13 Mistakes To Avoid When Growing Hydrangeas This Season

Hydrangeas are some of the most popular ornamental shrubs planted around the world. But they can be sensitive, making them prone to many common mistakes by both new and experienced gardeners. In this article, gardening expert Jill Drago walks through the most common mistakes she sees when gardeners decide to plant hydrangeas.

Blue Hydrangea Flower After Color Mistake

When the lazy days of summer are in full swing, hydrangeas are doing anything but taking a nap. These bountiful blooming shrubs will be in full bloom filling all of us with dreams of the seaside. Well loved for their large flowers in an array of soft colors from white to red, hydrangeas have become a very common and popular shrub in landscapes. Hydrangeas have so many uses in your garden from hedges, to foundation plantings to container gardens.

There’s nothing more depressing than seeing someone’s yard practically bursting at the seams with hydrangea flowers floating on top of lush green leaves when your hydrangeas are looking anything but inviting. Hydrangeas can be tricky to get accustomed to, and they have a few little quirks that could give novice and veteran gardeners a little bit of trouble.

I love to learn by trial and error, but let’s take the error out for you! Growing hydrangeas does not need to be intimidating, in fact, it is really easy once you get a few of the basics down. Follow along and pick up some tips and tricks that you can incorporate into your gardening routine that will help you and your hydrangeas have a happy summer.

Planting too close

Planting Shrub With White Flowers in Garden
When planting hydrangeas, leave enough space for their possible growth.

When you purchase your hydrangeas from the nursery they will likely be in a one to three gallon container. The size of these shrubs will not be the size that the hydrangea will grow to. Hydrangeas can grow anywhere from two to six feet tall, and much taller if you are growing a climbing hydrangea.

 It might be difficult, but you will need to resist the urge to plant your hydrangeas too close together. Aside from your garden becoming overcrowded and messy, planting hydrangeas too close together can be detrimental to your plants for a few reasons.

  1. Hydrangeas that are growing too closely will be compete for water and nutrients.
  2. Dehydration over a long period of time can lead the plant to deteriorate.
  3. You may notice flower or leaf wilt that is unrecoverable in hotter weather.
  4. As hydrangeas grow larger and closer together the air flow will be constricted.
  5. This can lead to an increase in fungal diseases.

Depending on what type of hydrangea you are planting in your garden, the spacing will be a little different. A good rule of thumb is to plant the hydrangeas a distance apart that is equal to what the full size plant will be. For instance, if your bigleaf hydrangea will be six feet tall and wide, plant it six feet away from the closest plant to avoid crowding.

Planting Under a Tree

Shrubs With Blue Flowers Under Trees
Although the hydrangea is a shade-loving plant, but they shouldn’t be planted under trees.

While you are selecting a location for your shade loving shrubs it may be tempting to plant your hydrangeas underneath a tree because trees provide such nice shade that many hydrangeas need to survive the heat. However, this will not be great for the longevity of your plant.

Planting under a tree will cause far too much competition between the tree’s feeder roots and the hydrangea. The tree will most likely be fine, but the hydrangea will have a hard time thriving due to the lack of water and nutrients available.

Hydrangeas grow best in well draining soil that has lots of organic material that is free for the taking. The tree’s roots will be more aggressive and will out compete the hydrangeas. The deep shade of the trees can cause leggy growth as well as small flowers, if any flowers at all.

There aren’t any rules that strictly prohibit you from planting your hydrangeas underneath a tree, however, it is not recommended as a long term home for your pretty shrubs.

Hydrangeas typically need four to six hours of sun in the morning to have strong stems and large flowers. Any place in your garden where your plants can be under these conditions will be a great choice for hydrangeas.

Skipping the Spring or Fall Clean-up

Healthy Purple and Pink Flowering Shrub
Regularly remove fallen leaves and weeds in the garden in order to avoid the appearance of fungal diseases.

While you are getting your gardens ready for the spring, or when you are getting ready to put them to bed do not skip cleaning up your flower beds. This is especially true for spring cleaning around your hydrangeas. It may seem like a task that is purely cosmetic, but leaf litter and weeds that are left untouched can cause all sorts of issues with your hydrangeas.

Leaves that remain in your garden can be hosts to a number of different pests. Fungus spores and insect eggs can live on leaves and on the soil around your hydrangeas over the winter just waiting to spread to your healthy plants when the right conditions present themselves.

Weeds, as we all know, can become really aggressive and take over your garden quickly if you don’t keep them in check. They will out-compete the hydrangeas for water and nutrients if they are allowed to take over your garden.

Keeping your garden clean is one of the easiest ways to keep your plants healthy. While you are removing your leaves and weeds from the soil, don’t forget to pull the leaves out of the crown of the hydrangea. This will help keep the air circulating through the plant, keeping fungal hydrangea diseases at bay.

Planting in Poor Draining Soil

Transplanting Plants in Garden
Hydrangeas grow well in well-drained soil.

Hydrangeas really prefer to be planted in soil that is well draining. What is well draining soil? Well draining soil allows water to flow through without any pooling.

