Bigleaf hydrangeas, also known as Hydrangea macrophylla, are the most popular variety of hydrangea. French hydrangea, garden hydrangea, and florist’s hydrangea are some more frequent names for this plant. Most likely, the hydrangeas at your neighborhood florist are bigleaf varieties.
Bigleaf hydrangeas come in three different varieties:
- Due to their huge, puffy bloom heads, mophead hydrangeas are the most recognizable and well-liked hydrangeas. They flourish in hardiness zone 6, and their blossoms can be purple, blue, or pink. Mophead hydrangea flower buds may not endure the winter since they are susceptible to the cold.
- With their flowers being the main distinction, lacecap and mophead hydrangeas are nearly identical to one another. They have little, fruitful flower buds in the middle, and the showy flowers surround the flower head’s margin. The main function of these gorgeous, sterile flowers is to entice bees and butterflies to the fertile buds in the middle. They flourish in hardiness zone 6, just like mophead hydrangeas do.
- The least frequent variety of bigleaf hydrangeas are mountain hydrangeas. Its scientific name is Hydrangea serrata, and while its flattened heads resemble those of lacecap hydrangeas, its flowers and leaves are much smaller. Mountain hydrangeas are a fantastic alternative for locations with late winter cold snaps because they have hardier buds and do well in hardiness zone 5.
True to its name, the bigleaf hydrangea’s trait that sets it apart from other hydrangea varieties is the size of its leaves. The leaves of bigleaf hydrangeas can get up to 4-6 long and 3-5 broad. The leaves have short stalks, are heart-shaped, thick, and lustrous.
Bigleaf hydrangeas like some shade, but not too much, as this can lead to fewer flowers. They prefer moist, well-drained soil, and their blooming seasons are in June and July. Given that bigleaf hydrangeas are drought-sensitive, it is crucial to consistently water them.
By adjusting the soil’s acidity, you can vary the color of your hydrangeas. Blue flowers can be grown on acidic soil with a pH of 5.5 or below. Pink flowers will grow on neutral or alkali soils with a pH of 6.5 or higher. Purple flowers or a hybrid of blue and pink flowers will grow in soil with a pH between 5.5 and 6.5.
What kind of plant are hydrangeas?
Popular shrubs called hydrangeas have vibrant flowers that bloom from the summer into the fall. They often flower in blue, purple, and pink hues, while some varieties also come in white, green, and red. The majority of hydrangea shrubs thrive in partial shade and are simple to grow in Zones 3–9.
How do hydrangeas appear before blooming?
The tips of the stems that Big Leaf and Mountain Hydrangeas generated last year are where they blossom (old wood). Some of those same stalks also have flowers on the sides (new wood). Still other plants bloom on stems they create this year (new wood). The old wood plants need to cling onto those blooms for approximately nine months, through late fall, winter, and early spring, beginning around August 1. Therefore, if you prune the stems of your old wood plants after August 1, you run the danger of losing the flowers that will bloom the next year.
No Pruning After August 1st
First rule: don’t prune them until the buds start to show, which may not be until June. The buds resemble little broccoli heads. Then you will know which stems and buds successfully overcame their seasonal obstacles.
If your shrub isn’t blooming, the first thing you should look at is whether or not you pruned it back. These plants often only require trimming to remove damaged, diseased, or dead stems.
Anthocyanin Pigments
Hydrangea leaves typically turn red because anthocyanin pigments are produced in the leaf cells. These pigments are produced by plants in response to a variety of stresses, such as temperature extremes, excessive or insufficient light, and pest attacks.
Over 600 different types of anthocyanins are found in nature, and researchers are still trying to figure out exactly how they defend plants.
According to studies, they boost the efficiency of photosynthesis, operate as a form of sunscreen against damaging UV rays, and serve as antioxidants that protect against free radical damage.
Solution
Making sure that plants don’t suffer any stress is the only way to avoid them from developing anthocyanins. This entails planting hydrangeas in rich, well-draining soil, giving them regular water without drowning them in it, and positioning them so that they receive morning light but enough of shade throughout the hottest part of the day.
They don’t require feeding if they are grown in the ground, but they will benefit from a compost mulch once a year. In containers, hydrangea-specific slow-release fertilizer that is used once a year is a suitable choice.
