Summer is not the season most gardeners think of for soil preparation — that is usually a spring or autumn job — but it is the season when the soil is warm, workable, and ready to be improved for the planting that follows. Beds cleared of early crops, soil baked hard by the sun, and ground that has been cropped heavily all benefit from summer attention, and the work done now sets up the fall garden and the following spring. The rules are different in summer, though: the soil is dry, the sun is strong, and digging a dry bed can do more harm than good. This guide explains how to prepare and improve soil in summer, in ways that work with the heat rather than against it. For soil testing and local advice, check your local extension service.
Reading summer soil
Start by looking at the soil you have. Is it baked hard and cracked on the surface, or soft and crumbly underneath? Does water soak in when you water, or run off the surface? Are there worms when you lift a spadeful, or is the soil lifeless? Summer is the season when soil problems show themselves most clearly, because heat and drought expose poor structure: a soil with little organic matter dries out fast, bakes hard, and then resists rewetting, while a soil rich in organic matter holds moisture, stays workable, and recovers quickly after watering.
The test is simple: push a trowel into the soil after watering, and see how deep the moisture has gone. If it has only wet the top few centimetres, the soil surface is likely compacted or water-repellent, and it needs organic matter and a mulch rather than more water. If the soil is sticky and heavy even in summer, it is clay, and it needs the same treatment — organic matter, added little and often, is the answer for almost every soil problem, in summer as in any season. For the watering side, see our summer watering guide.
Compost: the summer soil improver
Compost is the best thing you can add to soil in summer, and the safest. Spread a layer of well-rotted compost over a cleared bed, and either fork it lightly into the top few centimetres or leave it as a mulch for worms to work in. Do not dig deeply into dry soil — a light forking is enough, and deep digging in hot, dry weather breaks the soil structure and brings dry, lifeless soil to the surface. If the bed is very dry, water it first, wait a day, and then work it, because soil that is slightly moist is far easier to improve than soil that is bone dry.
Compost improves every type of soil: it helps sandy soil hold water and nutrients, it helps clay soil drain and crumble, and it feeds the soil life that does the real work of keeping soil healthy. A bed that receives compost every summer will need less fertiliser, less water and less digging with every passing year. The compost ratio calculator can help you keep a heap producing, and our summer composting guide covers the heap itself.
Green manures and resting beds
A bed that is empty in summer should not be left bare. Bare soil in summer bakes, dries, loses organic matter, and grows weeds, while a bed sown with a green manure — a fast-growing plant sown specifically to improve the soil — stays covered, shaded and alive. Suitable summer green manures include buckwheat, phacelia and crimson clover, depending on your climate and the time available; sow them on a cleared bed, let them grow for a few weeks, and then cut them down and dig them in or leave them as a mulch before the next planting.
Resting a bed does not mean abandoning it. A bed rested under a green manure or a thick mulch is being improved, not wasted, and it will be in better condition for the fall garden than a bed left bare. If you have a bed that has been cropped heavily — tomatoes, squash or brassicas, for example — give it a rest and a green manure rather than planting straight into it again, because heavy cropping depletes the soil and builds up pests and disease. Rotation, rest and organic matter are the three habits that keep soil healthy over years.
Dealing with hard, dry and compacted soil
Soil that has baked hard in summer needs patience, not force. Water it slowly and deeply, using a soaker hose or a slow-running hose, so the water has time to soak in rather than running off the surface. A mulch layer over the top will keep the moisture in once it has soaked in, and a light forking once the soil is moist will break the crust without destroying the structure underneath. Do not try to dig a bed that is bone dry — you will break your fork and the soil, and the result will be clods that take months to break down.
Compacted soil, where feet, wheelbarrows or heavy rain have pressed the surface down, needs aerating rather than digging: push a garden fork into the soil at intervals and rock it gently to open up channels for air and water, then add compost and mulch. Paths should be kept separate from beds, so beds are never walked on, and raised beds are the simplest answer where soil is badly compacted, because the soil in a raised bed is never walked on at all. If the soil is waterlogged rather than dry, the problem is drainage, and the answer is organic matter and, where needed, a raised bed — not more digging.
Preparing beds for fall sowing
The most useful summer soil preparation is the preparation of beds for the fall garden. Clear the bed of the finished summer crop, remove roots and debris, fork in compost, level the surface, and water it well. Then sow or plant the fall crop — brassicas, kale, chard, peas, carrots and beets — into soil that is moist, fed and ready. A bed prepared this way in summer will give a far better fall crop than a bed planted into tired, dry soil, and the work takes an afternoon at most.
If you are sowing seed directly into a summer-prepared bed, water the drill before sowing, sow, and mulch around the seedlings once they are up. If you are transplanting, plant in the evening, water well, and mulch immediately. The fall garden is the reward for summer soil work, and it is worth doing properly: a bed that is fed, watered and mulched in summer will carry its crops through autumn with very little further attention. Check your local extension service for fall sowing dates and varieties in your area, and see our summer planting guide for what to sow.
What not to do to soil in summer
Do not dig wet soil after a heavy summer storm, and do not dig bone-dry soil in a heatwave — both destroy soil structure. Do not leave soil bare in the sun if you can cover it with mulch, a green manure or a crop. Do not add fresh manure to a bed you are about to plant, because it can burn roots and may carry weed seeds; use well-rotted compost instead. And do not assume that a fertiliser can substitute for organic matter — fertiliser feeds plants, but only organic matter improves the soil itself, and it is the soil that will feed your plants for years.
Summer soil preparation is mostly about restraint and timing: water first, work the soil when it is moist, add compost little and often, and keep the ground covered. A garden treated that way will have soil that is darker, softer and more alive every year, and the difference will show in every crop you grow. For the rest of the summer routine, read our summer mulching guide and browse the guides hub and the planting calendar for the full seasonal series.
Frequently asked questions
Can I improve soil in summer?
Yes — summer is a good time to add compost to cleared beds, sow green manures on empty beds, and mulch bare soil. Work the soil when it is moist, not bone dry or soaking wet, and fork compost lightly into the top few centimetres rather than digging deeply in hot weather.
What is a green manure?
A fast-growing plant sown specifically to improve the soil — such as buckwheat, phacelia or crimson clover — that covers bare ground, suppresses weeds, and is then cut down and dug in or left as a mulch. It is the best use for a bed that is empty in summer.
How do I fix soil that has baked hard in summer?
Water it slowly and deeply so the moisture soaks in rather than running off, then mulch the surface to hold the moisture. Once the soil is moist, fork it lightly to break the crust, and add compost. Do not try to dig bone-dry soil.
Should I dig beds in summer?
Only lightly, and only when the soil is moist. Deep digging in hot, dry weather breaks soil structure. Fork compost into the top few centimetres, or leave it as a mulch for worms to work in, and save deep digging for cooler weather.
How do I prepare a bed for fall sowing in summer?
Clear the finished crop, fork in compost, level the surface and water well, then sow or plant the fall crop into moist, fed soil. Check your local extension service for fall sowing dates in your area.