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Raised Beds: Preparing your Garden Beds for Spring

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Early spring preparation will yield rewards throughout the growing season.

By Greg Seaman, Eartheasy.com Posted Mar 15, 2011

Raised Garden BedsThis may sound odd to you, but my favorite season in the garden is early spring, after our raised beds are prepared but before anything is growing.

The sight of the raised beds topped up with rich soil, moist and crumbly, free of weeds and ready to plant is a brief moment of perfection, full of promise, a blank canvas awaiting the gardener’s vision.

When raised beds are well prepared, the hardest part of gardening is also done. And the better the garden beds are prepared, the less work there will be during the growing season, and the more likely the gardener’s vision will come to fruition.

Here are some tips for preparing your raised beds for a bountiful growing season.

Work from outside the beds.

When gardening in raised beds, try to adhere to the one basic ‘ground’ rule: Don’t step on the soil within the raised beds. The biggest advantage of raised bed gardening is the light, fluffy, well-drained soil you’re able to develop which facilitates vigorous plant growth. Stepping on the bed will compact the soil, reducing aeration and slowing the activity of valuable microorganisms beneath the soil surface.

When you build or buy raised beds, be sure you’re able to reach every part of the bed without having to stand in it. (Our raised beds are 4’ across.) If you must stand on the raised bed, lay a long board across the bed and ‘walk the plank’ while tending the soil. If the ends of the board can be set on top of the sides of the raised bed, so much the better, as this will take some pressure off the soil.

Turn under, or smother, green manure cover crops.

‘Green manure’ cover crops are commonly planted between crop rotations, or over winter, to add organic materials back into the soil and provide a nitrogen-rich fertilizer. These cover crops should be turned under before they go to seed, and several weeks before the bed is replanted.

Turning under a cover crop can be done several ways. You can cut the crop close to soil level using a grass whip, a shears or weedeater. Save the cuttings for the compost or for use as mulch. The remaining stubble can then be chopped and turned under using a hoe. For gardeners growing in raised beds, however, using the hoe can be awkward near the sides of the bed because you don’t want to cut into the bed sides or push the sides outward by the digging action. This can be accomplished though with some care.

Some gardeners do not bother turning under the stubble because it’s less work and they don’t want to disturb the soil. Instead, they plant in between the stubble. The new seedling roots will break down the cover crop root clumps over time.

Another method for turning under cover crops, which puts no stress on the sides of the raised bed, is to ‘smother’ the cover crop by laying down a thick layer of mulch and covering the mulch with black plastic sheeting. This method has the advantage of breaking down the cover crop without having to cut it down or deal with the stubble, and the underlying soil remains undisturbed. This method, however, takes time. In sunny weather, which increases the heat beneath the sheeting, it may take 2 – 3 weeks to effectively smother the cover crop. In cool weather this will take longer.
Seaweed mulch is used to smother the cover crop. The bed on the right shows a 'green manure' cover crop before the mulch is applied.

Inspect each raised bed for needed repairs.

The soil in raised beds gets wet and heavy over the winter, and the added weight can exert pressure on the corners of the beds and can bow the center of long spans outward. Now is the time to fix anything that needs attention, before you start sowing seeds or transplanting seedlings, since any repair will disturb the soil.

Raised beds which have corners screwed or nailed together can sometimes have a corner work loose. If this happens, you’ll usually need to dig back a few inches of the soil to be able to get the corners together. For fixing the corners on cedar beds, we have used coated deck screws for repairs, with good results.

Most raised beds which are sold commercially have corner constructions which won’t work loose. The manufacturers use designs such as mortise-tenon, half-lap with through pin, interlocking hardware, or winged brackets to ensure the corners hold together.

If the sides of your raised beds are bowing outwards in the center of long spans, this can be corrected in two ways. You can set a stake on the inside of the bed and screw the bowed side into the stake. This may last a season or two. A better method is to pull the bowed side in and attach it to the opposing side of the bed. Use ½” aluminum flat stock and drill a hole in each end for screws. Attach this bar to the top edge of the lower boards (if the bed is two boards high), or bend the stock to a 90 degree angle and screw it to the inside of the boards. Manufactured raised beds usually are designed with cross-supports or center pins so bowing does not occur.
Raised Garden Bed with Cross braces

For raised beds made from untreated wood, you can apply a non-toxic wood treatment to protect against sun exposure, water and fungal decay. A single application will last a lifetime, saving time and money required to maintain and replace wooden boards.

Pull or block any invasive roots.

