Q&A

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Q: I am considering transplanting several wild oakleaf hydrangea from a roadside to our backyard on the edge of a wooded area that receives full sun in the afternoon. What are your recommendations in plant depth and initial stabilization?

A: Transplanting "wild" hydrangeas can be very successful, but you have to start with the season. Hydrangeas dug from the woods will transplant with a much higher success rate if moved when dormant - December through late February. This is a really, REALLY bad time of year to try to move one.

Regardless, dig as much of the root system as possible - it will extend out about as wide as the plant is tall ON EACH SIDE! If you don't have a long way to go, try setting the plant on cardboard or a sheet and dragging it to its new location.

Another idea is what is called "bare root". Once the plant has been loosened, the soil is either shaken or washed off, and the plant immediately taken to its new home. A good, fine-textured soil mix is essential for this method as you want to soil to "flow" around the roots when replanting.

Water well and fill voids with the soil - notice the type of soil the plant is growing in - probably a sandy loam with some small rocks. They like well-drained soils.

Incorrect planting depth is the killer of more plants than one can imagine. A rule of thumb is to never plant a container-grown plant deeper than 2/3 the height of the soil ball, not the container, and slope the soil away. Keep the hole shallow and wide - don't over-excavate as you will never get the depth to settle correctly. If anything, underestimate the depth. Too shallow is far better than too deep.

Now for the real killer: Oakleaf Hydrangeas grown in the wild need to be transplanted to a similar growing condition. If the wild guys are in the shade and you move them to the sun, your potential for success will be extremely low regardless of the season of transplant. Oakleaf, as do most hydrangeas except the paniculatas, like morning sun/afternoon shade. They may grow in the afternoon sun, but will never thrive. It is not a water issue as much as it is heat on the leaf surface. The afternoon sun simply bakes the leaves.

Honestly, I suggest simply buying some small Oakleafs from a nursery or garden shop and put your time and energy into something with a high potential for success. Your success rate will skyrocket because you can transplant now, get ALL the roots and by the end of the summer, the plant will almost double in size. We even have some quart-sized Snow Queens here at the Gardens leftover from our plant sale that are super at $10.00 each. If the wild plants have emotional value to you, take cutting, collect seed or try layering - bending a branch to the ground and holding it there with a brick. Roots will emerge where the stem touches the ground, then you simply cut off the rooted portion and transplant THAT.

I hope this helps. I love doing the transplant thing, but if not done at the right time, you could be wasting your time and energy AND killing a perfectly happy plant!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: I'm moving to a new home in August. When would be a good time to plant some hydrangeas?

A: Container-grown plants can be transplanted almost any time of year provided adequate maintenance is given. Generally people have activities and vacations in the middle of the Summer that create lapses in maintenance (watering), which makes the Summer the least desirable time for planting.

The optimum time is definitely late Fall or early Spring, during the plant's dormant period.

If you can ensure adequate care, plant this summer. If not, hold off until the Fall!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: When do you expect the hydrangeas to be at their peak?

A: We would normally say the middle of May, but it appears everything is 2-to-2 1/2 weeks behind schedule right now because of the cool spring. I would guess this year early June would be beginning of peak.

Come on out and visit!
Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: On a Master Gardener trip maybe three years ago, I bought from you a Snowflake Oakleaf hydrangea and planted it in full sun and it has never done well. It is smaller, but still alive.

I'm wanting to transplant it in morning shade, but I suppose I should wait until February and hope it can survive this summer?

A: You have the exposure reversed. Snowflakes HATE full sun! We recommend morning SUN and afternoon SHADE. If it is doing poorly, it is almost certainly a sun exposure problem. Locate it where the shade begins around 11:00 a.m. and it will be happiest!

As for when to transplant, I would wait until the late Fall if at all possible. Don't wait until February given how mild our winters have become. But, if the plant is REALLY suffering, perhaps it is worth the risk to move it now before it gets any further into the growing season. Plant it high, make sure you get as much of the root system as possible, and make sure it gets adequate water.

Hope this helps!
Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: When is the best time to relocate hydrangeas?

A: You really have run out of time this Spring. It would be best to wait until the plant goes dormant next Fall, and be sure to complete before March 1 at best.

You can try it now, but chances are about 50/50 that it will survive, maybe a little higher on the survival end, but you are at the iffy end of the season.

Good luck!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: Our soil is mostly compacted clay with one half of the yard in shade and the other side 8 hours of sun. How do we plant in these conditions?

