Hardy Hydrangea Care

Wiese Acres hydrangea

There are different schools of thought on the best places to plant your hardy hydrangeas.  Some sources say in northern climates, they need full sun to bloom. Others say morning and / or late afternoon sun, but shade in the hottest part of the day.

My experience is that in most full sun locations in North Dakota, there is also full wind.  The two together are a little much for the hydrangeas in my yard.  I plant mine in nice loamy, well-drained soil in part shade, namely where they are shaded from the hottest midday sun.  I’ve had some in full sun and find that they tend to sunburn and wilt during the heat of the day.  I end up with a plant that is chronically stressed and can’t do its best.  Most of my hydrangeas are planted in a location where they receive either dappled sun all day long; direct sun from morning until early afternoon; or morning and late afternoon / evening sun.  The exception is my Limelight.  That one thrives in full sun, but in a location where it is somewhat sheltered from strong winds. 

I’ve learned by trial and error where the various hydrangeas do their best.  Hydrangeas are one of the rare shrubs that has a small, compact root ball and is very forgiving of being moved from one location to another.  I start mine in sheltered, part shade, rather than in the full sun they supposedly tolerate. If a mature hydrangea doesn’t bloom well, they may be a bit too shaded and need to be moved to a slightly sunnier, but still protected location.   

 

Transplanting is best done when the shrub is dormant, either early spring or late fall.  If transplanting is done in the fall, allow at least six weeks of time with soil temps above freezing to allow roots to establish themselves, and then mulch it heavily the first year.

All hydrangeas like to be planted in well-drained, fertile, loamy soil.   Whether planting new shrubs or transplanting existing shrubs, they should be planted to the same depth they were planted, either in the container or in their previous location.  The hole should be about twice the diameter of the root ball, and should have a good amount of rich, organic matter, such as compost, mixed into the planting hole.  As a rule of thumb, I replace about 1/3 of our clay soil with rich organic matter (compost)when planting shrubs, trees, or perennials that like a good, loamy soil.

 I add a couple inches of compost around the base of my hydrangeas each spring to give them that rich, organic matter they need to do their best.  This also works as mulch and helps keep weeds at bay.  Hydrangeas may also need some supplemental fertilizer to bloom their best.  A balanced liquid fertilizer can be fed in early spring and then about mid-July, or you can work an extended release fertilizer into the soil in spring and leave them be after that.  It is important in northern climates to stop feeding hydrangeas by August.  Too much fertilizer later in the summer will encourage a flush of new growth which will not have time to mature and harden off before freezing temperatures.  Young growth is very vulnerable to frost damage and death. 

 

 Hydrangeas like to be kept evenly moist, but not soggy.  When watered, they should be watered deeply and less frequently rather than a little bit more often.  I use drip irrigation and give the hydrangeas about one inch of water one time each week.  In very hot, windy weather, I may need to increase the rate or the amount to keep that even moisture, but I never go to smaller amounts of water more frequently.  Because hydrangeas tend to have shallower, more compact roots to begin with, I don’t want to encourage even shallower root development by frequent, shallow watering.

Hydrangeas rarely need any more extensive pruning than trimming out dead wood in the spring.  They can be pruned to maintain a shorter, smaller stature, if you wish.  Paniculatas and arborescens bloom on new wood, so pruning can be done pretty much anytime except when the flower heads are forming in the spring.  Rather than pruning for size, it is better to not plant a hydrangea that will want to grow to 10 feet tall in a location that will only support a six foot tall shrub.  Choose a more suitably sized hydrangea to start with, rather than having to commit severe pruning against your shrub every year.

Hydrangeas are relatively disease free.  If moisture is allowed to stand on the foliage, there may be some problems with powdery mildew or rust.  Mild cases can be treated with just good hygiene around the plant and pruning back overgrown areas to allow for better air circulation.  Severe cases may need treatment with a fungicide.

Choosing the right hydrangea for the right location and giving it the right amount of water and fertilizer will re-pay you with a gorgeous, relatively care-free, dramatically flowering shrub.