Soil Preparation
for the Organic Vegetable, Flower, and Herb Gardening
We actively grow a vegetable garden here at The Natural Gardener 365 days a year. What began as a heavy clay soil in 1993 has been transformed into a deep, rich “chocolate cake” texture that supports an abundance of produce year-round. Many visitors ask us how we sustain such a beautiful garden. The key to successful gardening starts with the health of the soil.
Following are the methods and materials that we use in our vegetable garden, along with alternatives. There are many different ways to be successful at organic gardening. Try various routes to find the ones that generate the most success. These recommendations can also be applied to growing annual and perennial flower gardens, as well as herb gardens. However, herbs and native perennials prefer less fertilizer. Experiment and enjoy!
Evaluate the planting site, add organic matter, and create depth
Ideally, a vegetable, flower, or herb bed should consist of amended soil at least 8 inches deep – the deeper the better. Only dig in the soil when it is slightly moist. Working the soil when it is too wet or dry can ruin the soil texture for years. The guideline is to only work the soil when it has a moisture level like that of a wrung-out sponge. Preparation depends on the kind of soil in the area:
- Deep, Blackland Prairie soil, “Builder’s Clay”, or any soil deeper than 5-6” – If there is sufficient soil, add compost to amend it. Residents of the east side of Austin will likely have a rich, deep, black clay as their native soil. A hefty amount of good quality compost should be worked into the soil prior to planting vegetables, annual flowers, or herbs. For example, add six inches of compost and mix into the top six inches of soil. For native perennial flower beds, far less compost is needed, if any; it depends on the natural growing preferences of the plant.
- Thin, Edwards Plateau Soil – Residents on the west side of Austin, probably have a very thin layer of native soil on top of solid limestone or caliche. A raised bed is needed for vegetable, flower, and herb gardens. Sides can be constructed out of cedar, other untreated lumber, cinder blocks, rock, or other non-toxic materials. Add compost to whatever existing native soil, as described above. Then, add a quality prepared soil to create a bed with a total depth of at least 8 inches. Slightly mix in the new garden soil to the native soil below to make the bed more homogeneous.
Veggies are heavy feeders! Apply a dry organic fertilizer, trace minerals, and beneficial streptomyces.
After the soil has the proper depth and right proportion of organic matter, it is time to add more nutrients. Vegetables and annual bedding flowers are heavy feeders, and need additional organic fertilizer. Mix a dry organic fertilizer into the top 4” of the soil before planting veggies and annuals.
Look for the proper ratio of nitrogen (N), phosphorus (P), and potassium (K) to get plants off to a good start. Generally speaking, plants use:
- Nitrogen to produce leafy growth
- Phosphorus to form new roots, flowers, and fruits
- Potassium for general health and stress tolerance
A soil test will provide the most accurate guideline for choosing a good fertilizer. Young plants and seedlings will benefit from a fertilizer with a good supply of nitrogen. When planting fruit-bearing vegetables such as tomatoes, and the soil test does not indicate an excess of phosphorus, make sure the fertilizer provides a good amount. As the plants mature they will require it to produce fruit.
At the same time, mix in a quality mineral supplement to add much-needed trace minerals. Another great step in improving the soil before or after planting is to drench the soil with a soil activator. To maintain soil health, apply once each season.
As an added insurance against common soil diseases, especially those that affect tomatoes, and for improved root development in any plant, also work beneficial streptomyces (ask for Actinovate) into the soil.
Now for the fun part – it’s planting time! Plant the tallest vegetables on the north side of the bed and the shortest on the south side.
When planting seed, spread a thin layer of worm castings on top of the soil before planting to help germination. Seeds must be kept moist until they sprout. Even the briefest period of dryness can spell death for a new seedling. Water lightly but frequently – multiple times each day in warm weather.
All vegetable, flower, and herb transplants, except for tomatoes, should be planted with their rootball level with the garden soil. Tomato transplants can be planted deeply – the stem may be buried in the soil and will produce more roots. Firm the soil gently around each planting, and water in immediately. The finishing touch: add two or three inches of mulch. Mulch holds in moisture, keeps out weeds, moderates soil temperature, keeps soil softer, keeps plants clean, and can help prevent some diseases. We use pine straw mulch. It is easy to move around when changing the vegetable garden with each season; it decomposes into a rich soil amendment, and it looks nice. Always remember to rake back the mulch before planting anything or amending the soil; do not mix mulch into the soil.
Finally, after the initial watering, you can follow up with a solution of fish emulsion. Fish emulsion is a mild fertilizer and a wonderful starter tonic for seeds and transplants, as well as a regular boost to the growing garden.
Voila! Now you have a wonderful new vegetable, flower, or herb garden!
Try planting by the moon, too! Plant vegetables that produce above ground (e.g. tomatoes, broccoli) when the moon is waxing, and vegetables that produce below the ground (carrots, potatoes) when the moon is waning. In addition, plan ahead for crop rotation. Crop rotation means that, for example, members of the tomato family should not be planted in the same area for two years. This helps to prevent the buildup of diseases and pests that are common to a particular vegetable family. Therefore, it is best to plant all members of the same family in a block together, and plant them in a different location for the next two years. See below for a table of the different vegetable families
Beet Family
Chenopodioideae
- Beet
- Lamb’s Quarters
- Spinach
- Swiss Chard
Crucifer Family
Brassicaceae
- Broccoli
- Brussels Sprouts
- Cabbage
- Cauliflower
- Collards
- Kale
- Kohlrabi
- Radish
- Turnip
Gourd Family
Cucurbitaceae
- Cucumber
- Melons
- Pumpkin
- Squash
Nightshade Family
Solanaceae
- Eggplant
- Pepper
- Potato
- Tomato
Every four to six weeks during the growing season, fertilize vegetables again using an organic dry fertilizer. If a soil test indicates a need for phosphorus, or if you’re growing summer veggies such as tomatoes, add an organic fertilizer higher in phosphorous. In addition, it is a good practice to foliar feed veggies and flowers with seaweed or fish emulsion, early morning or late evening. Regular foliar feeding can help prevent diseases and pests, and stimulate flowering and fruit set. Spray two to four times a month for best results. It is also helpful to drench the soil with these products while you’re at it. Foliar feed herbs once a month with seaweed, and apply compost twice a year as their only maintenance. The same holds true for native perennials. For additional nutrition, apply organic dry fertilizer in spring and fall.