A: The sun issue is a tougher one - you have to use Hydrangea paniculatta as they will tolerate full sun.

The soil issue is not impossible. The rule of thumb, especially with compacted clay soils, is to dig wider, shallow holes. Don't go crazy amending the soil because you will create a "pot" type condition. Take the soil that was removed, even if it is clay, and mix a bit of organic matter (three-parts clay to one-part organic by volume), then mix THAT with some sand (three-parts mix to one-part sand by volume) and plant in that.

Make sure you don't plant any plant deeper than 2/3 the root ball soil mass - you may even need to go to 1/2 the soil mass - above the ground. Then slope the soil away from the top of the soil mass. Dig the hole about 3 to 4 times wider than the root ball, just very shallow. This will provide the drainage that is needed, and also allow the plant to acclimate to the clay soil it will ultimately grow in.

I hope this helps!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: Last summer, a few of my oak leaf hydrangeas, that had been in the same location for many years, began to "wilt" from the top down and eventually die. This spring two more of the group did not come out. The remaining plants in the same area look healthy for now. What could be the cause?

A: This sounds like Armillaria Root Rot, as the plants die from the top down. This is a particularly nasty problem, one which has attacked several of our older Snowflakes here at Aldridge Gardens. There is no known cure for this as the plants are gone by the time they are symptomatic, showing a wilting type appearance. Unfortunately, the solution is total elimination of the diseased plant AND not planting again in that site.

Here is some lengthy but good info from the Alabama Cooperative Extension Service bulletin on Hydrangeas:

Mushroom root rot, which is also called Armillaria root rot, is
a common disease in landscape plantings of hydrangea, particularly
the oakleaf hydrangea. The causal fungi Armillaria mellea or
A. tabescens are soil inhabitants that attack a variety of common
shrubs and trees, particularly many oak species. These fungi
are especially aggressive root rot pathogens on drought-stressed
trees and shrubs. The sudden wilting of one or
more shoots that previously appeared healthy is often the
first symptom of mushroom root rot on hydrangea.
After watering, these wilted leaves will not regain their
normal form. The remaining shoots wilt within a few weeks
and the diseased hydrangea quickly dies. White fan-shaped
mats of fungal mycelia develop under the bark of the root collar
at or just below the soil line. In addition, the characteristic black
branched threadlike rhizomorphs of Armillaria fungi
can usually be found on the surface of damaged roots and the
root collar, as well as in the surrounding soil. Flattened black
rhizomorphs may also be seen under the bark on the roots or
root collar. In late fall after a heavy rain, clusters of up to 100
honey-colored mushrooms appear on the damaged roots or
within the drip zone of the diseased shrub or tree.
Armillaria fungi are common soil inhabitants and
often live in association of their hosts with no apparent damage.
The fungi can colonize the roots of vigorous plants, but are more
likely to attack shrubs previously weakened by drought or other
stress factors. Although wounds on the roots are important infection
sites, Armillaria fungi can also penetrate into undamaged
roots and colonize the cambium and sapwood. Mushroom root
rot is often seen on hydrangea interspersed between diseased
trees.

Good growing conditions are the best defense against mushroom
root rot. Establishment of hydrangea on sites where they are best
adapted and proper site preparation will reduce the risk
of disease development. Also, avoid planting oakleaf
hydrangea on sites where oaks or other trees have succumbed
to mushroom root rot. During periods of summer drought,
thoroughly water established hydrangea every 4 to 7 days.
Fertilizing according to the results of a soil fertility assay is
also suggested. Diseased hydrangea should be removed
and destroyed.

Fungicides will not control mushroom root rot.

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: I have a blue mophead that was given to me in a pot for Easter. It is around 2 feet tall but has giant blooms. I have now planted it under some tall trees in my front natural area. I have heard that planting from potted flowering hydrangeas does not always go well. Is there anything I can do to help it survive?

A: I don't know that I can say there are strong reasons why plantings under tall trees do not go well EXCEPT that the competition for water is certainly greater under established trees.

I would recommend specific watering of the hydrangea until it is well-established - just be careful not to water too much.

Make sure it is NOT planted too deeply. Roughly one-third of the dirt mass that was in the container should be above the ground, and the soil pushed up to and sloped away from that exposed one-third. A wider hole, not a deeper one, is better. This allows the plant to breathe and prevents it from getting water-logged.

