Ask Mr. Smarty Plants

We are assuming that what you have is Yucca filamentosa (Adam's needle), which is the only yucca native to Pennsylvania and tolerant of cold in areas away from the desert Southwest where they are usually seen. On the subject of getting rid of yucca plants, that's going to be difficult, because yuccas are tough desert native plants, and they resist being exterminated. However, you are not the only one who has wanted to either get rid of or thin out their existing yuccas.

Members of the Genus Yucca are all similar enough that we can talk about them in general terms. You do have a problem getting rid of your unwanted plants. Yucca has a root you wouldn't believe, big and going deep. It propagates itself both by seed and by offshoots, or pups, from the main plant. The first thing is to avoid further propagation by seed. If your yuccas are blooming, get the blossom trunk down and disposed of before the seed pods turn dark brown. Then you can go on to the rest of the plant. 

There is no magic potion. You are going to have to arm yourself with heavy clothes, long leather gloves and goggles to protect your eyes from those stilleto-like leaves, as well as some serious cutting equipment. First, cut down as much as you can of the leaves, or blades, if you prefer. You probably already know that their edges are sharp, their tips are sharp, and they are tough. Begin with the offshoots and work your way in. Any piece of root left in the ground will sprout a new plant. Dispose of these cuttings in heavy paper bags (they'll rip plastic to shreds) and send them to the trash. Don't put them in the compost, or pile them somewhere, they stay lethal for a long time. Although we have no documentation to prove this will work, you might ask your nursery to recommend some herbicide that is meant to be painted on cut-off trunks to kill the roots. Cut the yuccas that you can't dig out down as close to the ground as possible, and then paint with the solution.You need to get the herbicide painted on the cut end within 5 minutes of cutting, as it will try to heal itself and keep the herbicide from circulating to damage the root. Don't get carried away, you don't want to contaminate the soil around the yucca, where you will presumably want to plant something else in the future. And don't spray! Spray can drift to other plants that you didn't intend to destroy, and probably do them more damage than the yucca.

You will have to continue destroying yuccas for some time. Don't let them get ahead of you, be vigilant to root out the offsets and destroy them before they get firmly entrenched. The yucca is a survivor, growing in some of the bleakest desert land in the country. There is one other remedy that has occurred to us-when you look up information on how to care for a yucca, you are always warned not to water it, not to let the roots stand in water, don't let it get wet. So, try flooding the roots and see if that helps. Never tried it, but it's cheaper than herbicide.

You probably should wait until early Spring, after the ground has thawed, to start your new plantings, which is fine, because you're going to need  time for your yucca demolition project.  For erosion protection, we usually recommend native grasses first. These will not be "mowing" grasses, but can be trimmed back to about 6" in the early Spring. With their long, fibrous roots, they will grab and hold the soil, are ornamental and offer lots of variety. We found some low growing shrubs and two sedges that will be attractive and help with the erosion. In your USDA Plant Hardiness Zone of 5b to 6a (average annual minimum temperatures of -15 to -5 deg. F) finding evergreen plants will be difficult, but there are a few. Follow each plant link to our page on that individual plant to find out more about its characteristics and go to the Google link on that plant at the bottom of that page for even more information.

Plants for Hillside Erosion in Allegheny Co., PA

Shrubs

Gaultheria procumbens (eastern teaberry) -evergreen, low woody ground cover, blooms white, pink June to August, part shade

Amelanchier stolonifera (running serviceberry) - sun, part shade or shad; more information and pictures

Arctostaphylos uva-ursi (kinnikinnick) -trailing evergreen, blooms white, pink April to June

Comptonia peregrina (sweet fern) - 2 to 4 ft. tall, blooms white, green May to August, low water use, part shade

Juniperus communis var. depressa (common juniper) - 3 to 6 ft. tall, evergreen, sun; more information and pictures

Salix humilis (prairie willow) - 2 to 5 ft. tall, sun

Symphoricarpos albus (common snowberry) - 2 to 5 ft. tall, blooms white, pink June and July, medium water use, sun, part shade or shade

Sedges

Carex blanda (eastern woodland sedge) - 1 to 3 ft. tall, evergreen, sun, part shade or shade

Carex texensis (Texas sedge) - to 1 ft. tall, sun or part shade

From Our Native Plant Image Gallery:

Yucca filamentosa

Gaultheria procumbens

Arctostaphylos uva-ursi

Comptonia peregrina

Salix humilis

Carex blanda

Carex texensis