Winter Blooming Jasmine (Jasmine polyanthum)
By Laurelynn Martin and Byron Martin
Winter Jasmine is known for its pink buds that open to delicate, 5-petaled, star-shaped flowers with an intoxicating fragrance. This climbing jasmine from China has a profuse display of fragrant white flowers that appear in the dead of winter. It is the national flower in many countries such as Indonesia, Pakistan and the Philippines. Jasmine is also a popular girl’s name in many countries including the United States.
Winter Jasmine is a fast grower whose vining branches can extend many feet in a single summer climbing on any structure that is nearby. Easy to cultivate in containers, it can be grown on a stake or trellis where periodic wrapping of the vining branches onto the trellis will keep it contained along with seasonal pruning of mature plants. It is also a good plant for hanging baskets where, with a little encouragement, it makes a spectacular specimen.
How do I get my Winter Jasmine to flower?
Flower bud initiation is caused by subjecting the plant to cool night temperatures in the fall and early winter. If this is done over a period of many weeks, flower buds will appear at the leaf axis near the terminal growth. As a rule of thumb, temperatures in the mid to low fifties down to just above freezing are needed for this chill period. It is important to keep the developing buds in this nighttime coolness until the bracts and individual flowers are visibly formed. If moved too quickly into a warm (above 60°) growing area, they will go back into vegetative growth and although a few flowers might reach maturity, the display will be diminished. For most growing areas, this means that the cool nights of fall and early winter are the best time to initiate the flowering cycle with a full blooming plant arriving in mid-February. Here at Logee’s, some years the flowers arrive in early January when we have a cold fall, in other years, flowers arrive in late February to early March if the prior fall was warm.
Practical tips for Flowering
In both the US and Europe, Winter Jasmine is used as a houseplant and although it will grow fine in a vegetative state in the home’s window, here are some practical tips to bring it into flower. Grow it on a windowsill in an unheated or poorly heated room or entryway. A sunny porch can work as long as the temperatures don’t go much below freezing. It can also be grown using grow lights in a cool basement. Winter Jasmine can take some subfreezing temperatures but if it is too cold, the plant will defoliate. If temperatures are below the mid twenties, the stems or the plant itself will die. Winter Jasmine can be grown outdoors in the summer and left outside until just before a hard freeze and even then moved back out in the milder weather that follows the early cold snaps.
Winter Jasmine is well known for its pink flower buds. We’ve found that flower bud color is more of a response to environmental conditions. The bud color can vary from pink to white depending on the light level and the temperature that the buds matured in.
Soil requirements and feeding your Jasmine
This plant is easy to grow using any standard potting mix and a balanced fertilizer throughout the summer. It’s best to discontinue fertilizing in the late summer so the growth slows and hardens off before winter. This can help with the flower bud initiation and it will also slow down the growth of the vigorous vines, which can get entangle in anything they get near.
Winter Jasmine does best in full sun although it can grow under partial sun and still flower.
It can handle some drought stress or a wilt as long as it’s not too prolonged. This will actually help in reducing some of the vines vigor much the same as reduced fertilizer.
When to Prune
Pruning on mature plants is done right after flowering is complete. This can be as severe as shearing back to a point where there is little foliage left. In no time, new growth will appear and the vining stems will once again grow with great vigor. If growth is excessive, another pruning can be done in mid-summer but by mid-August it’s best to let it grow, as these branches will be the ones that initiate flowers.
When to Repot your Winter Jasmine
Plants can be repotted as needed, until the maximum container size is reached for the growing area. The best time to repot is right after flowering. A Winter Jasmine plant can remain in the same container for many years as long as it gets regular applications of fertilizer along with proper watering. In time, an old plant can get so root bound that it pushes the soil up higher than the pot’s rim making watering difficult. At this point, if one wants to keep the plant and not repot, then it needs a root pruning. We hardly ever recommend root pruning because this puts tremendous stress on the plant but we have found that Winter Jasmine tolerates root pruning quite well. To root prune your plant, remove the plant from its pot. Cut the foliage back to about one-third of the original size. Cut the roots back about one-third around each side of the pot. The best time to root prune is right after flowering. Root pruning can only be done if the top foliage is cut back as well. Generally, Winter Jasmine has a resilient root system.
Insects and Disease
The biggest insect problem with Winter Jasmine is spider mites, which can affect plants that eventually end up in a warm, dry house. Careful attention needs to be given to early infestations so they can be treated. Neem oil or a cold water spray will bring spider mites under control. If grown in a cold growing area, the spider mite problem is greatly reduced. Warmth and low humidity with the lack of natural predators cause spider mite populations to explode and this can damage the plant.
With a little attention to good growing conditions and cool nighttime temperatures in the fall and early winter, you will be rewarded with an abundance of fragrant flowers in the middle of winter just when the gardener’s senses need it most.
- Logee's Greenhouses Spectacular Container Plants by Byron E. Martin and Laurelynn G. Martin (Willow Creek Press, 2001,2005)