Gardening by Judith Adam pH of soil, the measure of acidity or alkalinity. In acid soil of 5.0 to 5.5, they will be blue; with less acidity at 6.0 to 6.5, they will be pink. Above the neutral middle point − pH7.0 − they will be creamy white. You can ask about the pH measurement of your soil at a local garden centre, or university horticulture department. The acidity/alkalinity of soil is controlled by underlying bedrock. Granite bedrock influences toward acidity, while limestone bedrock pushes soil toward alkalinity. (Hydrangeas planted near a concrete sidewalk will also absorb alkalinity from the concrete.) The Muskoka region of Ontario and stretches of the eastern seaboard of North America (as examples, Massachusetts and New Jersey, whereH. macrophyllasurvives the winter outdoors) have acid soil that reliably produces blue mop head hydrangeas. Southern Ontario has alkaline soil, producing pink mop head hydrangeas, andmany kinds of consistently creamy white hydrangeas grow throughout all of these regions. The deep blue and pink coloration of corner store hydrangeas is produced in the nursery by feeding plants with acid-inducing chemicals. This can be achieved in the home garden, but results are temporary and require repeat applications approximately every six weeks. Garden centres carry soil acidifier chemicals in their fertilizer sections. (Acidifiers are also suitable for other acid-loving plants such as blueberries, holly, azaleas and rhododendrons.) Acidifier products may contain elemental sulfur and gypsum. Boxed aluminum sulfate is also sold as a soil acidifier, but its toxic properties can damage hydrangeas with repeated use. Pelleted sulfur is sold as a natural soil acidifier, and it can be dug into the soil surrounding hydrangeas. It is slowly released and may not be effective enough to produce true-blue petal coloration. If you love blue and pinkmop head hydrangeas enough to follow these guidelines, then have at it! But other beautifully coloured hydrangeas are reliably consistent in their coloration, requiring no acidity/alkalinity consideration. Fortunately, the large group of panicle hydrangeas (H. paniculata) are hardy to zone 5 and have generous flower clusters, many opening white, turning to pink and red as they age, with pink-bronze colouring into early winter. Among the pink and red varieties, look for ‘Fire and Ice’, ‘Fire Light’, ‘Vanilla Strawberry’, and ‘Pinky Winky’. Sorry, no blues; but these will certainly light up your summer garden. CSANews | SUMMER 2021 | 59
RkJQdWJsaXNoZXIy MzMzNzMx