5 Things You Should Never Do When Planting Hydrangeas
By Stacey Hirvela for Proven Winners ColorChoice Shrubs
Everyone wants to get their new plants off to the best possible start, and sometimes that can lead to problems – especially for hydrangeas. It’s not that they are finicky or difficult; in fact, it’s actually the opposite: they’re quite easy to grow and resilient, and many people tend to do too much at planting time, smothering them with a bit too much love. Here at Proven Winners ColorChoice Shrubs, we’ve heard from gardeners across North America who have done just that, so we’ve learned about these oft-made mistakes firsthand. So, with that, here’s our list of things that you shouldn’t do when planting hydrangeas.
Little Lime Punch panicle hydrangea and Let’s Dance Sky View hybrid hydrangea
Don't amend the soil
Plant your new hydrangea directly into your natural, native soil, without adding anything to the hole.
This one comes as a surprise to lots of people, but we stand by it, especially since improper soil amending is the number one reason we see new plants struggle and even die – especially hydrangeas, and panicle hydrangeas specifically. While it seems like adding a bunch of nice, fresh topsoil, compost, manure, sphagnum moss, or potting mix to the hole would make a rich and luxurious home for your new plant, it actually leads to problems.
It’s called the bathtub effect: all that amendment has large spaces between its particles and is able to hold a huge amount of water. By comparison, the surrounding natural soil has very small spaces between its particles and holds much less water. So once you’ve planted and you water your hydrangea in, you end up applying quite a bit of it.
As gravity takes its toll and the water starts to drain through the soil, it comes to a screeching halt because that large volume can’t drain into the small pore spaces. It’s kind of like a huge crowd trying to run through a small door, and what happens is that the water then sits around the roots while it waits until it can percolate through, and that leads to root rot.
Panicle hydrangeas are by far the most sensitive to these conditions, but we still don’t recommend it for any hydrangeas. The best thing to do is to simply plant into your natural soil and put down a good 2-3” layer of shredded bark mulch over the roots. If you truly believe you must amend the soil, then it is imperative that you thoroughly incorporate your natural soil with the amendment until they are essentially indistinguishable from one another. Do this not just for the backfill that you remove, but also take some extra soil from the planting spot and mix it in to break the bathtub effect.
Do not put down landscape fabric/weed barrier.
Not only is it expensive and annoying to install, it’s not particularly effective at controlling weeds and can harm sensitive plants – especially hydrangeas.
This is probably the second biggest culprit of struggling or dying new hydrangeas. While landscape fabric seems like it will be helpful in controlling weeds, it’s far more likely to cause drainage issues or even carbon dioxide buildup around the roots.
The fabric makes it difficult for water to reach the roots of the plant, and if the soil is wet, it makes the drying out process very slow, once again leading to a lot of water sitting around the roots and root rot. It also disrupts the natural gas exchange between the roots, soil, and atmosphere, and can trap unhealthy levels of carbon dioxide around the roots. On top of all that, it’s not even particularly effective at controlling weeds.
If you already have landscape fabric in the area where you are planting, you can still plant – just cut it away for a good 2’ around the center of the new plant; cutting away more is even better.
Let’s Dance Big Band bigleaf hydrangea
Do not mulch with rocks.
Hydrangeas roots like cool, moist conditions, and rock mulches create just the opposite.
This one goes hand in hand with #2, as it seems that rock mulches are most often used in conjunction with weed barrier. However, all of the liabilities I just outlined are substantially exacerbated when there’s a layer of rock over the fabric. But even without a weed barrier, rock mulches and hydrangeas just don’t get along, and the hotter your climate, the worse it gets. Rock mulches attract and trap a lot of heat, which makes the root zone of the hydrangea hot, and can also lead to burning of the leaves and flowers. In short, it causes a lot of stress to the plant, which will impact its overall health and vigor, as well as its flowering – and no one wants that.
You should absolutely mulch your hydrangea, however. Use an organic mulch (one made of natural materials that break down), like shredded bark, wood chips, or pine straw. Hydrangeas are naturally shallow-rooted, which makes them susceptible to drying out, as well as heat and cold stress. Mulch acts as an insulator against both, plus organic mulches break down over time, improving soil texture and fertility, and conserving water.
If you already have rock mulch, don’t panic! Just clear it away for a good 2’ or so around the center of the hydrangea, plant it, then cover that space with shredded bark mulch instead of rocks. Though this will be visible if you are looking down on the plant, it won’t be visually disruptive if you are looking at the planting straight on.
Do not let your new plant dry out completely during its first year.
Keep the soil moist but never wet for optimal root growth – that’s what will get your plant established quickly.
When you plant a new shrub, the first thing it’s going to devote its energies to is growing roots in its new home. But for roots to grow quickly and vigorously, the soil needs to be moist. It should never be wet, because wet soils are low in oxygen which is just as important for healthy root growth as soil and moisture. It’s impossible to give an exact amount or number of times to water since it depends so much on the weather, the amount of sun your plant gets, and your soil type, but basically, it should never become thoroughly dry during that first crucial year.
You are the best judge of that, but if you aren’t sure if your plant needs water, just peel back the mulch and feel around in the top inch or so of soil. If it feels cool and moist, you’re good to go! If it feels powdery and dry, give it a good, thorough watering. I like to leave the hose running slowly, or use a spot sprinkler, for a good 15-20 minutes for each time I water.
Though some hydrangeas – notably panicle hydrangeas and oakleaf hydrangeas – can exhibit some pretty impressive tolerance to hot, dry conditions once they are established, for them to achieve that resilience, they first need to develop a good root system. Also be aware that though these hydrangeas can tolerate dry soil, they will look and bloom their best if they don’t experience severe stress, even once established.
Don't fertilize.
Save your time and money and fertilize when it counts – once your hydrangea is established.
Once again, while of course you want to get your plant off to the best possible start, fertilizing your plant during its first season is simply not necessary. First of all, it will have been amply fertilized by the grower and garden center before you purchase it, and most growers already incorporate a time-release fertilizer into the soil which will easily sustain its nutrient needs through that first summer and fall.
Plus, there’s just no benefit to excessive fertility in this period where the plant’s energies are going exclusively toward root growth.
You can start to fertilize during the second season if you wish, and this may be particularly helpful if you started with a small plant and/or are growing your plant for privacy or screening. One application of fertilizer in early spring is sufficient in most areas, but you can fertilize monthly through late July if you wish. We recommend a granular (not liquid) fertilizer formulated for woody plants, like a rose fertilizer. It’s a great all-purpose fertilizer for all your shrubs, not just hydrangeas.
Incrediball Storm Proof smooth hydrangea
Speaking of “not just hydrangeas,” all of this advice applies equally to all of our flowering shrubs. And as you can see, it’s not complicated or tricky – all of this actually means less work and expense than most people typically associate with a planting project. Within a couple of years, you’ll have a vigorous, healthy, beautifully blooming hydrangea that requires virtually no special care or attention.
When you are ready to plant, you’ll find Proven Winners® ColorChoice® hydrangeas at your local garden center.
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