A Little Bit of This & That

The creativeness of a creative woman

Those Heavenly Hydrangeas – Part 3

So you’ve picked out your favorite Hydrangea, or 2 or 3……….now what?

When & Where to Plant
In that spring is on the way, it’s important to know the best time of the season for the hydrangea to establish a good root system. It’s best to wait to plant until the last chance of frost has passed so that the plants have the best possible chance at survival. A late frost can nip the buds and reduce the number of blooms. There isn’t one universal answer for planting time and it really depends on your weather.  If your temperatures are less than 40 degrees, it’s probably too cold. The most active growth period for hydrangeas is April through September and if they must battle cold to get their root systems established, it may be too much for them to do both vital tasks of root establishment and setting buds to bloom.  At the other end of spectrum, Hydrangeas can be planted in late summer, however good root establishment will not occur in severe heat due to the stress put on the plant. If the weather is over 85 degrees consistently, it’s probably too warm. This also holds true for transplanting Hydrangeas.

Where you plant will determine the amount and quality of blooms you’ll get. A too shady location will result in fewer blooms, while a too sunny location will result in bloom wilt. Hydrangeas love a location where they can get morning sun and afternoon shade. They will grow in locations with afternoon sun, but will need more supplemental watering and as mentioned above could result in bloom wilt. In either situation, Hydrangeas can not take full sun. Some varieties are cited as ‘Full Sun’, however the large leaves of hydrangea result in more water loss (transpiration) in the heat of summer, so all hydrangeas need a break from the sun at some time during the day.

Hydrangeas need 3-4 hours of direct sunlight to put on the best bloom show, and thus a too shady location will reduce the number of blooms. The exception to this is the Oakleaf hydrangea. TheGeorgia native is stunning as an understory shrub beneath mature trees. As long as it receives good slanted sun in either early morning or late afternoon, it will bloom fine. Avoid planting any hydrangea in locations that stay soggy or very dry.

The All Important Soil
You always hear about the importance of good soil with good drainage for hydrangeas. Most areas don’t have perfect soil but there are lots of things you can do to improve your soil and grow better hydrangeas (and other garden plants). Good soil is important for root growth and supplying water to the hydrangea’s leaf and stem structure but most importantly, the flowers. But how do you know what kind of soil you have? and if it’s not optimum then how do you improve it?

Soil science can be complicated and I could spend months on the topic, however I’m just going to touch on the information needed for gardening. There are 5 different soil types that gardeners and growers usually work with. All five are a combination of three types of weathered rock particles that make up the soil – sand, silt, and clay. How these three particles are combined defines the soil type—how it feels to the touch, the drainage, and nutrient content.

Types of Soil

Sandy soils  have a high proportion of sand and little clay. It has the largest particles among the different soil types and is dry and gritty to the touch. Because the particles have large spaces between them, it can not hold water and thus the water drains rapidly past roots, particularly those of seedlings. Sandy soils dry quickly and are low in nutrients, because they are swiftly carried away by the extensive and fast drainage.  When conducting the ‘ball roll’ test (moistening the soil and rolling it into a ball to check the predominating soil particle) sandy soil will not form a ball and will easily crumble through your fingers.

Silty soils are comprised mainly of intermediate sized particles, are fertile, fairly well drained and holds more moisture than sandy soils, but are easily compacted.  Due to its moisture-retentive quality, silty soil is cold, drains poorly, and is poorly aerated. This soil is smooth to the touch. When moistened, it’s soapy slick. When you roll it between your fingers, dirt is left on your skin.

Clay soils  have over 25 percent clay. Also known as heavy soils, these are potentially fertile as they hold nutrients bound to the clay minerals in the soil. But they also hold a high proportion of water due to the capillary attraction of the tiny spaces between the numerous clay particles. They drain slowly and take longer to warm up in spring than sandy soils. Clay soils are easily compacted when trodden on while wet and they bake hard in summer, often with a noticeable cracking. When moistened this type of soil feels sticky, rolls up easily, and will form into a ball or sausage-like shape. 

Loamy soil is the type of soil plants and gardeners love. It is comprised of a mixture of clay, sand and silt that avoid the extremes of clay or sandy soils and are fertile, well-drained and easily worked. They can be clay-loam or sandy-loam depending on their predominant composition and cultivation characteristics. It has higher pH and calcium levels because of its organic matter content. Loam is dark in color and is mealy—soft, dry and crumbly—in your hands. It has a tight hold on water and plant food, yet drains well since air moves freely between soil particles down to the plant roots. The ball test for loam yields a smooth, partly gritty, partly sticky ball that crumbles easily.

Saline soil occurs in extremely dry regions and is usually brackish because of its high salt content. It can cause damage to and stall plant growth, impede germination, and cause difficulties in irrigation.
The salinity is due to the buildup of soluble salts in the rhizosphere. The high salt content prevents water uptake by plants which leads to drought stress. If you have saline soil, you’ll probably see a white layer coating the surface of the soil, your plants are growing poorly, and they’re suffering from leaf tip burn, especially on young leaves.

