Backyard Discovery publishes "winds up to 100 mph*"; the asterisk means "anchored as specified in the instruction manual." The page stops there, so here is the rest: it ships with 16 concrete anchors and 16 ground stakes on the XL, 10 of each on the smaller sizes. Among the best-equipped kits here for holding itself down.
Greenhouse comparison
Every wind rating assumes anchoring.Here is what you actually get.
We compare 34 greenhouse kits on the things that decide whether one survives your site: what it is rated for, whether it ships with anything to hold it down, what the warranty actually covers, and what it costs at each retailer. Most of that is not on a product page. We have done the digging, so these pages give you the answer rather than the homework.
- 34 models
- 26 brands
- 11 price-tracked daily
Planta's product page rates the Sungrow 20 at 60 mph; the real figure is 65. More usefully: roof vents are not included, an upsell the product page does not make obvious. Budget for them.
The Palram Essence 8×12 is rated 55 mph and 15 psf — the weakest here by some distance, and published on neither retailer page. Anchoring is a warranty requirement, and the hardware is not supplied. Two costs the sticker price hides.
The headline number is the least useful part
Palram's 55 mph comes with no anchoring hardware and a warranty that depends on anchoring.
Backyard Discovery's 100 mph comes with 16 anchors and 16 stakes in the box. The gap between
those two purchases is far wider than the gap between the two numbers — and none of it is on a
product page.
The Sungrow ships with no roof vents at all
Planta is blunt about it: "Roof vents are not included in this kit. We highly
recommend adding Sungrow automatic roof vents to your order." Ventilation in the box is
two end windows and two doors, for 200 sq ft. The product page does not make that
absence obvious. Worth knowing before you buy, not after.
Yardistry excludes the thing buyers fear most
The Meridian publishes no wind or snow rating at all, and its warranty explicitly excludes
"acts of nature, including but not limited to wind, storms, hail, floods." On the most
common owner anxiety there is neither a figure to compare nor cover if it fails. The structure
carries one year; lumber and panels get five.
Harbor Freight publishes no rating, and says so plainly
No wind figure, no snow figure, nothing numeric anywhere — only a warning that
accumulated snow "can cause parts of this greenhouse to buckle suddenly", and a
disclaimer that "you are responsible to ensure the greenhouse is anchored." It is the
most-discussed greenhouse on Reddit and the least documented here.
The best guidance came without a number attached
Janssens publishes no mph or psf either — but it tells you exactly what to do in a
windy spot: additional PRO210 anchors at every vertical glazing bar, embedded in
concrete, plus a stainless cable and turnbuckle across the sidewalls for snow. Advice
you can act on beats a headline number you cannot.
And the Essence hides a second condition
Anchoring is "required to complete this stage in order for your
warranty to be valid" — and that ground screws and spikes are not
supplied. Skip the separately-sold anchoring kit and the warranty goes with it.
Neither retailer page mentions this.
Side by side
The five kits
Every value links to where we got it. not published means we looked and the manufacturer does not state it — that is a finding about the product, not a gap in our research. Hover any cell for the caveat.
