Ask Mr. Smarty Plants

Congratulations on having a collection of butterfly attracting shrubs at the Estero Llano Grande State Park and your foresight in creating a cultural guide for the care of these plants.

While there are some general pruning “rules” ultimately you will probably find that each plant will have to be treated individually and have slightly different times when pruning is best done (and differing instruction on what and how much needs to be pruned). After a few seasons and as the volunteer gardeners get to know the plants, it will become apparent that even the rules and guidebook have to be modified at times because the weather (mainly), an unusual fungus attack, or hungry rodents don’t adhere to the rules. So put as much as you can into your guidebook but be aware that it will need to be updated every couple of years!

The first place to look for tips and clues to pruning information about each plant is the Native Plant Database. 

Be on the lookout for general information like “Dies back to the roots in hard winters.” (Chromolaena odorata).

Also very important is the Blooming Time section such as “August to October“ (Chromolaena odorata) as pruning a shrub hard (or even lightly trimming the tips of the branches) just before the blooming time could remove all the bloom.  It is best to prune after the blooming time or well before it starts to bloom.

Also check the Growing Conditions comments section for each plant for comments such as “Because of leggy growth habit, it should be cut back once per year. Dies back to the roots in hard winters. Can be trained as an espalier.”  (Chromolaena odorata)

The Propagation/Maintenance section is also a great place for important pruning information such as “Prune plants to keep compact. Cultivated cenizos tend to become leggier with fewer blooms than in nature. Tip prune to increase density.” (Leucophyllum frutescens)

Lastly, the Benefit/Use Wildlife section has information about whether various wildlife feeds on the seeds or fruit and therefore should be left on for habitat sustainability. Plants with notes such as “seeds for granivorous birds” should have pruning delayed so that the seeds are left as wildlife food. (Chromolaena odorata)

If you can’t find specific information about any of your butterfly shrubs, there are some general principles about when to prune flowering plants that relate to when they bloom. Here’s a previous Mr. Smarty Plants answer about pruning native plants:

For spring-flowering bushes or trees, it is best to prune after they have flowered in the spring since the flower buds are setting in the fall and winter pruning will remove them. Your safest time for pruning summer flowering bushes or trees is in the winter (late November through early February). However, if your plants have gotten too bushy or rangy, you could probably do some judicious pruning almost anytime, being careful not to remove flower buds or too much of the plant at one time. The bottom line is that your pruning strategy pretty much depends on the plant.

Two other places to look for general pruning techniques information is the Texas A&M AgriLife Extension website article, Proper Pruning Techniques and the Pruning Native Plants article from the California Native Plant Society.

Below are the links to the Wildflower Center Native Plants Database for the plants you are researching:

• Chromolaena odorata (crucita or blue mistflower)
• Leucophyllum frutescens (cenizo or Texas sage)
• Aloysia macrostachya (Rio Grande beebush or sweet-stem) 
• Aloysia gratissima (whitebrush)
• Trixis inula (Mexican trixis or tropical threefold)
• Viguiera stenologa (skeleton-leaf goldeneye)
• Plumbago scandens (Mexican plumbago or  summer snow plumbago)
• Malvaviscus arboreus var. drummondii (turk’s cap)
• Lantana achyranthifolia (brushland shrubverbena or desert lantana)
• Lantana urticoides (Texas lantana)