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Designing with permaculture

Catch and store energy

Terra Humana editorial teamLast updated: 2026-10-168 min read

After an autumn storm, a ring of clear rainwater stands around a young tree on a small mound on a dry Mediterranean slope

In brief

The second of Holmgren's twelve permaculture principles: gather water, sunlight, fertility and seed while they are plentiful and hold them for lean times.

What the principle says

Catch and store energy is the second of the twelve design principles of David Holmgren. It starts from a plain observation: what a landscape needs does not arrive evenly. Rain falls in bursts and seasons, sunlight is strong in summer and weak in winter, plants grow fast in spring and stop in drought. A design that uses only what arrives today lives from hand to mouth. A design that catches the surplus and holds it can carry a time of plenty into a time of need.

Holmgren uses the word energy in a wide sense. It includes heat and fuel, but also water, the fertility of the soil, the growth of plants, seed, preserved food, and the skills and knowledge of the people on the land. All of them can be gathered when they are plentiful and kept for later. Modern economies live largely from stores laid down long ago, above all fossil fuels, which are sunlight caught by plants millions of years ago. The principle turns attention back to the stores a place can build and renew by itself.

In permaculture practice the most valuable stores lie in the land rather than in tanks and sheds: water held in the soil and the slope, humus, living trees and seed. They cost little, they grow with care, and they serve many uses at once. A tree stores water in its tissue and in the shaded soil beneath it, carbon in its wood, and food in its fruit, and its leaves feed the soil life every autumn.

Catch and store energyLearning panel on principle 2 of 12: Catch and store energy. Proverb: make hay while the sun shines. Carrying plenty into need: in the time of plenty come rain, light and growth; in the time of need the stores give back. The stores lie in the land: trees with wood, fruit and shade; seed, a season's growth; pond and cistern for what the soil cannot hold; and soil and humus, the largest store, which holds water like a sponge. Let water soak in first, then store what remains. What to watch for: the window is short, and water that runs off in the rainy season is lost until the next autumn. Slow the water first and let it soak into the soil. Mulch and plants keep the stored moisture from evaporating. Saving seed keeps the adaptation of a plant to its place for the years ahead. In the TerraWiki the principle works in infiltration, the swale, roof water and cisterns, humus, the food forest and the seed cycle. TERRAWIKI · LEARNING PANEL · PRINCIPLE 2 OF 12 Catch and store energy Proverb: “Make hay while the sun shines” 2 1CARRYING PLENTY INTO NEED Time of plenty rain, light, growth Time of need the stores give backTreeswood, fruit, shade Seeda season's growth Pond and cisternwhat the soil cannot hold Soil and humus the largest store, holds water like a sponge Let water soak in first, then store what remains. 2WHAT TO WATCH FOR The window is short: water that runs off in the rainyseason is lost until the next autumnSlow the water first and let it soak into the soilMulch and plants keep the stored moisture from evaporatingSaving seed keeps the adaptation of a plantto its place for the years ahead 3WHERE IT WORKS IN THE TERRAWIKI InfiltrationSwaleRoof water and cisternsHumusFood forestThe seed cycle Basis: David Holmgren, Permaculture: Principles and Pathways Beyond Sustainability (2002)

The old saying: make hay while the sun shines

Holmgren pairs this principle with the proverb make hay while the sun shines. Grass can only be dried into hay on a run of dry, sunny days. A farmer who waits for a more convenient moment may find the weather has turned and the chance is gone.

The saying holds a sense of urgency that is easy to forget in an age of supermarkets and piped water. Many resources can only be caught in a narrow window. On a Mediterranean slope most of the rain falls in the cooler half of the year, often in a few heavy storms. Water that runs off then is lost until the next autumn, and no amount of effort in July can bring it back.

How it looks in nature

Living things have stored energy for as long as there have been lean seasons. Many Mediterranean plants, among them the asphodels common on Sardinian hillsides, keep reserves in bulbs, tubers or thick roots, let their leaves wither in the summer drought and sprout again with the first autumn rain. Seeds are perhaps the most perfect store of all: a season's sunlight packed into a small, durable form that waits for the right moment.

Animals store as well, and some of their stores plant forests. Jays bury acorns one by one in scattered places through autumn and live on them in winter. Studies of jays and oaks, from the Netherlands to Mediterranean oak woodlands, show that the acorns they do not recover can grow into new oaks, often tens of metres or more from the parent tree, in places its own falling acorns could never reach. A store that serves one creature becomes, through what is left over, the beginning of the next generation of trees.

The largest store of a landscape, though, lies beneath it. A soil rich in humus holds water like a sponge and releases it slowly to roots and springs, long after the last rain.

Where the principle works in the TerraWiki

Many techniques in the TerraWiki are ways of catching and storing energy in one of its forms:

  • Rainwater harvesting: the general art of catching rain where it falls, on roofs, paths and slopes, instead of letting it run away.
  • Swale: a ditch on the contour that holds runoff long enough for it to soak into the slope and fill the soil store.
  • Half-moon, zaï pit and microcatchment: small earthworks that gather the rain of a larger area around a single plant.
  • Infiltration: how water enters the soil, and why the soil is usually the cheapest reservoir there is.
  • Retention pond and roof-water cistern: stores for the water the soil cannot hold, for animals, plants and the dry months.
  • Water retention landscape: many such stores linked across a whole landscape, so that rain stays where it fell.
  • Humus and mulch: humus holds water and nutrients for years, and mulch keeps the stored moisture from evaporating.
  • Biochar: turns part of the carbon in prunings into a form that lasts far longer in the soil than fresh plant matter.
  • Food forest: a living store of wood, fruit and shade that grows larger every year it is cared for.
  • Herb spiral and rock mulch: stone that catches the warmth of the day and gives it back at night.
  • The seed cycle: saving seed keeps a season's growth, and the adaptation of a plant to its place, for the years ahead.

