Responsible lawn care help

Asked August 13, 2015, 7:34 PM EDT

We have a rather large back yard, and our property adjoins Piscataway park so we get lots of wildlife and plant invasions. While I don't need a perfect lawn, we have had a rather nice tall fescue lawn for years. Now, however, I have polygonum taking it over. Last year I tried to treat just it (mostly) with Roundup and reseed, but it's back now and even more prevalent. I don't know what to do about it. Is it a native that I should let flower for the bees and butterflies and just decide to like it (I despise it right now)? It seems that neither deer nor groundhogs care to eat it (darn it). Or, should I work gradually to kill it off and replace my lawn with zoysia which I heard will shut out anything else? I have also heard that Zoysia is considered invasive, but don't know. I have used corn gluten twice a year to try to fend off weed invasions (and little to no fertilizer, relying on grass clippings), but it seems to do nothing to prevent the spread of polygonum. Help, please.

Prince George's County Maryland

3 Responses

These are great questions. We'll break down the answers.

1. Are you referring to polygonum cuspitatum , Japanese knotweed/Mexican bamboo? This is a terrible non-native invasive plant. Have no qualms about killing it. Here is some help from our webpage under Invasives:
And our video about how to get rid of it:
If this is not the weed you have, please send us a photo or try to find it on our website's weed gallery.
No grass will be able to out-compete the Mexican bamboo.

2. Zoysia is expensive and takes times to establish. It needs full sun. Healthy fescue should be as vigorous and able to out-compete weeds as zoysia. (Do not plant Bermudagrass. This becomes a weed itself.)

3. In order to have healthy fescue, it needs to be fertilized every year in the fall. To protect Maryland waters, follow the state fertilizer regulations. Here's a simple fact sheet about managing lawns:
Also, soils get more and more acid over the years, make the pH too low for grasses. Test your soil and add lime as it recommends. There is soil testing info on our website (right side of homepage.)

4. Corn gluten is not an effective weed control. It must be used for many years and build up in the soil to achieve any results. It also contains Nitrogen and so much must be used that it actually exceeds the limits of nitrogen fertilizer permitted in Maryland.

5. It is normal for lawns to need overseeding after years go by. Drought and other stress tends to thin it out--and then the weeds move in. Your lawn may be due for an overseeding. Here is an excellent fact sheet from our website about successful lawn care:


Thank you for your prompt and encouraging (believe it or not) response. Yes, corn gluten has had little effect, although I always consider that it would have been far worse had I not used it.

Our weed is polygonum cespitosum (about 6-8 inches high with pink-red flowers in weedy spots where I have not cut them). It is mostly growing in a shady area, but I think that's because it's the point of entry into the yard. Should I still follow the elimination instructions you already gave for P. cuspitatum, or are there new ones?

I had a soil test done in March (U of Delaware) and the results for front and back yard are as follows: Ph 6.3/5.6 (front/back, respectively); P 270/210; K 127/50; Mg 272/147; Ca 277/171. So nearly everything except Ph is way too high (and this is without fertilizing, so I wonder if I screwed up the soil sample, but too late now). Their recommendations: Aug15-Oct 1 Front apply 4 lbs 26-0-3 per 1K, turf-type fertilizer with no P. Back apply 25 lbs ground limestone /1K sq ft.; 4 lbs 24-0-11 turf-type fert. per 1K sq. ft. with no P. Oct. 1-Nov. 15 Front apply 4 lbs 26-0-3 turf type fert. per 1K sq. ft., Back apply 4 lbs 24-0-11 turf type fert. per 1000K sq feet.
Do you agree with these recommendations? And, should I expect to be able to find these fertilizers relatively easily? Also, if I plan to re-seed (at least part of the back and all the tiny front) using your instructions, should I be using a different fertilizer mix?


Controlling P. cuspitatum will require persistence on your part. Pull it when you see it before it goes to seed, and consider using a chemical pre-emergent weed control in late winter (late February, early March).
As for your fertilization scheme. The pH of your front lawn is adequate for maintaining a healthy lawn, so no additional limestone is necessary. As far as your choice of fertilizer, it is important that you select one that has no Phosphorus. You don't have to look for fertilizer with those exact numbers, as long as the middle number is 0. However, the next important thing is measuring the nitrogen you apply. As you will have seen in the publications we recommended earlier, Maryland residents are required to only apply nine tenths of a pound of nitrogen per application and to limit the total annual amount to 2.7 pounds of nitrogen. That is not the weight of the fertilizer straight from the bag. For example, the first number on the bag (nitrogen) indicates the percentage of free nitrogen in the bag by weight. In other words, a 48 pound bag of 24-0-11 contains 11.5 pounds of nitrogen, i.e., 24% of 48 = 11.5. This doesn't make it easy for the average homeowner. But, that 48 pound bag of fertilizer will provide the appropriate amount of nitrogen for one feeding on almost 13K sq.ft.
Again, try to stay as close to the legal limits as possible. The following publication may be helpful: