Hydrangea Questionnaire Replies

Monday, April 27, 2020

Hydrangea Questionnaire Replies

In lieu of our April 27th meeting here are replies to members’ hydrangea questions

Dear Fellow AHS Members, 

As you know, with the cancelation of the AHS Spring Meeting, we requested our members submit their hydrangea questions to the board. We had planned to discuss them during the April meeting but since we cannot, we will instead hopefully answer your questions in this email.  Fair warning, the replies are our own personal observations and suggestions of what we have experienced over the years – not from a studied document. Thank you to everyone who sent us your questions. A few of our AHS Board members along with AHS member, Hillary Thompson, have tried to answer, with the best of our knowledge, and with the information we received. Hillary and Mike Thompson are AHS members and owners of Cutting Edge Plants Nursery. We are very grateful to them for taking their time to make three videos concerning some of your questions. The videos cover propagating hydrangeas, watering needs of hydrangeas, and pruning hydrangeas. The links to the videos are below and will take you directly to the Cutting Edge Plants YouTube videos. 

I hope you are enjoying peace and health in your gardens. 

Until we can meet again, 
Eva Kinney, AHS President


1. What other plants that have similar needs as hydrangeas? Name 10 other favorite plants to mix with hydrangeas.

GW – Boxwoods, Hostas such as Guacamole, Sum and Substance, Halcyon provide great contrast of leaf form and color. Japanese Maples, Dogwoods especially Kousa dogwoods, astilbes, ajuga, Sweetbox Sarcocoa, Reeves Spirea, assorted ferns, and Cephalotaxis harringtonia ‘Prostrata’. For sunnier locations specifically with paniculatas and arborescens  Southern Shield Fern, ornamental grasses provide movement and contrast of form. Clematis are perfect planted under/near hydrangeas which makes a great natural trellis for them to climb. They love their crown/roots in the shade and their foliage in the sun! A tip to protect clematis is to put half of a broken terra-cotta flowerpot over the crown to eliminate the possibility of damaging the plant. Other perennial companion plants in sunnier locations would include: Penstemons, Rudbeckias, Becky Daisies, lobelia Cardinalis that all provide a strong contrast in form and color!

JP – Carex, Asarums, Epimediums, Hosta, Bohemeria, ferns, Mahonia ‘Soft Caress’, Polygonatum, Persicaria, Beesia, Rhodea, Begonia grandis,

DWS – clematis, hosta, ferns, hellebores, camellia, woodland poppy, heuchera, conifers, fatsia, euphorbia, solomons seal, ajuga, aquilegia,

DL – Hostas of different colors, various ferns, I love to put Camellias in the background as they are evergreen and bloom at a different time, Gumpo azaleas, Carex, Pieris, Astilbe, Euphorbia 

LM – Autumn ferns, Japanese painted ferns, astilbe, hellebore, hosta, dogwood trees, heuchera, trillium, Japanese maples, Mahonia ‘Soft Caress’. Can you tell I have more shade than sun?

EK – Hosta, ferns, yews, euphorbias, lungwort, heuchera, coleus, caladiums, clematis, fatsia, other contrasting color or different leaf hydrangeas. I love a row of dwarf boxwoods in the front with Encore azaleas behind them and finally paniculata hydrangeas in the very back. 

2. Which hydrangeas are the most shade tolerant?

GW – It is vital to remember that all hydrangeas need/require at least 4-6 hours of sun preferably morning sun.  No hydrangea will bloom in dense shade. “Limbing up” the lower branches of trees and shrubs allow more light, not to mention more planting space!!! The heat and direct sun from late afternoon sun does not do any favors for hydrangeas. Flowers will age and burn more quickly. Which explains why they prefer morning sun. That being said, mophead cultivars that can tolerate some shade, just not dense shade, include: ‘Sister Teresa’ ‘Goliath’ and ‘Nigra’. Lacecaps for light shade include ‘Lemon Wave’, and ‘Veitchi’.

DL – I have found that Lady in Red does very well in our garden in a much more shaded area. Oakleafs, Aborescens, Lemon Daddy.

