Maryland Grows

Filling Your Raised Bed

Healthy soil will help you produce healthy crops. Ideal vegetable garden soil should be loose, deep, and crumbly. It both holds water for root uptake and allows excess rainfall to quickly percolate downward. So how do you fill a raised bed? Should you add topsoil, compost, or potting soil? The answer depends on the situation. Read the scenarios below to learn about options and develop an approach that works best for you!

Scenario 1:

Reduce costs by foregoing an enclosure.  Photo credit: Jon Traunfeld

Reduce costs by foregoing an enclosure.
Photo credit: Jon Traunfeld

Raised beds without a wood enclosure- formed by “pulling up” loose, fertile topsoil into a 2-6 inch raised bed with gently sloped sides. Spread 1-2 inches of compost on the area before forming the beds.

Scenario 2:

This raised bed is almost 6 inches above grade and was filled with  existing soil and compost. Photo credit: Jon Traunfeld

This raised bed is almost 6 inches above grade and was filled with existing soil and compost. Photo credit: Jon Traunfeld

Raised bed with an enclosure located in an existing garden- If the soil is in good shape (topsoil intact, not compacted, drains well) increase the soil depth by adding add 4-6 inches of compost (homemade or purchased) and mix it with the top 4-inches of soil. You could also add a 2-3 inch layer of topsoil from the walking space around the raised bed and replace it with woodchips, bricks, or weed barrier fabric.

Prior to adding the compost, loosen soils with high clay content by pushing in your garden fork and rocking it back and forth. Move the fork 6-8 inches and repeat  across the entire bed. Photo credit: Jon Traunfeld

Prior to adding the compost, loosen soils with high clay content by pushing
in your garden fork and rocking it back and forth. Move the fork 6-8 inches and repeat across the entire bed. Photo credit: Jon Traunfeld

Scenario 3:

Raised bed placed on lawn– kill the grass and weeds by covering the area with plain cardboard multiple layers of newspaper, or weed barrier fabric (can take 6-8 weeks). Then fill the bed with a mixture of compost and purchased topsoil in a 1:2 or 1:1 ratio. There are vendors who sell topsoil mixed with compost.

You could also fill the bed with compost and a soilless growing mix in a 1:1 ratio. The latter contain ingredients like peat moss, bark fines, vermiculite, perlite, coconut coir, and compost. As in Scenario 2, you can also remove add the topsoil adjacent to the raised bed.

Turf and weeds were smothered and raised beds built on top of the ground without disturbing the soil. It was filled with adjacent soil, compost,  and soilless growing media. Plant roots will grow through the raised bed soil into  the ground below. Photo credit: Jon Traunfeld

Turf and weeds were smothered and raised beds built on top of the ground without disturbing the soil. It was filled with adjacent soil, compost, and soilless growing media. Plant roots will grow through the raised bed soil into the ground below. Photo credit: Jon Traunfeld

If the raised bed is at least 6 inches deep and it’s time to plant it’s ok to cut the grass and weeds at ground level and cover the area with the selected growing medium. The vegetation will die and decompose in place.

An example of a soilless medium. It’s more economical to purchase  a compressed bale of media. Products containing peat or coconut coir are  hydrophobic (repel water) and should be thoroughly moistened before adding the raised bed. Photo credit: Jon Traunfeld

An example of a soilless medium. It’s more economical to purchase a compressed bale of media. Products containing peat or coconut coir are hydrophobic (repel water) and should be thoroughly moistened before adding the raised bed. Photo credit: Jon Traunfeld

Scenario 4:

Raised bed on hardscape or heavily compacted soil- should be at least 8 inches deep for leafy greens, beans, and cucumber, and 12-24 inches deep for pepper, tomato, and squash. Fill the bed with compost and a soilless growing mix in a 1:1 ratio. Topsoil can be added (up to 20% by volume) for beds that are at least 16 inches deep.

This bed sits on a concrete library balcony. It’s about 16 inches  deep and is growing a nice crop of tomatoes. Notice the perlite (white specs)  in the soilless growing medium. Photo credit: UME Master Gardeners, Frederick Co.

This bed sits on a concrete library balcony. It’s about 16 inches deep and is growing a nice crop of tomatoes. Notice the perlite (white specs) in the soilless growing medium. Photo credit: UME Master Gardeners, Frederick Co.

