Can Fiberglass Planters Stay Outside in Winter?

Every fall the same question arrives: does this planter have to come inside? For fiberglass the answer is usually no, and the reason has nothing to do with how tough the material is. It is about where the water goes.

Why does terracotta crack and fiberglass not?

Because one absorbs water and the other does not. Unglazed clay and ceramic draw moisture into the wall itself. When that water freezes it expands, and the wall fails from the inside. NC State Extension puts it plainly: those pots “absorb water, which will freeze and crack the pot”, and should not be left outside through winter.

A fiberglass planter has no absorbent wall. The body is a molded composite, non-porous by nature, so freezing air alone does not damage it. Unsealed concrete sits closer to terracotta than to fiberglass here, which is why concrete planters in freeze-thaw climates are usually sealed and resealed.

That is the whole of the material advantage, and it is worth being precise about it: fiberglass removes the wall as a failure point. It does not remove water as a failure point.

What do the manufacturers actually require?

Both are explicit, and both say the same thing. Not covers, not wrapping, not moving the planter indoors. Drainage.

DrainageBoth brands name it as the winter requirement, and on Jay Scotts it is a stated condition of the warranty.

The Jay Scotts owner's guide gives the mechanism directly: drilled drainage “ensures water does not freeze and expand in colder climates, which can cause excessive expansion of the planter”, and “helps maintain the structural integrity of large planters, preventing warping or distortion”. Their warranty then places the duty on the buyer: it is “the responsibility of the purchaser to ensure that water be able to drain sufficiently from the containers with outdoor use”, and this is “notably important in regions that are subjected to freezing conditions”.

Cosapots say the same in their own warranty: for all outdoor use the planter must be drilled so that water can drain sufficiently, and they too single out regions with freezing temperatures. They publish a per-model drilling matrix, and they add that misuse is not covered by the warranty.

Both drill free on request. On Jay Scotts the holes are cut to their published standard of 1 to 2 inches every 12 inches of planter space. Cosapots ship sealed and are drilled to their own specification on request. Choose it at the point of order: a drilled planter is final sale, and an undrilled one cannot be drained later without tools.

Do you need to insulate the planter?

The planter, no. The roots, sometimes.

Wrapping the outside of a fiberglass planter protects a wall that was never at risk. What insulation actually buys you is a slower temperature swing in the growing medium, which matters for the plant rather than the container. If you are going to wrap anything, wrap for the roots and be clear that is what you are doing.

Two things help more than wrapping, and both are free. Group planters together so they shelter each other rather than standing alone in the wind. And use the largest planter the position allows: a bigger volume of medium changes temperature more slowly than a small one, which is the same reason a large planter dries out more slowly in summer.

Will the planting survive?

This is the real winter question, and it is about roots rather than the plant's label. Rutgers NJAES states it directly: “Root hardiness is the most important factor affecting the winter survival of container-grown ornamentals.”

A plant in the ground has the entire earth insulating its roots. The same plant in a planter has a wall and a few inches of medium, so it experiences cold its in-ground twin never feels. That is why a plant rated hardy for your zone in a border is not automatically hardy in a container in the same garden.

The practical margin comes from University of Nevada, Reno Extension: leave plants out when they are “cold hardy to one zone below yours and they are in a large pot made from a material that can withstand winter weather”. Fiberglass satisfies the material half of that sentence. The zone half is your decision.

Which materials can stay out, and which cannot?

The dividing line is porosity. A material that draws water into its wall is at risk every time the temperature crosses freezing; one that does not is not.

Material	Absorbs water	Outside through winter
Fiberglass	No	Yes, if it drains
Fiberstone	No	Yes, if it drains
Glazed ceramic	Through chips and the unglazed base	Risky; empty and shelter it
Unglazed terracotta	Yes	No, bring it in
Concrete, unsealed	Yes	Only if sealed and kept sealed
Wood	Yes, but tolerates it	Yes; it weathers rather than cracks

Glazed ceramic is the one people get wrong, and it is the reason that question gets asked every fall. The glaze is a coating, not a seal: water still enters through the unglazed foot, through crazing in the glaze and through any chip. Once inside, it behaves exactly as it does in terracotta. A fiberglass planter has no such route in, which is why it is the usual specification anywhere the temperature crosses freezing regularly.