| Specification | Backyard DiscoveryBellerose 11x7 | Backyard DiscoveryBellerose XL 13x11 | Palram CanopiaEssence 8x12 | PlantaSungrow 20 (Gen III) | YardistryCedar Greenhouse Meridian 6.7x7.8 | Harbor FreightGreenhouse 6x8 | ExacoJanssens |
|---|---|---|---|---|---|---|---|
| Size | 11x7 | 13x11 | 8x12 | 10x20 | 6.7x7.8 | 6x8 | — |
| Floor area | 83 sq ft src | 143 sq ft src | 96 sq ft src | 200 sq ft src | — | — | — |
| Frame | cedar src | cedar src | aluminium src | hot-dip galvanised steel src | cedar src | aluminium src | — |
| Glazing | 4-wall polycarbonate src | 4-wall polycarbonate src | 4mm clear twin-wall polycarbonate src | 6mm UV-protected polycarbonate src | — | — | — |
| Panel thickness | 10 mm src | not published | 4 mm src | 6 mm src | — | — | — |
| Wind rating | 100 mph src | 100 mph src | 55 mph src | 65 mph src | not published | not published | not published |
| …which assumes | Product must be anchored as specified in the Backyard Discovery instruction manual src | Product must be anchored as specified in the Backyard Discovery instruction manual src | Anchoring is mandatory: 'Anchoring this product to the ground is essential to its stability and rigidity. It is required to complete this stage in order for your warranty to be valid.' src | Rated to 65 mph provided the specified loads are not exceeded; the manual states panels need not be removed in winter provided those loads hold src | not published | not published | Manufacturer's high-wind procedure: additional PRO210 anchors at EVERY vertical glazing bar, embedded in a concrete foundation; or PRO210 cut into 4-inch L-brackets from the base into the concrete; or long anchor bolts through the frame beneath the glazing bars src |
| Anchoring included | Yes src | Yes src | No src | Yes src | not published | not published | — |
| What ships for anchoring | 10 x 3-inch concrete anchors (recommended method, needs a 5/16in masonry bit) AND 10 x ground stakes src | 16 x 3-inch concrete anchors (recommended method, needs a 5/16in masonry bit) AND 16 x ground stakes src | none supplied — manufacturer anchoring kit sold separately, or ground screws/spikes (explicitly not supplied) src | galvanised steel legs set about 1 ft into the ground, plus included ground anchors / angle brackets src | — | — | — |
| Snow load | — | — | 15 psf src | 75 psf src | not published | not published | not published |
| Snow depth | 30 in src | 30 in src | not published | not published | — | — | — |
| Roof vents | not published | not published | 2 src | 0 src | — | — | — |
| Side / end vents | — | — | 0 src | 2 src | — | — | — |
| Opening windows | 2 easy-open window(s), manual src | 4 easy-open windows, manual src | not published | No src | — | — | — |
| Powered fan included | Yes src | Yes src | No src | — | — | — | — |
| Panel retention | not published | not published | not published | not published | — | panel clips src | — |
| Warranty | 5 years src | 5 years src | 5 years src | — | 1 years src | — | — |
| Expandable | — | — | — | Yes src | — | — | — |
| Live price | checking… | checking… | checking… | checking… | checking… | checking… | checking… |
Full detail per model, with every figure linked to its source document: Palram Essence 8×12 · Planta Sungrow 20 · Bellerose XL · Bellerose 11×7 · Harbor Freight 6×8 · Yardistry Meridian
Prices are advertised prices, fetched live. Shipping is only added where a retailer states it, so a delivered price is shown only when it is genuinely known.
Why these rows
What actually decides whether it survives
We picked these specifications by reading what greenhouse owners actually argue about, not by copying retailer filters.
- Wind, and its conditions
- The most common structural worry among owners by a wide margin — and it is usually fear of losing the whole structure, not of gradual damage. The rating alone is close to meaningless without the anchoring it assumes.
- Snow depth, not pounds
- Backyard Discovery publishes total pounds — 3,700, 5,700 and 9,200 across the three Bellerose sizes — alongside a constant 30 inches. Pounds scale with roof area, so inches is the figure that compares between models. We do not convert to psf, because that arithmetic would be ours, not the manufacturer's.
- Ventilation, counted honestly
- The Essence has two roof vents and zero side or end vents for 96 sq ft, and ships no fan. Owners in hot states report interior temperatures well above 100 °F even with powered fans running. Stock ventilation is routinely the first thing people have to upgrade.
- Panel retention
- How the glazing is actually held in — clips, screws, or a channel. Panels working loose is the characteristic failure of cheap kits. Not one of these five publishes it, which is itself worth knowing before you buy.
Before you buy
How to read these numbers
Every figure here is the manufacturer's own, measured under its own conditions. That means a 100 mph rating from one brand and a 55 mph rating from another are not the same test, and the difference between them is not what it looks like. Treat them as claims to compare against each manufacturer's small print, not against each other.
Every rating assumes anchoring. None of them describe a greenhouse sitting loose on soil. Wind, snow, permitting and foundation requirements vary enormously by site, so confirm anything that matters with the manufacturer and your local building authority before you buy. We have not tested any of these greenhouses, and reporting a rating is not endorsing it. Prices are what each retailer advertised when we last checked and exclude shipping unless stated.
Found something wrong — especially if you make or sell one of these? Tell us and we will fix it.