For the physics behind all of this, the page on energy flow explains why stored energy always leaves in the end, and the water cycle shows why holding water in the slope comes before any tank.

At Sa Medada

Sa Medada is a slope in Jerzu, in Ogliastra on the east side of Sardinia. The winters are mild, and the dry season lasts roughly from May to September. Light and warmth are plentiful; water is what this land must catch and keep. The LiDAR wetness map shows a comparatively dry main area and moister channels along the edges, which suggests where water already gathers.

Project Eden therefore begins with water retention, pioneer plants and ground cover. Plants and mulch shade the soil so that the water it holds is not lost to the summer sun, and every root that grows into the slope helps the next rain soak in. Swales are planned; none has been built yet. An old olive grove covers part of the land, a store of many years of sunlight in wood, roots and shade. A laboratory analysis of the soil does not yet exist, so we make no claims about how much water or humus the soil holds today.

The previous principle, observe and interact, shows where the land receives more than it can use. The next one, obtain a yield, asks that what is caught and stored should also feed the people who care for it.

Frequently asked

What does catch and store energy mean in permaculture?

It is the second of David Holmgren's twelve design principles. Resources such as rain, sunlight, heat, plant growth and fertility arrive unevenly: plenty at one time, little at another. The principle asks us to design systems that catch these flows while they are abundant and hold them for the months when they are scarce. In permaculture, energy is meant in a broad sense: water in the soil, humus, wood, seed, stored food and even skills all count as stores.

What is the proverb for this principle?

Holmgren pairs it with make hay while the sun shines. Hay can only be made on dry, sunny days, and a farmer who waits loses the chance. The saying reminds us that the window for catching a resource is often short. In a Mediterranean climate most of the year's rain falls in the cooler months, and whatever is not caught then is gone until the following autumn.

Does energy really get stored, if it always flows away in the end?

Yes, for a while. As the TerraWiki page on energy flow explains, energy does not circle; it arrives as sunlight and finally leaves as heat. Storing it means delaying that departure: sunlight held as sugar in fruit, as wood in a tree, as humus in the soil, or as water held in the ground that plants can still use in summer. The longer energy stays on the land and the more uses it serves on the way, the richer the system.

What is the best place to store water on dry land?

Usually the soil itself. A soil rich in humus and covered with plants or mulch can take in a large part of the rain and release it slowly to roots and springs, without pumps or tanks. Swales, basins and half-moons help water soak in where it falls. Ponds and cisterns come next, for the water the soil cannot hold. Many designers follow this order: slow and sink the water first, then store what remains.

How does Terra Humana apply this principle at Sa Medada?

Sa Medada is a slope in Jerzu, Sardinia, with a dry season lasting roughly from May to September. Project Eden therefore begins with water retention, pioneer plants and ground cover, so that rain soaks into the slope and bare soil is shaded. Swales are planned but none has been built yet. The old olive grove is already a living store of many years of sunlight on the land.

Hens scratching through leaf litter beneath fruit trees, a henhouse on wheels behind themNext in this themeChickens in the systemHens as part of a permaculture design: they scratch, eat pests and scraps, give manure and eggs, and need shelter, space and protection in return.

Related terms

Morning sunlight falls through several layers of leaves onto covered ground on a Mediterranean slopeEnergy: The Flow That Drives EverythingThe one-way path of sunlight through leaves, plants, animals and soil life until it leaves as heat. Energy does not circle; it drives every cycle that does.Mediterranean hillside after the first autumn rain, mulched soil around young trees, water in a small earth basin, mist over an old olive groveThe Water CycleThe path of water from rain through soil, plants and air back to rain. On land it stays closed only where water is held, soaks in and is passed on by plants.Two swales along the contour after rain: still water in the level trenches, mulched berms with plants belowRainwater HarvestingHolding rain where it falls: soaking it into ditches and basins, storing it in dams and cisterns, spreading it along the shape of the slope.A level ditch along the contour of a dry hillside holding rainwater evenly, with a mulched earth bank of young trees below itSwaleA level ditch dug exactly along the contour of a slope, with the soil heaped into a planted bank below it, so runoff stops, spreads and soaks in.Hands holding dark, crumbly soil with fine rootsHumusThe dark, stable fraction of organic matter in soil, the part that holds water and nutrients and gives a living soil its colour, smell and structure.Aerial view of a Mediterranean permaculture smallholding at golden hour: a house, a pond, round keyhole beds, a straw-covered compost heap, chickens under fruit trees and a food forest, all linked by pathsCycle thinking in permacultureThe permaculture view of land as linked loops of water, nutrients, carbon, material and seed, all of them driven by sunlight.

Mentioned in

See this in practice

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Further reading from around the world

Freely available sources we recommend for going deeper.

Sources

  • David Holmgren, Permaculture: Principles and Pathways Beyond Sustainability, Holmgren Design Services (2002, revised edition Melliodora Publishing 2017)
  • Holmgren Design, Principle 2: Catch and store energy, permacultureprinciples.com (accessed October 2026)
  • Brad Lancaster, Rainwater Harvesting for Drylands and Beyond, Vol. 1: Guiding Principles, Rainsource Press (2006, 3rd edition 2019)
  • Bossema, Jays and oaks: an eco-ethological study of a symbiosis, Behaviour 70(1), pp. 1-116 (1979)
  • Pons and Pausas, Acorn dispersal estimated by radio-tracking, Oecologia 153, pp. 903-911 (2007)
  • Koohafkan and Stewart, Water and Cereals in Drylands, FAO and Earthscan (2008)

Last updated: 2026-10-16