vent the cold-frame.
So when it's sunny and temps reach that 35 degree - 40 degree F. mark, I'll crack the cold-frame open a bit. But if temps reach 45 - 50 degrees, I may have to open the cold-frame entirely.
It just depends on the type of winter we have! I'll keep you posted on how it goes!!
Don't get me wrong, I'm in love with the Biostar 1000, it's a fabulous cold-frame.
I'm just not in love with the initial setup instruction booklet.
Largely a pictoral guide, I needed more words to accompany those close-up shots.
The instructions you do get are mostly in two foreign languages, neither of which I am familiar.
If you knew what you were doing, assembling this product would be a breeze. But studying pictures without being able to understand the words that accompanied them hindered our progress.
Now that we have nailed the assembly process, we won't have problems taking the Biostar 1000 apart to store for the winter if we chose to do so.
Actually, Tom and I just kept looking at the box the product was shipped in for assembly clues!
Biostar 1000 Cold Frame Features...
Sliding top panes offer excellent ventilation while netting keeps harmful destructive pests.
- Made in Austria
- Double layer roof window: polycarbonate and mosquito netting
- Unique "no-drip" coating prevents condensation on plants
- 8mm twin wall polycarbonate
- Strong enough for 6 ft of snow
- Child safe rounded edges
- 40"w x 30"d x 17"h / 15.6 lbs
- Polycarbonite has 10 yr UV guarantee
- Warranty: 3 years
- Includes 4 corner stakes
How the Juwel Biostar 1000 cold-frame warms my heart.....
2.) The fine netting under the sliding panels that keep the bugs and slugs at bay. My kale starts to resemble Swiss cheese after the bugs do their damage. Yuck. It can get so many holes I just won't eat it. The screen prevents such catastrophe!
3.) Speaking of those sliding panels, what great design for ventilation! So easy to slide and unslide giving my plants the exact amount of air flow they require. Funny that it's just as easy to kill plants from excessive heat and drought in cold frames than from cold damage.
4.) The lid. It's a single lid that can be propped up with clips if you so choose. So easy to open and shut!
5.) The size. The size of the Biostar 1000 is spot-on. At 40"w x 30"d x 17"h it's the perfect place to house a mix of plants and grower flats. But it's not so big that it would be cumbersome to move if we so desire.
6.) Polycarbonate is extremely lightweight! The Biostar 1000 is technically not considered a portable cold-frame, but at just over 15 pounds, it can easily be moved to a new location with a second pair of helpful hands.
7.) It you want to move your Biostar 1000 or disassemble it prior to the blows and snows of winter, that's easy enough to do. The product lays flat for easy storage.