I look after a rose of sharon that grows in a small stone planter across from my house. This spring (as of June 11th), there’s not a leaf on it, but the twigs seem to still be green inside. Do you think it will ever leaf out and flower, or is it another casualty from this brutal winter?
Rose of Sharon, Hibiscus syriacus, are late to leaf out in spring but then flower in late summer and into early fall. This late flowering is one of the main reasons they are popular, as they put on a lovely show when many other plants have finished blooming.
Rose of Sharon are susceptible to winter kill during severe cold temperatures, which is what we experienced last winter here in Toronto and Southern Ontario. If you are unsure if the tree/shrub is alive, take your thumb nail and gently scratch the outer brown bark on a few branches to see if there is green plant tissue underneath. If you find green, then there is life and hope. Remember, our spring is quite delayed this year and we haven’t had a good period of continued warm weather, so your plant may just be slower than previous years in leafing out. That being said, if you don’t find green tissue anywhere, then it is likely that the plant is indeed dead. If no leaves appear within the next few weeks, consider replacing it with a more hardy, cold winter tolerant tree or shrub.
You don’t mention the size of this Rose of Sharon but you do mention that it is in a small stone planter. There are two problems with this. Firstly, being in an above ground container throughout this past frigid winter, may have exposed and killed off root tissue. There would naturally be more root protection and insulation if it was planted in the ground. Secondly, these trees or shrubs ideally like to grow in sunny or part shade conditions in rich, moist, humusy soil that drains well. Your plant may well be rootbound in the planter and may not have enough space for more root growth. Also, it may not be getting enough water and nutrients from the soil that is currently there.
If you determine that the plant is alive, have patience, leaves will eventually appear. After leaf out, prune out any dead, damaged or diseased branches using clean secatuers. Top dress with well rotted compost or sheep manure and water really well. A one inch layer of mulch over the entire top surface of the soil will help retain moisture within the container.
The application of a balanced 10-10-10 fertilizer after dormancy and when leaves are emerging will give the plant a spring boost. A mid-summer application of a low nitrogen 0-10-10 fertilizer will promote root health and flower production. Always follow the fertilizer package directions carefully and water the plant well before the fertilizer application in order to protect roots from chemical burning.
Early next spring (2015), prune for shape in order to keep the size of the plant maganable considering it’s container home. Also next spring, remove some of the present container soil and replace it with a fresh mix of potting soil & compost.