Weeds
 

IMHO all companies use chemicals diluted to the point of being useless. Buy a sprayer and concentrated long term Roundup. Spray as needed. I suggest the whole area initially then spot treat as necessary. Pine straw and bark require constant replenishment, blow around in the wind and also get weeds as much if not more than stone.

Get the super strong vinegar salt little dawn it works great and fast

I would start spot spraying my self if you can do it. I get some (very very little) weeds in my thick pine bark so you will probably always have a little bit of a weed problem.

You can probably cover the stones if you so choose, however I wouldn’t recommend that. I would remove the stone first if it were me. That’s another cost to deal with.

The difference between 9” pine straw and 14” pine straw is the tree species source. There are 3 pine species that are used for most of the pine straw in this area: loblolly pine (4”-6” needles), slash pine (7”-9” needles) and long leaf pine (9”-16” needles).
They each have different replacement times based on their characteristics so they probably cost different amounts. Longleaf will last the longest before needing refreshed. It also has a redder color than slash pine.

I’ve had pine straw, bark mulch and stones and pine straw seems to attract the most insects. All three will have weeds and have different life spans between replacing or refreshing.

One note of caution on pulling some weeds: nut sedges will grow more prolifically if you pull them. They have multiple means of spreading rather than just seeds. Once pulled, the plant reacts to that stress by putting out more underground “runners” and you’ll be totally frustrated when you se the increased spread. Use a chemical control on this weed. There are others that do the same thing.

I walk around my stone and mulch covered landscaping several times each week patrolling for and eradicating weeds.

RANGER is the only brand I use! Recommended by a Florida Landscaper years ago…. A little goes a long way… it will rectify the OPs issues… Ranger is a Monsanto product…,

Green Gobbler works great in non grass areas. It’s all we use.

go get yourself a couple gallons of white vinegar and soak the area - problem solved

I’ve been a Floridian for only 5 years but I’ve had properties at the Jersey shore where the weeds came through the stones as well. The first response pointed out that dust and debris settles in the rocks making the perfect place for airborne seeds to plant themselves. Also birds eat seeds from plants and their droppings can fall in your yard (my grandson told me that) and grow. My opinion for wood chips is that they decompose and I still don’t understand pine straw. Seems to me that it’s a great place for snakes to hide. I take care of my weeds with a spray that quickly takes care of them and the new battery operated sprayers is the way to go. I just don’t spray anywhere my dog goes. And BTW, you don’t need grass for your dog to go potty. Good luck in whatever you decide.

color
 

what color are the snakes around there?

40+ years in landscaping here... and licensed to kill... weeds...

Do not cover stone with straw, that would make a mess.

Straw/mulch does not go over weed barrier, stone does.

Buy a sprayer. Spend a couple of bucks and get the battery operated one. Mix both a Roundup product (glyphosate - which is Ranger or any number of products) with Weed-B-Gone (or any other broadleaf weed killer). Start at a rate of 2 oz per gallon of each and go up until you get the effect you want.

The Weed-B-Gone products act like a strong fertilizer and accelerates growth, burning the weed. That acceleration helps the Roundup work too.

Spray early morning when it is cool. Plants do not take up weed killer unless they are growing. Add a little Dawn dish soap if you want. That helps spread and stick the product.

Once a month should be all you need.

If you are hiring a company, they are likely not coming in the morning. But if you are unable to spray yourself, at least leave your sprayer out for them to use. They have to mix according to the label, and that may not be strong enough. And surely, they will not mix the two products.

Groundclear buy it at Lowes. The gallon size is ready to use and has a battery spray wand. It works flawlessly.

Vinegar
 

Spray a mixture of vinegar and water, plenty of diff. mixtures on internet, it’s cheap safe and effective

We had red lava rock, installed by the previous owner. I definitely agree that the weeds grow on top of the barrier underneath the rock. We replaced the lava rock with granite river rock, which produces much less dust for the weeds to sprout in. What I wonder is, would a pre-emergent herbicide like Preen be worthwhile to prevent the weeds from sprouting?

No mater what, no matter where you will have weeds. Nature hates a vacuum.
"White stone," it should be on top of weedblock fabric. The fabric can be torn, have gaps in it etc. Chemicals? May well damage your plants. I've used preen but it is only partly effective. It kills seeds but not weeds that spread by runners as in grass. Simple solution, when you see a weed, pull it.

We have pine straw. Nothing is perfect. Advantage of pine straw is that you can use tools on the weeds. You still end up pulling some. I would not put pine straw on top of pebbles.

And the MGs also will tell you that pine straw has a natural component in it that inhibits seed germination. It works! No weed barrier fabric necessary.