Frost damages plants when the foliage loses moisture faster than the plants can replace it. This can happen because the soil is dry or because the water or moisture in the ground normally available to the plant is frozen. But most frost damage can be prevented by understanding and following a few basic principles.

There are definite warning signs that can help determine the possibility of a hard frost. If you notice low temperatures (45° or lower at 10 p.m.), a clear sky, little to no breeze, and dry air at bedtime, bring any potted plants that might be at risk into the garage or at least under a porch roof or eaves.

For plants in the ground (and outside potted plants), make sure the soil is moist when frost is expected. Moist soil holds and releases more heat than dry soil, which will help create a more humid environment around the plant when the frost pulls moisture from the foliage of the plant. Never hose down a plant in the morning after a frost. Allow the plants to thaw naturally and gradually, or you may rupture the plant cells in the leaf tissue.

There are products that can help prevent frost damage. Spraying frost-tender plants with an anti-transpirant such as Anti Stress® 2000 will help provide 2-6 degrees of extra insulation from the cold by reducing the amount of moisture a plant gives off. Anti-transpirants are non-toxic and dry clear.

If you don’t already have mulch around your plants, add a 2-3″ layer of mulch or top dressing. This helps the soil retain moisture and stay warmer, as well as giving the roots some insulation from the cold.

Another protective measure is to cover tender plants with burlap or plastic. DeWitt® N-Sulate is a great reusable fabric as well. This can help prevent frost damage by providing an extra 2-6 degrees of protection. Make sure to fasten the material you use securely over frames or stakes so that it does not touch the plant; otherwise it will transfer the cold directly to the plant. Remove any covering during the daytime to allow the plants to absorb sunlight.

Wait to prune frost-sensitive plants until after the danger of frost has passed and new growth has started. If your plant is injured, leave the damaged foliage on the plant so it will act as a protective layer to the foliage beneath. Trimming the plant too early may stimulate new growth that can be damaged by further frosts. You may also end up pruning out more foliage than is necessary; some of that dead-looking foliage may still be alive. When you do prune, the idea is to let the frost damage guide the pruning. Prune only the areas that are not showing new growth.

If you have any questions about which plants to protect, just ask a garden expert. He’ll be happy to help you make sure you’re equipped properly to fend off the damaging effects of frost.

by Paul Ingraham, Vancouver, Canada

You are a colony of (at least) ten trillion cells, both your own cells and stupefying numbers of guests.1 That is what a human being is — a very large social gathering of cells. Ten trillion is a conservative estimate, but it is one heck of a lot of cells. That is about 200,000 times more cells in a single person than there are people on planet Earth. That’s the sort of number that you really can’t get your head around. Even if you have a very big head.

So how do ten trillion cells walk into a bar?

How do they walk, I mean? Or even stand up? It’s a bit of a trick for ten trillion cells to do that. Individually, they certainly couldn’t pull it off. A single cell would be have trouble walking six inches for a hot date with another single cell.2

It’s a co-operative effort, obviously. There are probably many committees, subcommittees and review panels involved. But, in spite of the biological bureaucracy, the end product — walking — is quite efficient. Walking is so efficient, in fact, that is constitutes one of the great mysteries of how people work. We3 still can’t make a bipedal robot that can walk, not like us anyway. We humans simply don’t understand the details of our own locomotion.

Rocket science isn’t all that difficult. It’s not brain surgery.

a rocket scientist

But we do have some idea how we at least stay upright. Even I understand it. This superficially simple thing of rising up to a height of six feet or more is an impressive feat for a bunch of cells who are, individually, shorter than a coffee stain. But together they pull it off, and that basic accomplishment is what I’ll focus on here. This is stuff that cells probably learn in cell kindergarten.

You aren’t stacked

Contrary to popular opinion, bones are not really stacked on each other like bricks. We do not really rest on our joints as much as you might think, nor in the way you might think. There is compression and friction in joints due to gravity, but this is not the supportive principle by which we manage to get upright each morning and stay that way.

