For hydrangeas to change from pink to blue, the soil must be acidic and contain salts of either aluminum or iron.
We all learned in chemistry classes in school that distilled water has a neutral pH of 7. However, in horticulture, a neutral pH is typically categorized as 6.5. Any soil with a pH below 6.5 is considered acidic, and any soil with a pH above 6.5 is considered alkaline. A pH testing kit can be used to check the pH of your soil, and Greenshutters Nurseries & Garden Centre has these on hand. The inexpensive pH meters that are available are often not precise, so I do not advise using them. Often, seeing surrounding gardens and the local plant life is a simpler approach. It’s likely that your soil is acidic if nearby Rhododendrons, Camellias, and Pieris are flourishing in the soil.
Peaty or sandy soils are typical of acidic soils. Clay soils are typically not highly acidic. Chalky soils have a high pH. By incorporating Irish moss peat or ericaceous compost, you can increase the acidity of your soil. Ericaceous compost has an acidic pH range of roughly 5.0 to 5.5, while regular multifunctional compost has a pH range of 6.0 to 6.5.
Irish moss peat is particularly useful for mulching since it has a pH of about 4.0, which is much too acidic for most plants to thrive in. However, when combined with neutral or alkaline soil, it lowers the pH of the soil. Once a year, mulch with Irish moss peat and let the worms to work the peat into the soil to maintain the acidity of the soil around a plant.
As an alternative, hydrangeas can be grown in containers. Although hydrangeas can thrive in both multifunctional and ericaceous compost, it is recommended to plant them in the latter if you want them to turn blue.
If your soil is deficient in aluminum or iron salts naturally, you can easily increase them by putting Hydrangea Colorant into the soil. People claim that adding rusty nails to the soil or compost will turn hydrangeas blue; however, as I have never tried it, I am unable to confirm if this is true or false. On the other hand, Hydrangea Colorant is a combination of Iron Salts and Aluminium Sulphate. When potting or planting, it can be added to the soil. For established plants, you can also dissolve the Hydrangea Colorant in water and give your hydrangeas a weekly drink during the growing season (March to September). Your light pink kinds will become blue if you do this, while your dark pink varieties will turn mauve-blue.
Grow your hydrangea in neutral or alkaline soil, though, if you want it to stay pink.
Which compost kind is ideal for hydrangeas?
According to John Negus, a garden expert for Amateur Gardening, “the ideal potting compost for shrubby plants is one with a high concentration of loam, such as John Innes No. 3.” The RHS (opens in new tab) suggests combining two parts of John Innes No. 3 and one part peat-free multipurpose compost for hydrangeas. Use an ericaceous compost as an alternative if you are growing blue hydrangeas and want to maintain the vibrancy of their color.
Even the best multi-purpose composts, according to John, “only have adequate nutrients for four to six weeks of growth, and after this is expended, plants will need supplemental feeding, either with a liquid or by top-dressing with controlled-release fertilizer.” From early summer to the end of flowering, feed with a liquid or top-dress in the spring.
John continues, “Loam-based composts retain moisture better than peat-based ones.” All potted plants, however, require constant watering because their roots are restricted and their compost is hidden by foliage, unless it rains heavily every day.
What kind of compost is ideal for hydrangeas grown in pots?
Generally speaking, a potting mix with a loam foundation is preferable. In mixtures with a variety of varying pH levels, hydrangeas can flourish. But keep in mind that you must select an ericaceous compost and sustain acidity over time if you are producing a blue variety.
Can you fertilize hydrangeas with compost?
We use the word “influence” since using lime or acids rather than compost is more common when adjusting soil pH to change the color of bigleaf hydrangeas. Composting your planting bed has kinder and healthier impacts than using powerful additives to make abrupt pH alterations.
Additionally, hydrangeas adore the rich, wet soil that compost produces. You have probably observed that hydrangeas require a lot of water each week. Your hard clay soil’s ability to hold moisture is improved by soil3.
Bigleaf hydrangeas come in both blue and pink varieties, and most gardeners are content with whatever color the soil pH produces. The health of your hydrangeas is the primary priority. By incorporating compost, you may enrich and care for the soil that supports your favorite hydrangea shrubs, allowing it to support the healthiest hydrangeas you’ve ever grown.
Read the Soil3 Story: Creating Hydrangea Heaven with Soil3 Compost to see how Drte Schmieta uses Soil3 in her hydrangea garden.
A client who lives close to our Orangeburg, South Carolina, farm emailed these photos of his prized hydrangea flowers, which he planted in a garden bed with Soil3. Because Soil3 neutralized the soil, you can see how some of them have taken on a reddish hue. He has every right to be proud of his Hydrangea macrophylla (also known as bigleaf hydrangeas), and we appreciate him sharing that pride in both our compost and his plants.
How can I increase the acidity of my soil to grow hydrangeas?