So how do you determine what you have and how it drains? I found a few tests you can do to determine what kind of drainage and/or soil you have in your garden.

Drainage test – Dig a hole about 6 inches deep and one foot wide and fill it entirely with water. Let the water drain out of the hole completely. Fill the hole again and record the time it takes to drain the second time.

If the water drains in three hours or less, your soil is most likely draining too quickly. Chances are your soil is somewhat sandy. If the water drains in four to six hours, your soil is draining just perfectly. You have rich, great soil for hydrangeas. If the water drains in eight hours or more, the soil has poor drainage typically common with clay-like soil.

Root test – Dig gently around a selected plant, preferably an annual weed or something that was going to be moved and thrown out anyway. Pull out the plant from the soil gently making sure that the root system stays intact. Check the root system of the plant. If there are many fine strands of roots that are bright white and healthy in appearance, you have great soil. If the roots are stunted, lopsided or otherwise dingy, your have poor soil.

Compaction test – Spear a wire rod ( 4mm or ¼” gauge wire) into the soil. Mark the depth of penetration – the sooner it bends, the more compact the soil. The ideal condition for shrubs is about one foot.

Dirty Thumb test – Dig a hole about 6 to 10 inches deep. Separate a section of your soil, intact, about the size of your two palms cupped together. Is your soil granular, powdery or clumpy? The best type of soil will clump in small but breakable consistencies.

Jar Test – fill a smallish jar with a soil sampling from your garden. Shake vigorously and let the soil settle overnight. Next day, you’ll see distinct soil layers. Sand stays at the bottom, clay at the top and silt in between. Their percentages will be your clue on your soil type.

So what about soil ph and the color of the blooms?

The flower color in H. macrophylla is dependent on cultivar and the aluminum availability in the soil. Aluminum is necessary to produce the blue pigment for which Macrophylla hydrangeas are noted. Most garden soils have adequate aluminum, but the aluminum will not be available to the plant if the soil pH is high. For most Macrophylla hydrangea cultivars, blue flowers will be produced in acidic soil (pH 5.5 and lower), whereas neutral to alkaline soils (pH 6.5 and higher) will usually produce pink flowers. Between pH 5.5 and pH 6.5, the flowers will be purple or a mixture of blue and pink flowers will be found on the same plant.

The best practice is to test your soil for it’s pH level. Once you have a starting number you can proceed to amend the soil to achieve the desired level needed for the hydrangea to produce blue flowers. Below is information on pH and how to change the level in your soil. (I copied it from Clemson University – hey, it was easier than typing it all out and I want to give credit, where credit is due)

Changing the pH of Your Soil
The soil pH value is a measure of soil acidity or alkalinity. Soil pH directly affects nutrient availability. The pH scale ranges from 0 to 14, with 7 as neutral. Numbers less than 7 indicate acidity while numbers greater than 7 indicate alkalinity.

The pH value of soil is one of a number of environmental conditions that affects the quality of plant growth. The soil pH value directly affects nutrient availability. Plants thrive best in different soil pH ranges. Azaleas, rhododendrons, blueberries and conifers thrive best in acid soils (pH 5.0 to 5.5). Vegetables, grasses and most ornamentals do best in slightly acidic soils (pH 5.8 to 6.5). Soil pH values above or below these ranges may result in less vigorous growth and nutrient deficiencies.

Nutrients for healthy plant growth are divided into three categories: primary, secondary and micronutrients. Nitrogen (N), phosphorus (P) and potassium (K) are primary nutrients which are needed in fairly large quantities compared to the other plant nutrients. Calcium (Ca), magnesium (Mg) and sulfur (S) are secondary nutrients which are required by the plant in lesser quantities but are no less essential for good plant growth than the primary nutrients. Zinc (Zn) and manganese (Mn) are micronutrients, which are required by the plant in very small amounts. Most secondary and micronutrient deficiencies are easily corrected by keeping the soil at the optimum pH value.

The major impact that extremes in pH have on plant growth is related to the availability of plant nutrients or the soil concentration of plant-toxic minerals. In highly acid soils, aluminum and manganese can become more available and more toxic to the plant. Also at low pH values, calcium, phosphorus and magnesium are less available to the plant. At pH values of 6.5 and above, phosphorus and most of the micronutrients become less available.

Factors Affecting Soil pH
: The pH value of a soil is influenced by the kinds of parent materials from which the soil was formed. Soils developed from basic rocks generally have higher pH values than those formed from acid rocks.
Rainfall also affects soil pH. Water passing through the soil leaches basic nutrients such as calcium and magnesium from the soil. They are replaced by acidic elements such as aluminum and iron. For this reason, soils formed under high rainfall conditions are more acidic than those formed under arid (dry) conditions.