Vertebrae in particular are not really made for “support.” We are one of the few creatures on Earth with an upright spine, the odd animal out; all other vertebrates on Earth has a horizontal spine, which is much more obviously not built for bearing weight by stacking. In fact, the spine we have is really not particularly well-constructed for verticality. It’s as though we borrowed a tool used by other species for hammering nails, and decided, “Let’s use this for screwing in lightbulbs.” It’s a bit queer, really.4

Bare skeletons, as a general rule, fall over very easily.

In fact, rather than being stacked, we are held together and upright by muscles. Bare skeletons, as a general rule, fall over very easily. In the living body, even when we think that we are completely relaxed, our muscles are actually sustaining a constant level of tension — called “resting tone” — that holds joints together.5 When we are anaesthetized, surgeons must be cautious not to dislocate joints,6 because they become quite loose. This constant tension is what we really “stand on” — not bone resting on bone.

This idea, in which the rigid elements of a system “float” in a continuous tension network, was called “tensegrity” (tension/integrity) by Buckminster Fuller. For a long time the ideas were more widely known among architects than biologists.7 Biotensegrity could seem like quite a flaky concept at first glance, and the idea has certainly been co-opted for dubious purposes over the years,8 but “tensegrity biomechanics” and “biotensegrity” are slowly coming into their own as an important way of modelling and explaining biomechanical function.

Bones float in muscle, functioning more like “spacers” than bricks. They provide rigidity for leverage and as foundations for complex arrangements of high-tension wires (muscles and tendons). We are pulled upright, and held upright, in much the same way a circus tent pole is erected and held upright — not because it is resting on itself, but because it is being pulled equally in all directions by ropes. Unlike a circus tent pole, we actually need to move around, so this arrangement is extremely dynamic and active, constantly at work even when we are sitting.

There is one other major principle that keeps us upright: hydrostatic pressure (“hydrostatic” meaning “latin for something”).

We are “bags of mostly water”

Once again, bones are of secondary importance to another more important substance: soft connective tissue. Some aliens on Star Trek: The Next Generation referred to humans as “ugly bags of mostly water.”9 And right they were, at least about the bags and the water. Ugly depends on which bag of water we’re talking about (but let’s not go there).

The point the aliens were trying to make was that humans are mostly water — and everyone knows that, right? More specifically, and less widely known, is that our water is contained in flexible membranes. A bag. The “sack” is made of our connective tissue, intricate layers of a substance somewhat like Saran Wrap that literally holds us together. We have more connective tissue than anything else.

The water (hydro) inside of us is under constant (static) pressure — hydrostatic pressure. The bag is tight. This is just like putting a tight elastic band around a water balloon: it squishes it into a more elongated shape. If you were to put several rubber bands in a row around a water balloon, it would start to look more like a tube than a balloon. In fact, it might start to resemble, say, a leg. If only it could balance, this “balloon leg” could stand upright — thanks to the pressure of the water inside.

The balloon analogy is surprisingly apt, because our anatomy actually is subdivided into balloon like subdivisions defined by thin, tough layers of Saran-wrap like tissue called “fascia” — same stuff as the gristle in steak. The compartments can swell even like a balloon (which can be quite disastrous).11 An even better analogy is that these are like sausage wrappings, giving the loose contents shape and firmness.

This is entirely how plants stand up. Spinach has no spine, no bones at all, but it still manages to stand up. Unless you don’t water it, and then it wilts — no water, no pressure, no standing up. Speaking of sausages, of course there is one part of the human body, the male human body specifically, that illustrates this principle perfectly.

Ta da!

Our ten trillion cells manage to walk into a bar by applying two major physical principles: biotensegrity and hydrostatic pressure. Our cells build tough membranes to tightly surround compartments of pressurized water, they make rigid bones to act as spacers and points of leverage, and they arrange themselves in complex systems of muscle tissue in order to literally “pull” us into the vertical position and keep us there like a tent pole.

How ten trillion cells order a tall cold one and generate bad pick-up lines is a completely different mystery altogether.