The pooling of water can deprive the roots of a hydrangea (or any plant for that matter) of much needed oxygen. You can test what type of soil you have by digging a hole about a foot deep and filling it with water from your hose.

Let it completely drain, and then fill it again. The water should be drained in about two hours. If the water does not drain in that time period, you will need to amend your soil if you are wanting to grow hydrangeas.

The best way to enhance your soil while also making it well draining is by adding organic matter. This could be anything from compost, to manure to dried up and shredded leaves to your existing soil. My favorite part about this easy fix is that it is the same advice for clay soils or sandy soils.

If you allow the water to pool around the roots of your hydrangeas you can be in for a world of issues. Your plant could become susceptible to root rot which will eventually kill your plant. Other signs of over watering could be wilting of the leaves, starting from the ground up, the leaves could also turn yellow and fall off.

Not Watering Enough

Watering Shrubs That Are Flowering
Do not let the hydrangea dry out in hot weather, water sparingly and regularly.

Of course there are two sides to each coin. Too much water can cause issues with your hydrangeas, but too little water can also cause some problems. Watering becomes very important when the temperatures rise. Allowing your hydrangeas to dry out will cause the plants to stress. Luckily hydrangeas can recover from drought stress with some T.L.C.

If you notice that your leaves have begun to droop towards the ground, your hydrangeas might be in need of a drink. Typically the leaves will perk back up after a good watering and a break from the sun. If your hydrangeas are left to dry out for too long your flowers will begin to fade and turn brown.

Once your flowers have gotten crispy there is no coming back for them this season, but don’t worry they will be back next year so long as you keep your hydrangea in good shape.

This is easy enough to prevent, and it all begins with plant location. Hydrangeas typically only like four to six hours of morning sun. This shade will give the hydrangeas a chance to recover after catching some rays. Once you’ve got your plant in the right place, adding mulch around your hydrangeas can help retain some moisture. Watering deeply twice a week will help to keep your hydrangeas nice and moist without overdoing it.

Using an Overhead Sprinkler

Watering Plants on Top Down
For hydrangeas, drip irrigation will be effective.

We have now established that hydrangeas are water lovers. Unfortunately, not all watering systems are made equal for all plants. When it comes to these beauties, overhead watering is not recommended.

There are so many really pretty sprinklers on the market that emulate rainfall in your beautiful flower gardens. While this type of watering could be ideal for some of your plants, this is not the case for hydrangeas.

If you have an irrigation system on your property, the best type of irrigation to use on your hydrangeas gardens is drip irrigation. Drip irrigation is really efficient at getting water to your plants. There is little water waste, and your leaves will stay nice and dry. If you are hand watering with a hose or watering can, focus your aim at the base of the plant. 

Because hydrangeas spend so much time in the shade overhead watering can keep too much moisture on the leaves that may not have a chance to evaporate. This lingering moisture can lead to fungal diseases.

The splashing of water on the surface of the leaves can cause the spores of the fungus to spread from leaf to leaf, and could eventually cause a real problem if left untreated.

Planting in a Container With No Drainage

Potted Shrub on Grass
When planting hydrangeas in a pot, make sure the pot is large enough and has drainage holes.

When you are planting a hydrangea in a container there are a few rules that you should follow to have success. The first is that the container is large enough for the plant to grow. Starting with a two gallon container is a good place to start. The second, and possibly most important is that the container has at least one drainage hole on the bottom.

As we have discussed, hydrangeas do not like wet feet. Planting anything in a container without a drainage hole will essentially drown the plant. Most containers on the market come with holes that are pre drilled.

If you have ceramic pots without holes you can use a drill with a glass or tile drill bit to drill a few holes in the bottom, and you will be good to go. If you need help choosing a drill bit ask someone at your local hardware for help.

The soil you use in your container should be potting soil, and not garden soil. The garden soil will be too dense for the hydrangea in a container. Many potting soils are available that are premixed with slow release fertilizer as well as moisture control materials.

Using Too Much Fertilizer

Fertilizer in ground with shrub
Don’t overdo it with fertilizers. It is recommended to fertilize the hydrangea once in the spring.

Fertilizer is a wonderful thing to help grow strong healthy shrubs, but there can be too much of a good thing. It is recommended that hydrangeas are fertilized once in the spring and then as the label recommends. 

Most plants like a fall application of fertilizer, however, this application could cause hydrangeas to push vegetative growth too close to the winter which could cause damage to the plant and the flower buds.

If you apply too much fertilizer you can burn the root system. You may notice that the edges of your leaves look burnt, this is actually from root burn due to too much fertilizer.

Using the wrong kind of fertilizer can cause other issues, such as a lack of flowers. Flowering shrubs need phosphorus to produce flowers. When you are picking out your fertilizer at a garden center look for a product that is specifically for hydrangeas, or for flowering shrubs and trees.

Many fertilizers can be heavy in nitrogen. Nitrogen is great for producing lush green leaves, but too much of it can inhibit the growth of those big beautiful flowers you are hoping for. When it comes to fertilizer, less is more. Oftentimes using good quality compost will provide the plants with all of the nutrients they need.