Application of fertilizers containing ammonium or urea speeds up the rate at which acidity develops. The decomposition of organic matter also adds to soil acidity.

Increasing the Soil pH: To make soils less acidic, the common practice is to apply a material that contains some form of lime. Ground agricultural limestone is most frequently used. The finer the limestone particles, the more rapidly it becomes effective. Different soils will require a different amount of lime to adjust the soil pH value. The texture of the soil, organic matter content and the plants to be grown are all factors to consider in adjusting the pH value. For example, soils low in clay require less lime than soils high in clay to make the same pH change.

Selecting a Liming Material: Homeowners can choose from four types of ground limestone products: pulverized, granular, pelletized and hydrated. Pulverized lime is finely ground. Granular and pelletized lime are less likely to clog when spread with a fertilizer spreader over turf areas. The finer the grind of the limestone the faster it will change the soil pH value. Hydrated lime should be used with caution since it has a greater ability to neutralize soil acidity than regular limestone.

Time of Application & Lime Placement: Lime needs should be determined by a soil test.  Soil samples should be taken in the fall for the succeeding year’s garden. If test results indicate a need for limestone, it can be applied in the fall or winter months. Generally, for best results, limestone should be applied two to three months prior to planting to allow time for it to neutralize the acidity.
The most important factor determining the effectiveness of lime is placement. Maximum contact of lime with the soil is essential. Most liming materials are only slightly soluble in water, so incorporation in the soil is a must for lime reaction. Even when properly mixed with the soil, lime will have little effect on pH if the soil is dry. Moisture is essential for the lime-soil reaction to occur. In the case of lawns, it can only be surface applied and watered into the soil.

Wood Ashes: Wood ashes can be used to raise the soil pH. They contain fairly high amounts of potassium & calcium, and small amounts of phosphate, boron and other elements. They are not as effective as limestone but with repeated use, they can drastically raise the pH value of a soil, especially if the soil is sandy in texture. Ashes should not come in contact with germinating seedlings or plant roots as they may cause damage. Spread a thin layer during the winter and incorporate into the soil in the spring. Check the soil pH annually especially if you use wood ashes. Avoid using large amounts of wood ashes because excessively high pH values and subsequent nutrient deficiencies may result. Coal ashes do not have any lime value and may actually be acidic dependent on the source.

Decreasing the Soil pH: Many ornamental plants and some fruit plants such as blueberries require slightly to strongly acid soil. These species develop iron chlorosis when grown in soils in the alkaline range. Iron chlorosis is often confused with nitrogen deficiency because the symptoms (a definite yellowing of the leaves) are similar. Iron chlorosis can be corrected by reducing the soil pH value.

Two materials commonly used for lowering the soil pH are aluminum sulfate and sulfur. These can be found at a garden supply center. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil. Sulfur, however, requires some time for the conversion to sulfuric acid with the aid of soil bacteria. The conversion rate of the sulfur is dependent on the fineness of the sulfur, the amount of soil moisture, soil temperature and the presence of the bacteria. Depending on these factors, the conversion rate of sulfur may be very slow and take several months if the conditions are not ideal. For this reason, most people use the aluminum sulfate.

Both materials should be worked into the soil after application to be most effective. If these materials are in contact with plant leaves as when applied to a lawn, they should be washed off the leaves immediately after application or a damaging leaf burn may result. Take extreme care not to over-apply the aluminum sulfate or the sulfur.

You can use the following tables to calculate the application rates for both the aluminum sulfate and the sulfur. The rates are in pounds per 10 square feet for a loamy soil. Reduce the rate by one-third for sandy soils and increase by one-half for clays.

Pounds of Aluminum Sulfate per 10 Square feet to Lower the pH to the Recommended Level
Present pH Desired pH
6.5 6.0 5.5 5.0 4.5
8.0 1.8 2.4 3.3 4.2 4.8
7.5 1.2 2.1 2.7 3.6 4.2
7.0 0.6 1.2 2.1 3.0 3.6
6.5 0.6 1.5 2.4 2.7
6.0 0.6 1.5 2.1


Pounds of Sulfur per 10 square feet to Lower the Soil pH to the Recommended Level
Present pH Desired pH
6.5 6.0 5.5 5.0 4.5
8.0 0.3 0.4 0.5 0.6 0.7
7.5 0.2 0.3 0.4 0.5 0.6
7.0 0.1 0.2 0.3 0.4 0.5
6.5 0.1 0.2 0.3 0.4
6.0 0.1 0.2 0.3

WHEW! did you make it here to the end? I know, lots of information all at once. Next update is how to prune each type of hydrangea and the nasty pests and diseases.

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This entry was posted on February 22, 2014 by in Gardening, Hydrangea, Soil, Soil pH.
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