|My Monrovia Trumpet Vine (Morning Calm) will not flower. It is four years old. It is in full to partial sun (although it can spread whereever it wants, it does not seek full sun). What's up with this plant?|
|Most vines, including this one, will take a few years to become fully rooted and established and perform their best. But I would have expected some flowers by now. You might be seeing the effect of climate. Campsis grandflora is winter hardy in zones 7 - 9, and according to your zip code you are in zone 7A or the coldest part of zone 7. Depending on the microclimate where it is planted, it may be as cold as zone 6. This could be delaying growth in the spring and shortening the growing season as well, either of which can delay blooming.
Make sure to mulch in late fall to cover the root area. Apply the mulch in a flat layer about four inches thick, do not allow it to touch the stems however. If the vine is planted in a windy spot you might also provide a wind break for it during the winter months.
This plant loves heat and sun and will grow best in a warm, full sun location. It also does best with soil that is evenly moist yet well drained, meaning damp like a wrung out sponge, not sopping wet/saturated and not dried out. Both of these are important for encouraging vigorous growth during the summer. Using a summer mulch will help keep the soil moister longer between rain or waterings.
If your vine is growing lushly but not blooming, it may be a lack of sun (a minimum would be six hours a day of direct sun including the hour of noon) and/or it may be due to excess nitrogen fertilizer. This plant does not need heavy feeding, an annual top dressing of compost should be adequate along with a year round layer of organic mulch. These will break down slowly over time and help feed the soil.
If your vine has not grown much and is not blooming, it may need more sun, more water during the growing season, or possibly more nutrients. Compost and mulch along with a complete slow release granular fertilizer such as 10-10-10 applied per the label directions might help. Or, it may be that it has never rooted very well which can be related to poor planting technique, limited root area, or some other unusual circumstance.
This vine blooms on new growth of the year, so you would not want to prune it during the summer as this would remove flowering wood. If you need to prune it, do so in late winter before it begins to grow for the season. Sometimes a Campsis vine can be encouraged to bloom better by pruning it fairly hard at that time as cutting it back will encourage new, denser and vigorous vine growth.
I hope this helps you trouble shoot.