I usually use preen with plant food as a spring boost startup. To feed plants and to keep weeds down. Is this about the best I can use?

No. That is aiming towards the worst thing you could do. A layer of hardwood mulch or other organic matter will feed the plants and keep weeds down the way God intended. Much better.

Preen on the other hand works to prevent seed germination because its mode of action is preventing new root growth. Any kind root growth. Because the chemical is acting on the cellular level stopping the process of mitosis. It can't tell the difference between a weed seed root and a daylily root. No root. No weed. No daylilies.

Don't use Preen. Impregnating your soil with a chemical the inhibits new root growth will never be a good gardening practice. Ever.

And yet......hundreds of thousands use this product with great success.

We should also be very clear on exactly how Preen works. Just as it has NO impact on existing weeds, it has NO impact on other established plants. That is the entire point of a pre-emergent herbicide - it can be used with impunity around any other plants. Your daylilies will be fine. You just cannot seed after use.

And it doesn't hang around all that long anyway. The product label states effective for 12 weeks but IME, that is overly generous. 6-8 weeks is more typical.

"Rhoda's" = rhododendrons? If so these won't like a fertilization regime that suits many of the other plants you listed. Otherwise if you are sold on the continued use of Preen in that location you should check the label in regard to safe use including what particular kinds of plants are considered compatible with this product.

U.S. EPA, Pesticide Product Label, PREEN THE WEED PREVENTER, 07/17/2003

it has NO impact on other established plants.

That is incorrect. The only reason Preen actually works as a pre-emergent is because it INHIBITS NEW ROOT GROWTH. The label is quite clear about how it can be harmful to plants in a number of settings. In the hands of many homeowners and at lethal doses, it is quite deadly to daylilies and any flowering perennial you care to name.

Impregnating your soil with a chemical the inhibits new root growth will never be a smart gardening practice. Ever. At least try not to inhale the crap.

There is no such thing as magic weeding dust.

The product label states effective for 12 weeks but IME, that is overly generous. 6-8 weeks is more typical.

So every two months then, go out and douse your soil with a chemical that interferes with new root growth by stopping mitosis at the cellular level. Don't worry your old plants don't need new root growth. Can it tell the difference between a root cell and a human cell I wonder? Mitosis is mitosis no matter whose cell it is.

I personally have not used the product in a planting bed - I prefer to hand weed - but I have used it in gravel pathways and spaces between flagstone. And it works like a charm.

If the product were so disruptive to roots then it seems highly unlikely that it would be recommended for use around existing plants and with the statement that any existing weeds must be removed by some other method. And that it is safe to plant seedlings as small as 2-3 inches after application. It does disrupt cell formation, which is what impacts seed germination and the development of seedling roots but I have seen no evidence that trifluralin has any effect at all on the roots of existing established plants. It is only applied to the soil surface, is watered to activate and then forms a surface barrier that prevents seed germination. If you disturb that surface barrier, you will only get erratic weed control.

Trifluralin also binds tightly to soil so minimal ability to leach deeper into the soil profile where the roots of more established plants are located.

Use of any herbicide is always a personal choice but Preen does what it states it will do and without any significant detrimental side effects.

For a community garden that only gets periodic (rather than daily) attention, pre-emergent weed control seems a reasonable choice.

"Can it tell the difference between a root cell and a human cell I wonder? Mitosis is mitosis no matter whose cell it is."

Fortunately, yes. The signaling processes for animal and plant cells is entirely different--plants, for instance, require copious boron for proper cell differentiation from the meristem. Animals don't (deprived of boron, rats develop normally, just a little smaller than they would otherwise, as well as their offspring...plants don't develop normally at all).

Most pre-emergents do root-prune existing plants, you're certainly right about that, so overuse at the 6 week level is not the best idea if it's not on the package.

Basically, never, never apply a chemical more often than package instructions...

While the root pruning isn't so extreme as to be able to stop bulbs or other perennials from returning, it certainly isn't anything you'd want, and it does happen even with normal application levels. You can find plenty online regarding root pruning; it happens at the root apical meristem (the end of the root tip) on the finest root hairs.