Does a bigger planter survive winter better?

For the plant, yes. A larger volume of growing medium changes temperature more slowly, so the roots sit through a gentler swing than they would in a small pot. It is the same physics that makes a large planter dry out more slowly in July.

That is why the advice to use a large, winter-durable pot and the advice to choose a plant hardy below your zone belong together: they buy margin at the same problem from two directions. If a planting is marginal for your climate, a larger planter is a real intervention rather than a cosmetic one, and our extra large sizes carry the most medium of anything we sell.

What to do before the first freeze

• Confirm the planter has drainage holes, and that they are clear rather than blocked by filler or compacted medium.
• Lift the planter marginally clear of the ground so water can leave and does not freeze it to the surface.
• Empty and store any saucer. A saucer holds a reservoir under the planter, which is the opposite of what you want in a freeze.
• Group planters together, and move exposed ones against a wall or under an overhang if you can.
• Check the plant's hardiness against your zone with a margin, not at the edge of it.
• Stop feeding in late summer so growth hardens off before the cold rather than going into winter soft.

Should you empty and store them?

Not for the planter's sake. A fiberglass planter can stay outside, planted, through a freezing winter, provided it drains. That is the practical difference from terracotta and unsealed concrete, both of which are routinely emptied and moved under cover each fall.

You might still empty one for the planting's sake, if the species is marginal in your zone and you would rather overwinter it somewhere sheltered. That is a horticultural decision about the plant, not a limitation of the container.

Shop the collection Fiberglass planters

Non-porous, frost-resistant and light enough to move, from Jay Scotts and Cosapots, with drainage drilled free on request.

Snow, ice and moving planters in the cold

Snow load is rarely the problem; meltwater that refreezes in a blocked planter is. Clear the holes rather than the snow.

Moving planters in winter is where damage usually happens, and it is a weight question. Fiberglass is the lightest premium material, but a planted large size is still heavy once the medium is wet, and a planter frozen to a paving slab can be damaged by being levered free. If a planter needs to move, move it before the ground freezes. Our tall planter guide covers weight by size, and the rooftop guide covers access and wind where the exposure is worst.

Frequently asked questions

Can fiberglass planters stay outside in winter?

Yes, if they can drain. Fiberglass is non-porous, so it does not absorb water and crack the way unglazed terracotta does. Both Jay Scotts and Cosapots require drainage for outdoor use and single out freezing regions specifically, so the holes matter more than any cover.

How do you keep pots from cracking in winter?

Stop water from being trapped and freezing. For porous pots such as unglazed clay and ceramic, NC State Extension advises not leaving them outside at all through winter, because the wall itself absorbs water that then freezes. For non-porous materials such as fiberglass, clear drainage holes and no standing saucer are what prevent damage.

Do I need to insulate outdoor planters?

Not for the planter's sake if it is fiberglass. Insulation slows the temperature swing in the growing medium, which protects roots rather than the container. Grouping planters together and using a larger size do the same job without materials.

Will the plant survive winter in a planter?

It depends on root hardiness, not the plant's rated hardiness in the ground. Rutgers NJAES calls root hardiness the most important factor in container survival, and University of Nevada, Reno Extension suggests leaving plants out only when they are hardy to a zone below yours and sit in a large, winter-durable pot.

Does a drilled planter risk freezing damage?

The opposite. Jay Scotts state that drainage “ensures water does not freeze and expand in colder climates” and helps maintain structural integrity in large planters. An undrilled planter left outdoors is the one at risk.

Should I empty my planters for winter?

Not for the planter. A fiberglass planter can overwinter outside planted, as long as it drains. Empty one only if the planting itself is marginal for your zone and you would rather overwinter it under cover.

What about snow sitting on the planter?

Snow itself is rarely the issue. Meltwater that cannot escape and then refreezes is. Keep the drainage holes clear and remove any saucer before the first freeze.

• Read nextPlanter Drainage: Holes, Sizes and Setup
• Read nextThe Best Material for Outdoor Planters