Experts tackle readers’ garden questions.
Q: Within the past year, we replaced our front lawn with low-water usage plants. All of the Goodwin Creek lavender plants we have planted are showing the same problem. They start out growing vigorously with abundant flowers. Then over time individual stalks begin to wither. Then finally, the whole plant dies. Neither the roots nor the foliage of the dead plants have any signs of insect infestation or over- or under-watering. Please give us a clue as to what the problem is.
Ken Hansen, El Dorado Hills
Bee garden writer Debbie Arrington: Lavender, a favorite low-water herb, can be problematic in home gardens. Almost always, their death can be traced to irrigation.
UC Davis grows hundreds of Goodwin Creek grey lavender (Lavandula x ginginsii “Goodwin Creek Grey”) on campus. It’s considered the best lavender for Sacramento gardens. A favorite of the UCD Arboretum staff, it’s more heat-resistant than most English lavenders and has a bloom season nearly nine months long. Goodwin Creek is one of UC Davis’ Arboretum All-Stars, a selection of well-adapted drought-tolerant plants for our area.
A midsize lavender, this perennial grows to about 2 feet tall with scalloped gray leaves that form a compact, attractive ball topped with wands of dark purple-blue flowers.
Goodwin Creek lavender prefers deep irrigation every other week. Too much or too little water can cause the plant to wither and die.
“With any new planting, proper application of irrigation is critical,” said Ellen Zagory, the arboretum’s director of public horticulture. “Check that your watering system is distributing water all the way around the plant and thoroughly wetting the ‘root zone’ – the area of the roots that were in the container (the ‘root ball’) when you planted it and also the area just outside where the roots need to grow to access surrounding moisture.”
Although lavender are drought tolerant, they need sufficient irrigation to get started.
“Newly planted plants need frequent irrigation despite being called ‘drought tolerant,’ ” Zagory said. “They generally have frequent irrigation when in a nursery where they grow in container soils that are well drained. Our gardens are generally not that well drained and the extension of roots out into the soil requires moisture enough to draw roots out so they eventually will have a greater water supply and then can go longer between irrigations.”
Too much water or standing water (an issue in heavy clay soils) can lead to crown rot and other woes.
“There are fungal pathogens that can attack lavenders, but would be exacerbated by overly moist conditions if drainage is poor, you have standing water, if mulch is piled up against the stems or it is irrigated too frequently,” Zagory said. “Check for those conditions before replacing the planting.”
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to email@example.com. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:
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