Portable augers are praiseworthy assets

You might think portable augers - sometimes called hole diggers - are "luxury" tools: nice to have but not very cost-effective. Yet portable augers can speed annual, perennial and bulb installations, simplify shrub and tree planting, and help install various hardscape items, such as fence posts and signs.

Determining which type and size of auger best suits your needs depends on your operation's needs. Do you plant trees and shrubs on a regular basis? Do you have multiple signs to post on site? Are you responsible for fencing? Do you have three seasons of flower rotations, from spring's bulbs to summer's annuals to autumn's chrysanthemums? From heavy-duty, tree-planting hole diggers to petite petunia planters, an auger is available to meet your hole-digging needs.

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Mounted augers Two basic types of augers are available for today's landscape managers: affixed or mounted augers and portable augers.

* Mounted augers. These units typically operate from the power take-off (PTO) or hydraulic system of skid-steer loaders, backhoes, front-end loaders, tractors and cranes. Auger bits for these units range from 6 to 36 inches in diameter. Bit lengths range from 4 to 6 feet. When needed, auger extensions allow you to further lengthen bits.

Some of the larger diameter bits on hydraulic-mounted augers are designed specifically for tree and shrub planting. These specialized bits feature pilot-hole diggers on the auger face. Pilot-hole diggers are the first set of teeth on a narrower piece of flighting at the tip. The purpose of pilot holes is to drill a smaller diameter hole before the second set of teeth on larger-diameter flighting finishes the hole to the correct size. If you dig in hard clay soil, pilot-hole diggers will give the auger additional power, plus they'll break up the tough soil for better backfilling. Our firm has found that standard auger bits with only one set of teeth don't cut through the heavy clay soils here in northern Illinois as efficiently as pilot-hole auger bits.

Some older, mounted augers attach directly to and are driven by a tractor's PTO shaft. However, the PTO-driven augers have some setbacks you don't usually encounter with hydraulic units. For example, hitting an underground obstruction can break the auger unit's shear bolts. In addition, you cannot reverse PTO-driven augers to dislodge an obstructed bit. PTO-driven augers also have more exposed moving parts, which can add to safety concerns.

* Portable hole diggers. These units are not as common as mounted augers. Nevertheless, they often are a better choice for grounds managers because they come in various shapes and sizes. The largest of the portable augers are self-propelled, walk-behind types. Our company uses a model that is similar in size to a walk-behind mower. This unit accepts an auger as well as rotary plows and mowing attachments. For us, the advantage of self-propelled augers is that crew members who plant all day are less tired by this self-carrying unit. In fact, we have gotten some good production rates from this type of auger. Specifically, with a walk-behind model, our crews can dig 600 holes per 8-hour day with a 10-inch-diameter auger. With a 14-inch-diameter auger, our crews can dig about 120 holes each day.

Additionally, you can take walk-behind augers into confined areas where a tractor or skid-steer loader can't fit. These walk-behind models can dig holes up to about 19 inches in diameter - a good size for planting 15- to 30-inch B&B shrubs. If necessary, you can enlarge holes by hand-digging.

Some medium-sized augers with top-mounted engines also can dig holes with these width and depth dimensions. These units have handlebars for one- or two-worker operation, depending on the size of the hole. These augers are ideal for fence- and sign-post installation, as they can dig deeper holes.

More portable still are the one-person, hand-held augers with top-mounted engines. These are comparable in size to a large power drill. These hand-held units usually weigh between 15 and 20 pounds. They can accept auger bits up to about 8 inches in diameter and are the perfect size for digging smaller planting holes. Ground covers, bulbs, annuals, perennials, chrysanthemums, seedlings - one worker can quickly install all of these with a hand-held auger. Use a 4- to 6-inch auger bit for best results. An added benefit to using augers for this task is that they leave the backfill soil nicely pulverized and evenly spread around the edge of the hole.

Soil and augers When deciding whether to use larger augers, consider the site's soil type. Sandy soil offers augers less resistance than heavy clay soils. In fact, when digging large-diameter holes with mounted units, heavy clay can bog down augers to the point where they won't work.

Keep in mind that different tractors have different hydraulic-pump capacities. Manufacturers match these capacities with various sizes of augers. Talk to your vendors to match your tractor's specifications to the range of available augers. Always field-test a potential purchase in the conditions you typically encounter to ensure it will do the job.

Hard clay and rocks are the archenemies of both types of augers. Even so, most manufacturers design their augers to accommodate such obstructions. For example, when using a PTO-propelled auger, if you hit a rock that won't dislodge, these units have shear pins that are designed to break. By breaking, the low-cost shear pins protect the permanent, mechanical linkage of the units. Hydraulic-powered augers don't have shear pins. Instead, when they encounter an unmovable obstruction, the hydraulic-relief valve opens and re-routes the flow of oil back to the reservoir. Plus, you can reverse hydraulic units, unlike the other type of units. On smaller hand-held units, however, you must take extra care. If they hit obstructions, they can - as mentioned - send the powered unit spinning even if it has a shear pin.

When dealing with a subterranean obstruction, remove the auger from the hole and hand-dig the area to remove the offending object. Then continue drilling the hole to the proper depth. Heavy clay soil, however, can bog down an auger's motor, sometimes to the point where the machine will stall. With a large-diameter bit in heavy clay, you may find that your auger only can dig part of the hole. In these situations, you also may need to hand-dig the remainder of the hole. Generally the larger the auger bit, the more resistance encountered in clay, even for powerful mounted augers.

Also in clay soils, augers tend to "glaze" the side of the holes. This glazing seals the sides of the hole, trapping water and creating a "clay bathtub" effect that impedes percolation of water and may lead to rootrot of the transplant. To minimize this glazing effect, score or hand cultivate the soil on the sides of the hole with a shovel, pitchfork or hoe.

Taking care Like many pieces of equipment, crews can push augers to their limits. These machines can work hard for many uninterrupted hours, but abrupt surges are bad for them. Don't let crews try to make a 12-inch auger dig an 18-inch hole by shifting the machine back and forth. Doing so stresses the engine. As with any equipment, ensure employees are adequately trained to operate augers properly. For example, educate your crew on the purpose of shear pins. They cost pennies, while transmissions cost hundreds of dollars. Therefore, always supply crews with plenty of shear pins; you don't want a crew member inserting a hardened bolt - because he or she didn't have the proper pin - and causing major mechanical damage.

When using smaller, portable augers, it is important to sharpen the auger bit's flighting blades and teeth every few days. Our firm often keeps two sets of auger blades for each machine so we can rotate and sharpen blades regularly with little or no downtime.

Owning a portable auger can greatly speed up any planting job. The smaller hand-held units can aid bulb, annual and perennial installations. Mounted augers can "turbo-charge" shrub and tree planting, as well as sign- and fence-post installation. The versatile walk-behind units can dig nearly any planting hole and then double as a mower or rotary cultivator. Given these assets, portable augers don't seem so much like "luxury" tools anymore, do they?

John Mitten is vice president of operations, Installation Department, D.R. Church Landscape Co. Inc. (Lombard, Ill.).

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