Rock gardens emulate rocky, high mountain environments where plants are exposed to tough conditions like intense sun, harsh winds and drought. In the home garden, a rock garden generally consists of an arrangement of native rocks, boulders and pebbles with carefully selected, low-growing plants nestled into narrow spaces and crevices.
Although rock gardens are sometimes located on sunny, open areas, they are often created where they add beauty and stabilize the soil on difficult slopes or hillsides. Speaking of soil, what can be found in a rock garden soil mixture? Read on to learn more.
Soil for Rock Gardens
If you’re creating a rock garden on level ground, begin by marking the perimeters of the garden with spray paint or string, then dig down about 3 feet (0.9 m.). Soil prepping a rock garden bed consists of creating three separate layers that promote good drainage and a healthy foundation for your rock garden plants. Alternatively, you can mound soil to create a raised bed, berm or hill.
- The first layer is the rock garden’s foundation and creates excellent drainage for the plants. This layer is simple and consists of large chunks such as old concrete pieces, rocks or chunks of broken bricks. This foundational layer should be at least 8 to 12 inches (20 to 30 cm.) thick. However, if your garden already has excellent drainage, you may be able to skip this step or make a thinner layer.
- The next layer should consist of coarse, sharp sand. Although any type of coarse sand is suitable, horticultural-grade sand is best because it is clean and free of salts that may harm plant roots. This layer, which supports the top layer, should be about 3 inches (7.5 cm.).
- The uppermost, all-important layer, is a soil mix that supports healthy plant roots. A good rock garden soil mixture consists of approximately equal parts good quality topsoil, fine pebbles or gravel and peat moss or leaf mold. You can add a small amount of compost or manure, but use organic materials sparingly. As a general rule, rich soil isn’t suitable for most rock garden plants.
Mixing Soil for Rock Gardens
Rockery soil mixes are as simple as that. When the soil is in place, you’re all set to arrange rock garden plants such as perennials, annuals, bulbs and shrubs around and between the rocks. For a natural appearance, use native rocks. Large rocks and boulders should be partly buried in the soil with the orientation of the grain facing the same direction.
Mixing compost with soil is an important step in preparing your garden. Adding organic material, such as compost, offers many benefits, including increasing the soil’s ability to hold water, decreasing compaction, regulating the temperature of the soil, promoting the growth of beneficial organisms and adding nutrients.
It is one of the most cost-effective ways to add organic material to your garden. Whether you make compost at home or purchase it from a garden center, adding the right amount of compost to your soil helps to create the ideal medium for your new garden to thrive.
In general, add about 2 inches of compost to the top 6 inches of soil. In some cases, you may need to add more, but this depends on your soil type and fertility.
Evaluating Soil Needs
Adding organic material not only adds nutrients but it also improves soil quality. If you have clay soil, then it is difficult for water to drain and for plant roots to grow. Sandy soil, on the other hand, doesn’t hold water or nutrients, making it difficult for many types of plants to thrive. However, there are other considerations before you begin amending your soil for planting.
If you are planting for the first time, it is a good idea to get a soil test through your local cooperative extension office. It will evaluate the soil sample and make recommendations based on the results. If you have fertile soil that has a good texture, you will only need minimal compost. However, if your soil lacks fertility, you may need to add nutrients to the soil along with compost.
Another thing the soil test will reveal is the soil pH. Most vegetables and flowers grow best when the soil pH is between 6.2 and 6.8, advises PennState Extension. If your soil falls outside that range, you will also need to correct the soil pH. Plants are not able to access the nutrients from the compost and fertilizer if the pH is too acidic or too alkaline. Ideally, get a soil test every three to five years.
Best Compost for the Garden
There are several types of compost you can add to your garden. Leaf mulch, or the leaves from deciduous trees, is one form of compost that incorporates several important nutrients, including boron, calcium, magnesium, phosphorus and potassium, advises Clemson University Cooperative Extension Service. Leaf mulch can also be added without composting but you should wait to plant whenever you add fresh organic material to the soil.
Composted manure adds nitrogen, phosphorous and potassium, but this can be high in salt. You can minimize the risk of plant root damage by mixing it with another type of compost or by adding gypsum to the compost. Fresh manure should not be used on vegetable plants and may contain herbicides and high amounts of ammonium.
Garden compost consists of yard scraps, such as leaves, grass clippings and brush. It only contains low levels of nitrogen, phosphorous and potassium. Many gardeners compost other items, such as eggshells, coffee grounds and fruit and vegetable scraps that can also be added to your garden.
Add Compost to the Soil
You can purchase compost at your local garden store or use what you have composted at home. One combination recommended by Clemson University Cooperative Extension Service is to use one part composted manure, one part shredded bark or soil conditioner and three parts garden compost.
When initially mixing compost with soil, start by adding 2 inches of compost and mixing it into the top 6 inches of soil. You can add more if needed to correct soil texture or as recommended by your soil test but do not add more than 4 inches of compost, advises Texas A&M AgriLife Extension. Mix it into the soil using a tiller or a garden spade. Take care not to till too much, as this can break down soil particles and cause soil to become compacted.
If you want to use compost on already-established plantings, you can use it as a top-dressing. It is also an effective amendment for your lawn to help repair bare spots.
Purchasing Compost for the Soil
If you don’t make compost at home, you can purchase bags of compost to use in your garden. Before you head to the store, make sure you know how much you need to buy. Determine how many cubic feet you need to fill. You can do this by first dividing the number of inches of compost you want to apply by 12. Then, multiply the length of your garden by the width of your garden by the result of your first calculation, advises Texas A&M AgriLife Extension.