Some tips and caveats:

  • Submit a soil sample to a soil testing laboratory if you will be using the existing soil (more accurate and complete and usually less costly than DIY soil testers). Pay for a basic soil test and have the lab test the soil for leadif you plan to grow food in your raised bed. The lab will send back results (soil pH, nutrient levels, etc.) and fertilizer and soil amendment recommendations.
  • Topsoil sales are not regulated in Maryland. Go to a reputable nursery or topsoil dealer and ask questions about where the soil comes from, how it’s been treated, and soil test results. Examine the soil before purchase or delivery. Topsoil should be dark and crumbly with an earthy smell. Do not purchase if the soil is foul smelling, has grayish mottling or a chalky texture. Some sellers have a mix of topsoil and compost which can make an excellent growing medium for raised beds.
  • Minimize the amount of digging and tilling needed to prepare the soil for planting. Disturbing the soil brings weed seeds to the surface where they can more readily germinate.
  • Over time the quality of the native soil below the raised bed will be improved through the addition of organic matter and root growth of crop plants.
  • Organic matter improves the structure of soils that are high in clay so that roots can better grow and take advantage of available water, air, and nutrients. It can be grown (cover crops and living plant roots), added as fresh organic materials (manure, grass clippings, leaves), or added to soil as compost. You need 3 cu. yds. of compost to add a 1 in. layer to 1,000 sq. ft. of ground or 8.33 cu. ft. (12, 5-gallon buckets) to cover 100 sq. ft.

 

By Jon Traunfeld, Extension Specialist

Garlic Mustard – Invasive Plant in Maryland – Featured Video

Professional Horticulturist Ellen Nibali identifies garlic mustard (Alliaria petiolata) and explains how to remove this invasive plant from your garden. This plant is popping up in Maryland right now, so be on the lookout!

Take a look at our Invasive Plants playlist on YouTube.

Q&A: How Can I Make a Naturalistic Garden Look Intentional?

blue sedge

Blue sedge. Photo: Ellen Nibali

Q: I would like to plant a more natural garden but am worried about irritating the neighbors who might think it is sloppy or not a garden at all! Any advice?

A: Make a natural garden look intentional. Here are three major design tips to make a garden’s intent obvious:

1) Give it obvious edges. Edges can be botanical, such as a row of blue sedges (pictured) or can be hardscapes such as pavers, bricks, a path, low wall, or low fencing.

2) Give it an obvious shape. This can be geometrical lines and angles (circle, triangle, parallelogram, etc.) but also can be flowing lines made obvious with big or repeated curves.

3) Within the beds, make plant choices obvious. Use blocks or ribbons of plants, repetition of key species, or a predominant plant family (e.g. grasses) with a few other species mixed in. Of course, banish all invasive plants. Use at least 70 percent native plants.

By Ellen Nibali, Horticulturist, University of Maryland Extension Home and Garden Information Center. Ellen writes the Garden Q&A for The Baltimore Sun.

Do you have a gardening question? University of Maryland Extension experts have answers! Send your questions and photos to Ask an Expert.

Have Your Garden and Travel Too!

I’m going on a trip next week! It’s a big trip; I’m very excited. Lots of new experiences, wonderful things to see, delicious things to eat, relaxation and exploration. I feel very lucky.

And let me just add: it was not my idea to travel in April, and I’m never doing it again. It’s spring! It’s gardening time! There are so many tasks that won’t get done, so many flowers I’ll miss seeing bloom. Being away now throws my schedule off for months. But so it goes: for this year, I have to adapt.

IMG_5140

None of us who are able to take vacations want to miss out, but we also want our gardens to keep growing while we can’t care for them. Given that we can’t take the plants along with us, how to cope? Let me toss out some ideas, and you can add your thoughts in comments. Read More

Monthly Tips for April

galls on Virginia cedar

Outdoor Garden and Yard Tips

  • Cedar-apple rust disease forms its galls on Virginia cedar (Juniperus virginiana) in April. The odd-looking galls are at first bright orange gelatinous balls with long “horns” or projections; they later turn brown and become hard. They are the alternate host structure for a disease that does very little harm to the junipers but can be quite destructive to apple trees, hawthorns, and quince.
  • Continue planting and transplanting trees and shrubs.  Choose quality trees: shade trees should have a single, straight trunk. Planting and transplanting should be completed before the end of June.

