In this undated photo, large and small pores abound in this well-aggregated soil, offering roots access to both air and moisture in New Paltz, N.Y. (Lee Reich via AP)

In this undated photo, large and small pores abound in this well-aggregated soil, offering roots access to both air and moisture in New Paltz, N.Y. (Lee Reich via AP)

Let’s talk dirt: soil terms every gardener should know

Good gardens start from the ground up, but to be a good soil steward you have to understand some basic terminology.

A few important terms associated with soil:

Soil TEXTURE describes nothing more than the size ranges of the mineral particles that make up a particular soil. Those size ranges are defined in three broad classes: clay (smaller than 0.002 mm), silt (0.002 mm to 0.05 mm) and sand (greater than 0.05 mm). Rare is the garden soil that is pure sand, silt or clay, so textures usually have such names as “sandy clay” or “silty clay” to indicate the mix.

Texture is important because particle sizes reflect the sizes of the pores between them, and that influences how much air and water the soil can hold. The smallest pores actually draw water in by capillary action, then hold onto it tightly. So clay soils can stay moist through long periods without rain.

ADVERTISEMENT
0 seconds of 0 secondsVolume 0%
Press shift question mark to access a list of keyboard shortcuts
00:00
00:00
00:00
 

Sandy soils have large pores, too large for capillary action, so gravity easily pulls excess water down beyond the root zone. Sandy soils tend to dry out quickly. On the other hand, they are well aerated because air fills those empty pores.

The ideal soil has a little of everything — sand, silt and clay — for both good aeration and good water retention. Such a soil, with roughly equal functional contributions from clay, silt and sand is, texturally, a LOAM.

You get what you’re dealt in soil texture, but fortunately texture isn’t the end-all when it comes to water and aeration. A soil’s mineral particles can clump together — or “aggregate” — into crystal-like, larger units, which give a soil STRUCTURE.

A poorly aggregated clay soil, its small pores filled with capillary water, leaves roots gasping for air. However, when a clay soil has good structure, the small particles aggregate together to make large particles with large pores between them. At the same time, water can be held in the small pores between particles within the aggregates. A well-aggregated clay soils offers roots the best of both worlds.

While it’s usually impractical to change your soil’s texture, there are ways to manage soil so that it has good structure. (Hint: Organic matter — see below — is the key.)

FRIABILITY and TILTH, while not meaning exactly the same thing, are closely related from a plant’s point of view. A FRIABLE soil crumbles when you squeeze it gently. TILTH is the physical condition of the soil as far as plants are concerned. A soil that is friable is in good tilth. Good structure puts a soil in good tilth.

A soil that is WELL-DRAINED allows water to readily percolate through it. Drainage, as you now know, is related to both texture and structure: Sandy soils generally have little structure but, with large pores, are well-drained. Clay soils, at the other extreme, are well-drained only if they have good structure, in which case they are also in good tilth. Texture, structure and tilth aside, ground where there is a high water table cannot be well-drained; there’s nowhere for water to go.

ORGANIC MATTER is the living and once-living component of the soil. The low percentage of organic matter in soils — usually only a few percent — belies its importance. Besides its positive influence on plant nutrition and health, organic matter also provides the glues that lead to aggregation, good structure and, hence, friability, good drainage and good tilth.

CULTIVATION, in gardening, has more than one meaning. One sense is to stir the soil, as with a hoe or rototiller. Such cultivation kills weed seedlings and loosens the soil surface so that water more readily percolates in. Cultivation also refers to plant care generally, in the same way you cultivate a friendship. Caring for the soil — keeping it in good tilth — is one component of plant cultivation.

More in Life

Students throw brightly hued powder into the air during a color run at Kaleidoscope School of Arts and Science in Kenai, Alaska, on Saturday, May 3, 2025. (Jake Dye/Peninsula Clarion)
Color run paints students with kaleidoscope of hues

Kaleidoscope School of Arts and Science on Saturday gathered parents and students… Continue reading

Artwork by The Art Gaggle is displayed as part of “What We Do” at the Kenai Art Center on Friday, May 2, 2025. (Jake Dye/Peninsula Clarion)
Local artists share ‘What We Do’ in May show at Kenai Art Center

An eclectic mix of local art makes up the May show at… Continue reading

People from various faiths stand together at the conclusion of a prayer by the Kenaitze Indian Tribe’s Heartbeat of Mother Earth Drum group during a National Day of Prayer Celebration hosted by the KPen Interfaith Community at Soldotna High School in Soldotna, Alaska, on Thursday, May 1, 2025. (Jake Dye/Peninsula Clarion)
Celebrating unity and diversity

An array of groups offered prayers and songs at The National Day of Prayer concert in Soldotna.

tease
‘What gives it teeth’

Indigenous author Lily H. Tuzroyluke spoke on her novel and writing process last week at the Homer Public Library.

Jake Dye/Peninsula Clarion
Donna Shirnberg rehearses”Picnic” at the Kenai Performers Theater near Soldotna, Alaska, on Saturday, April 26, 2025.
Small town America grapples with big emotions

Kenai Performers stage playwright William Inge’s Pulitzer Prize-winning drama “Picnic.”

Attendees gather to dance and to listen during a performance by Blackwater Railroad Company, part of the Levitt AMP Soldotna Music Series on Wednesday, June 7, 2023, at Soldotna Creek Park. (Jake Dye/Peninsula Clarion)
Soldotna Music Series announces lineup, starts June 4

The Levitt AMP Soldotna Music Series will bring performances to Soldotna Creek Park each Wednesday.

Individual Artist Awards logo. Photo courtesy of the Rasmuson Foundation
Rasmuson Foundation accepting applications for Individual Artist Awards

Project Awards are for short-term projects that clearly benefit the artist and their development.

File
Minister’s Message: Noticing the gorilla

Where we turn our attention determines what we can and cannot see.

Nikiski Bulldog Theatre actors rehearse “All Shook Up” in the Nikiski Middle/High School Auditorium on Saturday, April 26, 2025. (Jake Dye/Peninsula Clarion)
Elvis-themed musical brings music and moves to Nikiski stage

“All Shook Up” combines the familiar tunes of Elvis Presley with Shakespearean narrative of romance and identity.

Most Read