Look for evidence of any fast-growing creeping roots from weeds such as horsetail, and pull them out toward the direction from which they came. In some cases, we’ve had to dig a hole in the pathway to pull the root under the side of a raised bed. Track the root to its source if possible and pull the whole root ball.

Tree roots are attracted to moist, fertile soil. If you have trees near your raised bed, you might want to dig into the soil of the bed to see if there is any encroachment of tree roots into the fertile raised bed. In our garden, we had roots travel over 50’ from a tall fir tree and grow directly under our prime garden beds. It was a big job to dig up the bed and remove the roots, and then install a barrier. You may be able to identify potential invasive roots before they grow into your beds. Is there a fruit tree nearby, a large tree a little further away, or large shrubs close by? Anticipate future growth and contain it before any problems arise.

Some gardeners will advise laying carpet or some similar ‘blanket’ barrier on the bottom of your bed as a barrier to invasive roots. I think this is a mistake because it slows drainage and limits root growth for some vegetables. Instead of blanketing the bottom of your raised bed, you can block invasive roots from the outside of the bed. A narrow trench can be dug on the side of the raised bed which lies in the path of invasive roots. We dug the narrowest trench we could, which was about 8” wide, and dug down to clay. The depth varied from 3’ – 4’. Then we slipped down, on edge, large sheets of HDPE recycled plastic which we got for free from a feed store. (These sheets were used under feed bags on pallets.) Corplast sheeting is another option. Some gardeners use sheets of metal roofing for this purpose, but this will rust over time. Once the trench is filled back in, trim off any excess at soil level. This will now serve as a permanent root barrier for your beds.

Blocking roots

Appraise the soil for amendments and top up the beds.

The soil in raised beds is constantly settling. In early spring, the soil level may be several inches lower than it was last fall. Take a spadeful of soil and see if it’s light, moist and crumbly. If the soil seems compacted, some peat may be needed to fluff it up.

If you are using the no-till method of gardening, amendments can be applied by top-dressing. Amendments such as lime, peat, rock phosphate and compost can be spread onto the soil and covered with a thin layer of mulch. Once the plants are up, more mulch can be applied which will top up the bed.

Soils with a pH below 6.2 will benefit from the addition of lime. 6.5 – 6.8pH is ideal. Dolomite is the finest grind, and is recommended. With ground limestone it will take twice as long for plants to derive any benefit from it. Ideally, lime should be added several weeks before planting. Hydrate lime, or “quick lime”, is not recommended, as it can change the soil pH so rapidly that plants may be damaged. Cover newly limed beds with plastic during heavy spring rains to prevent runoff. Soil pH can be determined by using a soil pH test kit.

Once the base garden soil is in place, it’s time to feed it. The preferred method is to till in compost. Compost can be purchased from a nursery in bags, but a preferable way is for the gardener to keep a homemade compost pile. Different models of composters are available to suit garden size and residential restrictions. ‘Compost tumblers’ are sealed composters which speed the composting process and deter pests. If you are interested in compost tumblers, read our comparison of different types of compost tumblers.

Manure is best applied about two weeks before seeding in the spring.

Set stakes or poles and trellises for tall crops.

If you plan to grow tomatoes, peas, pole beans or other plants which will need support, now is the time to set these supports in place. If you wait until your plants are in, driving the stakes into the soil may disturb the young spreading roots of your vegetables.

For tomatoes, we recommend building a simple structure overhead and cover it with 6 mil clear plastic sheeting, or corrugated clear fiberglass panels. The purpose of this is to keep the rain off the tomato leaves, which will prevent tomato blight. During the growing season you will need to hand water your tomatoes, or use a soaker hose, taking care to avoid wetting the foliage. Once the tomatoes are established, adding a generous layer of mulch will reduce the amount of watering needed, and will also protect the plants during dry spells.

In our garden, we screw the upright supports for the tomato shelter directly into the inside face of the raised bed. This is simple to put together, and easy to disassemble in winter when we want the beds exposed to winter rains. Leaving the shelter on through the winter results in the soil being over-dry, which drives away the worms and other beneficial organisms which need some moisture in the soil.

Growing tomatoes

Cover the soil with mulch or plastic sheeting.

Covering the soil in your raised bed is a good practice throughout the year. It is especially useful in the early spring, after amendments and fertilizer have been added. The cover helps retain warmth which helps the amendments break down and ‘cure’ before seeds are planted or starters transplanted. The cover also serves to shed water so your valuable amendments aren’t washed away in heavy spring rains. The cover also discourages the sprouting of weed seeds which may lie dormant in the garden soil.