Trying to Change Color

Pink Flowering Shrub Color Change
Some varieties of hydrangeas are able to change the color of their flowering depending on the pH level of the soil.

Hydrangea macrophylla and Hydrangea serrata have big beautiful flowers that are sensitive to the pH of your soil. This is very easy to do, and we will get to that in a second. However, if you have any other type of hydrangea you should avoid using any of the color changing additives to your soil.

They will not change the color of your hydrangea flowers, and they will be altering your soil structure. Another group of flowers that cannot be color changed is white Hydrangea macrophylla or white Hydrangea serrata. These flowers are white, and they will remain white.

Hydrangea flowers in shades of pink, purple, blue or red will be easily changed by lowering or raising the pH of your soil. Starting with a soil test is always a good idea.

For blue flowers, you will want to add aluminum sulfate to your soil to lower the pH. There are many products available for the bluing of flowers, and you will want to follow the package instructions for this. Less is always more. If you are not in a rush to blue your flowers you can slowly lower the pH of your soil by adding more organic matter, such as compost, to your soil.

To raise the pH of your soil and for pink flowers the product you will want to use is garden lime. Again, follow the package instructions for application rates. Fertilizing your pink hydrangeas with a higher nitrogen fertilizer can help to balance out the pH of your soil. Use this sparingly however, too much nitrogen can decrease the number of blooms.

Too Much Sun

Shrub Blooming in Full Sun
Hydrangeas need 4-6 hours a day of sunlight to produce gorgeous flowers.

Hydrangeas need some sunlight to produce happy flowers and strong stems to support those flowers. Four to six hours of sunlight is recommended for most hydrangeas. It is also recommended that those hours of sunlight be in the morning before it gets too hot.

If shade loving hydrangeas are left in the sun for too long the flowers and leaves will begin to burn. They will also be in need of water much more frequently, making more work for you. Hydrangeas are susceptible to a symptom called hydrangea leaf scorch.

It may look like a disease, but in fact it is just a symptom of being too dry. The large leaves have a big surface area for water to evaporate from, leading to brown and crispy edges.

If you have full sun and you are craving some of the beauty of hydrangeas you are in luck. Hydrangea paniculata loves full sun. These hydrangeas are tough, and there are plenty of full sun varieties available. The colors of these flowers typically range from green to white to pink. The large shrubs make really nice hedges, or borders.

Too Much Shade

Plant With Blue Flowers in Shade
With too much shading, hydrangea flowers will be smaller or not bloom at all.

Just as hydrangeas can get too much sun, they can also be planted too deeply in the shade. If your hydrangea is getting less than four hours of sun you may experience some undesirable symptoms.

Hydrangeas require sunlight to produce strong and prolific flowers. With too much shade the flowers may be much smaller in size, or they may not bloom at all. It is a plant’s nature to reach for the sunlight, this often can cause the growth of hydrangeas to become leggy and weakened. Weakened stems will not be able to support the weight of the large flowers, if there are any.

If you have deep shade and you would like to enjoy hydrangeas, climbing hydrangeas or Hydrangea anomala is a great choice for you. These climbing hydrangeas do best growing up the trunk of a tree or a fence. They can grow to 50 feet tall and are covered in foamy white flowers. 

Pruning at The Wrong Time

Pruning Shrubs in Bloom
Hydrangeas do not need to be pruned until they bloom in autumn.

All hydrangeas can be broken into two groups: new wood blooming, or old wood blooming. If you don’t know what type of hydrangea you have you run the risk of pruning your flower buds right off.

New wood bloomers will bloom on wood that is grown in the spring. Old wood bloomers will flower on wood grown in the previous season. New wood bloomers can be pruned in either the fall after the flowers fade, or in the spring before too much new growth has come in. Old wood bloomers need to be pruned in the fall, just after blooming ends so you avoid accidentally snipping off the flower buds.

The easiest way to figure out what type of hydrangea you have is by reading the plant tag. If you have lost your plant tag, this may be a bit tricky. Avoid pruning your hydrangea until after it blooms in the fall. Keep your eye on your hydrangea through the next growing season to try and figure out where your hydrangea flower buds are forming.

Not Checking For Pests

Pests on Blooming Shrub
The most common hydrangea pests are aphids, Japanese beetles and spider mites.

Hydrangeas are resilient plants, and are not easily taken down. However, if you don’t keep your eye out for some of the more common pests, you could get yourself into a bit of a pickle.

As far as insects go, hydrangeas don’t attract anything out of the ordinary. Aphids, Japanese beetles, and spider mites are at the top of the list. Most of these insects are easily removed. You can remove them by hand or by using a general pesticide that you can purchase at your garden center.

Because of the shade loving nature of hydrangeas, fungal diseases are common occurrences. Keeping your gardens clean is the best way to eliminate fungus. If you do end up with a fungal disease on your hydrangeas using a copper fungicide can help.

Final Thoughts

Despite all of these potential mistakes which might make growing hydrangeas seem daunting, they really are a breeze. Doing some planning before you plant your hydrangeas is the best way to avoid some of these issues. With regular check-ins and basic care, this prolific blooming shrub can be a wonderful addition to any garden!

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