Cold Weather
Hydrangea leaves typically become crimson as the temperature drops before falling off the plant. This occurs naturally as part of the life cycle and is typically unimportant.
There are deciduous hydrangeas. This implies that their leaves drop off in the fall and then sprout in the spring. A deciduous plant becomes dormant throughout the winter, which means it doesn’t grow or need as much water or nutrition.
The chemical that gives plants their green color, chlorophyll, is produced less by deciduous plants’ leaves before they fall off the plant and more by anthocyanins.
As a result, more orange and red hues are visible as the chlorophyll deteriorates. This makes it possible for leaves that are close to dying to keep producing as long as they can.
Your deciduous hydrangeas will lose their leaves in the winter, but as long as the temperature doesn’t dip below 0 F, they can stay outside unprotected (-17.7 C). They will develop new growth in the spring, and it will be green, not red.
Some varieties of hydrangeas are evergreen, which means that plants won’t turn red and lose their leaves over the winter. Try the climbing Hydrangea integrifolia or Hydrangea seemanii if you’d like a plant with lush green leaves all year long.
Growing In Full Sun
The optimal conditions for hydrangea growth are direct sunlight during the chilly morning hours and afternoon shade.
Your plant will produce anthocyanins, which make the leaves red, to defend itself if it is exposed to direct sunlight all day.
Although they are harmless and serve to shield the leaf cells from harm, these pigments are a clue that the plant is not in its ideal environment.
Make careful to place your hydrangea where it receives morning sun but not afternoon sun. Some varieties require more or less sunshine than others, with the majority preferring roughly 46 hours every day.
If you are unable to transfer the plant, think about how you can give it some shade during the warmest time of the day. To offer cover, you could plant additional trees or shrubs or construct a building like a fence.
Lack of Light
As anthocyanins can enhance cells’ capacity for photosynthetic activity, hydrangeas growing in an overly shaded location may also develop crimson leaves. Therefore, if your plant is becoming red and only receives four hours or less of sunlight each day, this may be the problem.
Lack of light frequently results in pale growth that slants toward the nearest source of light, or occasionally a mix of pale and red development.
Verify that your plant is receiving adequate sunshine. If it is completely shaded, you should move it to a brighter location while making sure it is not directly in the sun.
If you are unable to transfer the plant, think of creative ways to enhance the amount of morning light it receives, such as by pruning adjacent trees and bushes.
Phosphorus Deficiency
Since hydrangeas are not heavy feeders, over fertilization may reduce the amount of flowers produced by the plant or possibly harm its roots. However, it’s a symptom of phosphorus insufficiency if you see that your plant’s lower leaves are becoming purple from the tips.
One thing to keep in mind is that Hydrangeas have trouble absorbing phosphorus when soil temperatures go below 55F (13C).
Wet soil exacerbates this issue and makes it challenging for the plant to absorb nutrients. Maintaining your plant in a well-draining environment is crucial.
You shouldn’t be concerned about the soil temperature in the fall and winter because most varieties of hydrangea go dormant in the winter and don’t need to absorb nutrients.
When planting your hydrangea, use a lot of high-quality compost, and cover it with compost once or twice a year. All the nutrients a plant requires are present in compost in a readily utilizable form.
You usually won’t need fertilizer unless your soil has a severe nutrient deficiency. If you do decide to use additional fertilizer, use one made specifically for hydrangeas and only use it once or twice a year, as directed.
Underwatering
The Greek words for water (hydros) and jar are the origin of the name “Hydrangea” (angos). You should now have a general notion of the plant’s water needs!
Although they dislike soggy soil, hydrangeas do require a lot of moisture. Even the most seasoned gardeners may find this to be a challenging balance!
It may be an indication that your plant needs more water if you see the leaves of your plant drying up, curling, and turning red.
But be cautious—before you increase the watering, check to see whether the plant has root rot, which can also manifest as dehydration symptoms.
This issue is simple to fix if you’ve established that the plant doesn’t have root rot. Just add more water to your plant!
You’ll most likely need to water twice or three times per week during the heat. To aid the soil in holding onto water, think about applying hardwood mulch.
Because hydrangeas dislike having moist feet and are susceptible to root rot, the soil must be well-draining. Reduce watering over the winter and only water the soil if it is entirely dry.