    Eastern Box Turtle

    Eastern Box Turtle

  • Viburnum leaf beetle is a serious pest of native arrowhead viburnum, cranberry bush, and many others. Look for feeding damage on viburnum and yellow larvae. Control them promptly since they can defoliate plants. Repeated defoliation can result in the death of native viburnums.
  • Eastern box turtles and various species of snakes are coming out of hibernation and may visit your yard. Box turtles are becoming scarce through much of Maryland because of road mortality and habitat destruction. Observe it but leave it in the wild.

Read More

Boxwood Blight in Maryland

Until last summer most people in Maryland weren’t aware of the new fungal disease infecting boxwood called boxwood blight. In 2011 professionals in the green (landscape and greenhouse) industry were informed of the disease but the outbreaks were scattered and insignificant. However, the rainy 2018 season greatly increased the spread of the disease. It has now become more noticeable in Maryland landscapes. In addition, on a few occasions, it has been observed on Japanese spurge (Pachysandra terminalis) in Connecticut and on sweetbox (Sarcococca sp.) in Maryland and Virginia. Essentially, boxwood blight occurs up and down the east coast.

Boxwood blight will infect all boxwoods grown in landscapes. However, some cultivars, especially English and American, are more susceptible than others. See the following photos for symptoms of boxwood blight.

boxwood blight leaf lesions

Dark leaf spots are a symptom of boxwood blight. Photo: Dave Clement

boxwood blight stem lesions

Narrow black lesions (cankers) on green stems are a key symptom of boxwood blight. Photo: Dave Clement

boxwood blight lesions on dead stems

Black lesions on stems of boxwood. Photo: Dave Clement

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So the question is what to do if your shrubs are diagnosed with boxwood blight? The best information for homeowner action is located on the Virginia Boxwood Blight Task Force website: Best Management Practices for Boxwood Blight.

Here is a quick summary of what to do in the landscape:

  • A strong suggestion is to avoid planting any new boxwood plants in your existing landscape or bringing in boxwood greenery, including holiday boxwood wreaths.
  • If planting, inspect your plants carefully and ask if the plants have been raised in a certified “cleanliness program.”
  • Observe and watch any newly planted boxwoods carefully for disease symptoms.
  • Send photos of suspicious symptoms to the Home & Garden Information Center’s Ask an Expert service.
  • If disease symptoms are diagnosed, immediately bag and remove infected plants along with fallen leaves. Mulch the area to bury remaining debris. Do not compost infected boxwood material. Launder all clothing, gloves, and shoes, and sanitize gardening tools.  Removal will not guarantee eradication of the boxwood blight pathogen since it can survive in resting structures in the soil for many years.
  • Fungicide sprays have shown some disease suppression in limited situations. However, these treatments do not eradicate boxwood blight and need repeated applications throughout the growing season.
  • Consider replacement of boxwoods with non-susceptible plants such as hollies and conifers.

By Dr. Dave Clement, Principal Agent, University of Maryland Extension, Home & Garden Information Center. For plant disease and pest updates, follow Dr. Dave on Facebook

Spring Lawn Care Tips & Bay-Friendly Lawn Workshop

Spring appears to be on schedule for most of Maryland as temperatures are slowly creeping up into the 50’s and 60’s for highs. One of the temptations for homeowners is to fertilize the lawn “to get the grass going” in the spring. Keep in mind that “spring green-up” is largely related to soil temperatures and, to some degree, whether fertilizer was applied in the fall. Fertilizing with the goal of getting the grass to “wake up” sooner will have a minimal effect since soil temperature is the main driver for this.

lawn grass

Spring “green-up” is largely related to warming temperature. Most fertilizing for the year should be done in the fall. Photo: Pixabay

Also, keep in mind that fertilizing in the spring favors more shoot and leaf growth at the expense of root growth. (Fertilizing in the fall tends to favor root growth. Most of the fertilizing for the year should be done in the fall.) Spring fertilization should consist of ~1 lb. nitrogen/1000 sq. ft. total in spring. Using a slow-release fertilizer or splitting applications into two 1/2 lb. rates spaced about one month apart should help to limit excessive growth that could add to the increased mowing frequency often necessary in the spring. Read More