What Your Hydrangea Needs in March to Stay Alive, Thrive & Grow Lots of Flowers: 3 Vital Jobs to Do Right Now

What you do with your hydrangea shrub in March affects how it grows for the rest of the year. Do nothing, and it’ll probably survive – but don’t expect an abundance of flowers! Give it an hour of your time right now, though, and your shrub will reward you with healthy growth and a glorious show of summer blooms.

These three vital hydrangea care tasks are easy, even if you're a beginner gardener. March is the ideal time to get hydrangea spring care sorted, once you're nearing or have passed your last frost date, depending on your USDA zone. Here's exactly what to do, whatever type of hydrangea you have, to give your shrub everything it needs for a standout summer.

1. Prune Your Hydrangea – And Be Brave!

Honestly, you don't need to be scared about pruning hydrangeas. To do a great joy, you only need to know one thing, and that’s whether your hydrangea is one that flowers on new wood, or one that flowers on old wood. Happily, it’s easy in spring to work out if your hydrangea is a new- or old-wood bloomer with a simple check.

If your shrub already has flowerbuds formed on its stems, then it’s either a bigleaf hydrangea (Hydrangea macrophylla), oakleaf hydrangea (H. quercifolia) or mountain hydrangea (H. serrata). These all flower on old wood so if you snip off stems, you chop off this summer’s flowers, too. All you need to do in spring with old-wood blooming hydrangeas is snip off last year’s flowers and remove any dead, or diseased stems (the three Ds of pruning).

If your shrub doesn’t have any flowerbuds on its stems, then it’s either a smooth hydrangea (Hydrangea arborescens) or panicle hydrangea (H. paniculata). These flower on new wood so need a hard prune now, reducing all the stems by a third, as well as removing any dead, damaged or diseased stems. If you want enormous blooms, though you’ll get a few less of them, you can prune your hydrangea even harder for huge flowers, reducing stems to 8-10 inches from the ground.

Do sharpen your hand pruners beforehand so the blades slice through rather than crush the stems. It’s a five-minute job with a sharpening tool such as this all-garden-blades sharpening tool from Amazon, and will make a big difference to how quickly the stem ends heal. Mature hydrangea stems are woody and tough to cut through with hand pruners: if you’re chopping stems any fatter than your finger, it’s far easier to use loppers like these from Amazon, which give more leverage.

2. Fuel Your Shrub for Lots More Flowers

Next, fertilize your shrub – but be smart about it. All hydrangea types will benefit from a spring feed, but do be judicious. If your soil is really fertile, and your shrub is mature, you can skip this step altogether: an established shrub in rich soil will have a good root system and be able to get all the nutrients it needs from the ground. Give it more food than it needs and you’ll fuel over-long stems that will need staking.

All good? Then use a balanced slow-release feed with an NPK ratio of 10-10-10, which will release equal parts of nitrogen (N), phosphorous (P) and potassium (K) over a few months, like this all-purpose fertilizer from Amazon. Steer clear of any fertilizer with a higher proportion of nitrogen as that will encourage your hydrangea to prioritize stem and leaf growth over flower production.

Sprinkle the granules around the shrub’s dripline, which is the ground beneath the outermost edge of its stems, as that's where there are lots of root tips, and work them into the top inch of soil.

Fertilizing will fuel lots of new growth but those fresh stems will be tender. If an unexpected hard frost is forecast, you can throw horticultural fleece over the shrub to protect it. But don't worry if you forget – your shrub will be fine, the frost will simply set that new growth back.

3. Water and Mulch to Lock the Moisture In

It’s wise to water any plant after you’ve pruned it, as being hydrated helps it cope with the stress of suddenly having lots of cut stems to heal. Water the soil all around the shrub’s base: hydrangeas are shallow rooters, only growing to a soil depth of two feet, but spread their roots wide.

Hydrangeas like to be kept well hydrated, which can mean watering two or three times a week during dry spells, so to lock the moisture in the soil and reduce evaporation, add a layer of mulch to the soil surface. You can use any organic matter, but make sure it’s well rotted or it may scorch those shallow roots. Homemade compost or pine needles saved from your Christmas tree are both cost-effective options, or use a manufactured mulch made from shredded bark such as Brut Organic Aspen Mulch, available from Amazon. Coconut husk chips are another sustainable option, such as Back To The Roots Mulch, also from Amazon.

There's another benefit to mulching, too: all this organic matter will gradually rot down to provide your hydrangea with nutrients, and improve the soil structure.

Be aware that your choice of mulch can impact the color of bigleaf (Hydrangea macrophylla) and mountain (H. serrata) hydrangeas because it can affect soil pH levels. Acidic mulches like pine needles or shredded pine bark will make these hydrangeas bluer; if you want pinker flowers, use a mulch with a neutral pH such as standard compost. Coconut husk mulch is typically slightly acidic to neutral.

Spread a three-inch layer, or a little less if you mulch every year so as not to raise the soil level over time. Extend the mulch to just past the shrub’s dripline as a minimum, and ensure it doesn’t directly touch the central stems.

And that's it! You can sit back and look forward to a fabulous display of flowers come summer.

In the meantime, keep your hydrangea watered in dry spells, watch out for powdery mildew (ensure you're watering the soil and not the leaves, and snip out a few stems at the base to improve airflow) and aphids (leave for a few days for ladybugs to deal with them or treat with a natural aphid remedy).