Xanthomonas and CercosporaLeaf Spot
It can be Xanthomonas or Cercospora leaf spot if you’ve seen red or purple spots on your Hydrangea that are slowly spreading from the lower leaves.
Xanthomonas and Cercospora are bacterial and fungal diseases, respectively, yet they share many of the same symptoms. Once established, they can be very difficult to treat because they spread through diseased organic debris.
However, these infections can also spread through equipment or even on your hands. Usually, bacteria or spores spread from infected substances to plants through splashing water, such as rain or when plants are watered from above. (Source: Extension Service of Michigan State University)
By clearing away fallen leaves and other decaying organic debris from the area around the plant, you can try to avoid both of these illnesses. By ensuring that there are few hiding spots for bacteria or fungal spores, infection risk will be decreased.
AXANTHOMONAS infection is difficult to treat once it has been established. The only thing you can do is remove the contaminated plant portions and hope for the best since there are no efficient bactericides on the market.
While some plants manage to withstand the infection, others cannot. The plant should ideally be destroyed if the infection is extremely serious.
If you detect Cercospora leaf spot early enough, fungicide can be used to treat it successfully. The plant has a decent chance of surviving if less than 20% of it is affected.
It’s usually best to eliminate badly affected plants and try again. Be careful not to reuse plant-infected soil or containers without properly disinfecting them.
Phytophthora Root Rot
The root rot fungus, Phytophthora, thrives in moist soil and is easily spread by splashing water or contaminated soil.
It kills all plants, but because Hydrangeas need a lot of water, it can be especially difficult while cultivating them. Your plant is more likely to get root rot if it is in wet soil.
Dehydration symptoms are typically brought on by root rot, which inhibits the plant from absorbing water through its roots. Root rot may be the problem if your plant’s leaves are drooping, dry, or reddening while receiving plenty of water.
Always ensure that the soil where your hydrangeas grow has good drainage. Never let it stand in soggy soil for an extended period of time. If the area becomes flooded, think about moving the plant or enhancing soil drainage.
Root rot is particularly difficult to treat after it has established itself. You can attempt by pulling out any infected roots—which will seem brown and slimy—replanting in drained soil, and waiting a while before watering.
The plant could survive. It may be preferable to remove the plant and try again because root rot is often the end of many plants.
Shape of the Flower Head
- A paniculata type is most likely present if the flower head is formed like a cone.
- It is either a macrophylla or an arborescens kind if the flower head resembles a ball or a flat disk. Visit the section on Flower Color.
Robert Pavlis’ photograph of a hydrangea arborescens from the side, highlighting the flower’s dome-shaped crown
Flower Color
- A macrophylla type is present if newly opened blooms feature blue, purple, or pink blossoms.
- An arborescens type is present if the flower buds initially seem green, then turn white, and finally turn green or greenish brown as they ripen.
- You likely have a macrophylla kind if the flowers are white when they first open and remain white as they age. Although they are less common, white flowered macrophylla varieties do occur.
Note: Recent breeding is beginning to develop arborescens with flowers that have a pink tint, such as “Eco Pink Puff.” Future cultivars should have a stronger version of this pink.
Should you prune your hydrangeas?
When should I prune my hydrangeas? is one of the most often asked gardening topics. We all have a tendency to want to hurry outside with the clippers and start hacking away when those billowy large flowers change from cheerful blues, purples, pinks, reds, and whites to uninteresting browns.
When to Cut Back Hydrangeas
The timing will vary according on the variety of hydrangea you have. First of all, be aware that hydrangeas do not require pruning unless the shrub has become unruly or too big for its location and requires some shaping up. Otherwise, simply deadhead wasted blooms and remove any dead branches from the plant.
How to Prune Hydrangeas02:07
But if you do decide to prune one, bear in mind to time it so that it blooms on old wood or new wood depending on the species of hydrangea you have.
If you wait too long, you can chop off the buds that are developing on old wood (stems from the year before the current summer), which would prevent flowers from blooming the following spring. Therefore, as soon as the flowers on these bushes have faded, they should be clipped.
The shrub should be clipped in the early spring before that new growth appears, but, if the shrub flowers on fresh wood (stems generated during the current season), which means that its buds are set inside the season.