How early is too early? When we dig clay.

When digging a garden is like baking bread

Reader S.U. emailed recently to ask:

I just moved into a condo and have very little space and there is almost nothing worth keeping planted here now. I would like to know if it is too early too start to try to loosen or till the very hard clay that surrounds the base of my house all the way around.

 

We work soil any time that the excess water's drained from it. It's not a calendar date because some places thaw and drain more quickly in spring or have more trees drawing water from within. Some get wet in summer. Sandy soil typically warms and drains more quickly in spring than clay, but sand on top of a poorly drained subsoil can stay wet weeks longer in spring than well drained clay, and be wet off and on all year.

Workability in soil is called friability. Soil condition is called tilth. Friable soil is ready to be enriched or planted. Digging or tilling too early in the year can ruin tilth, like beating all the air out of biscuit batter. The first test for friability is to take a lump of the soil in hand and squeeze. Then, open your hand and prod that ball with a finger. If it crumbles at a poke, it's ready to go.

Workability in soil is called friability. Soil condition is called tilth. Friable soil is ready to be enriched or planted. Digging or tilling too early in the year can ruin tilth, like beating all the air out of biscuit batter. The first test for friability is to take a lump of the soil in hand and squeeze. Then, open your hand and prod that ball with a finger. If it crumbles at a poke, it's ready to go.

So do the squeeze test.

It's described above, right. Do it before you work any bed.

Don't expect anything that's hard packed to become fluffy loam overnight. Do expect it to become better during one growing season if you introduce air and organic matter (compost or leaves work well). The soil and beds you see here all grew well their first year and had significantly better tilth by year end.

 

Then aim to add air and organic matter to that soil.

We often do no more to hard packed soil than to pop it up in big clods, leave it rough and spread a layer of compost over it, then mulch. The compost fills the spaces and the mulch becomes the smooth surface we humans love. (Nope, plants don't have to have "smooth.") Plants' roots love a clod-compost bed, and love the nutrient-rich, moisture retentive clay too. Meanwhile, moisture and organic life go right to work on the clods' exposed surfaces, crumbling and remixing the particles.

About drainage

Drainage in gardening is not about how water runs along a surface and out to a storm drain! It's about how well the water falls into and through the soil. Most garden and landscape plants grow well only where the soil is well drained -- where excess water falls through soil within a day, drawing air in to take its place.

 

Right: We broke up this hard-packed loam and added compost in fall. We planted trees and shrubs there right away -- easier to plant big balls than small pots in such a lumpy bed; the perennials could wait until spring! By spring the plants had 18" of roots out in all directions through the compost-filled channels and myriad tiny roots forming webs around those rich clay chunks.

Below: This 18" deep hole had better drain completely in 12 to 24 hours or we'll need to make a raised bed. If 6" of water is left in the hole after 12-24 hours, we'll raise the bed 6". Then, plants' roots will be up out of the soggy soil that will be there after every rain or watering.

Clay? Maybe. Even sand can be hard packed

Many people call a soil clay simply because it's hard packed. Yet this is sandy loam that was worked with machinery when it was still wet in spring. Being pressed and whipped with all that water destroyed the delicate connections between particles that made the soil crumbly. It collapsed into a brick just like over-kneaded dough or badly beaten batter would turn into rock hard bread or biscuits.

Retire that rototiller

If you use a rototiller do it only to make the first break into tough soil or to turn under amendments lightly, like "folding" in ingredients into a batter. Don't go over and over a bed to make it smooth or you can ruin the soil's tilth.

It's especially bad to till soil that has enough clay in it to feel sticky or slippery. The rotating tines of an 8hp tiller beat DOWN on the soil below their rotation with (surprise!) eight horse power. That can pack the subsoil so hard that water backs up into the bed, ruining drainage by creating a perched water table.