Personally, I use Prodiamine (Barricade) at the 9-month level in the lawn and gardens, applied in fall to confound some weeds I get that are fall sprouters (in the Poa genus) and the protection then runs around the year-clock to midsummer to cover crabgrass as well (not very well as it's pretty thin by then, but that's OK--the lawn is so thick I mostly only get crabgrass in a few spots in the garden and the pots anyway).

That level is on par with package instructions, which allow 2 to 9 months of coverage on bluegrass lawns and most flower gardens. Other lawn types vary and may thin out a bit with overuse--due to that noted root pruning.

"Is this about the best I can use or is there something else out there for a good start into spring."

Now, to actually answer the question...rhodies aren't actually that spring-hungry and would prefer to be fed after they bloom, not before. That's generally true with most things that bloom before Mother's Day, although there's an exception or three, and some things don't care (I'll boost my late lilacs before they blossom and they don't mind it).

Nothing else you listed will be particularly annoyed with that feeding schedule, and even the rhodies will deal with it if they have no other choice, so if that's what you can do and can't change it, then they'll manage. If you can slip in there to feed again in late May and hit the rhodies, do them at that point instead--they'll prefer that.

Everybody would also really enjoy a "Thank You For Being Pretty This Year" feeding around Labor Day if you have the time. Just a bit of a gentle scatter to give them some nitrogen they can process into energy and food to get through the winter. Think of it as Plantsgiving.

What food you choose is your business. :-) Realizing you volunteer this time and energy (you've implied that you do), just get whatever. Something balanced for a yearly feeding is nice, like 10-10-10 or the like, or a good organic like Milorganite (5-2-0) to slowly feed for some time before it peters out. But if you prefer something else or get something cheap, use whatever you want.

As far as the Preen, if it works for you and makes life easier, use it. It's not the cheapest, best, or most efficient, and it's not the longest-lasting, but it helps a little. Don't worry overmuch about root pruning or other problems (it does happen and is a real thing, but it's also really only going to make the difference between "prizewinning" and "nice" in the normal garden).

The one minor concern is that Preen covers a certain spectrum of weeds. Over the years, you select automatically for weeds it does not cover (because those are the ones that will sprout and grow--your typical natural selection process). Changing it up every now and again would help to cover different sets of weeds. So going with Dimension or Barricade every once in a while might help.

But even that's not a huge problem. It just means you'll end up with weeds the Preen won't cover. Eventually.

So take what gardengal and morpheuspa just said and put that in the hands of your average homeowner who thinks they just bought a big yellow bucket of magic weeding dust. What do you think the results are going to be when millions of pounds of the stuff are spread over the surface of the earth?

The ultimate result is lots of happy bacteria via bacterial decay; pre-emergents are strongly soil-binding. The reason they have time limits is that they're decayed off by being consumed by bacteria, which happily consider them food.

The ultimate result is mostly carbon dioxide and water, really, with some probable ancillary sulfates and whatnot. I'd have to research the whole chain but, given the diversity of bacterial enzymes, it won't be anything with any significant binding energy left to it. I'd put it on my To-Do List, but most of January's and February's spare time is being used up by watercolor lessons.

One of the most exciting new herbicides in the last decade was Tenacity. It's both a post- and pre-emergent for many weeds, an extract from the bottlebrush plant, and decays via bacterial action. It's also won the least-toxic medallion.

Most of this creative chemistry has been derived by observing the natural allelopathy of plants and determining the chemicals that do it, emulating those, and turning it into an applicable powder or spray. The last time nature didn't have a natural decay path was the Carboniferous. Which is why we call it the Carboniferous.

Plus I've only suggested using a legal product in a legal manner in a location where it's legal according to the label instructions and over legal time frames.

Well if you just ignore the root pruning and the inevitable natural selection to resistant weeds and that "This pesticide is extremely toxic to freshwater marine, and estuarine fish and aquatic invertebrates including shrimp and oyster. Do not apply in a manner which will directly expose canals, lakes, streams, ponds, marshes or estuaries to aerial drift.", then long term it's all just happy bacteria, carbon dioxide and water. No worries.

