Weed killer will harm Costus/Ginger?

[David E. Ross]

If it is oxalis, new plants will arise from pieces of stem. When you pull them, they will regrow unless you also remove the root. And the plant is perennial; if it appears to have died, it is only dormant.

If you let it bloom, the tiny seed pods (about 1/2 inch long) will release their seeds explosively, scattering their seeds widely. Walking across an infested lawn while wearing shorts, the seeds feel like gnats keep flying onto my legs. The seeds are slightly sticky and are thus easily spread by humans and other animals walking over a patch of oxalis.

As I indicated earlier, I use a paring knife to ensure that I get some of the roots. I attack oxalis before it can bloom. If I see it, I stop whatever else I'm doing and remove it. Fortunately, prior use of ammonium thiocyanate (YES!) eliminated the worst of the infestation.

[brooklyn1]

You obviously got lousy advice... who's the imbecil who told you to place stone chips over cloth weed barrier?!?!? DUH Stone chips go over heavy polyethelene sheeting that won't decay fro many, many years... used where you never want anything to grow, in lieu of concrete... the stone chips (hopefully decorative) are for hiding the ugly poly and to keep it from blowing away. Your weed barrier cloth didn't work for one reason and one reason only, you used the crappy el cheapo kind. Buy premium weed barrier cloth, even use it double in problem areas, like slopes... then cover with shredded bark, wood chips, or any other organics that will slowly decompose, adding fresh as needed. Stone chips do absolutely nothing to improve soil, and even if laid down a foot thick weeds will grow, because some weeds can push through from below and some seeds will fall on the chips and will root through... plus bits of organic matter and clumps of soil will constantly sift through creating a very nice substrate for all manner of native plants to propogate... I suggest you get rid of all those stone chips before you find them strewn all over your property... save them for when you plan to mix up a batch of concrete, or add to a crushed stone driveway.

[MiamiCuse]

Yes I try to pull the weeds, sometimes I was able to get the roots out, sometimes the stems broke.

Here are some pictures. The first picture are the Costus with the weeds underneath, and the second one is of the weeds.

MC

[Una]

Now we're getting somewhere. That looks like Oxalis. Try chewing one. If sour, probably it is an Oxalis. Trifolium (clover) has a flavor that reminds me of grass. In mid-day full sun do the leaves droop (not wilt!), as in this photo?:

you find any in flower (look in lawn adjacent to your Costus bed)? The flowers of Oxalis and Trifolium are easy to tell apart.

Here's a pamphlet about Oxalis in Florida:

are distributed like seedlings, so from seeds falling there after you laid the gravel. Source is likely your lawn or your neighbor's lawn. Explore a bit in the crushed stone to see if the roots are little bitty seedling roots or what. Some Oxalis produce bulbils on their roots and when you pull out the root you are likely to leave the bulbils behind. The bulbils sprout new plants.

Here's what I do with seedling crops. I first wait for most of them to die. That is the fate of most seedlings. Or I would lightly rake the rocks with a gardening claw, taking care not to damage the Costus. Any seedlings that survive I would dig out using a gardening tool to ensure I get enough of the root that it does not come back.

To prevent future seedling crops, find and eradicate the source. If this is Oxalis, you can treat with the specific herbicide others have mentioned. But if you don't eradicate the source, it will return.

Are the Costus growing on top of the fabric, or did you puncture it for each plant?

You have a "stone mulch" there. If you decide you don't like it after all, now is the time to take it all out and replace it with an organic mulch. I like organic mulches in part because it is easy to add more right on top of a seedling crop like this and kill the seedlings. However, if cats messing in the flowerbed are a concern, the stone mulch should discourage them.

Hope this helps,

Una