Homegrown: Desert landscaping, prickly pear cactus

I have desert landscaping, mostly river rock, with several small cactus gardens. My question is what product can I use for weeds in the cactus that will kill weeds only and not hurt the cactus?

— Thank you, Shirley

I’m afraid I don’t have any easy answers for you. Spraying herbicides around cactus can be tricky. Most of them will damage your plants to one extent or another. An herbicide’s effect on cactus tends to be muted a bit since most of them have a thick waxy coating. That helps to shed the spray but there’s usually enough to get the plant — maybe not kill it (though that’s possible), but damage it.

Having said that, there are a couple of herbicides that could help with certain weeds. If you’re fighting annual weeds, then a preemergent type herbicide will help a lot. These herbicides work by killing the seeds as they try to germinate without affecting existing plants like your cactus. You have to be sure that your weeds are annuals since this won’t help with perennial weeds nor will it help if the annual weeds have already emerged—you have to apply it before you see them. The particular product I like best is a High-Yield product called Turf and Ornamental Weed and Grass Preventer Containing Dimension. That’s a mouthful. We usually just call it Dimension.

The other type of weed killer that may help is a Fertilome product called Over the Top. It does a pretty good job killing most grassy weeds without affecting non-grasses. It won’t help you if the weeds are broad leaves as well, but it might help thin your weed problem down a bit.

Most people pull weeds in a cactus garden. I know it sounds crazy, but you need two things. First, a good pair of leather gloves to protect your hands if you happen to get a bit too close. The second thing is a good pair of tongs to reach in and grab the weed to pull it out. Regular kitchen tongs often don’t grab well enough to work well, but you could try some. Medical type clamps, like hemostats, will really grab what you’re trying to get hold of. Make sure they’re long enough to reach clear down to the soil because that’s where you need to grab the weed, otherwise it will probably just break off.

You can also use the tongs (or a straight dandelion digger for that matter) to push the cactus off to the side a bit so you can reach in with your leather gloved hand to grab them yourself. You can also use the dandelion digger to loosen the weed first before grabbing it with the tongs.

In extreme cases, I’ve heard of people digging their cactus up completely, roots and all, to thoroughly clean the weeds out of the bed and then replanting it. If you go to that extreme, consider putting some weed barrier fabric down around the replanted cacti before covering it with gravel to help prevent new weed infestation.

I have a prickly pear cactus that is overtaking my flower bed. The needles on it are deadly! How can I make it a more manageable size without totally killing it? The needles go right through gloves.

— Thanks, Sandy

The only way I’m aware of is to get a long-handled shovel and a pair of heavy leather gloves and dig the clump up, divide it into smaller pieces and replant what you want. The only requirement for the parts you replant is that they have both the top growth and roots on the same piece. That way you have a complete plant. Even without roots, they will usually survive; these cacti are pretty hardy.

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Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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