3. Best on-line source to get ideas? 

GW – www.cuttingedgeplants.comwww.hydrangeasplus.comwww.whiteflowerfarm, www.hydrangea.comwww.Woodlanders.net

JP – Fine Gardening and other online publications are great but best way to see combos that will work in your garden is to see them in local gardens

DWS – Pinterest hydrangea boards, “The English Garden” magazine and other magazine websites, YouTube gardening videos,  

DL – American Hydrangea Society

EK – Garden Answer YouTube videos, Fine Gardening, Cutting Edge Plants, Hydrangeas Plus, Pinterest, Houzz

4. How do I get my variegated lacecap hydrangea to bloom more prolifically? I’m lucky to get two blooms on it. It has now been in the ground for two years/seasons. Does it need more sun?

GW – I believe you are referring to Hydrangea macrophylla 'Maculata’  which can be a challenge. Do not feel alone in your frustration!  This variety in particular is the LEAST Cold Hardy! If you live in the SE, we often have late Spring frosts and freezes which kill the flower buds!  So….if you have time or inclination to cover your plants, please do so with a breathable fabric anchored to the ground sufficiently! The late Ryan Gainey use to say that this cultivar is so beautiful it is worth growing JUST for the variegated foliage!

JP – Not enough light? WHICH VARIETY? If it is a not very cold hardy cultivar, flower buds could have been killed back try planting somewhere else more sheltered/more filtered light. Cover and mulch well when we have late Spring frosts

DWS – It might need more time to establish. For me some hydrangeas need up to 5 years to bloom prolifically. Use mycorrhiza when planting or a water-soluble solution and water with that for established plants.

DL – Move it to a sunnier location

5. Ideas for pruning limelight hydrangea so it won’t flop sooo bad - 

HT – Pruning Hydrangeas video: https://youtu.be/pCQRKPQNxP8

EK – I prune mine back to about 2-1/2 – 3 feet so the stems will be stronger. You could use a metal plant supporter similar to a tomato cage until you prunes/grows  for stronger support.

GW – Prune in the late winter or very early Spring cutting the uppermost branches shorter and staggered cuts on the other branches which allows every bloom to stand out on it’s own.

JP – Don’t cut back so hard for a couple of years. Let it develop a supporting framework. Remember that this is a large plant- if you are cutting back hard every year, you are promoting lots of long whippy growth. Think of it like a crape myrtle.

DWS – Let it get to the size it wants to be and only remove dead and really old canes as well as spent flowers. I want mine to grow to 8 feet or taller.

DL – A. cut it to about 12 inches in February; B. plant in a sunny, very large area and prune it to tree form

OJ – cut out the smaller stems and limbs. Only cutting to a growth bud will not result in a stronger stem on these. 

6. Is there a pruning guide available for all the different types of hydrangeas?

DWS – UGA pruning guide has a pamphlet gives good instruction. 

OJ – Most Nursery web sites that grow and sell hydrangeas offer guides. Proven WinnersWilkerson MillsHydrangeas PlusBailey (‘Endless Summer’) and your County Extension office offers guides. 

7. When's the best time to get rid of those bare sticks on a macrophylla?

EK – I wait until late April when the leaves are emerging and to make sure the bare sticks are dead.

GW – Late Spring (April) when the stems have begun to leaf out. In the SE the Farmer’s Almanac states that April 15th is theoretically the last of any freezing weather. Mostly true but not always.

JP – When they are big, light gray, and “shreddy” you can cut them out altogether. I do this when I have time – which is usually late winter

DWS – When the hydrangea is actively sprouting in Spring and you can tell the difference between old unproductive canes and younger bloom supporting ones

DL – I wait until the hydrangea has leafed out fully and then cut out the dead wood

OJ – Bare sticks don’t mean dead sticks necessarily. Scratch the stem and if there is no green underneath it is dead so prune. 

8. Best pro practices and how they vary across the different varieties?

How many weeks on average does it take for propagation to reach a decent size? 

I grow native azaleas from seed, and wondered if growing hydrangeas from seeds collected from recent cultivars would yield reasonably good hydrangeas? Understandably they likely won't be as good as the parents.

Are aeroponic cloning machines a good method for propagation?

Hillary answered all the questions in her video. 