Like coffee itself, coffee grounds have an acidic pH. The acidity of the soil around hydrangeas is increased by mixing in dried coffee grounds, which enhances the hydrangea’s capacity to produce blue and its capacity to absorb aluminum from the soil. With a pH test kit, track the soil’s pH over time; a range of 5.2 to 5.5 is ideal for blue flowers. Coffee grinds occasionally scattered on the soil’s surface or placed there will slightly raise the acidity level.
Do hydrangeas require specific types of soil?
In dappled shade that is neither very sunny nor overly dark, wet, well-drained soil is excellent for hydrangeas. Avoid sites that face south, especially if the soil is quite dry. Grow Hydrangea anomalasubsp. petiolaris, a climbing shrub, in an extremely shady area like a north-facing wall. Avoid planting in a frost pocket and plant away from strong winds in the spring since the tender new growth is vulnerable to frost damage.
Most soil types, including alkaline and acidic soil, are suitable for hydrangea growth. The color of some types’ flowers will vary depending on the pH of the soil. If the soil is acidic, some plants that typically produce pink flowers will instead produce blue ones.
When to plant hydrangeas
Hydrangeas grow best in the spring or fall when the soil is warm and moist. It is possible to plant in the summer, but you must monitor the soil’s moisture content.
How to plant hydrangeas
If your soil is thin, bulk it up with moisture-retaining organic matter before planting hydrangeas because they thrive in damp soil. A good hour or so before planting, thoroughly water the plant. A hydrangea should never be planted any deeper than it was in the pot. Well with water. After planting, add a layer of mulch. Leaf mould is preferable, but compost or well-rotted manure can also work. Throughout the plant’s first spring and summer, make sure it gets plenty of water.
Train climbing hydrangeas initially onto galvanized wires before planting. They have roots that attach to themselves, so after a season of growth, they will find their own way.
Watch this Gardeners’ World video to learn how to plant lacecap hydrangeas:
Do hydrangeas love acid?
1. I have a number of substantial, healthy hydrangeas that
2. I made the decision to plant gardenias and hydrangeas in my flower bed this year. I now have some Texas Salvia and caladiums in this bed (Victoria). I’m not sure if I should transfer my Salvia and Caladiums because my Gardenias need acidic fertilizer.
Your gardenias and hydrangeas not only require acidic soils, but also lack thereof will result in their death (pH 5-6 minimum) which an acid fertilizer can never completely complete. For your growing mix, you must use acidic parent material so that while decomposition takes place, the plants will always have the correct pH from which to draw minerals and nutrients. Because your soil is so buffered (very alkaline due to calcareous parent material), adding an acidic fertilizer alone won’t ever alter the soil’s pH level. Excavate a portion of the planting bed’s soil, and then replace it with a potting mix made up of two thirds spaghum peat moss and one third washed (Builders Sand) sand. Additionally, you can use this mixture in containers to grow hydrangeas, gardenias, or azaleas. To ensure success, make sure this planting position gets early sun and afternoon shade. In this environment, the caladiums and Victoria salvia will grow even more successfully. Before you start planting, you might wish to add some Osmocote Slow-release fertilizer pellets to this mixture (follow the label directions for the amount for the volume of bed). Then, every week, water with your acid-based water soluble fertilizer, such as Peters 20-20-20, MiracleGrow, or Miracid.
3. Q: Despite my best efforts, I haven’t been able to maintain a healthy hydrangea plant in my garden’s shaded spot under an Angel’s Trumpet tree. It does not receive any early sun, although receiving some in the afternoon. Despite the fact that I water it every day, the plant appears to be shrinking away from the sun and the edges of the leaves are turning brown. Although I’ve heard that hydrangeas can tolerate sunlight, I’m not sure if zone 9 is the right temperature for them. I need some advice as to what these people may be doing to maintain these shrubs looking beautiful because I have noticed several healthy bushes around the area.
A: Hydrangeas can survive some light shade, but they won’t bloom as much and will grow leggily if they are in severe shadow. I believe that overwatering is your main issue. Depending on the kind of soil (thick, clay soil requires considerably less watering than sandy soil), once per week is sufficient if the hydrangea is in the ground. Watering it daily is excessive. Therefore, resume watering. Brown-around-the-edges leaves signify a root issue, which can be caused by either too much water that rots the roots or too little water that dries out the roots. I’m betting on too much water! Additionally, when you do water, water with a water soluble fertilizer like Miracle Grow, Rapid Grow, or Peters 20-20-20 after a week or 10 days. Check to see if the plant does better after using this water-soluble fertilizer every second or third watering.
3. How frequently should I fertilize my potted hydrangea plants?
A potted hydrangea requires the same maintenance as any other houseplant. Maintain a moist root zone that is neither too damp nor too dry. Follow the directions on the label when fertilizing once a week by watering with a water-soluble fertilizer, such as Miracle Grow, Rapid Grow, or Peters 20-20-20. (how much to put per gallon of water). Keep it as close to the sun as you can, or if you’re going to put it outside, choose a spot that gets morning sun and afternoon shade.