How to kill Oxalis

Killing Oxalis is not that difficult if you have enough time. I
understand that you removed all plants you want to keep from the
infested bed so that there is no need to care for any desirable plant
amongst the weed.

If you have time to wait a full growing season, my recommendation is to
cover the whole bed with a material which excludes light. I understand
that the Oxalis in question is not Oxalis pes caprae but another species
which produces bigger bulbs than pes caprae. But to my knowledge any
bulbous Oxalis forms a new bulb each season (Please correct me if I am
wrong). To do so the plant needs light to photosynthesize. My
recommendation is based on the experience I made here in Portugal with
Oxalis pes caprae.

Some parts of my new garden are so heavily infested with this Oxalis
that it smothers practically everything else. It gets worse when the
soil is worked, especially after rotovating. So I used the woven black
plastic cloth which is used in nurseries to stand potted plants on. It
lets air and water through but not light. (There are different qualities
available, use the heaviest one) This was spread on the soil after it
was rotovated, raked even and the cloth fixed with stones. The Oxalis
sprouted beneath and was so dense that it lifted the cloth from the
ground but the shoots were pale yellow. I walked over the cloth to
smother the pale shoots under the plastic and to avoid it being lifted
high enough to let light in at the edges. The plastic was left until
late spring and and then the area was planted with vegetables and
irrigated. To my surprise in autumn, when Oxalis pes caprae started to
sprout in other parts of the garden, nothing came back in the previously
covered area. I was apprehensive because the shoots were so dense under
the cloth.

This way I did not use herbicides nor did I do any weeding. But the area
was clear of any plants and could be covered entirely and I had the time
to wait. I use the same technique now in between established plants
regardless if the weed is winter or summer growing or both. A good
material is strong cardboard which is flattened and weighed down with
stones (I have plenty of stones...) Cardboard lasts long enough to kill
the Oxalis or other weeds but then disintegrates and can be worked into
the ground like other mulch material. Sometimes I also use cut open
compost bags. They are of strong plastic and resist the UV light but
have to be removed and do not let air and rain through. it is okay in
small patches. A disadvantage of these methods is that they privide
cover for pests like rodents or slugs.

I would also like to share another experience I made with Oxalis: I lost
a whole collection after it moved from my old greenhouse with acrylic
glass in the roof to the new one with laminated true glass in the roof.
The building permission for the new greenhouse forced me to install a
laminated glass plus an extra pane of safety glass which means in total
4 layers of material. This absorbed so much light during winter (not
detectable to the human eye) that my Oxalis dwindled away during two or
three seasons. In both greenhouses the Oxalis was housed close to the
glass in the roof.

I have no personal experience with the solarizing method Nan recommends
but have my doubts that it would work in winter.

Hope that helps,

Uli

_______________________________________________
pbs mailing list
pbs@lists.pacificbulbsociety.net
http://lists.pacificbulbsociety.net/cgi-bin/…