Discover how to plant, grow, and nurture hydrangea plants of all varieties, year-round and force bursts of color to rebloom year after year. Indoors, outdoors or a mix of both…
What is a Hydrangea
Hydrangea plants are the master of all florals. They can be shrubs, climbers or trees, and there’s generally five different types, however within the Bigleaf species of hydrangea, there are even more sub-categories.
A List of the Various Types of Hydrangea
- Bigleaf hydrangea
- Mophead hydrangea
- Lacecap hydrangea
- Mountain hydrangea
- Smooth hydrangea
- Panicle hydrangea (also known as the tree hydrangea)
- Oakleaf hydrangea
- Climbing hydrangea
Within the five types, there’s up to 75 species with each of them able to grow themselves without much care and attention on your part, provided the foundations are in place to provide the nourishment needed for these plants to thrive in the right conditions.
Most hydrangea plants are perennial shrubs, but there is also the climbing variety that can reach a peak height of 15 feet. These plants will bloom from early spring, lasting right through the summer into late fall.
In any garden, these plants are true showstoppers with their bustling blooms, but potted, they’re also a master gift and extremely popular for a Mother’s Day present and because of the gorgeous colorful and large blooms found on these, they’re also popular as centerpieces and favored by wedding planners.
An important difference between the potted variety of hydrangea (usually bought at a florist as a foil-wrapped bunch of hydrangeas) is that both foil-wrapped and pre-potted hydrangea that are bought at the store are often grown in greenhouses to speed up the flowering process.
This makes caring for hydrangea different for indoor potted varieties than the ones you grow outdoors in your yard.
For the most part, hydrangea plants given (or received) as a gift, rarely last until the next season as there are steps need taken to allow for the plant to hibernate for a few months before repotting to rebloom the following season.
Both indoor care and outdoor care is covered here. Starting with the outdoor care of hydrangea plants because that’s where they grow best. They then can be cut and arranged for indoor floral displays.
The very first thing to do is know where you’re going to plant your hydrangea…
Planning to Plant Hydrangeas
Hydrangea plants are mainly sun tolerant but most do prefer partial shade. Especially for the early afternoon when south facing gardens get full sun. If you plan to grow in an area of your garden that’s prone to full sun, the most sun tolerant hydrangea is the panicle variety (Hydrangea paniculate).
All other varieties will favor climates with partial shade and some full sun, so long as you remember to water them. The hotter it is, the thirstier these plants become.
For the best-looking shrubs or climbers, it will make a difference to plan where you want these to grow because used in combination with a good garden design, they’ll become an integral part to your garden landscape.
You can use these to create floral borders along a garden path, to provide some afternoon shade around your garden bench, or plant some climbers several feet apart to create your own little secluded spot in the garden.
For inspiration without hiring a landscape designer, check out Gardenia.net’s flowering combos with hydrangea plants or view entire galleries of hydrangea gardens, centerpieces and outdoor potted variances of designs with hydrangeas on Pinterest.
Getting the Soil Just Right
The soil used for hydrangeas cannot be heavy. Waterlogging is this plant’s worst enemy. If your soil feels heavy, adding organic matter always works like a charm. As does adding a course sand through the soil or extra compost.
For indoor plant soil, use a potting soil mix with some peat moss then apply a thin layer of shredded bark across the top of the soil to help with water retention.
For outdoor hydrangea, if you’re growing blue or pink varieties, you need to get the pH of the soil absolutely spot on. Otherwise, the colors will change.
You may be head over heels in love with this idea because it means from one year to the next, you can control the color of bloom by controlling the alkaline level of the soil. If you have kids, this will be a fascinating project for them to get involved in and watch how things change.
How Soil Acidity Affects the Color of Blooms
Not all species of hydrangea will change color based on the soil acidity. The only ones that are do are part of the bigleaf species, mainly mophead hydrangea and lacecap hydrangea.
These mostly produce blooms in blue hues, shades of pink and with a little in-between on the soil acidity, you can get them to produce violet blooms (although that usually happens by accident).
Annabelle, Oakleaf and panicle hydrangeas produce white and cream color blooms and there’s nothing you can do to change those so if you want color combos, it’s the bigleaf hydrangea varieties you’ll want to plant.