Since you have been to Aldridge Gardens, you know we have quite a number of hydrangeas planted under the trees. Based on our experience, I cannot say that there is a universal problem that would prevent locating your plant there.

Good luck!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: Do some hydrangeas need full sun and some shade? Is there a way to tell the difference?

A: Yes, there are hydrangea varieties that like (or tolerate) sun while others prefer shade. A general rule of thumb is that the hydrangeas that bloom or start blooming in the Spring prefer a shady environment, while those that bloom in the mid-Summer until Fall will grow in sun. These sun lovers are Hydrangea paniculata, and Limelight and PeeGee are popular varieties.

Some Spring bloomers will tolerate more sun than others, but the rule of thumb on the Spring bloomers is morning sun, afternoon shade. And after noon is the key here. The post-lunch sun is far too intense and hot for most hydrangeas as they will lose water so rapidly they scorch.

Hope this helps!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: I have 3 oak leaf hydrangeas that I've had for 7 years. They are not hybrids. It looks like they might have been dug from the woods, but I did buy them at a nursery. These 3 always put on a show for me, but this year the wood is dead as can be. There are small ones growing inside and outside of the mother shrub, but the mother shrub is dead. I don't want to make the same mistake of replanting the same shrub in this same place. They did get a lot of sun, perhaps this was the problem?

A: Sorry to hear about your hydrangea. There could be many things going on that could have caused the die-back. The most common is a fungus that is in all soil, but warm, wet weather causes it to become active, and a weakened plant (one that's gotten too much sun) can be infected. That may or may not be the case here, but a good rule of thumb is morning sun, afternoon shade. Afternoon sun can devastate an Oakleaf Hydrangea.

This winter/spring was about as weird as any we can recall. Temps were warm, then we got a freeze, then warmed up again. It is also possible that you have bark split caused by freezing then a quick warm-up - which you wouldn't get with gradual warming. That can kill a large plant to the ground without injuring the roots, which is why you have emergent growth.

I would play the wait-and-see game for a month or two, to see if the emergent growth takes off. With a mature root system fueling it, you may have a BIG plant in no time!

Of course we'll have plenty of smaller hydrangeas at the May 9-10 plant sale - and all very affordable. We hope to see you there!

Rip

Rip Weaver, CLARB, ASLA
Executive Director, Aldridge Gardens


Q: I’m ordering an All Summer Beauty Hydrangea for my mother-in-law. Can I request a blue one?

A: In short, no. The color of a hydrangea bloom is determined ONLY by soil acidity.

Here’s the longer answer:

To get a blue hydrangea, aluminum must be present in the soil. Aluminum sulfate may be added to the soil around the hydrangeas to make sure there is enough aluminum present.

Authorities recommend that a solution of 1/2 oz (1 Tbsp.) aluminum sulfate per gallon of water be applied to 2 to 3 year old plants throughout the growing season.
Important: Water plants well in advance of application and put solution on cautiously. Too much can burn the roots.

To make the aluminum available to the plant, the pH of the soil should be low - between 5.2 and 5.5. Adding aluminum sulfate will tend to lower the pH of the soil. You can also add organic matter to the soil, such as coffee grounds, fruit and vegetable peels, grass clippings etc., to lower the pH.

If the soil naturally contains aluminum and is acid (has low pH), the color of the hydrangea will automatically tend toward shades of blue and/or purple.

The choice of fertilizer will also affect the color change. A fertilizer low in phosphorus and high in potassium is helpful in producing a blue color. 25/5/30 is good. Superphosphates and bone meal should be avoided when trying to produce blue.

After stating this with much certainty, I hasten to add that it is virtually impossible to turn a hydrangea blue for any length of time if it is planted in soil with no aluminum and that is highly alkaline (chalky). One would have to be very diligent in keeping the soil properly conditioned as stated above.

Perhaps the best idea for growing blue hydrangeas in an area with alkaline soil would be to grow them in very large pots using a lot of compost to bring the pH down. The above suggestions for bluing would also work for a potted plant. Reduce the strength of the aluminum sulfate to 1/4 ounce per gallon of water. In a pot, it will be much easier to control the requirements for bluing.

One last suggestion for those who are serious about this process: It is important to have your water tested so that it will not "contaminate" the soil that you have so rigorously balanced. The pH of the water should not be higher than 5.6.

Rip Weaver, CLARB, ASLA
Aldridge Gardens Executive Director