Soil Sampling Essentials

by Andrea Laine, EMGV

Our master gardener office has fielded a lot of calls lately about soil sampling. And, we are a little more than six weeks away from the end of soil sample “free” season, so a refresher on how and why to prepare a soil sample seems appropriate.

Let’s begin with the end: November 28 is the last day soil samples will be accepted in the Durham  County Extension Master Gardeners office at 721 Foster Street, Durham. The Extension office is open Monday through Friday, 8:30 a.m. to 5 p.m.

Why bother with testing soil? It is the best way to set your garden up for success. The test results will tell you exactly what nutrients need to be added to the soil to grow what it is you desire in that spot.

Who tests the soil? The folks who analyze soil samples work for the N.C. Department of Agriculture & Consumer Services (NCDACS) in Raleigh. They are agronomists – soil scientists — and can also help you understand your soil sample report; Do not hesitate to call the telephone number on the report.

Master gardeners figure prominently during “free season” because one of us transports your collected samples to the right place in Raleigh for you. If you ask me, that’s even better than being free! Homeowners who sample soil between December 1 and March 31 must deliver the sample to the NCDACS themselves and the cost per sample is $4.

What will you need for this task and where can you get it? In addition to basic gardening equipment, you will need:

  • soil box
    soil sample box

    One soil sample box for each area of your yard that you wish to test. (See photo to left.) Do not assume that all the soil in your yard is the same. And know that it is perfectly acceptable to sample the soil in a raised bed.

  • A Soil Sample Information Form. One form has room for up to six areas.

So, that’s one form and multiple boxes. Soil boxes and forms are available from the Master Gardener office  and local garden centers (usually at the cash register). The boxes and forms are free.

How to obtain a good soil sample? Follow these five steps:

  1. Choose a day when the soil is relatively dry. Digging in wet soil is rarely a good idea.
  2. Prepare by cleaning and clearing; You want to begin with a clean stainless-steel shovel and a clean plastic bucket. Then clear away grass, twigs and leaves from the soil’s surface.
  3. Dig a V-shaped hole (strive for eight inches deep for a garden, four inches deep for a lawn).  Take a one-inch slice from one side of the hole and place it in the bucket. Do this at least six to eight times. To obtain one sample, you must dig several (or more) shovelfuls of soil from different spots within each area being sampled. This will ensure accurate results.
  4. Using a clean tool, mix the soil. Remove rocks and other large pieces of organic material. From this mixture, fill the soil sample box to the red line. Close the box. (If you have difficulty closing the box, don’t despair, try again. It will close eventually. Please do not tape the box.)
  5. Complete the Soil Sample Form. Two important points here: First, for each sample, you must choose a 5-character ID and place it on the sample box and on the sample form. That’s how you will know which results belong to what samples. I generally choose geographic descriptions like “fence,” “front,” or “woods” to distinguish the location from which I took the sample. But use whatever is meaningful to you. And it never hurts to write it down in your garden journal for future reference. Secondly, choose a “planting code” for each sample. This is a multiple choice question; choices are listed on the back of the form.

    soil codes
    One of these “planting codes” must accompany every soil sample.

Bring the sample(s) to the Master Gardener office within the Durham Cooperative Extension building at 721 Foster Street in downtown Durham before Nov 28. You will receive an email when the results are ready. The email will contain an online link to your report.

If you have questions at any stage of the process, feel free to contact the master gardener office by phone (919-560-0528), or by email (

NDDA&Cs Agronomic Division, Soil Testing Section

NC Cooperative Extension Services, Durham County Master Gardener Volunteer Program, Urban Horticulture Note No. 5: Submitting Samples for Soil Testing, October 23, 2007

Further Reading
A Gardeners’ Guide to Soil Testing

Photo credits: Andrea Laine

Learn With Us, week of October 14

Durham Garden Forum: Approaches to Planting Design
October 16, 2018, 6:30-8pm
Sarah P. Duke Gardens
420 Anderson St, Durham, NC 27705

A landscape design will take shape before your eyes as Preston Montague, landscape architect and artist from Lift[ED] Landscapes, builds a landscape design in ‘real time.’ He will work to meet a user’s goals while also exploring options and possibilities that become evident through the process of design. Learn about contemporary design strategies and how you might apply these in your own landscape. Meet in Doris Duke Center.

$10, payable to Durham Garden Forum (Forum members free with $25 annual membership). For membership information, email No charge for Parking.

To Do in October

by Gary Crispell, EMGV

Well, wasn’t September fun?! Dry, wet, dry, OMG wet. Heartfelt sympathies to those who suffered loss by Florence. For those of us whose gardens were only moderately affected (or not at all) here is the October calendar.

Not much to do here unless you are planting spring flowering bulbs. Should that be the case, incorporate a little balanced fertilizer (10-10-10 or equivalent) into the soil as you plant. Store any leftover fertilizer in a dry place for the winter.


  • The above-mentioned spring flowering bulbs (e.g. hyacinths, tulips, daffodils, crocuses, etc.).
  • Pansies! Those plucky members of the Viola genus who can brighten up a gray winter day should be on everyone’s list unless, of course, there are deer nearby.  Apparently, the pansies make a great dessert after a meal of azalea branches.  Plant them soon as the more established they are when it gets cold the better able they will be to withstand the cold.
  • “Fall is for planting.” It’s not just a slogan from the nursery industry. It is gospel. The very best time to plant any new landscape plants you have been planning is now.
  • Peonies can be planted or transplanted now.
  • In the vegetable garden consider a nitrogen fixing cover crop like red clover, hairy vetch or winter rye. This will help keep down the weeds and add nitrogen to the soil. In the spring just till it into the soil to add nutrients and organic matter.
  • If you happen to be one of the foresighted people who have a cold frame now is the appropriate time to plant a winter’s worth of salad. Lettuce, green onions, radishes, carrots, spinach and other leafy greens will grace your salad bowl all winter if planted now.

