Thursday, August 9, 2012

Hydrangeas (Self-sowing annual #6)

Hydrangea are bushy plants with large clusters of flowers. They come in many colors, but are predominately blue, pink, and white. They are one of my favorite plants!

Harvesting and Planting Hydrangea Seeds

 The best way to collect hydrangea seed is to take a bloom that has completely dried - in the fall is the best time - put in a zip-lok bag and shake it for all your worth. The fine dust you'll see in the bottom of the bag is your seed. Get rid of as much chaff and debris that you can, lightly scatter the seed on to a prepared seed flat of moistened soil. Hydrangea seeds require light to germinate so make sure you sprinkle them on the surface of the soil in the starter pots or on the ground outdoors in the garden. Do not cover them with additional soil. Simply firm the surface of the soil gently with your hands, which will help ensure the seeds are in good contact with the ground. Mist the seedbed daily with a fine spray from a hose nozzle until germination occurs in 10 to 14 days.

Be advised that the eventual plants you get from seed may, but probably won't resemble the plant and blooms from which you gathered the seeds. Most varieties sold through nurseries are hybrids. Propagation from hybrids never breed true to the parent plant. You will still get a viable plant from the seed, it just will have some different characteristics.

Propagation with Cuttings


If you choose to propagate with cuttings, cut a tender shoot that is at least six inches long. Remove the lower sets of leaves and Cut largest leaves down to about half their size. Dip the cutting in a rooting compound. You can purchase this product at any garden center. Stick the cutting one inch into a good potting mix. Be sure to thoroughly wet the soil prior to planting.

Finally, cover the pot with a clear piece of lightweight plastic. Place the pot in indirect sunlight on an east window seal or under fluorescent lighting. After two weeks, check to see if the plant has rooted by slightly pulling on the stem. If you feel resistance, remove the plastic covering and be sure to keep the soil moist, but be careful not to over-water. Water only when the top of the soil begins to feel slightly dry. Over-watering will cause cuttings to rot.

Tip: Place cuttings in bright light, but not direct sunlight. If it gets too hot, it will cook in the plastic.

Caring for Hydrangea

Although they prefer moist, rich soil, they will grow well in other types of soil, as long as they receive adequate moisture.

Tip: Protect them from high winds; water evaporates easily from their large leaves.

If you wish to cut hydrangea flowers for arrangements you should read this great post on how to keep them looking fresh by Love of Family & Home.

Changing the Bloom Color of your Hydrangea

First of all, not all hydrangeas produce blue or pink flowers. Hydrangeas with white or cream flowers, such as Annabelle hydrangeas, oakleaf hydrangeas and members of the PeeGee family, can only produce white or cream flowers. Sometimes their blooms take on a pink tinge at the end of the season, but that's about as colorful as they get.

Hydrangeas with bloom colors that range from pink through blue and purple usually belong to the hydrangea cultivars known as mopheads and lacecaps. These types of hydrangeas have the interesting ability to change the color of their blooms based on the chemistry of the soil.
The main influence that affects flower hydrangea color is soil pH, which is a measure of the soil’s acidity. The pH scale is from 0 to 14. Seven is the midpoint and is neutral. PH levels above 7 indicate alkalinity, while those below 7 represent increasing degrees of acidity. The average garden soil is slightly acidic in the range from 5.5 to 6.5. The pH range of 4.5 to 7.5 is not uncommon in garden soils. Blue hydrangeas require a highly acid soil, while pink hydrangeas are produced in a neutral or slightly acid soil.

Again, even the variety ‘Nikko blue’ hydrangea, if planted in a neutral soil, will produce pink hydrangea flowers. At a pH of 4.5, the color will be deep, vivid blue hydrangea, but as the pH scale goes upward toward neutral, the color will begin to change from blue to purple, from purple to mauve, and from mauve to pink.

A starting point to manipulating hydrangea flower color is to know exactly what you soil pH is.

To Raise Soil pH

The most common way to raise the pH of your soil (make it more alkaline and less acidic) is to add powdered Garden Lime. Dolomitic limestone will also add manganese to the soil. Apply it in the fall as it takes several months for the effects to be noticeable.
Wood ash will also raise soil pH. It works more quickly than limestone and adds potassium and trace elements to the soil. But use caution when applying wood ash. It is very concentrated, and applying too much of it can drastically alter the pH and cause nutrient imbalances. Wood ash can also "burn" foliage, so for best results, apply it directly to the soil in the winter. Apply no more than 2 pounds per 100 square feet, every two to three years, and test your soil each year to monitor the effects.
To raise the pH of your soil by about one point:

In sandy soil: add 3 to 4 pounds of ground limestone per 100 square feet.
In loam (good garden soil): add 7 to 8 pounds per 100 square feet.
In heavy clay: add 8 to 10 pounds per 100 square feet.

To Lower Soil pH

Soil can be made more acidic by adding Soil Acidifier, ammonium sulfate or aluminum sulfate. Follow application rates on the packaging. You can also lower pH levels by incorporating naturally acidic organic materials such as conifer needles, sawdust, peat moss and oak leaves. Coffee grounds are also slightly acidic. Remember to retest your soil to monitor effects over time.
To lower soil pH by about one point using elemental sulfur:

In sandy soil: add 1 pound ground sulfur per 100 square feet.
In loam (good garden soil): add 1.5 to 2 pounds per 100 square feet.
In heavy clay: add 2 pounds per 100 square feet.

Tip:  If the pH of your soil is naturally quite high (alkaline) it will be very difficult to get blue flowers — even if there's plenty of aluminum in the soil. Alkaline soil tends to "lock up" the aluminum, making it unavailable to the plant. (However, you can grow fabulous pink hydrangeas!)

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