What Is The Best Potting Mix for Potted Shrubs?

“I will be planting shrubs in containers. Which potting mix between Fafard and Black Gold would be the best choice and longest lasting? I would prefer something more permanent so as to not have to change out the potting mix every few years. I live in zone 7. Thank you for your response.” Question from Mel of Atlanta, Georgia

Answer: When recommending the best soil for potted shrubs that will be there for the long term, I always suggest filling the pots with 1/3 quality topsoil or ground soil and 2/3 quality potting mix. Mix the two evenly before filling the pots. I like to add ground soil because potting mixes tend to acidify over time, and ground soil, which is primarily inorganic, helps buffer the acidification process, and it will not break down and shrink over time. You might also consider adding some other ingredients, such as sand or pebble, depending on the shrubs grown. Finally, be sure to refresh the pot with new potting mix seasonally. The addition of dolomitic lime can also reduce acidification.

With that said, I would choose the following mixes for long-term potted shrubs.

Feed your shrubs seasonally in the spring with a slow-release fertilizer. It is also important to note that potted shrubs are most apt to survive winter if they are at least two zones hardier than your zone because they are more exposed.

All the best,

Jessie Keith

Black Gold Horticulturist

How Much Cactus Soil Do I Need For My Pot?

“How many bags of Cactus Soil will I need to fill up a 4.5-gallon container that measures 20″ x (top) x 8″ at base x 10″ deep. I am taking my barrel cactus out of the ground and planting them in this container. Can you suggest a good draining pot? Thank you for your time.” Debra of Nevada

Answer: This is the perfect job for our retail bag to pot calculator. It allows gardeners to determine how many bags of mix will be needed to fill a pot. Another easy tool to try is a gallon to cubic foot conversion calculator.

For our tool, you must answer the following:

Step 1: Select your container and size. (We provide this information.)

Step 2: Use the keypad to enter the number of containers of your size. (Make your choice, but your exact pot size is not in the calculator. I made a good guestimate by choosing a pot of the closest size.)

Step 3: Choose your bag size. (Black Gold Cactus Mix comes in 1 CF and 8 QT sizes, information that you can find on the product page.)

Our calculator and the gallon-to-cubic-foot calculator determined that 1 CFL bag of Black Gold Cactus Mix will be needed to fill the pot.

We also recommend that you read our article about Planting a Golden Barrel Cactus Safely. It has super tips from cactus expert, Maureen Gilmer!

I hope that this helps!

Happy gardening,

Jessie Keith

Black Gold Horticulturist

My Mix Has Slime Mold! Is It Dangerous?

Here a yellow slime mold is growing on a fallen tree in nature.

“I bought 8qt of Black Gold Cactus Mix and started repotting my plants. The first bag looked fine, but the second one was covered in orange/rusty colored powder and some fuzzy white blooms. I haven’t used it, but will this happen to the other one as well? What should I do with it?” Question from Rusty of St Louis, Missouri

Answer: It may look funky, but there is no need to worry. The reddish-brown growth found on the top of the potting mix is a harmless saprophytic slime mold. These exist in healthy natural environments and obtain food from dead or decaying organic matter, such as peat moss, rotting stumps, and decaying leaves (also compost). They are rarely able to grow in bags of mix, but clearly, there was enough air, moisture, and warmth in the plastic packaging to allow this misplaced saprophyte to grow and feed on the peat (or decaying organic matter). The saprophytic mold will not harm your cacti, succulents, or other plants in any way. In fact, once the bag is opened, the saprophyte will dry up, dissipate, and never return.

I hope that this helps!

Happy gardening,

Jessie Keith

Black Gold Horticulturist


My EarthBoxes Stay Too Wet. What Should I Do?


“I have a problem with my EarthBoxes (self-watering containers) staying too wet. I need better drainage. Which of your products would you suggest I try?  Thanks!” Question from Larry of Mooresville, Indiana

Answer: There are several things that you can do to fix this problem. First, remove all of the old potting mix from the boxes, and make sure that the self-watering system and holes are free and clear. It is not uncommon for them to get plugged up with soil and roots over time. Next, choose a very fast-draining potting mix. I suggest using Black Gold Natural & Organic Potting Mix and boosting its drainage with added Black Gold Perlite. Consider four parts potting mix to one part perlite. Finally, be sure not to overwater the boxes. Allow them to dry somewhat between watering. I hope that these tips help!

Happy Gardening!