Frank sorry for hijacking your question. I knew this would happen, Just mulch your beds and apply a general 10-10-10 feeding and all will be well.

Nothing yet has come out of the lab that will kill a weed faster than a good hoe on a hot day, except maybe a flame thrower and if you have fire adapted weeds, even that might not work.

apply a general 10-10-10 feeding and all will be well

Not if any of those 3 (or other chemical nutrients included in the product) are already present on the site in adequate amounts. Particularly the second primary nutrient (phosphorus) which has a history of being overapplied to gardened sites, does not leach with any rapidity at all. So that when a toxic amount has been built up through overapplication the affected soil has to be dug up and replaced in order to eliminate the problem.

Better gardening through chemistry hasn't really worked out glitch free has it?

10-10-10

Once a year. Given leaching--and phosphorus does leach--and usage, a normal app would be low to replace what's being lost to leaching. We'll be quite low in terms of potassium.

For regular application, a soil test would be recommended. This is not a regular application, as noted by the OP.

If, however, you have a better recommendation rather than merely being contrary, I'm sure we'd all simply love to hear it.

"Better gardening through chemistry hasn't really worked out glitch free has it?"

Better farming through chemistry is the only thing feeding eight billion people so...well, yes. Glitches, sure, but it's better than resource wars.

If, instead, you'd prefer to be a Third World farmer, well, we could give up most of our farming technology and return to the 19th century. I'd prefer not to.

Now that it seems to have turned into a gripe-fest, I'll sign out. Frank, good luck. You're apparently going to need it.

Well I guess I will prween myself off of the preen this coming year and do some research on using Milorganite or 10-10-10 to use either on both the flowers and my lawn

Saturn

Seems like Milgoranite might be my choice by researching it looks like it is good for lawns vegetables and flowers and although I did see different Milgoranite products I guess any one may be used for all purposes

Saturn

Pre-emergents are strongly soil binding, so once applied and watered in, they're not going anywhere.

That is a comforting thought at least. A friend of mine's husband is a ship captain. He travels the US coastline, Atlantic, Gulf and Pacific, operating very high tech ships that dredge harbors and shipping channels because they are always filling up with dirt. There is this thing called erosion. There is also a massive and growing dead zone in the Gulf of Mexico devoid of oxygen because that comforting thought that all these chemicals stay were you you put them is false.

As I recall the leach rate for phosphorus is thought to be something like 1/4 in. per year. This in combination with a history of routine overdosing of American home gardens resulted in plant production and maintenance practices researcher Carl E. Whitcomb stating that many properties had become in effect "low grade phosphate mines".

Sandy soils in rainy outer coastal areas and other situations (including heavily watered plants growing in soilless container media) where there is heavy leaching of soils may benefit from phosphorus applications. Otherwise nitrogen may be the only primary nutrient that needs routine replacement on gardened soils in many areas. With fertilization using products supplying a range of nutrients as a recurring maintenance procedure not being desirable or needed.

I'm simply ignoring the spitting negativity for now. If people don't want to use logic or sense, that's fine by me, but I refuse to respond to it. :-)

"Seems like Milgoranite might be my choice by researching it looks like it is good for lawns vegetables and flowers and although I did see different Milgoranite products I guess any one may be used for all purposes"

It's a good product, and releases its nutrients slowly over a period of time. Any other organic would do the same, so don't feel locked into that specifically if it's not available--I suggested it because it tends to be the one at the best price point. The one you'll usually get is Milorganite in the mostly blue and white bag, 5-2-0 (it does have potassium, but it measures at just under 1%). It also contains tiny amounts of just about every other nutrient at maintenance levels, so that's always nice.

If you want to discontinue the Preen, that's not a problem either. Just plan on doing more manual weeding or using more herbicides to control weeds. If it's a choice between Preen or herbicides...I'd use the Preen. It does less damage overall environmentally.