Garden Soil for Beds Built on Top of the Ledge

Most gardens in this state are not dug, they are built. Stony glacial till with granite a foot or two down does not turn into a vegetable bed with a spade, however good the intention was in March.

So the bed goes above the ground rather than into it, and garden soil is what fills it. A blend of soil and organic compost, sold here as Garden Soil, mixed to plant into as delivered.

Can I just work compost into what is already there?

Sometimes. It depends what the bar tells you.

Push a bar down in four or five spots across the plot. If you get eighteen inches or more of soil before anything stops it, amending in place is reasonable work and cheaper in effort than it looks.

If the bar stops at six or eight inches on ledge or a boulder field, stop planning to dig. Roots will not go where a bar will not, and a season of turning stony till by hand usually ends with the same beds getting built anyway.

The third case is the common one. Enough depth, but the till is dense and the drainage is poor. There, building up gives the roots a working layer above ground that stays wet into June.

How is garden soil different from the loam?

Different jobs.

Screened loam is a mineral soil run over a screen to pull the stones and roots out. It is what lawns go on and what you regrade a yard with. It arrives as soil and nothing more.

Garden soil is that kind of material blended with organic compost. The compost is there to hold moisture through a dry August and to feed the soil life that makes nutrients available to a plant.

Fill dirt is neither. It is unscreened material for raising grade and nothing grows in it deliberately.

Rule of thumb for a camp property: loam for the lawn and the rough grading, garden soil where you intend to harvest something.

How deep does a bed need to be over rock?

Twelve inches of soil will grow most vegetables. Eight will grow greens, herbs and shallow-rooted flowers.

Where ledge is genuinely at the surface, that twelve inches is the whole root zone and there is nothing below it, so err upward. Carrots, parsnips and anything that goes down want fourteen to eighteen.

Do not lay soil straight onto rock without thinking about where water leaves. A bed on ledge with no fall to one side is a basin, and the plants drown in a wet spring rather than dry out in a dry one. A shallow bed of coarse stone under the soil, or simply siting the bed where ground falls away, solves it.

What fills a terrace, a rain garden and a shoreline buffer?

Three places on a sloped property where a planted bed earns its keep.

The terrace behind a low wall is the obvious one. The soil goes in the planting space, not against the wall itself. Behind the stones there should be a column of clean stone such as #57 Stone so water has a way out, otherwise winter pressure pushes the wall out over a few seasons.

A planted bed at a downspout takes the splash that used to cut a channel in the lawn. Dish it slightly, plant it with something that tolerates wet feet and a dry spell, and let it soak rather than run.

A planted strip along a pond or lakeshore does the same on a larger scale, holding the bank against wave wash. Ground disturbance near the water is regulated here, so check what applies at the town office before you start.

How many yards for a 3 by 12 terrace, a 6 by 8 rain garden and a 40 foot buffer?

Three hypothetical beds. Blended garden soil runs about 2,000 lb per cubic yard on this site's published figures, which is a convenient 1.00 ton per yard.

Terrace planter, 3 ft by 12 ft, 12 inches deep

• 3 x 12 = 36 sq ft
• 36 x 12 / 12 = 36 cu ft
• 36 / 27 = 1.33 cu yd, so about 1.3 tons

Rain garden at a downspout, 6 ft by 8 ft, 8 inches deep

• 6 x 8 = 48 sq ft
• 48 x 8 / 12 = 32 cu ft
• 32 / 27 = 1.19 cu yd, about 1.2 tons

Shoreline buffer strip, 40 ft by 5 ft, 6 inches deep

• 40 x 5 = 200 sq ft
• 200 x 6 / 12 = 100 cu ft
• 100 / 27 = 3.70 cu yd, about 3.7 tons

All three on one delivery comes to 6.2 cubic yards. Order seven and put the rest in pots. The soil calculator handles circles and odd shapes.

Where should the pile land if the beds are uphill?

Set the quantity and pick a date on this page. Delivery is arranged at checkout by ZIP code, and the truck needs firm ground with room to back and raise a body.

Soil is the one material where the drop spot decides the whole afternoon. A wheelbarrow of it weighs a good deal more than the same wheelbarrow of bark, and every foot uphill counts twice.

Put the pile at the high end of the run if the ground allows it, on a tarp, and cover it if rain is coming. Wet blended soil is heavy and it smears rather than spreads.

New Hampshire Rock Supply lists the rest of the bed materials on the products page if the same trip can bring mulch.