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Soil Building 101 for Dahlia Gardens

Posted on: March 29th, 2018 by Aimee Sherrill

Soil is the first step in a successful garden, because plants are only as good as the soil they are planted in.   Replacing nutrients lost over the winter months is essential to how well your plants will produce during the growing season.  Growing great gardens takes a lot out of the soil from year to year, and it’s important that we put that nutrients back into the soil from year after year.

Prepare your beds: Add Compost

Add a 4″ layer of compost to your planting beds, then till or work in with a pitchfork to mix the compost and the native soil together.  This will drive the nutrition back into your soil that was depleted from last years garden.  Compost improves the soil by adding  organic matter to make the soil softer, compost allows the soil to drain better, adds oxygen to the soil by improving drainage and attracts beneficial insects, worms and micro-organisms to you soil.  The benefits of compost is endless, but too much is not a good thing either.  Your plants don’t like to grow in straight compost, they need the micro-nutrients that comes from your native soil as well.

Clay soils will become more loose in texture allowing for better drainage.

Sandy soils will hold more moisture and nutrients by adding compost.

Small gardens options vs Larger gardens options for compost:

If you have a small garden area, pick up a few bags of compost at your local garden center or nursery.  It will tell you

Working our compost pile

on the bag, how many square feet of ground 1 bag will cover.  If you have a larger garden area and a truck, buying compost by the yard is a better option.  It’ll also be cheaper than buying the same amount of bagged soil.  Nurseries in your area often have compost by the yard that they load with a tractor directly into your truck or trailer.  Take it home and put a 4″ layer all over the area you want to plant.  Turn in with a rototiller and you are good to go when it’s planting time.

Time your dahlia planting just right:

Planting your dahlias at the right time is the key to successful dahlia growing.  Timing is everything in dahlias.    Plant your dahlias when your soil has warmed to 60 degrees and is not too wet or soggy.  A good rule of thumb to follow is to not plant your dahlias until you are safe to plant your tomatoes, potatoes or corn in your area.  Planting your dahlias should be one of the last of your spring plantings.

 Soil Testing:

The best time to test your soils nutrient levels is from February to April.  Basic soil test kits tell you about N-P-K, N-Nitrogen, P-Phosphorous Soil Test kitand K-Potassium and will measure the amount of nutrients you have in your soil.  They can also tell you where your soil pH is at.   The pH level in your soil is important because it can effect nutrient uptake by your plants.  If the plant doesn’t like where the pH level is at, the amount of fertilizer that plant will absorb can be hindered.

Why your soils pH level is important:

PH has a range from 0-14, with 7 being neutral.  You want your soil pH to be about 6.3 – 6.8 or so for dahlias because dahlias like ‘slightly acidic’ soil.  Most soils will fall between the range of 6-8.  6 would be more on the acidic side and 8 would be more on the alkaline side.  Most acid soils are found by trees that drop their needles every year and cause the soil to be more acid.   Soil test kits can be found at any home improvement store this time of year.

What to do if your soil is too acidic or too alkaline:

Too acidic:  Add Lime to raise the pH level in your soil.

Too alkaline: Add Ferrous Sulfate (iron) to lower pH

The pH level in the soil is what would cause a hydrangea to be pink or blue in color.  By adding lime to your soil and raising the pH, the hydrangea will be pink.  By adding ferrous sulfate (iron) and lowering the pH, this will cause the hydrangea to be blue.


The process of changing the pH levels won’t happen overnight.  Often it will take months up to a year to see the full results.  But knowing now, and taking steps to correct it will grow a better garden in the future.  Try to make it a yearly chore, to test your soil.


 What’s Happening at The Dahlia Barn right now?:

We are at full speed with shipping dahlia tubers and perennials all around the country right now.  We’ve shipped the southern states and will start shipping to the central and northern United States during the month of April and we’ll continue to ship through May, no matter where you are in the country or until we are sold out for the season.  The barn will be open for Dahlia Tuber & Perennial Sales starting April 7-8, 2018 and we’ll be open every weekend in April.  Hours are Saturdays-Sundays 11am – 4pm.  If you are within driving distance, please take a drive out some weekend in April to our barn that is loaded with dahlia tubers, plus many other bulbs, perennials, begonias, hostas, peonies, phlox and more!  Our barn is filled with what you need to create a colorful garden.

Hope everyone has a very Happy Easter!

5 Responses

  1. Sunny says:

    We have moved to a retirement residence with a large balcony and I’m wondering if I can successfully grow 3-4 dahlias in a large grow bag? ( I used the bag for potatoes so it’s quite large)

  2. Roger Michalski says:

    Dahlias are my favorite. Love all the good tips on growing them.

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