The first year leaf of garlic mustard (typically called the leaf rosettes).
What is garlic mustard (Alliaria petiolata)? This cool-season biennial’s leaves and stems emit the smell of garlic or onion when crushed. Plants are 12 to 48 inches in height, and in their second year, produce numerous white flowers with four separate petals. Garlic mustard is the only plant of this height in the woods with white flowers in May. Hand pulling before flowering is recommended. It is believed to have been brought to North America by European settlers for use in cooking and medicine.
Here is the link to a brochure created by the Oregon Department of Agriculture: http://www.oregon.gov/ODA/shared/Documents/Publications/Weeds/GarlicMustardBrochure.pdf
How does it spread? This weed spreads exclusively by seed. The plant exudes a toxin from its roots into the surrounding soil and kills off competing seeds (the allopathic substance actually prevents germination of any seeds except its own!). It also stunts the growth of nearby plants. English Ivy in all its evil glory can’t hold a candle to this marauder. It’s clearing the way so this plant can take the next area over.
Why it’s bad, very bad: The concern surrounding garlic mustard comes from its ability to aggressively invade a woodland community and displace the native plant community to include grasses, shrubs, perennials, and tree seedlings.
How to remove it: Mowing is not an effective control because plants will still bolt and seed. Mowing spreads garlic mustard seed like wildfire – do not mow when seed pods are present (May through September). Hand pulling the weed is easiest during early bolt (2nd year). Difficult during rosette stage (first year) except for small patches. Multiple years are needed to exhaust seed bank. Pull at base to avoid breaking stem. All pulled plants should be bagged and removed from site (seed will set and/or plant will re-root).
Mature garlic mustard
If you must use chemicals, use a product that contains glyphosate or Tricloypr. To avoid damaging native forbs, spray the rosette stage during late winter/early spring. If not sure how to identify rosette stage, you can spray during flowering. Fall application to the rosettes (after some rain evens so plants are growing again) may also be effective. Sprays at height of summer will not do much. Use aquatic formulations when spraying near any body of water. A combination of chemical and hand pulling is very effective – pulling bolted plants and spraying right after pulling.
I am not suggesting growing it for cooking, but while eradicating it from your property, you could get even with it by making a very tasty pesto from the leaves. Here’s just one recipe I found on line: http://www.mnn.com/food/recipes/photos/6-edible-invasive-species-recipes/garlic-mustard-pesto
Five Important Garden Tips You Need
Treating blackberry and ivy with Roundup in the spring and early summer is pretty much useless. There is a time when these plants are most susceptible to herbicide. It’s a million times more effective in late summer and early fall. In an ideal world we would not use herbicides at all, if you are going to use them you want to use them sparingly and at a time when they will be effective. For information on how to do it right see my blog: Treating blackberry and ivy .
Over watering or under watering new plant material. Your common sense will kill your plants if you don’t have the specific information for the specific plant type. You can’t water a new tree the same way you would water your petunias. I insist my garden coach clients have a written watering plan for the first two years of their new landscape. I tell them how long to water and to hand check the soil to see if their efforts are successful. Last, but not least, if you’re watering every day you are in line for losing a lot of new plant material.
Colorful tough ground cover for full sun
Plant labels lie. Trust me it’s not a conspiracy, but they write the label so that it makes sense for the entire country. In the Northwest we have the ideal growing conditions so plants will grow taller and wider than indicated. In addition, just because a plants’ mature size is 15’ tall, does not mean it will stop growing once it gets there.
Light. Labels don’t have enough room to explain the complexities of sunlight, let alone the four different kinds of shade. Great Plant Picks is a great information resource in many ways, and has an excellent explanation about the different kinds of shade. There is no perfect solution, even checking the Web will get you four different suggestions for light requirements on a single plant. This is why experienced gardeners often move plants that don’t seem to thrive in the first location they select. Others hire designers who know these things first hand.
“Thank you so much for all your information today and your helpful phone call Saturday. I was pulling out plants in my mind as I was going to sleep last night. I can’t wait to get started!” D’Anne Oneill
Pruning. My best advice is don’t let your father-in-law prune your Japanese Maple! Do not do hedge pruning on plants that are not hedges. You need to learn how to do a thinning style of pruning. While I certainly advocate for hiring a garden coach (since I am one) you can learn from a local nursery, community college or someone who has trees and shrubs that don’t have a bunch of stubs on them. We want pruning that will enhance a plant’s natural and unique shape.