Mulching succulents is a bit controversial among succulent enthusiasts. Some say mulch makes soil way too moist for succulents and therefore advise against mulching where succulents are grown. Others say light applications are fine as long as succulents are planted in a raised bed or on a slope.
So should you mulch your succulents?
In our opinion succulents should be mulched as there are many benefits to mulching. But, as with everything, there is no one size fits all and whether or not to mulch succulents can depend on your climate, position the succulents are grown in and the type of succulents.
The main advantage of mulching is water retention. The mulch acts as a barrier and slows evaporation of water from soil underneath. Mulch also stops soil becoming hydrophobic. Hydprophobic soil is soil that has become too dry and has lost its ability to soak up water. This means that water is not getting to the plants roots, causing them to be too dehydrated and potentially resulting in death. Exposed soil can dry up fast. Covered up with mulch, it will stay moist and cool for longer.
Another important advantage of mulch is that it protects the soil from extremes. Soil that has nothing on it on a hot day will almost be too hot to touch. Add mulch and voila, the soil stays nice and cool, helping your succulents get through heatwaves. Same theory applies with frost although the majority of succulents are not frost tolerant and are likely to die if exposed to long periods of frost and snow, mulch or no mulch. Mulch may, however aid succulents that are frost tolerant in surviving deep winters as it will act as barrier to frost penetrating the ground.
Wood and leaf mulch also decompose adding nitrogen and other nutrients to the soil. While succulents will happily grow without any fertilizers the nutrients produced by slowly decomposing mulch is unlikely to do any harm. In our experience, it makes them grow better.
Dried out, hydrophobic soil is likely to be lacking any beneficial animals such as worms. Mulching will not only make it easier for the little critters to live but will also provide food. In return, the beneficial organisms in soil will help make it better for the plants by producing bodily wastes (plant food) and also make small tunnels, helping the soil become more airy.
Although weeds are very persistent and hard to control, mulching your gardens can help to keep weeds in check and stop them from spreading and germinating.
Our succulent gardens are heavily mulched with plain woodchip mulch. It is natural, abundant, inexpensive, does the job of retaining water well, is fuss free and looks great as it weathers. Because it decomposes, woodchip mulch needs to be reapplied every year or two.
Straw is a great mulch, ticks all the ‘benefits’ boxes and can be used around succulents, though is not very aesthetically pleasing.
If you want to mulch your succulents ahead of a dry spell and don’t have anything else but straw at hand, by all means use it. It will not do any harm. We have previously used straw and lucerne on our succulent gardens which we grow for succulent cuttings, and it works a treat. It just does not look very pretty. Be careful with lucerne as it almost solidifies after getting wet. It is best to leave a bit of lucerne-free circle around your succulents.
If you live in a climate with frequent rain, straw/lucerne might not be the best choice as it stays quite wet during rain and could rot some succulents.
Pebbles are not a mulch that will decompose and add nutrient, but more of a decorative top dressing. They do look absolutely fantastic in succulent gardens and pots and can really bring out the colour of the plants. The many shapes, sizes and colours allow for some creative work.
Pebbles and stones will not break down and so do not have to be reapplied, but they can be a bit high maintenance as dead leaves or exposed bits can spoil the look.
Pebbles will also help retain water, as long as they are not too big and leave lots of soil exposed. Also, beware of using black and dark coloured pebbles as they can heat up quite a bit when the sun is shining directly on them.
This is also a very effective mulch, although it can retain a bit of moisture and therefore make the surface wet. If using composted leaf mulch try and leave a small mulch free circle around the base of the plants. Many succulents will spread over the top which, in our experience, is fine.
Composted Leaves break down quite quickly and will need to be reapplied approximately once a year.
Our nursery succulent gardens are heavily mulched, but then we live in sunny Australia. We do, however, get rainy spells during which our succulents are constantly in moist soil for weeks. The nursery is based in the Blue Mountains west of Sydney and it is not uncommon to have heavy rain and very humid days. Has the mulch ever caused any rot? We are happy to report that none of our succulents planted in the ground with a healthy dose of mulch on top have ever rotted. They are all thriving despite being planted in poor soil.
If you live in a climate with hot summers and temperatures that easily go over 35 C (95 F) mulching your succulents is likely to help them get over the hottest part of the day. It is good to remember that temperatures in direct sun are much higher than what the weather forecasts says. What you see in the weather forecast are shade temperatures. So while you think it’s 'only' 35 C outside, if you were to put a thermometer in direct sun in the middle of the day, it would more likely be 45 C (113F). Dark surfaces, like exposed soil, will be even hotter. All of this can have a cumulative effect on your plants and cause them to burn or die.
We found that when the roots are nice and cool, succulents will get through 45 C + (113F) days. Mulch is of great help to plants on very hot days.
In tropical and subtropical climates or in countries where it rains often (Ireland for instance), mulch should still be beneficial to use around succulents. If there is any concern about rotting, a ring without any mulch can be made around the base of your succulents, so the soil dries out faster. It is important to make sure that succulents are always planted on a slope or in raised gardens, so they do not sit in stagnant water when it rains heavily.
Succulents grown in a full sun position, on a slope or in a raised beds will only benefit from being mulched. A slope or a raised garden bed will aid the drainage and the succulents will never sit in stagnant water and can enjoy the benefits of being mulched.
Same applies to a part sun position, where the plants will get at least 5 hours of sun.
Although a lot of succulents will grow in shade, they may be more susceptible to rotting (unless they are shade lovers such as haworthia, gasteria, sanseveria etc.). Sun loving succulents will survive being grown in shade, but they will loose their colour and compact shape. Mulching in this case may not be very beneficial for the plants.
Although the great majority of succulents will enjoy a good top dressing of mulch there are species out there that prefer being on the dry side most of the time.
They are mostly collector’s plants and hybrids such as some Agavoid Echeverias like Romeo, Ebony & Lipstic or the extremely popular but super expensive Echeveria Compton Carousel. We do grow the above mentioned Agavoid Echeverias outdoors and do not move them when it rains (so far so good and no rot related deaths), but our potting mix is top notch which, we think, allows us to subject our plants to a bit of tough love (this makes them more hardy than greenhouse grown succulents) and grow them outdoors without a problem. We have, however, heard countless times from other people that they can be a bit sensitive to rot if over-watered in the wrong potting mix.
Other plants that can be sensitive to too much moisture are Peperomia Graveolens, Euphorbia Mammilaris, Cacti in the genus Astrophytum, Echeveria Blue Bird and Echeveria Chihuahuensis.
When it comes to plants people can have different experience with the same plants and that is fine. Our advice is based on our many years of experience as a commercial succulent grower and in our experience (which may differ from other peoples), most Succulents planted in the garden will benefit from mulch and are highly unlikely to rot because of mulch.