My rose of sharons have a white substance at the base of the stems just above the ground level. What is this?
A photo would assist in my identification but I will give this my best shot.
It could be southern blight:
https://www.gardeningknowhow.com/plant-problems/disease/controlling-southern-blight.htm
http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Article%20Images/SouthernBlight09.jpg
Or a type of white mold:
http://utahpests.usu.edu/ipm/htm/ornamentals/landscape-insects-and-diseases/white-mold/
Planted two bare root Rose of Sharon shrubs middle of April. It's been a cool spring in Western NY. The shrubs do not show any 'life' in them. Stems are flexible, and scratching the bark on the stem does show green. When do they usually start to show leaf buds? Should I apply any soil additive or fertilizer? If so, what proportions to nitrogen, phosphorus and potash?
Fall is actually the ideal time to plant a Rose Of Sharon shrub.
Spring planting of dormant plants is also fine. The ground is still cold and as it warms and the roots began to grow, your plant will began to grow.
Make sure you are watering regularly but that the roots do not sit in soggy soil.
Do not fertilize the shrubs until they are actively growing.
Here is a link to refresh you on the care requirements.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
How quickly do rose of Sharon shrubs grow? We are considering a property hedge using Rose of Sharon, but do not want to wait 10 years for the shrub to reach full height.
Plan for the new shrubs to grow between 13 to 24 inches per year.
Full size of Rose Of Sharon is 8 to 12 feet tall with a spread of 4 to 10 feet.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
This spring after growing gloriously for 10 years, our Rose of Sharon is not even sprouting leaves. They limbs are still green inside and are not dead. Please help! It started to sprout leaves and then just stopped.
I would give the plant some more time. Rose Of Sharon plants do usually leaf out later then other spring plants.
Rose Of Sharon can live 15 to 20 years if in good health and growing in optimum conditions. They live for shorter periods if they are exposed to harsh weather conditions, uneven watering and fall prey to insects and fungus.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
What kind of root system does it have? Is it a taproot? How deep are the roots? Our roof garden has only about 18 inches of soil and I am afraid the root could damage the roof.
Rose Of Sharon has a fairly shallow roots system with many of the roots just under the surface of the soil.
Rose Of Sharon do get to be 8 to 12 feet tall with a width of 4 to 10 feet.
18 inches of soil would not likely sustain this plant.
You can however grow a Rose Of Sharon in a container.
A very large container, such as a half whiskey barrel will work.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
it started getting leaves on it and today some leaves are ok but look like they are dying off. I wanted to know what makes it do that. Did I feed it too much or is it bugs? I don't see anything on it. Thanks, Tammy
Over fertilizing a Rose Of Sharon can damage the shrub and cause the plant to yellow or turn brown.
Your plant may also droop or wilt as if it needs water if it has excess salts in the soil from over fertilizing.
You can try to flush the fertilizer from the soil with water, if you feel this may be the case.
Your plant needs only a light application of an all purpose fertilizer in the spring, again in summer. Follow the package directions but stay on the light side.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
My rose of Sharon gets buds but fall off before blooming.
Usually buds drop off of Rose of Sharon bushes when the plant has been distressed in some way. Not enough water or (if you live in a harsh winter climate) damaging hail or winds can cause it. This article may help you: https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm