A Mountain of Orchids

Needle ice?

What the heck is going on? All those nice people keep telling you its o.k. to plant in the fall, even BEST to plant in the fall. Now it's early spring and all of last year's treasures have popped right out of the ground and are laying on their sides like ship-wrecks washed up on the beach.

It's the annual heave...and though that's exactly what you feel like doing, you rush to and fro, tucking plants back into the ground and cursing the evil garden gnome that ran around last night, and is now hiding behind some mossy rock snickering wickedly at your helplessness.

No garden is immune from frost heave, but why does it happen and can we do anything about it? This condition is a natural one exacerbated by our gardening practices. It's one of the nefarious children of the famous freeze/thaw cycles that gardeners in temperate climates hear so much about.

It's caused by a phenomenon known as "needle ice." Needle ice is formed in the spring and fall of the year when water in the ground and near its surface comes into contact with air with the temperature below freezing. It happens at these times of the year because it's then that soil can be warmer than the air, yet still come into contact with freezing temperatures.


The power of needle ice demonstrated in a flat

As the surface of the soil freezes and needle ice continues to be formed under ground, the pressure of the water in the soil pushes its frozen crown upward above the surface taking soil, and rootballs with it and pushing your plants out of their carefully dug holes. (These crystals are usually up to 3cm in length but can be much longer).

What can we do about it? Well, for starters, realize that your gardening practices may be part of the problem. While planting in fall is a fantastic way to give perennials a jump-start for next season, they've got to have time to root in. Soil has to have enough time to settle back down before winter.


*Needle ice crystals*

Needle ice is most common in soil that is worked late in the season and hasn't had time to re-compact, and places where mulch has been applied thicker than a dusting. It only affects plants that have been planted late in the season, or that have not had their roots teased out properly so that searching roots can penetrate the soil beyond the planting hole, anchoring them in before winter.

A plant that hasn't had a chance to anchor itself in its new home, soil that hasn't had sufficient time to resettle before freezing, and areas of thick mulch, are all prone to being pushed UP by the action of moisture in the ground forming needle ice. The pictures on this page are graphic evidence of the power of these formations. This seed flat was left out in fall. It was subjected to fall rains, and then a freeze. Needle ice formed pushing the entire surface of the flat skyward, pulling seedlings right out of the ground. The only other place this happened was in the mulched areas of the woodland garden.

How can you reduce the effects of needle ice, frost heaves, and the freeze thaw cycles? By all means continue to plant perennials in the fall but NOT TOO LATE! Make sure that you tease the roots out, particularly in plants that have become pot-bound, with roots circling aimlessly. Firm them in so the the newly-worked soil is not too fluffy. Always scan your gardens in early spring to determine whether any of your plants need to be reset.

Now you know why your plants seem to be popping out of the ground. Paying attention to these simple matters will keep your garden from looking like a killing field. Mother Nature giveth, and she taketh away. Tilt that equation in your favor...

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