In colder, wetter climates, covering the bed with a layer of black poly sheeting will be more effective than mulch at helping warm up the soil in early spring. We usually wait until the weather warms up before putting down a thick layer of mulch.

Divide perennials. Clear and mulch perennial beds.

Existing perennial beds can be cleared of old plant debris and mulched to prevent weed growth. Perennials are easiest to divide when emerging shoots are only 2 to 4 inches tall. Early perennials like asparagus should have last years’ stalks cut at ground level and put in the compost. Prepare new beds for perennial flowers by spreading a 6-inch deep layer of organic matter (i.e. peat moss, compost, rotted manure) and work in deeply. Plants growing in deep, rich soil are less likely to suffer from summer drought. Mulch should be applied around, but not over the sprouting root mass of each plant.
Asparagus

Wait till the soil is warm before planting.

Avoid the temptation of planting your garden at the first sign of a warm spell. If you work the soil when it’s too wet, you’ll risk losing all of its natural air pockets and your seeds will suffocate and rot. As a general rule, wait until the soil is 60 degrees F (15 degrees C) before sowing seeds. 68 – 80 degrees F (20 – 30degreesC) is optimum for germination. Even early spring ‘cool weather’ crops like peas will do best when the soil is about 75 degrees F. When a handful of soil feels and looks more like crumbly chocolate cake than either an ice cube or mud pie, its likely ready for spring planting.

It may sound like a lot of work getting your raised beds ready for spring, but routine garden maintenance throughout the year makes the early spring chores manageable. Most gardeners are eager to get outdoors in the spring, and these preparations are a labor of love. And the rewards will last all summer as your garden vision unfolds.

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GregAbout Greg
Originally from Long Island, NY, Greg Seaman founded Eartheasy in 2000 out of concern for the environment and a desire to help others live more sustainably. As Editor, Greg combines his upbringing in the cities of New York, Boston and San Francisco with the contrast of 31 years of living ‘off-grid’ to give us a balanced perspective on sustainable living. Greg spends his free time gardening, working on his home and building a wooden sailboat with hand tools.

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  • anna

    Hi, I have an area along the entire side of my home that floods pretty badly when it rains. We have already installed a French drain to reroute some of the water but the flooding still remains. We decided to add dirt to the area and possibly make some flower beds in the areas that get a ton of water. When I say flower beds I mean dirt, mulch some pavers with pots sitting on the pavers. No more planting flowers in the ground. Anyways, I’d like to lay down cardboard first to kill the remaining grass and weeds that are not quite dead and then lay dirt on top of that until it’s high enough and level then add mulch and some flower pots. What happens once the cardboard breaks down? Will I have to dig everything up and replace it with more cardboard? I’m using the cardboard strictly to keep the weeds from growing, but I’m wondering how long these weeds will stay away?

    • You could also try solarizing the weeds by using black plastic sheeting instead of cardboard. The direct sun on the sheeting will bake the soil beneath it, killing the weeds seeds.
      If you overlay with soil, this will further suppress weed growth, especially if the added soil is 6″ or more. Bear in mind this new soil may also contain weed seeds. If not, weeds will still find their way to any available exposed soil, so you’ll still need to do some weeding from time to time.

  • Melissa

    Hi Greg,

    I’m writing from the Wairarapa, New Zealand. (James Cameron from Avatar lives just down the road!). We are just coming into spring and I have just dug over the first of my raised beds. They had fallen considerably so I have added ‘veg mix’ which is two parts top soil, one part mushroom compost and one part bark fines. I dug this through the existing soil which is dark, friable and rich. In addition I have added four year old horse manure which was friable and sweet, as well as blood and bone. I think though that I over did the digging and have mixed the additions to deeply into the old/new soils. I dug deeply to aerate the winter compaction. Would you advise adding another layer of my own vegetable compost and more blood and bone and just mix lightly into the surface now, or not add anything extra at this point. I don’t want to over fertilise the soil, but do want my plants’ shallow roots to be able to access the nutrients.

    Thanks
    Melissa

    • Each spring your beds will show compression from the prior season. To bring the soil level back up, we use a turning fork and just give it a light ‘twist and lift’ to break the clods and open the soil. Try to do this with minimal soil disturbance. Now peat can be added, it will fall into the furrowed soil. Add some lime to balance the peat. Using a hoe, mix and till the top 6″ of soil to ready it for planting.
      If your beds are topped up to your satisfaction, then hold off on adding more nutrients. Some of the amendments you have added will remain in the top few inches of soil to help your starters get established. You can always top dress with some compost if you feel the starters need a boost.

