“What’s the best way to ensure that my blue [bigleaf] hydrangea stays blue?” Question from Gaye of Saint Peters, Missouri
Answer: It all has to do with soil pH. There are two hydrangeas that have flowers whose color changes depending on whether the soil is acidic (3.5-6.8), alkaline (7.2-10), or neutral ( around 7). These are bigleaf hydrangeas (Hydrangea macrophylla, Zones 5-11) and Japanese mountain hydrangeas (Hydrangea serrata, Zones 6-9). If your flowers are on the pinker side then your soil is more alkaline, and if they are erring towards purple then your soil is more neutral. To achieve flowers with a bluer hue, you will need to lower your soil pH. There are several ways to do this.
“Why aren’t my roses growing? My rose bushes do not grow, and I fertilize them once a month, but they don’t grow. Soil is clay-like. They are semi-shade, I have a lot of big trees. They do flower. What else can I do?” Question from April of Dresden, Tennesee
Answer: There are three key factors that are likely keeping your roses from growing, thriving, and flowering to their fullest. They are:
Sunlight: Roses need full sun to grow and flower at their fullest. Six hours per day is the bare minimum they need to really perform well. Eight to twelve hours is even better. The morning sun is preferable to dry leaves early in the day, which dissuades fungal diseases.
Soil: Roses require a fertile, well-drained soil that is slightly acidic (pH 6.5-7) and high in organic matter to perform at their fullest. Amend the soil where they are planted to encourage better root growth and performance. Black Gold Garden Soil and Black Gold Canadian Sphagnum Peat Moss are two excellent amendments to consider
Competition: Tree roots quickly drain water and nutrients from the soil. It is wise to plant roses away from tree roots to avoid competition.
Please watch the video below to learn more about growing roses organically.
“What is the soil pH of Black Gold Natural and Organic Potting Soil?” Question from Michael of Pueblo, Colorado.
Answer: At production, the peat moss in our mixes has a pH range of 3.5-5.0, but we add liming agents to bring all of our potting mixes up to a more neutral pH range of 5.5-6.5. Keep in mind, mix pH will change depending on your growing environment, irrigation water, the fertilizer you use, and the plant species you grow. For a highly detailed article on managing mix pH, read the Sun Gro article titled Managing Low pH in Growing Media for Reliable Crop Performance.
“What is the average pH range of your various gardening soils? I bought 2 varieties – the Waterhold, and the Natural & Organic Potting Mix + fertilizer.” Question from Michael of Scottsdale, Arizona.
Answer: Great question Michael! The right pH is essential for growing good potted crops and container specimens. That’s why Black Gold mixes are fortified with alkaline Dolomite Lime to naturally increase their pH to a target of 6.5–a close-to-neutral pH ideal for many garden plants. We then test our mixes to make sure their pH is within the correct range.