For example, if you are adding 3 inches of compost, divide 3 by 12 to get 0.25. If your garden in this case is 10 x 10 feet, you will multiply 10 by 10 by 0.25, which gives you the result of 25 cubic feet. Compost is generally sold in 1- or 2-cubic-feet bags, so when you get to the store, you know exactly what you need.
Other Soil Amendments
While compost may be one of the best organic soil additives, your soil may need additional amendments depending on the results of your soil test. If your soil is too acidic, you will need to add lime to the soil. Lime contains calcium, which also helps to improve clay soil. Use the results of your soil test to determine how much lime to add to the soil. Be sure to wait several months before planting, as the pH will take some time to adjust.
In some cases, the soil may be too alkaline. This can happen when you have a lot of lime in your natural soil or when you want to grow acid-loving plants, such as blueberries (Vaccinium spp.). In this case, you need to add sulfur to increase soil acidity, following the soil test results and recommendations. Elemental sulfur is usually the best option since it is cost-effective, works quickly and adds sulfate to the soil, which is a necessary nutrient for plants, advises North Carolina State University Cooperative Extension.
You can also consider adding mulch to the top of the soil after planting. This helps to maintain soil moisture, keep soil temperature stable and reduce weed growth. In addition, mulch slowly adds organic material to the soil as it decomposes throughout the year. Mulch is usually sold by the cubic yard. Calculate how much you need by taking the number of cubic feet that you calculated and dividing that by 27.
- PennState Extension: Soil Management in Home Gardens and Landscapes
- Clemson University Cooperative Extension Service: Soil Conditioning – Establishing a Successful Gardening Foundation
- Texas A&M AgriLife Extension: Soil Preparation
- Texas A&M AgriLife Extension: How Much Compost, Soil or Mulch?
- North Carolina State University Cooperative Extension: Calculating the Rate of Acidifiers to Lower the pH of North Carolina Soils
Maureen Malone has been a professional writer since 2010 She is located in Tucson, Arizona where she enjoys hiking, horseback riding and martial arts. She is an outdoor lover who spends her weekends tending her raised garden and small orchard of fruit trees.
Allyson from Kennesaw, GA raised a question about the best vegetables for growing in a small garden area: “I am a first time gardener and I don’t know what to plant that will not over load my very limited garden space.”
“After reading your site, I have determined I could handle a few bush green beans, and some lettuce. I will plant zucchini in a couple of separate deep containers, but really want to plant some potatoes and onions.”
“I did plant some green onions in a pot plant container. Thank you for having such a well done site, full of needed and helpful information.”
Organizing and Arranging the Small Veggie Garden
You’re very welcome Allyson, and I’m glad that you found this site useful and informative in growing your first garden, and hopefully many, many more! There are plenty of vegetables that are suitable for planting in a container, EarthBox, or even the tiniest back yard garden.
If space is at a premium then I would focus on crops that grow lower to the ground, that way you can keep the entire growing area open to receive full sunlight and avoid shading any of the limited growing space that you have available.
Check the path that the sun tracks across your garden and arrange taller plants along the rear or edges of the garden where they won’t block sunlight from reaching the shorter veggies. Situate your spreading and climbing plants where they can grow up a building, across a path, or spill over onto adjacent lawn areas.
Selecting Vegetables to Grow in a Limited Amount of Space
Leafy greens such as kale, spinach, and mustard will do well in a small garden and provide you with good production over an extended period of time. Another leafy vegetable that would work great is lettuce, especially the loose leaf varieties. The greens can be kept harvested to confine the plants to a smaller growing area.
Beets and turnips would make good selections as they don’t take up much space and would perform double duty by yielding a harvest of nutritious greens in addition to the delicious roots that are dug as the plants mature. Carrots and radishes are other great options when space is in short supply in the vegetable garden.
Other veggies to consider for a small garden area include: Swiss Chard, shallots, potato onions, celery, oriental vegetables, arugula, tatsoi, and even garlic. If there are empty gaps here and there throughout the garden you can fill them in with individual herb plants or edible flowers such as calendula, borage, or nasturtiums.
Tips to Double Your Garden Space Overnight
There are all sorts of herbs that can be planted in containers and moved around as you please. And a lack of space doesn’t mean that you can’t grow some fruit or berries. Try raising strawberries in a strawberry jar, plant a fig tree in a container, or grow a compact blueberry bush in place of ornamental shrubs.
Irish and Fingerling Potatoes tend to sprawl and take up too much precious space, but some gardeners will stack tires or make a cylinder out of fencing and continue to fill in these make shift containers with additional soil as the potato vines grow taller. Once the vines mature and die back remove the tires or fencing and harvest loads of spuds.
Take advantage of any opportunities that you may have to grow vines and climbing type plants skyward, or along the side of a structure. You’ll get more production in a small area by growing pole beans than you would from bush beans if you have a way to trellis them. And growing vertically may also provide the opportunity to grow cucumbers, melons, and other space hogs in a garden that is cramped for growing room.
Probably the best way to put your small space garden to more efficient use is to grow it in a raised bed type pattern rather than to sow your garden in the typical row format. Using raised beds or planting in a grid format allows you to grow plants closer together and to utilize more of your growing area, instead of losing precious garden territory to pathways and empty, unproductive space between rows.