HT – Propagating Hydrangeas video: https://youtu.be/HBf1bI0EZzU

DL – My favorite method is layering. If you put a pot of dirt under the limb to be layered, scrape it, put on Root tone, bury in soil with rock on top to secure, it is very easy to clip from mother plant and you have a potted, rooted plant. 

OJ – (Seedling question) Yes. If successful seedlings will have some of the characteristics of the parent. If variegated, double flowered or mophead, results will be mixed if that form is what you are after. The more seedlings you grow, the more chances you have. 

9. Besides covering with fabric, what else is good to cover plants?

EK – It depends on where you live and how long/cold winter you have. Where there are extended cold winters you can enclose them in chicken wire and pile leaves or straw around them to keep them warm. Frost cloth or bed sheets can be used but need to be held above the plants so as not to burn the leaves. Make sure the bottom covers the ground so the cold wind does not freeze the new buds. In the southern areas be sure to uncover during the heat of the day. I plant more remontants so I do not have to cover as many hydrangeas.

GW – Large boxes with weights on top. NEVER plastic .

JP – I like to mulch the crown of the plants that I am fond of with leaves and pine straw. That way even if flower buds get killed back I can be reasonably assured that the plant itself won’t die.

DWS – warm blankets, large not too heavy tarps, towels, leaves, bath robes...

DL – I have totally given up on covering. 

LM – I have used frost cloth.

10. When do I move my smaller plants from winter storage to the outdoor environment?

JP –
Which plants is this referring to? Have not experienced hydrangeas needing winter storage. Any tender plants I have are moved out in stages and often brought back in at night until night time temps are consistently in the upper 40s. I always move them into very shady places at first as that early Spring sun is strong. Once trees leaf out and the light is more filtered they can move into their Spring/Summer homes.

DWS – After all danger of frost has past or be prepared to move them inside and outside again several times.

DL – When the danger of frost is over. I would start in a more shaded area and gradually move into a more sunny location. Most of the time I leave them out all winter.


11. What type of soil is best to mix with clay? Add organic matter.
GW – I like Natures helper of very fine pine bark.  I have use gypsum as well.

JP – I don’t mix. I top dress beds with heavily with compost and mulch with old leaves. This improves the soil considerably. I wouldn’t plant in pure clay – I would find another spot until the whole area can be improved. Amending a planting hole in a clay soil bed is a recipe for disaster.

DWS – Permatill, Mr. Natural, or “CLM” (“complete landscape mix” containing mulch, mushroom compost, permatill) available at local nurseries. Soil3 cube compost. If planting around trees build a mound with good compost and leaf mulch and plant the hydrangea into that to lower root and water competition

DL – I put a little garden soil, throw in some Osmocote.

12. I have two Limelights that are well established. They have been in the same spot for probably ten years. I'd like to move them to a different location. I'm guessing I should wait until fall, but October, November? How much can I cut them back before I transplant them?

JP – If it were me, I would take cuttings of a 10 year old plant, grow them out and then plant the new plants. I would never bother with moving an established 10-year old plant unless it was rare or hard to find. Actually I would probably take advantage of the situation to try a different paniculata!

DWS – once it has dropped all foliage and is “dormant”, weather is cool and soil workable after rain

DL – I would cut them back to a foot or so and move anytime from November to February or even March. They are very hardy.

OJ – Dig now but leave in the ground until plant goes dormant in late fall. It will have re-rooted with fine roots closer to the plant and have less transplant shock. 

HT – Watering Hydrangeas video: https://youtu.be/hIDdENW6ZJo

13. Better to water deeply and less frequently or more often and keep moisture level constant? 

EK – A drip system works best for me though I enjoy hand watering. It gives me time to enjoy and assess my garden. Deep watering less frequently is better. Even if the hydrangea is getting enough water, in the south,  the leaves are going to look wilted in the hot summer sun but will perk up again in the evening. 

GW – Deeply and less frequently BY HAND ONLY to encourage deeper roots. Hand watering or soaker hoses helps prevent mildew, fungus, and diseases.

JP – The first one is better for the plant and will help it get established better

DWS – deeply and less frequently, 1” a week

DL – Water deeply in the am. Less diseases. They will wilt in the hot sun even if they have been watered. 

