Care of arborvitae
I have an arborvitae hedge approximately 20' in length and about 20' high. We have had it for about 30 years now and would definitely like to keep it healthy. The interior of the bushes are bare of foliage, is that normal for plants this old? Would it be beneficial to prune out the dead branches in the middle? Will the bushes ever fill back in? Also, when is the best time of year to fertilize it, I have heard both spring and fall. It does get full sun all day and I water it about once a week during the summer since it runs along the edge of our front lawn. What would be the better ground cover, compost or bark dust and would I spread it up to the base of the plants? I am also thinking of adding a few perennials for some color, any suggestions on plants that would be compatible? Something easy to care for and not too big. Thank you for your help.
Multnomah County Oregon arborvitae
Congratulations on your 30 year old arborvitae hedge. You must be taking very good care of it. Full sun and excellent drainage are critical to success with arborvitae. Watering, especially with the hot dry summers we've been having is very important. Arborvitae are long-lived trees, so you should have many more years to enjoy them.
Having the interior of the trees bare of foliage is normal. Conifers differ from most deciduous in not having buds on the trunk or the brown part of the branches. If you remove the dead branches or prune branches past the green growing sections, nothing will replace them. Removing the dead branches doesn't affect the health of the tree, but the appearance of the tree is a consideration. Prune lightly and carefully. This article Arborvitae Stand Tall as a low-maintenance Hedge https://today.oregonstate.edu/news/arborvitae-stands-tall-low-maintenance-hedge has excellent information on growing arborvitae.
Your hedge has done well for 30 years. With mature plants unless you're seeing abnormal foliage color or vigor your plants are doing well with your management plan. This article has good information on fertilizing evergreens, Fertilizing Evergreens https://extension.umn.edu/trees-and-shrubs/fertilizing-evergreens.
Compost would be a great ground cover, but bark dust is good too. The good thing about ground covers is that the soil organisms mix it into the soil for you at a slow and steady rate which doesn't upset the soil balance. Ground cover should be spread in a donut shape, not up to the base. Compost up against the trunk will keep the trunk moist, inviting disease.
There are many plants you can add to the base. Arborvitae have a wide soil pH tolerance so your choices are wide ranging - just depends on your preferences.