Butterfly bush

Asked September 27, 2020, 10:06 PM EDT

Dear Expert, I planted this Buzz variety butterfly bush June 9th. I watered every other day until it was growing well and flowering well. After the tropical storm August 4th, I did not water it any more, the soil seemed to stay moist. I have clayish type soil. Not total clay, but it has a tight feel to it. I noticed the blooming seemed to have slowed, so I considered watering again, but it rained about .75 - 1 inch yesterday. I went out this morning and some of the blooms looked as shown in the photos. We had showers several times in the night. I know what the blooms look like when they fade and dry up from base to tip. But this is different. The dark pinkish/purple is the color of the flowers. But why did some of the blooms turn peach color? It’s not drying. The peach colored parts are soft and fall off when I touch them. This is my first season for butterfly bush, so maybe this is normal for this time of year? Also how do I know how to water going into fall? I was told not to mulch butterfly bush, so I cleared the soil under the bush. Thank You, Wendy Warner

Cecil County Maryland

1 Response

Hello Wendy,

Butterfly Bush are drought-tolerant shrubs which do not prosper when kept constantly damp, so we suggest continuing to monitor the plant regularly for water but reducing the frequency to once a week or less, weather-dependent. (In cooler weather the plant will use even less water.) Root stress from poor oxygen levels in the soil (due to soil wetness) could be causing above-ground plant parts (like the blooms) to age prematurely. While a few Buddleia varieties are known for changing color as the individual flowers age, this does not seem to be a trait among the Buzz series. Though we do not have information on whether or not Buddleia is particularly sensitive to this, ethylene gas (produced by ripening fruit, included in natural gas, and produced by rotting roots) triggers flower abortion for many plants, which in this case means shedding flowers before they desiccate or otherwise fade due to old age. The ease at which these discolored flowers fall off suggest they are aborting due to this reason or another stress factor.

Is this plant in a full sun exposure? Butterfly bush need at least six hours of direct sun (in summer, at least) per day to thrive and flower normally. Sometimes, too much shade can impact flower pigmentation. We do not know why you were advised to not use mulch, but it will help minimize evaporation of moisture from the surface soil as well as moderate its temperatures and keep weeds from growing too close to its roots. A mulch layer would be beneficial if it is between about 1 and 3" deep, keeping care not to touch the base of the main stems with mulch - keep the mulch a few inches a way so it gets good air circulation.

For watering in general, regardless of season, it's best to feel the soil prior to watering to make sure the plant actually needs it, as the surface moisture can be deceptive in relation to how damp or dry the soil truly is among the roots. About four or five inches down, feel how moist the soil is; if damp, the plant should not need water; if fairly dry, then a soaking of the root area will be beneficial. How often sufficient drying will happen will greatly depend on your growing conditions and the weather, so there is no set schedule to follow and the interval will be changing throughout the year. In the cooler weather of spring and autumn (as the nights cool off too), plants will need watering less often. Similarly, for drought-tolerant shrubs like this, once established they need minimal intervention except in times of high summer heat with dry weather or during weeks of drought in autumn. It's always best to err on the side of a bit drier between waterings if you aren't sure about when to water. For the short term, this will only risk wilting and not permanent damage. Over-watering, on the other hand, can begin to damage roots and promote rot from which they cannot always recover. Here are basic watering guidelines for trees and shrubs, if helpful: https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs

If the plant's leaves look to be in good condition (as they do in the photo), then keep an eye on it going forward and water it less often, checking the soil and adjusting your watering frequency as needed. If the plant's overall health does not decline, the quirk of flower coloration should correct itself on its own (perhaps not this year, as they're almost done flowering, but next year).

Miri