  • We find buckwheat to be very easy to chop and till when the crop has matured.

  • Hi Jack,
    Straw will be a good addition to your beds over winter. You can dig the straw partially under, this speeds its incorporation into the soil over the winter months.
    We are careful to not step on the beds, or to overwork the soil when turning things under. A turning fork is helpful for this process, it seems to result in the least soil disturbance.
    Your small tiller should be ok, but use your judgment – is it compressing the soil? We’ve only used hand tools – a turning fork and a sharp hoe can also get the job done pretty quickly.

  • Turn the soil with a shovel or a turning fork to see what it looks like. It is probably free of rocks and debris but dense and heavy since it’s been compressed by rain for some time. You will likely want to keep this soil as a good starter, then amend it as needed, e.g. add peat to lighten and aerate, start a compost bin so you’ll have that to add prior to planting. You may need to add some lime, and will surely want to add some rock phosphate. You can take a look at some our articles on soil building, especially this one:
    http://learn.eartheasy.com/2012/01/6-tips-for-building-soil-for-your-raised-garden-beds-and-planters/#comment-2458674252

    • newgardener

      Thanks a lot Greg!

  • Lori

    I piled up leaves in my raised garden bed last fall. I live in the Northeast, so it has been cold & somewhat wet this past few months. Should I scrape off/remove the leaves that haven’t decomposed, or try to break them up into smaller bits and work them into the soil? (The beds are only one year old and filled with “good” soil from the local garden center last Spring. I’ve already planted one season of vegetables, e.g., tomatoes, cucumbers, peas, peppers, etc.) Thanks,

    • Well, if the layer of leaves is thick there may be some matting which reduces surface soil aeration. If so, you could lightly turn them into the soil with a turning fork.
      But more likely, the layer is not too thick and will continue to break down. In late winter, a blanket of leaves can help maintain soil warmth.

      • Lori

        Thanks for the advice! It was about 2 to 3 inches of fluffy dry leaves at most, so less than that when wet and matting over the past few months. I’ll peek under the leaves in late April, when I’ll start prepping my raised bed for the new plants. If it is less than half an inch of matted leaves by then, I can turn it into the soil? Would covering the leaves now with a black plastic top or breaking them up into chunks speed up the decomposing?

        • Sounds like you’re fine with the way things are going. A week or two before planting you can lightly turn in any matted leaves. Try to disturb the soil as little as possible when doing this. We use a turning fork (pitchfork) for this. It’s ok if some leaves still poke through.
          Covering the leaves with black plastic is not going to speed up the decomposition process significantly, although we use black plastic to shed excessive rains which might wash away our valued soil amendments.

  • Filling the bottom portion of the beds with a layer of wood mulch should work for you. Just be sure the wood is clean (untreated wood, no chain oil residue if chainsawed), and avoid using woods such as cedar which is more acidic. Otherwise, you are planning something like a ‘hugelculture” which is popular with some gardeners.
    After a few seasons the wood mulch will have broken down and incorporated into the soil. So continue working to keep your soil light and well draining, and by all means keep up with the mulch once your plants are established.

    • Eric

      Thanks for reply.

  • The best time to fertilize is a week or two before planting, but you can “top dress” your plants with fertilizers now that the crops are sprouting. Read our blog article “Up, Down, All-Around” which will be posted in a day or two from now, this has advice on applying fertilizers and micro-nutrients.
    Go easy on the fertilizers, too much will shock the young plants and delay growth. Once you have top-dressed your plants, put down a layer of mulch to keep the top few inches of soil (where most of the root growth occurs) from drying out.
    I am not familiar with Jobe’s, but an organic fertilizer should benefit your flowers. Be sparing with the herb garden – our experience is that herbs have more taste when they are grown in more spartan conditions, and with lots of sun.

  • Brennan

    Hi Greg,

    New to gardening here and was wondering if it would be a good idea to place gardening fabric weed preventer over the flower beds just before winter. I have many bulbs planted along with some other perennials and wasn’t sure if this would be helpful or if it could possibly damage what lies below. Any advice would be greatly appreciated!

    BG
    Nashville

    • You can cover beds with landscape cloth over winter but I’m not sure how useful this is, since weed growth usually subsides during the winter months.
      We sometimes cover beds with sheet plastic over winter to help shed excess rainwater which may wash out our amendments or cause some erosion.
      Another option is to cover your perennial beds with mulch. This will break down over winter and early spring, adding organic matter to your beds which typically need replenishment.

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