14. When is the best time to water my plants, am or pm?

EK – in the morning

GW – Always early AM by hand around the roots below the foliage (with coffee in hand!) This prevents water on the leaves which when the sun hits the foliage creates the dreaded “Measles” or Cercospora and Anthracnose. If you plan to cut fresh blossoms for arrangements be sure to water those specific bushes the night before in particular to better hydrate the blossoms before cutting the next morning.  Always take a bucket of water out to the bushes to place the cut flowers in! 

JP – Whenever you have time! Just water!

DWS – am/ early morning, so the leaves can dry quickly so as to not develop diseases.
LM – Morning so the leaves have time to dry before evening if you are overhead watering.
15. How do I keep the deer from dining on my plants?

EK – Plantskydd has worked the best for me. I found the trick is to spray the plants when they first sprout leaves in the spring. It helps to train the deer that they do not want to get near that area. Plantskydd has lasted for 1-2 months depending on the amount of rain. Robert Mallet of Jardin Shamrock told me he uses mirrors to trick the deer into thinking there is a deer already there. 

GW – Good luck!!!...Plantskydd granular or liquid (lasts longer) or Bobbex R!! An 8’ fence helps too!

DL – Bobex

LM – Big budget answer: install a deer fence, Low budget answer: Plantskydd or liquid fence – apply often

16. I have Annabelle hydrangeas in full sun. They are beautiful through mid-July then the flowers and leaves curl and turn black.  What can I do to prevent this?

EK – Move them to a location where they are protected from the afternoon sun or plant something taller nearby that can protect them. I have seen people use umbrellas to protect their hydrangeas. 

GW – They do much better in part sun.

JP – Arborescens, which ‘Annabelle” is, do not really like full sun. Dig it up and put in part shade and plant a paniculata in its place.

DWS – move them to where they will receive afternoon shade

DL – Move them to a more shaded area. Morning sun, afternoon shade. 

OJ – It seems like you have a drying out problem. If you increase moisture so the plants do not get too dry, at least that should stop the scorching. Giving afternoon shade will help also. 

17. Leaf spot – any ideas to reduce or stop?
EK –
No overhead watering, water early in the morning. Use a drip system or soaker hose. Collect and throw away all affected leaves.

GW – See earlier answers on watering

JP – Try not to water overhead. Plant fun things in front to distract from the inevitable. Lower your expectations.

DL – Rake up any leaves underneath. Pick them off and dispose of them. There is a spray to use early but we rarely do because I think I recall Dr. Dirr said you would have to do it every time it rained. Replace it with something else that is a lot less work. :) 

18. ID most threatening / damaging ones, particularly any new ones that are serious threats

DL – Leaf borers, there was an article in the 2020 Winter Newsletter by Lisa Bartlett. 
19. What are best on-line sources for information?
Cutting Edge Plants
Hydrangeas Plus
Proven Winners
Endless Summer
American Hydrangea Society
Your County Extension Office or Department of Agriculture of your state. 
State Universities 

20. When, how often, and what type of fertilizer should I use for mophead hydrangeas? 

EK – In late winter to early spring. I use a slow release fertilizer about 4 ounces or a couple of tablespoons placed at the base and throughout the drip line. Remember – too much nitrogen will cause leaf growth but less blooms! Do Not fertilize after August.  

GW – Early Spring April early May after frosts. Timed release Osmecote or Organic Espoma, or top dress at the crown with Soil3, which I call “black gold”, also excellent to plant with.

JP – prefer top dressing with compost because it breaks down slowly and improves the soil structure which is really the game changer. I have a couple of varieties that sometimes get chlorosis – I spot treat them with chelated iron when I remember to do so.

DWS – Hollytone, Dr. Earth organic for acid loving plants, Espoma fertilizer

DL – I only use Osmocote now because I am old and it is easy. Doesn't burn. I fertilize once or twice a year whenever I think about it. 

21. I have an oakleaf in dappled sun that has never ever bloomed? Does it need more shade or more sun? 

GW – Probably more sun.

JP – How old is never? Do you ever prune it? If so, you could be cutting off the flower buds… Most quercifolia do fine in part shade/ dappled sun

DL – Probably more time to grow. We have them in different areas and they take a little longer in more shade. 


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