Once frost (It’s October. It is going to frost!) has finished the decimation of the perennial garden cut off all the dead tops and throw them on the compost pile. Root prune any trees or plants you plan to move in the spring.

Unless you have a lace bug problem, it is time to clean up and winterize the sprayer and store the pesticides in a secured, dry location that will not freeze. As for the lace bugs, they are active whenever the leaf surface temperature is warm enough (i.e. whenever the sun shines on the leaves). A horticultural oil spray can be helpful in controlling both feeding adults and egg stages.

Lawn Care
Maintain adequate moisture levels for any newly seeded or sodded lawns.  Avoid leaf buildup on lawns.

Tall fescue and bluegrass (not the fiddlin’ kind) can still be planted in October.

Keep an eye on any new cuttings in the cold frame (the one without the salad greens in it). They should be checked at least twice a month and watered as needed.
If you are a gardener lucky enough to be able to grow rhubarb now is the time to dig and divide it.

Other stuff to do that will keep you outdoors while the leaves turn color:

  • Take soil samples while they are still FREE. NC Department of Agriculture will charge for them from November to April.
  • Put those raked 0r blown leaves into the compost bin or till them into the veggie garden.
  • Clean fill and put out the bird feeders.
  • Dig and store (cool, dark, dry) tender summer flowering bulbs (E.g. gladioli, dahlia, caladium) before frost.
  • Clean up lubricate and otherwise prepare lawn and garden equipment for its long winter’s rest.

A mea culpa. This writer neglected to inform you that it is time to band trees that are susceptible to canker worm invasions. This involves wrapping and securing the trunk with a coarse material like burlap or quilt batting about 4 or 5 feet above the ground. That in turn is wrapped with a corrugated paper wrap that is then covered with the stickiest gooeyest stuff you’ve ever played with. All these materials are available at some nursery/garden centers, one of which is very proximal to the Durham Cooperative Extension office.

For a fun activity now that will yield fresh living flowers in the bleak mid-winter try your hand at forcing spring flowering bulbs. Plant bulbs in pots early in October and place them in the refrigerator. In twelve weeks bring them out into the house and watch them grow and bloom. Kids love it.


Enjoying a Morning Cup of Coffee with My Houseplants

by Jane Malec, EMGV

A morning cup of coffee is a necessity at my house. It is just a part of getting the day started and I love everything about it — making it the night before, turning the pot on in the morning, and the aroma when it’s brewing. Over the years our coffee habits have changed due to the ever-fluctuating studies on the healthiness of, optimum consumption levels, or brew strength of a cup of coffee. It’s mostly decaf and fewer cups for us now.  Still, it remains a force of habit to pour the same level of water and ground coffee beans into the brewer regardless if we are running out the door or having a leisurely morning. Even if I reheat a cup later in the day, there is always a little left over brew sitting in the pot.

So I often walk around the house pouring the remaining cold coffee onto thirsty house plants. Our current home has a private well and I am ever more conscious of water usage. I make sure to pat myself on the back over my dedication to water conservation with every cup of coffee that soaks into the potting soil. I even wander outside to share the wealth with my container plants. A win-win, right? Or, maybe not. If there is a debate on human coffee consumption, I suddenly wondered if there might be one on plant consumption.

Coffee comes to us through a complicated path. To begin with, there are several species of coffee plants or trees, the two most commonly grown are Coffea arabica and Coffea canephora which is also called Coffea robusta. Arabica coffee is considered superior and commands a higher price than the robusta. Coffee production is a labor intensive process. The berries are picked by hand, sorted and allowed to ferment which removes a gelatinous tissue layer. Then they are washed with large amounts of fresh water. The seed of each berry, which is the bean, is roasted and then ground before becoming the beverage we enjoy. The degree of roasting the beans will determine the flavor, but not the caffeine level. Interestingly, the lighter roasts contain more caffeine so watch out you breakfast blend drinkers!

Which leads back to my curious question — is liquid coffee good for plants? There is a good amount of anecdotal information (on the Internet) concerning the use of brewed coffee for watering plants. However, there is little research-based information on this nor on liquid coffee’s benefits to soil.

However, there are some basic guidelines to help us understand if my “coffee watering practice” is helping or harming to plants. While coffee grounds tend to have a pH around 6.5 to 6.8 which is nearly neutral on the scale (neutral is 7), brewed liquid coffee is reported to have a pH level ranging from 5.2 to 6.9 depending on the type of coffee and how it is prepared. The lower the pH the higher the acidity; A drop in one full pH equals a factor of 10. For example, if the brewed coffee is 5.5 pH and the grounds are 6.5 pH, the brewed coffee is 10 times more acidic than the grounds.

Understanding that most plants like a slightly acidic to neutral pH and factoring in that most municipal water is slightly alkaline (pH greater than 7), it is possible that the acidity of the coffee could benefit plants. Also there are small measurable amounts of magnesium and potassium which are plant nutrients. Keep in mind that this information can only serve as a guideline as there can be other factors in play, for instance, if you have a private or community well, and whether or not you use a water softener.

The best recommendation is to follow some simple rules. Make sure the coffee is cold and then water it down. Never water with coffee if you add milk, cream or sugar. Know your plants pH happiness levels and then watch the impact this is having on your plants over time.  Adjust your morning coffee routine.   

Remember too much of a good thing is, well, too much of a good thing. Resign yourself to pouring some of the leftovers down the drain or on your compost pile. 

Maybe I could starting singing to my plants instead?  Hmm. 


Coffee as Fertilizer?

Yard and Garden

Clay soils