Can You Grow Hydrangeas in Hardiness Zone 10?
Do you live in hardiness zone 10, but aren't quite sure if hydrangeas will stand up to your heat and humidity? Hydrangeas are gorgeous shrubs, but they typically thrive in the right environments. In this article, gardening expert Jill Drago examines what you can expect when growing hydrangeas USDA hardiness zone 10.
Hydrangeas are well-loved plants for a good reason. Their flowers are beautiful. You can grow hydrangeas individually, as a hedge, or in containers. You can use their flowers in fresh or dried arrangements. Their foliage is a lush green. Hydrangeas are very versatile shrubs. They love sun and shade in any combination that you choose.
They are southern favorites, but how far south is too far? Many climates closer to the equator get both very hot, and also very humid. This makes it a challenge for hydrangeas, despite their well-known perennial hardiness and climate tolerance.
So, if you are you considering adding some hydrangeas to your zone 10 garden, know that this is definitely doable! It may just take a bit more consideration when you are choosing your hydrangea variety, and the location of the plant.
The Short Answer
The short answer, is yes, hydrangeas can be grown in USDA hardiness zone 10. You’ll want to choose a heat friendly variety, and find a good location in your garden for them to grow successfully. The macrophylla and paniculata varieties are the likeliest varieties to perform well this climate.
What is Zone 10?
USDA Hardiness zones are different regions in the United States that are classified according to the average low temperature in the wintertime. Zone 10 experiences average winter lows ranging from 30-40 degrees.
Zone 10 is made up of the southern tip of Florida, the most southern point of Texas, some areas in southern California (both coastal and inland), and some small sections of Arizona. It is fair to say that while these locations are all warm regions, they have drastically different climates.
The rainfall amount will differ, as will the humidity. These factors will affect the number of supplemental watering hydrangeas may need, as well as if they should be planted in the sun or the shade.
When to Plant
There is a lot more flexibility to when you should plant a hydrangea in zone 10 than there is in say zone 6. But the same rules apply; plant in the fall or the spring. Since frost is not a common concern you can also plant over the winter.
In zone 10, you need to be more worried about the heat as opposed to the frost. The cooler temperatures will reduce transplant shock and will encourage the roots to take hold. Planting in the fall will give your shrubs more time to take hold before the blooming season.
If you choose to plant in the spring your plant will still be successful, it just may not have the stunning blooms in its first season that you may have hoped for. Hydrangeas need a lot of water to become established so be sure to choose a cooler season to get your plants in the ground.
How to Plant
Planting a hydrangea itself is quite simple. Dig a hole twice the size of the root ball, and a little deeper. Be sure that the base of the plant is buried as deep as it is in the pot, no deeper.
Adding compost or your choice of organic matter is helpful as hydrangeas love rich soil that is well-draining. Water the plant really well. A great way to help your plant hold in moisture is by mulching around the plant, one to two inches should be sufficient. The mulch will retain moisture from rain, humidity, or supplemental watering.
What to Plant Where
The following plant and tips will help you select the right species of hydrangea for your area. Situate the plants on a north-facing wall or at the bottom of a slope to keep them from drying out.
Hydrangea anomala is a salt tolerant species, making it a great option for a cooler coastal area. The climbing hydrangea is sensitive to hot temperatures and also to humidity. In order to have a prolific bloom the plant needs about six weeks of temperatures below 65 degrees. If these conditions match your climate the climbing hydrangea can be used to climb up the trunk of a tree, or as a ground cover underneath a tree in deep shade.
Hydrangea macrophylla would be more apt to grow in zone 8 and below, this variety should grow quite well in the coastal areas of zone 10.The morning sun would be great for the bigleaf hydrangea, but it will need shade in the afternoon to protect it from the heat of the sun. Another consideration is to keep the bigleaf hydrangea out of any area that gets too breezy. This will help to keep the plant from drying out.
Hydrangea paniculata, or the panicle hydrangea, is the most sun-loving hydrangea and probably your best bet in zone 10. These plants grow to large heights and make excellent hedges and privacy screens. Even still, in zone 10 I would not situate your plant in full sun. Make sure your plant gets some shade in the afternoon so it has a break from the heat.
Hydrangea serrata, or mountain hydrangea is hardy up to zone 9 making it a great choice for zone 10. Similar to bigleaf hydrangea they require only morning sun with afternoon shade. They are not tolerant of wind, or particularly cold or hot temperatures. This means that keeping your mountain hydrangea in the shade, and well-watered is a must!
When it comes to maintenance, there’s many important factors with this ornamental shrub. Hydrangeas are fairly tolerant to a little neglect, but to keep them blooming to their fullest potential, you’ll want to engage in routine care. If you don’t tend to them properly, it can result in your hydrangea losing the big blooms they are most well known for.
Deadheading and watering are the two most important aspect of maintenance. Color management is also important if you plan on keeping your hydrangea’s beautiful blue blooms. Let’s take a deeper look at maintenance in zone 10.
Since hydrangeas don’t go dormant in zone 10, you will not need to prune your hydrangeas. It is a good idea to deadhead the flowers to encourage new blooms for the next season. Once your flowers start to dry out just simply cut the stem below the flower and just above the next set of large leaves. This will not cause your flower to bloom again in that season, it will simply neaten your hydrangea plant.
Hydrangeas are water lovers. Similar to zone 9 hydrangea gardeners, ensure that where you have planted them receives a good amount of water, perhaps an area on your property where water collects naturally. This will help the plants out, and save you some water.
Hydrangeas in zone 10 require good watering three times a week. Avoid overhead watering as the leftover water droplets on the leaves can leave brown spots, or burns. A soaker hose, or drip irrigation is a really good option for deep watering if you have irrigation available.
Controlling the Color
Hydrangea macrophylla, or bigleaf hydrangea will react to the pH of your soil. Soils that are more acidic, below 5.5 pH, will favor blue flowers by allowing the hydrangea to absorb more aluminum. Whereas soils that are above 6.5 pH, or “sweet” soils, will produce pink flowers on your hydrangea. Before amending your soil with anything a soil test is recommended.
To enhance the blue of your flowers use aluminum sulfate. Aluminum sulfate is readily available, and the best product to use. A drench of one tablespoon of aluminum to one gallon of water is the safest application rate. If the plant is dry, water before applying this solution. This method should only be used twice a year; once in April and once in May.
If you are wishing to enhance your pinks or reds, using garden lime will be your best tool. Apply a powder form of lime to the base of the plant in April and again in October.
I can’t say that I have ever seen a hydrangea while visiting southern California or Florida… but I don’t think I would ever have been looking for them! My eye is always searching for those tropical plants that I long to see when I am trapped away in the snowy winter of the northeast.
But who’s to say hydrangeas can’t have that same tropical vibe? Their leaves are rich green, and their flowers are equally as showy, if not more so than a lot of the bright orange and pinks of tropical landscapes.