As a rule of thumb for soil acidity…
- Blue hues require low pH levels with a target range of 5.2 to 5.5.
- Pink hues require higher pH levels with a target range of 6.0 to 6.2.
Something to remember here is that the type of hydrangea you buy doesn’t necessarily mean that’s the color that’ll bloom. You can buy Blue Billow hydrangea and find the blooms are pink.
Likewise, you could buy the Golden Sunlight (Hydrangea Serrata) and expect it to produce pink or violet blooms, then find out it blooms in blue.
It’s all in the chemistry of the soil.
If you’re determined to grow a particular shade, test your soil first. Given that rainwater is acidic, if you live in an area with a high amount of rainfall, you’ll likely find that your soil is acidic.
If you have a naturally high pH level in your soil, fertilizers can be used to alter the pH before planting. It’s safer to do this than to drastically alter the pH after the root systems have become acclimatized to the soil type.
Unless you plan to grow a large climber or wide shrub, it may be easier to grow your hydrangeas in pots as it’s easier to control soil acidity in smaller amounts than it is on large areas of soil in your backyard or front lawn.
How to Test Your Garden Soil pH Level
A basic test you can do to determine if your soil is alkaline or acidic is to take some soil, put it in a container, pour some distilled white vinegar on it and watch what happens. If it fizzes, it’s alkaline, if not, it’s acidic. That will only tell you if it’s under a pH 7 or over.
That basic test will not give you the accurate result you need to know to control the color of flowers your hydrangeas produce. Remember, for blue florals, you want 5.2 to 5.5 and for pink, between 6.0 and 6.2.
To get those exact readings, you need a good soil test kit. The most accurate will be having your soil laboratory tested, however there’s a range of soil test kits available that are suitable for the home gardener. A digital soil test kit will be the easiest to use.
Once you know your soil acidity, then it’s just a matter of controlling the numbers.
Lowering pH Levels in Soil
To lower the pH levels in soil, the fastest way is to add aluminium sulfate. An alternative that’s not as fast-acting is adding sublimed sulfur. If you’re not in a hurry, the slower (and cheapest) way to go is gradually adding organic matter into the soil.
You’ll often hear that adding coffee grounds is a natural way to alter soil pH levels. It won’t! Fresh coffee grounds are acidic but most of the nutrients are water soluble, so if you’re going to use used coffee grounds, those are nearly pH neutral (between 6.5 and 6.8) so they’ll take forever and a day to have little effect.
What may be worth trying on potted hydrangea indoors is leftover cold coffee, diluted 50/50 then added.
For outdoor areas, and any pots with a large amount of soil, the surest way to lower the pH is to add some aluminium sulfate or sublimed sulfur.
Increasing Soil pH
Liming soil is the process used to increase the pH of soil. It’s done using lime materials, mainly Garden Lime available at your local garden center. Another type is Dolomite Lime. Other materials you can use to raise the pH level is calcified seaweed and ground chalk.
The main ingredient of lime that has an effect on soil is calcium carbonate. However, if you run a soil test and find your soil lacks magnesium, Dolomite Lime contains both magnesium and calcium and is the richest liming material available for quick results.
With that being said, given that altering the pH of soil is effectively changing your plant’s diet, it’s always best to alter the pH before planting, rather than treating inefficient soil later. Lime works best when tilled into the soil, rather than layered on the surface.
How, When and Where to Plant Hydrangea Plants Outdoors
Timing can be important for many types of hydrangea. You don’t want it too hot or too warm so most will do best when planted in early spring or late fall.
If you regularly check in at your local garden center, when you begin seeing blooms ready to purchase, that’s the time to plant hydrangea.
An ideal location for most types is somewhere that receives partial shade in the early afternoon, but gets plenty of morning sunlight. Also, take into account for wind changes as the flowers on these are delicate, so they’re best planted somewhere that’s not out in the open where stronger winds could damage the flower heads or stems.
For planting directly into your garden soil, dig a hole deep enough for the root ball, but go two to three times wider to give the root system plenty of space to develop. If you’re planning to plant more than the one, follow the instructions that come with your plant because spacing differences can vary anywhere from 3 ft apart up to as wide as 10 ft apart.
