How can I eliminate Chinese poppies from my garden? They have become highly invasive and a nuisance even though they are beautiful.
The poppy is in the Papaver genus and while there are none that are known by the common name Chinese poppy, there are some called Oriental, Iceland or alpine poppies. Typically, Papaver plants are not considered invasive although they often reseed given the right climate and placement. It is unlikely that you are having difficulty with invasive Oriental, Iceland or Alpine poppies.
Oriental poppy (Papaver orientale) is the familiar poppy with crepe paper-like flowers that range from 4 to 11 inches in diameter and have dark, shiny black splotches at their base, plus black stamens in the center of the flower. There is a vast array of cultivars and the colors range from white and pastels to shocking reds and oranges. The stems look sturdy but often bend over under the weight of the heavy flowers, especially after a rain. After blooming, in the heat of the summer, the foliage dies back to the ground, leaving a bare space in the garden. Good neighbors to fill in the space in a perennial bed are baby’s breath (Gypsophila paniculata) and Russian sage (Perovskia atriplicifolia). Seeds can be planted directly into the soil and transplanted when young, but they don’t like being moved once their taproot has been developed. Since they resent disturbance, wait until the plants are overcrowded (4 to 6 years) and dig them up carefully and divide.
Iceland and alpine poppies will grow well in our area as biennials or short-lived perennials. Cool summer gardeners get to enjoy how floriferous and long-blooming they are. In cool summer areas, they’ll live for years and bloom practically all seasons. In our zone 5, with the moderately hot summers we have been having, these poppies will bloom in spring and early summer for a year or two before dying, but they usually self-seed before dying out. Iceland and alpine poppies produce ground hugging tufts of light green, hairy, lobed leaves and wiry, hairy, leafless stems of lightly scented, cup-shaped flowers. They bloom late spring through early fall as long as the summers are on the cooler side. The alpine poppies are like miniature Iceland poppies.
As far as the plant you refer to in your question, we believe it could be one of two options. First, it could be the plume poppy (Macleaya cordata). Its countries of origin are Japan and China, so you may have been told that this highly invasive plant is called a Chinese poppy. This plant needs a lot of room because its 6- to 10-foot tall plants spread rapidly by rhizomes and form large colonies. The leaves of the plume poppy are lobed, light green above, and gray-green beneath. The young plants are particularly handsome with cream-colored flowers held in long plumes at the top of the plants in early to mid summer.
If this is indeed the plant you have, you have some work to do to eliminate it. Deadhead religiously and don’t allow them to reseed. Mulch the bed heavily with soaking wet cardboard and keep replenishing it. Dig out the volunteers and get the roots. Do not put them in a compost pile. This could be an ongoing battle for two to three years.
If the plant you are talking about is not tall, then the second option would be a wood poppy or celandine poppy (Stylophorum diphyllum). These are beautiful plants in a woodland setting, as they provide bright yellow, early spring flowers even in heavy shade. They have light green, deeply cut basal leaves and the flowers are 1 to 2 inches wide. They look beautiful with Virginia bluebells and both die back when finished blooming. These plants are prolific re-seeders and can become significant in numbers in three to five years. If this is what has happened, the best way to decrease the population is to pull them up when they emerge and not allow them to re-seed. The good news is that they are relatively easy to pull out of the ground, roots and all.