I would like to grow wisteria vine. Please provide input on the different species, such as their bloom times, which ones smell the best, etc. Is the American species less aggressive than the Chinese? If so, how aggressive is it? Will I be pruning weekly?

There are two exotic species: Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda). American wisteria (Wisteria frutescens) which is a native, is more successful in the southeastern United States than here in Michigan. Although it is cold tolerant to zone 5, you are more apt to find the Japanese here in the north since it will tolerate zone 4 temperatures.

Wisteria is a member of the pea family and climbs by twining its stems around whatever support is available. They’ve been known to consume fences, warp power poles, demolish trellises, and obscure people. All three can reach heights of 25 to 30 feet.

The Chinese is very showy, with flower clusters up to a foot long, which open before the foliage has expanded. The familiar blue-violet blooms appear in early to mid-May but are only faintly scented. There is a white form (W. sinensis ‘Alba’), which is very fragrant. Chinese wisteria may bloom within 3 to 4 years after planting.

Japanese wisteria is aggressive, producing perfect blue-violet blooms on old wood from mid-April to May. Again, depth of fragrance depends on the cultivar you select. Often, you will find the showier the blossom, the less fragrant it will be. ‘Macrobotrys’ (reddish violet), ‘Naga Noda’ (pale violet), and ‘Snow Showers’ (white) all offer significant fragrance.

If you have a sunny and moist site, the American wisteria will produce 6-inch long, pale lilac flowers in June to August on the current season’s growth. Blossoms appear after the foliage has developed. It is a handsome plant in both leaf and flower, showing greater restraint than the Asiatic bullies, according to Michael Dirr, a well-known woody plant book author. Because of the different bloom times, you may want to combine one of the Asian species with the American, although not necessarily in the same location, unless you have steel beams for support.

Whichever species you choose, select a named variety and plant in deep, moist, well-drained, and loamy soil with a soil pH of 6.0 to 7.0. A soil test will determine the pH and if amendments are necessary. The site must get 6 hours or more of sun. Prepare a 2- to 3-foot diameter space for the trunk and add peat moss, compost or aged manure to improve soil aeration and drainage. Wisteria can be trained as a single trunk tree or allowed to climb a structure. It must be supported by a strong pressure-treated wood arbor, pergola, or pole. Young plants should be fertilized annually until they fill the allotted space. Fertilizing encourages vegetative growth so don’t look for blooms. Once established, do not fertilize. Water only if foliage wilts. Both fertilizer and too much water produce green growth and limit flower production.

Certainly not weekly, but some pruning is required to maintain plant quality and promote flowering. Simply keep in mind to single out one strong leader from each main framework branch. Cut off the ends of all new side shoots just beyond the sixth or seventh compound leaf. Do this in summer. In winter, concentrate on pruning back the leader shoots by at least one-half. Cut side shoots to only one or two inches from their base.

It isn’t necessary to be a pruning guru to grow a wisteria of any make or model. Generally the famous frustration of lack of bloom comes from too much TLC—too much fertilizer, too much water and not enough drainage.

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.