Hydrangeas are hardy and fast-growing plants. And as a savvy homeowner, you have heard that some kinds of shrubs can bore into pipes and foundations underground. So you might be wondering if your gorgeous but aggressive Hydrangeas will damage your plumbing or your house, if Hydrangeas have large roots, and how deep they grow?
The slender and fibrous roots of Hydrangeas aren’t strong enough to dig into pipes or foundations, and they’re not thick enough to crack them from seasonal swelling. The only risk is if you have a pipe that’s already leaking, in which case your Hydrangea’s roots might infiltrate and clog it.
If you’re planting Hydrangeas near your house, make sure to give them enough space to allow for air circulation. They won’t do well if they’re pressed right up against the boards. And tall varieties like PeeGees are probably not ideal for foundation plantings.
How Big Are Hydrangea Roots? How Deep Do They Grow?
Looking at the vigorous growth of a Hydrangea’s stems, it’s easy to assume they must be matched by a deep and stubborn root system underground. But Hydrangea roots are actually surprisingly shallow. They don’t form a central taproot like rhododendrons and shrubs. Instead, they grow in a loose, spreading mass of fibers often referred to as a root ball.
The vast majority of a Hydrangea’s roots will stay within the top six inches or so of soil. However, they do tend to spread quite a bit in the horizontal direction. Many a gardener has discovered this to their dismay when stray Hydrangea stems began infiltrating their walkways or popping up stems far from the main mass of the plant.
As a rule, you can assume that your Hydrangeas roots probably extend at least an inch or two past the dripline (the horizontal circumference of the plant’s leaves).
Can You Plant Hydrangeas Close To Your House?
By itself, the fact that your Hydrangeas are shallow-rooted isn’t necessarily a plus when it comes to concerns about damage to your home.
After all, many problem trees cause issues precisely because their roots don’t go very deep – instead of looking for water far below the ground, they spread into leaky portions of the basem*nt, foundation, or plumbing system.
However, shallow-rooted means something very different for a tree than for an ornamental shrub. Most of your major pipes will be at least a foot below the ground and probably deeper if you live in a colder region. It’s rare for Hydrangea roots to reach that depth.
If you are experiencing root infiltration from Hydrangeas, chances are you have a plumbing problem, not a gardening problem! Any plant’s roots will grow toward a steady source of water – so a slowly leaking pipe is irresistible.
If you’re thinking of planting a Hydrangea near a shallow pipe, you should consider whether it’s an older clay pipe or a newer concrete or PVC tube. Newer materials will do a better job of resisting infiltration.
And Hydrangea roots aren’t generally sturdy enough to disrupt an intact foundation. That’s more of a concern with larger trees that have thick, heavy roots. With those plants, fluctuations in moisture or temperature can cause their root systems to expand and contract, which can sometimes burst pipes or crack foundation blocks from sheer pressure.
The main reason not to plant Hydrangeas too close to your house is for their own health. These shrubs do best with at least three feet of space from obstacles or other plants. Taller varieties may need close to ten feet.
If you’re looking to use Hydrangeas as foundation plantings, consider dwarf varieties like:
Little Lime. This is a compact version of the popular Limelight variety, with blooms that begin light green but shade to red in the fall.
Tiny Tuff Stuff. A smaller Lacecap Hydrangea which will produce sprays of tiny purple blooms ringed by larger flowers.
Mini Penny. A popular Mophead variant, with flowers that change color depending on soil acidity.
Glowing Embers. This will grow into a mid-sized shrub that blooms in vibrant hues from pink to red.
Cityline Rio. One of the more compact options available, this dwarf Bigleaf produces blue flowers with striking green and purple centers.
Whatever variety you use, check the estimated growth and assume that it will probably reach the maximum listed size. A good rule of thumb is to calculate one and a half times the estimated maximum width of your Hydrangea and plant it at least that far from your house.
And as always, you should take sun exposure into account. Most Hydrangeas do best where they can get sun in the morning and shade in the afternoon, but in colder areas, they may prefer full sun.
Do Hydrangeas Grow Well in Pots?
Another option when using Hydrangeas as foundation plantings is to grow them in containers. If you’re going this route, just be aware that they’ll need plenty of space there too! A pot that’s too small for your Hydrangea won’t remain moist long enough or give the plant’s root system enough breathing room.
Go with a container that’s at least two feet in diameter, and adjust upward if you’re using a larger Hydrangea variety.
Adequate drainage is also crucial, and your planter should have enough holes at the bottom to ensure that all excess water can run out from the pot so that the roots don’t rot. A layer of rocks at the base can improve drainage as well.
Mixing in compost is also a good way to enhance the soil quality – it will add nutrients in addition to making the soil drain better. For more information about the best compost for your Hydrangea, click here.
Can You Dig Up and Move Hydrangeas?
If you’re worried that you have planted your Hydrangeas in the wrong location, you might be wondering if you can move them to a better spot.
You’ll be glad to hear that transplanting Hydrangeas is relatively easy, thanks again to their fairly shallow root systems. And these plants are survivors – they’ll bounce back from the shock of relocation reasonably quickly, as long as you shield their roots with mulch and give them plenty of water in their new space.
If you are planning to move your Hydrangea, wait until it’s gone dormant and lost its leaves. Mid-autumn is a good time in a colder climate. If you live somewhere that doesn’t get winter ground freezes, you can wait until after December. For a more in-depth discussion on relocating Hydrangeas, take a look at our article on the subject.
Which Plants Will Cause Damage?
If you’re worried about your foundation or plumbing being damaged by plant roots, here are a few species you should watch out for.
Trees:
Willow. These trees prefer moist areas like river banks, and if your yard isn’t as damp as it would like, it may spread its roots far and wide in search of moisture.
Magnolia. The spreading, ropy roots of this plant are great at worming their way into cracks in pipes.
Poplar. These popular shade trees can have root systems twice or even three times as wide as their trunks are tall.
Oak. Sturdy, slow-growing, and prone to putting out large lateral roots that can infiltrate plumbing systems.
Ornamental Plants:
Common or English Ivy. This aggressive creeper can easily sneak into crevices both above and below ground.
Boxwoods. Though these are common foundation plantings, their spreading root systems are great at finding and exploiting weak points in pipes and foundations.
Holly. Another popular choice for planting around the base of a house, these shrubs tend to spread far and wide if they’re not getting enough nutrition and can easily wind up clogging pipes.
Putting It All Together
Hydrangea roots are shallow and fibrous enough that you won’t usually have to worry about them sneaking into your pipes or burrowing into your foundation. The only exception is if you already have a steady leak that’s less than seven or eight inches below the ground.
But that doesn’t mean you should feel free to plant them right beside your walls. These plants need a fair amount of space to thrive. And don’t forget that your Hydrangea is going to get a lot bigger after it’s had a year or two in the ground!
