Weed Watch: Hairy Bittercress

Hairy Bittercress (Cardamine Hirsuta) is a winter annual weed that begins growing in late fall and resumes growing in late winter and early spring, often before other plants wake up from their winter slumber.

This weed forms a rosette of leaves in the fall and usually waits until spring to flower. It forms small white flowers on stems above the foliage. The flowers turn into long thin seed pods. When the seeds are ripe, the pods explode when disturbed, shooting the seeds up to 16 feet according to some sources.

Hairy Bittercress is an annual and is usually shallow rooted and easy to pull out. The secret to its success as a weed is the prolific amount of seed and the ability to spread it by explosion so early in the season when other plants have not yet emerged to cover ground.

The best way to manage this weed is to pull them before they make seeds. Removing the rosettes in the fall or early winter can reduce the springtime invasion.

However, Hairy Bittercress does have some wildlife value for early butterfly caterpillars and specialist bees.  If possible, leave a patch in your yard for the caterpillars to munch.

Fun fact… Hairy Bittercress is part of the mustard family and is edible. It apparently has a mild, peppery flavor.

Want more information? Here are some links:

Brooklyn Botanic Garden Weed of the Month

North Carolina Extension – Cardamine hirsuta

Weed Watch: Japanese stiltgrass

A grassy invader

Stiltgrass

Japanese stiltgrass (Microstegium vimineum) is a non-native, invasive, annual grass. It has lance like leaves with a silvery stripe down the center, arranged alternately on a thin, wiry stem somewhat like a very miniature bamboo. It normally is 2-3 feet tall at maturity in late summer with seed heads at the top of each stem.  

Stiltgrass was probably introduced into this country as packing material in shipments of goods from China in the early 1900’s. Since then it has made itself at home in open woodlands, paths, roadsides and of course lawns and flowerbeds.

Stiltgrass has the ability to form dense stands that crowd out and smother native and desired plants. The stems root at the nodes, allowing a single plant to advance across the ground.  While stiltgrass is an annual and the parent plant dies in winter, it creates an enormous amount of seed and quickly builds up a bank of seeds in the soil. Each plant can produce up to 1000 seeds and they remain viable in the soil up to 5 years. The key to control is preventing new seed production and preventing germination of the existing bank of seeds.

Stiltgrass close

The plants are shallow rooted and can be pulled by hand. Plants should be removed before mid-August when the seed matures.  Cutting or breaking the plant stems earlier in the season may stimulate them to create and drop seed early, so try to remove each plant completely. The process of weeding may disturb soil and expose more seeds from the seed bank, encouraging new weeds. Mulching directly after weeding will help prevent germination of new seeds. Planting desirable plants densely to leave less open garden area may also help prevent stiltgrass germination.

Plants in a mowed lawn will still create seeds at the lower height. If possible, wait until just before the seed matures to cut large stands of stiltgrass so there is not enough time before winter cold for seed development.

There are some options for chemical control of stiltgrass.  This article from Penn State Extension describes those options.

Want a little more information? Here are some links:

Penn State Extension – Controlling Japanese Stiltgrass in Your Garden

PA Dept. of Conservation and Natural Resources: Japanese Stilt Grass PDF

The Humane Gardener – How to Fight Plants with Plants

Weed Watch – Lesser Celandine

Lesser Celandine may have cheerful yellow flowers, but don’t let it fool you. This is an aggressive, non-native thug that is wreaking havoc in our natural landscapes (not to mention front yards, back yards, flowerbeds and lawns).

Lesser Celandine (known as Ficaria verna but sometimes still listed as Ranunculus ficaria ) was brought from Europe in the 1860’s as an ornamental plant and escaped cultivation. The plant has shiny, dark green, kidney shaped leaves and bright yellow flowers. It typically emerges in late January to early February.

Because it emerges so early and creates a very dense mat of leaves, it smothers many of our native spring wild flowers by blocking out light, air and growing space before they can even get started. Our native insects are then deprived of the pollen and nectar they need early in the season.

Lesser Celandine is an ephemeral and is usually dormant by late June. This can cause problems in wetlands because other plants have been snuffed out so there is not as much vegetation left to prevent soil erosion in late season flood events.

Lesser Celandine is a very vigorous spreader, mainly through underground tubers and bulblets attached to the leaf stems. It prefers moist soil, but can survive in drier areas. It can colonize an area very quickly.

The tubers and bulblets can be spread by animals, by flooding and even by well meaning gardeners. It is often seen along stream banks where it has been spread by water flow.

Managing Lesser Celandine is very difficult. Small infestations can be weeded out, but you must remove all the tubers and bulblets. Weeding can actually spread the weed if you are not careful. To help contain the spread, keep in mind:

  • Never put removed Lesser Celandine in the compost.
  • Do not pile it on the ground or rake it up, put it directly in a disposal container. You may need to dispose of some soil along with the tubers to ensure you have removed it all.
  • Mowing Lesser Celandine can fling the small bulblets into other sections of the lawn.
  • When the plant is dormant, its easy to move the tubers from one part of the garden to another when transplanting other plants.

It is possible to eliminate Lesser Celandine with herbicides, but the window of opportunity is small. Here are a few references that discuss the use of herbicides.

The weeds in my beds blues

Those wicked, winter weeds…

Spring is coming – honest, and with the change in the weather the cold season weeds are ready to explode. I usually have a very nice selection of early season weeds.  I thought I’d just share a few…

I’m not sure everyone calls them by the same common name, so I added botanical names – even though I hate giving them any sort of respectability.

Hairy Bittercress – looks innocent until the seeds start exploding

Right now I have tons of Hairy Bittercress (Cardamine Hirsute). This is a winter annual that gets little white flowers on pretty tall stems.  The flowers turn into these long seed pods.  When the seeds are ripe, the pods explode when disturbed – shooting the seeds all over.  Apparently, the seeds can fly up to 16 feet! The best way to manage them is to pull them before they make seeds, but in my garden they like to hide inside other plants.  I think I’ll have them forever.

Purple deadnettle

Another weed growing now is Purple Deadnettle (Lamium pupureum).  I get this all around the edges of my vegetable garden and flower beds. It has square stems – always a warning sign because square stems belong to the mint family, usually very hardy and fast growers.  It gets pretty blue flowers, but it’s dangerous to let it go too long.  I try to pull it out of my vegetable beds whenever I see it and I put it in my brush pile, not my compost so it does not re-root.

I think my most hateful weed (at least this time of the year) is Creeping Charlie (Glechoma Hedoracea), also known as ground ivy.  This weed is a bit of a thug.

Creeping Charlie overgrowing a perennial geranium

It continues to grow in cold weather while many other things are dormant – twining its way around, over and under all the other plants, smothering them.  It grows over and under barriers, through small cracks in raised beds, and roots all along its stem. 

Usually I can work this weed out from around other plants, but sometimes I have to dig up the desired plant, untangle the creeping charlie and then replant.

Some say a weed is just a plant out of place, and its true that some plants we call weeds are actually very valuable to native insects and pollinators (like common violets for instance).

My approach is to try to maintain a kind of peace between my desired plants and the weeds. I think its OK to have a few weeds here and there.