Q: There's this invasive ground cover with little white flowers that's growing all over our yard and intruding into the vegetable garden. There's also a green plant with spadelike leaves. What is this stuff and is there any way to get rid of it?
My mother says it's actually sold in gardening catalogs, but it's moved in on us and is proliferating like mad. It isn't welcome.
– Liz Bredberg, Sacramento A: Judging by your photo and description, you have two mystery plants. And your mother is right; these are sold in garden catalogs, and easily can become invasive.
According to UC Master Gardener Bill Pierce, the little plant with the white flowers is sweet alyssum (Lobularia maritima).
This plant is often used like a wildflower or ground cover for mass display and scented air. The seeds are often windblown. It spreads very easily.
Each plant can produce thousands of seeds. The trick is to pull it out before it goes to seed, then keep pulling out new plants.
The one with arrowhead-shape leaves is Arum italicum, also known as Italian arum. It has a flower shaped like a calla lily.
After the flower fades, the stalk is covered with reddish berries that the birds like to eat. The birds excrete the seeds around the community and you get volunteer plants like those in your garden.
Arum is extremely hard to eradicate. Pulling out problem plants is a start, but arum tends to leave behind corms that resprout. It's very tough and resistant. (Even deer won't eat it.)
One possible solution: Paint full-strength RoundUp (glyphosate) on the foliage. The plant will carry the herbicide down to the roots, but it will likely take multiple applications. Follow label instructions.
Q: Could you please look at my sample and tell me what is infecting my redwood tree? It has been in the ground at my home for about three years.
– Dena Runyan, Roseville
The sample you sent from your coast redwood (Sequoia sempervirens) exhibits a needle blight or scorch condition, said UC Master Gardener Bill Pierce.
This is an abiotic condition (caused by the atmosphere), not a pathological disease. Causes may include alkaline water, drought stress, dry wind, high temperatures or salt spray on foliage.
Redwoods also shed their branch tips and grow new ones. It's related to the same process that causes deciduous trees to drop their leaves in the fall.
With a young tree like yours, it should be deeply watered approximately every two weeks during the dry season. The frequency will depend on your soil type.
You should give it enough water to wet the soil to a depth of 18 to 24 inches. A soaker hose – wound under the tree starting at the branch tips and running 8 to 10 hours – is the easiest way to supply that water.
A 3-inch thick mulch of organic matter (compost, straw, fine bark, shredded newspaper or other material) spread under the tree (but kept 6 inches from the trunk) will help retain moisture in the soil.
Giving the tree a shot of tree food is not necessary since the plant is making its own fertilizer.
GARDEN QUESTIONS?
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 h&g@sacbee.com. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:
• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays
• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu
• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays
• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays
• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned
• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message
• Shasta, Tehama, Trinity: (530) 225-4605
• Solano: (707) 784-1322; leave a message and calls will be returned
• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays
• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned
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