Naturally, you don’t want these too close together as they’d wind up competing for nutrients in the soil.
Once the root is planted, only half fill the hole with soil, water it, let it drain, fill it in with the rest of the soil, then give it a really thorough watering.
Hydrangea Care with Pruning
Pruning hydrangeas isn’t something you should do just whenever you’re in the garden tending to your plants. The pruning frequency and technique to use is determined by the type of hydrangea plant you’re growing.
Check out this explanatory video discussing how different varieties of hydrangeas grow and bloom:
The general gist of pruning hydrangeas is this: Don’t prune hydrangeas that grow on old wood.
- Some types of mophead hydrangeas
- Climbing hydrangeas
- Oakleaf hydrangeas
- Mountain hydrangeas
These varieties sprout buds one year, carry them through the winter to become next season’s flowers. If you do prune in late fall before the plant goes into hibernation, you’ll be removing the flowering buds, resulting in less or no flowers next season.
That being said, there is a good technique to ensure this variety continues to produce vibrant blooms year after year. The ideal time for pruning old wood hydrangeas is right around the time the flowers begin to fade.
As flowers lose their color, the plant is about to use its energy to produce next year’s buds. To get the best blooms, that’s when to spend your time pruning it to increase the vigor and strength of next year’s plant.
When pruning these, you want to snip the spent blooms just beneath the flower head. For the wood canes, inspect them to remove damaged or diseased canes, keeping the healthiest parts of wood to increase the strength for next season.
Without removing damaged canes (they’ll look straggly and be a lighter shade than the rest of the wood), you’ll find that because of the size and weight of the flowers produced, it can cause the bush to wilt under the pressure. Especially if the flowers and leaves take a thrashing from a heavy summer downpour.
You can also remove some of the taller canes to control the height that the plants grow to.
Speaking of height, panicle hydrangea is the only type you can (and should) prune right back, unless you’re going for a tall climbing look.
New wood hydrangeas include:
- Smooth hydrangeas
- Panicle hydrangea varieties
Both of these types can be pruned in late fall and early spring as the buds grow the same season, unlike on old wood varieties that carry the flowering buds over winter.
Something to remember with hydrangea paniculate varieties is that every year, it’ll grow the same height. If you only prune a couple inches, it’ll keep on growing.
However, the taller it becomes, the less structural integrity it’ll have, unless you’re continually snipping off dead and dying wood to maintain a robust framework to support the plant’s weight.
Have a look at the different types of hydrangea and take notes on the pruning advice for each from Clive Lodge of FineGardening.com:
Overwintering Hydrangeas Outdoors
Hydrangeas, like most plants, do not do well with frost. They need winter protection. Both from frosty climates and heavy rainfall that can really compact the soil, decreasing aeration.
The best protection for hydrangeas throughout the winter is to layer the soil with mulch. The more the better. It’s not uncommon to use non-garden material to protect shrubs.
As Judy Lowe explains on CSMonitor.com, she’ll keep either a quilt or an old mattress protector near hand so that if a frost is predicted, the quilt or mattress protector can be used to retain the heat needed to prevent buds from freezing.
If you have a garden shed, it may be an idea to keep some kind of blanket on hand to use when you need it. Just one night of frost is enough to kill buds, preventing your hydrangeas from blooming in the spring.
For the best frost protection, use wooden stakes roughly about 18” taller than your plant and put them around the plant to use as supporting posts to put a blanket over the entire plant and weigh the bottom down with bricks, stones or another heavy object to keep the frost out and the heat in.
This doesn’t just apply to hydrangeas. Any of your perennials that need frost protection can benefit from the same technique.
If you aren’t using a blanket, the least amount of protection to use is at least 4-inches of mulch over the soil to protect the plant roots. This should be sufficient for panicle hydrangeas and smooth hydrangeas as the buds aren’t produced until it’s ready to bloom, unlike other varieties that grow buds at the end of the previous year’s season and carry them through the winter before blooming in early spring.
For old wood varieties – Oakleaf, climbing varieties and Mountain Hydrangea varieties – draping material over the entire plant is the safest way to ensure the buds don’t get frost damage.
Hydrangea Care Indoors
Did you get a potted hydrangea as a gift?