Jessie Keith

Black Gold Horticulturist

Help Me Understand Cacti and Succulent Mix Components and Characteristics

I belong to the Michigan Cactus and Succulent Society, and I like to create my own mixes. To perfect my blends, I am always trying to figure out what materials will provide the characteristics I need for drainage, aeration, water-holding capacity and so on. I also want to understand how particle size impacts the performance of primary mix materials. Does the blend of ingredients matter the most or the particle size? Depending on the plant, I add pumice, perlite, Turface® and/or chicken grit in varying proportions to increase mix drainage. Which of these items will increase drainage and lessen root rot due to organic additives? I tend to under water and don’t water the cacti in the winter. Plus, I bring many of my plants outside in the summer (some of them) where they are subject to unpredictable weather, rain, heat, humidity. What mix will best help them under these conditions? Question [shortened] from Carol of Harrison Township, Michigan

Answer: I will try to address all of your questions in full. Covering different cacti and succulent mix ingredients and their characteristics is a good start.

Mix Ingredient Qualities

Some common mix ingredients

Let me start by saying that the particle size does impact porosity and therefore aeration and drainage. Larger particles mean more air space and less water-holding capacity. All of the mineral additives you mention will increase drainage and lessen the chance of root rot as a consequence. Here are the main C&S mix components and their characteristics. (Keep in mind, some of the products mentioned we do not carry.)

Organic ingredients with high water-holding capacity: Coconut coir, compost, earthworm castings, and peat moss. All of these ingredients hold moisture, and many also contain beneficial microbes and natural nutrients (earthworm castings and compost). It is essential to include some organic ingredients to cacti and succulent mixes. Those with low nutrient value, such as peat moss and coconut coir, are best if you want to establish your own controlled feeding program.

Inorganic ingredients with high water-holding capacity: Vermiculite and Turface®.

Organic ingredients with low water-holding capacity that increase porosity and drainage: Bark.

Inorganic ingredients with low water-holding capacity that increase porosity and drainage: Cinders, Gran-I-Grit, fine lava rock, perlite, pumice, coarse sand, small pebbles, and rock dust.

Cactus and Succulent Mix Recipes

As you know, different cacti and succulents have different levels of tolerance with respect to organic matter and drainage. You could always plant in bagged succulent mix, such as Black Gold Cactus Mix, which contains a very high percentage of horticultural perlite in addition to pumice and cinders and a low percentage of earthworm castings, compost, and bark. But if you are keen to mix your own, start with the general formula.

Cacti and Succulent Mix Formula: Most professional cactus and succulent mixes by volume are 50% solid (45% mineral, 5% organic) and 50% pore space (25% air space and 25% absorbed water). Recipes vary far and wide, but it’s wise to not stray too far from this formula. Here are some succulent mix recipes that you might consider.

Recipe 1: 30% (three parts) coarse sand, 30% (three parts) fine rock like Gran-I-Grit, pumice, etc., 30% (three parts) coconut coir, 10% (one part) compost.

Recipe 2: 50% (five parts) perlite, 30% (three parts) all-purpose potting mix, 10% (one part) coarse sand, 10% (one part) rock dust.

Recipe 3: 30% (three parts) fine bark, 30% (three parts) Gran-I-Grit, 20% (two parts) Turface®, 10% (one part) compost.

Growing Potted Cacti and Succulents Outdoors in High-Rain Areas

This hardy succulent rock garden at my home is placed under an eave to protect it from excess rain.

This one is easy. I bring my many cacti and succulents outdoors in summer, too. To protect them from excess moisture, I keep the pots on my sunny porch and below eaves away from heavy rain. A covered patio would also be ideal.

Still, I find that the hardy succulents and cacti in my Mid-Atlantic yard perform well, even through hurricane weather and cold winters, because they are planted in high rock gardens with sharply drained soil (Black Gold Cactus Mix plus added pebble and compost). I also mulch them with a cover of pebbles to keep any succulent parts from touching surface soil.

I hope that these tips help. Please let me know if you have any additional questions.

Happy gardening!

Jessie Keith

Black Gold Horticulturist

Can I Make Seedling Soil Blocks With Black Gold?

“I realize that you sell several potting soils. The one that I want to use to make soil blocks is your organic potting mix.  Do I need to add anything besides water to it to act as a binder?” Ken from Washington State

Answer: Black Gold Natural & Organic Potting Mix is perfect for seedling block making.  All you need to do is fully moisten the soil, gather it in a pile, and punch it down with a soil block maker. The compacted blocks should be firm and stay together when handled. Then place them in leakproof flats with no bottom drainage holes. No extra binder is needed. This method is nice because it offers a plastic-pot-free way of starting seedlings.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

Black Gold® All Purpose Potting Mix Our #1 Best Seller

Black Gold® All Purpose Potting Mix 0.13 – 0.04 – 0.13 is a premium quality, rich potting mix for indoor and outdoor growing. It contains high-quality Canadian Sphagnum Peat Moss, Composted or Aged Bark, Compost, Earthworm Castings, RESiLIENCE®, and Horticultural Grade Perlite. It even feeds plants for up to 6 months! Give your potted plants the best this season!

Click here for an informational pdf.