Observation: Looking for succulents for fire protection

As part of our fire protection strategy, we have plenty of succulents in our site. While they don't prevent a fire and should not be used as an insurance against fire, we use it as an additional tool in a vast toolkit to minimize the fire hazard.

Looking for what makes a plant fire-resistant, we found the following criteria:

• Store water in leaves or stems.
• Produce very little dead or fine material.
• Possess extensive, deep root systems for controlling erosion.
• Maintain high moisture content with limited watering.
• Grow slowly and need little maintenance.
• Are low-growing in form.
• Contain low levels of volatile oils or resins.
• Have an open, loose branching habit with a low volume of total vegetation.
  

This list comes from a CalFire old PDF that is no longer available but consistent with other sources. The important piece to remember is that fire-resistant doesn't mean fire-proof. Eventually, any plant can burn.

Moving on, here you can find the design used for our fire sector. Currently, we are looking for something that would work both as a ground cover, and as a resilient foot path. Bonus points if it feeds other animals.

Geoff Lawton, one of the Permaculture gurus, surprised us, recommending the Hottentot Fig for this.

It makes sense: this plant grows very well and quickly in temperate climates, it is resilient to mild frosts, poor soils and droughts. The plant roots as it spreads, so it could be an easy solution. Even if it can have a rampant growth, the constant stepping on it and clearly defined area would help keeping it in check. Unfortunately, it also spreads by pollination of seeds, which means it can easily end up elsewhere - both in our plot and our neighbours. The main issue is that, it has been considered so aggressive and harmful in this country that it was outlawed, and it is now illegal to plant or transplant it.

So, we went on a hunt for alternatives. The best way to start was, of course, observation, and we went for a local nearby, in the dunes. This is the closest almost-natural system to us, and it shares some important characteristics: no shade/partial shade, sandy, well drained soils, nutritionally poor, exposure to strong winds. Additionally, it needs low maintenance to grow and propagate.

And here is what we found, as far as we were able to identify:

• Sea Purslane (Halimione portulacoides)
• Sarcocornia fruticosa, although looking at this flora site they haven't been found here
• Golden Samphire (Inula crithmoides)
• Bugloss (Anchusa calcarea), Buglossa
• Pale Stonecrop, Sedum sediforme, an actual succulent

On higher layers, we found:

• Mastic tree, Pistacia lentiscus
• Maritime Pine (Pinus pinaster) Pinheiro bravo
• Tamarix, most likely tamarix africana
• Zimbro das areias (Juniperus turbinata, Juniperus phoenicea)

Nearby, but already in areas significantly managed by humans, we found:

• Pampas-grass: Cortaderia selloana
• Spanish Dagger: Yucca gloriosa
• Sweet alyssum: Lobularia maritima

And, finally, in people's gardens:

• Bay Tree (Laurus nobilis), Loureiro - already in our garden+
• Oleander (Nerium oleander) Oleandro - toxic
• Fruit trees, such as: citrus, figs, quince, apricot, apples, pears, olives and chestnuts.

Considerations:

• Sea Purslane and Sarcocornia fruticosa, could potentially be interesting, but it is hard to find out if they simply tolerate salt or if they actually require it.
• The golden sapphire requires lots of water and salt, so we won't include it.
• Bugloss (Anchusa calcarea), Buglossa. Although it is not a succulent, it is a good option to add to our garden, and increase flower diversity. However, it wouldn't work as the main ground cover
• Pale Stonecrop, Sedum sediforme, an actual succulent! It does clump instead of spread so it is not an ideal. Most importantly, it prefers a slightly alkaline soil, while the area we want to add it to is acidic.
• Sweet alyssum Lobularia maritima. This is an intriguing option to add to our garden, to increase the variety of flowers. It attracts wildlife and adds beauty. It does not, however, work as a ground cover.
  

Conclusion:

The main succulents on the run for perennials, evergreens, low height, attracting wildlife are the crassulaceae, where the sempervivum stands out. This is a plant we already have in our garden but only a few units.

One option could be to divide and propagate the sempervivium generously across this area of the garden, and then complement with some uva-ursi, which provides food, as well as the Sweet Alyssum and Bugloss.