Potted hydrangeas, aka: foil wrapped hydrangeas, have different needs based on how they were grown. Most florists speed up the growing process of potted hydrangeas using greenhouse conditions. It still produces a quality bloom – for the first year.
Getting a potted hydrangea to rebloom next spring and summer, that’s a challenge not everyone who tackles will successfully accomplish.
To achieve the best chance of reblooming a potted hydrangea plant indoors, try these steps:
- Once the plant stops flowering, cut back the shoots and leave just two leaves. Also, when cutting your stems, you want to cut diagonally at a 45-degree angle to allow the stem to absorb water better.
- You’ll need a new plant pot. Choose one that’s two to four inches deeper than the current container.
- For the soil, use a potting soil with peat moss. If it feels heavy, you can add some perlite into the mix.
- When repotting the hydrangea, separate the roots then sit it on top of the soil.
- Gently press the soil around the roots to get rid of any air pockets.
- To increase water retention, put a thin layer of shredded bark over the soil.
- Keep the potted plant either in a place near a south facing window where it can get plenty of sunlight, or use a bright artificial light, paying close attention to the heat that comes from artificial lighting.
- In the spring and summer, put your potted plant outdoors in early morning where it can make the best of the morning’s sunlight that isn’t as heat intensive as the early afternoon sunlight.
- Feed your potted hydrangea plenty of water and use a balanced fertilizer periodically. The frequency depends on the type of plant. Smooth hydrangeas only need fertilizer once in late fall. Oakleaf and Panicle varieties do best with fertilizer added to encourage blooming one in April, and again in June. Bigleaf varieties of hydrangea plants favor fertilizing every ten days or so throughout March to June.
- By early fall, it’s time to let the plant hibernate over the winter. For this to be effective, use a cool room in your home, or alternatively a garage where there’s limited light – the darker the better. Temperatures for overwintering hydrangeas should be 35oF to 45oF. Around six weeks before you want the plant to rebloom, gradually increase the light the plant receives and increase the room temperature by 20oF.
Watering Guidelines and Feritlizer Frequency for Indoor Hydrangea Plants
For watering indoor hydrangea, the rule to follow is not to let the soil become waterlogged. It’s best to finger test the top inch of soil twice daily and water the plant before it dries. Hydrangeas need consistently moist soil but never too moist that the soil waterlogs.
Signs of watering problems include wilting, yellowing leaves and leaf drop. If any of those are present, it’s likely the plant requires watering more frequently.
During bloom, a lot of watering is required to keep the plant’s energy levels up. When flowering stops, so will the need for as much watering. By using a finger test on the soil instead of sticking to a watering frequency or schedule, you’ll be able to adapt watering frequency to suit your plants requirements.
In terms of feeding indoor hydrangea, they need more fertilizer than those grown outdoors. Generally, a water-soluble fertilizer at half strength once weekly when the plant’s in bloom is sufficient.
But, stop using fertilizer at the end of August to allow the plant to go into dormancy. A weaker solution once monthly can be used when the plant isn’t in bloom.
Where to Put Hydrangea Plants Indoors
An ideal location for indoor hydrangeas is somewhere that gives the plant morning shade and afternoon sun, is free from drafts and away from direct heat sources. It’s the reverse of outdoor growing conditions because it’s warmer indoors.
Rooms with average to high humidity are favorable. The ideal temperature in flowering season is 700F, dropping to 600F during the night and for bud development, 6-weeks of temperatures at 650F, dropping to between 35oF and 45oF for a six-week dormancy period.
To Wrap Things Up
Whether you received a hydrangea as a gift or intend on introducing these mighty florals to your garden landscape, the above guidelines will have you growing hydrangea like a pro.
The only way you can really go wrong with a hydrangea is to prune it at the wrong time of the year. Prune too late in the season and you run the risk of snipping off next year’s blooms.
When you grow healthy hydrangea outdoors, a snip at a 45-degree angle to each stem can give you gorgeous blooms ideal for creating your very own centerpieces to display indoors.
The easiest growing method for hydrangeas is the potted route because it gives you far more control over the soil acidity. That’s especially handy for blue and pink varieties that require specific pH levels to control of flowers produced. Change it up for next season if you like.