Test your soil
important step to growing healthy vegetables is providing healthy soil. Make
this a priority in your first year of gardening.
- From a DC Master Gardener: "Even if the only thing
you accomplish in your first year of gardening is building a great soil, you
will be ahead of the game and richly rewarded later. Before planting
anything, have your soil tested by a reputable soil laboratory. Do not try to do
this yourself with one of the amateur kits sold at garden centers. You need a
thorough assay of the structure and nutrients in your soil, as well as any
hazardous materials. Urban gardeners should be concerned about the potential for
heavy metals or other toxins in their soil, especially lead and arsenic. Lead in
soil is almost a universal condition in urban areas, especially near older
buildings that might have shed lead paint and near heavily trafficked roadways,
where lead in automobile exhaust has drifted into yards. Purchasing soil for a
new garden or raised beds is no guarantee that it is pure. The potential danger
of lead being taken up by vegetables is highest in leafy greens and root
vegetables. Lead does not appear to be a problem in fruits or fruiting
- From another DC gardener: "By far the most dangerous aspect of soils with
high lead levels is airborne contamination, inhalation, oral ingestion from
hands touching lead-laden plants, clothes, shoes, etc." Lead is very stable and
therefore difficult to remove from soil. Brassica plants (e.g., broccoli,
cauliflower, cabbage, brussels sprouts) tend to take up more lead than others,
so brassicas (and all root crops) might not be the best choice in soils with
lead. "I recommend the University of Massachusetts soil testing lab." It’s
inexpensive and you can get information and recommendations on soil fertility,
pH, toxins, etc. In soils with high lead levels, take precaution and do not
plant directly into the soil. Use raised beds (high enough to keep roots away
from lead-laden soil). To create a good soil mixture inexpensively, use the
"lasagna gardening" method (described in more detail below).
- Another DC gardener adds: "There is no agreed-upon definition of top soil
and no standards. Even within a brand, unlike with potting soil, there’s no
standard or consistency. The last time I looked at the ingredients of top soil
at Home Depot and Lowe’s, fly ash was one of the main ingredients. I’d never
want to grow vegetables in that (probably contains lots of heavy metals). I grow
vegetables in raised beds with pure compost made by me. But I still get my soil
tested (but not the compost)."
- If you have concerns about lead in your soil, make sure to thoroughly wash
and peel root vegetables before eating.
- Not all soil labs test for lead. Check with the lab before sending in your
sample. The Maryland Cooperative Extension has a list of regional soil test labs
on its website.
- A basic soil test will also help you determine the soil’s pH and nutrient
levels. Soil pH governs the uptake of nutrients by plants. Vegetables grow best
in soil that has a pH between 6.0 to 7.5 (around 6.8 is ideal).
- From a DC Master Gardener: "Plants need certain macro-nutrients to thrive,
especially nitrogen, potassium and phosphorous. A professional soil test should
indicate whether your soil contains adequate levels of these nutrients. The test
should also indicate the level of vital micro-nutrients, especially calcium and
magnesium. Even more important is "saturation percentage" of calcium and
magnesium, and the relative saturation of one to the other. The desired range is
65% to 75% for calcium and 10% to 15% for magnesium."
- Test your soil once every three years.
- Organic Gardening’s website has a good section on Understanding Soil.
to I prepare my location for planting?
- Remove stones, grass, weeds. Check the consistency of your soil. A squeezed
handful of soil shouldn’t clump (too much clay) or crumble (too sandy).
Vegetables grow best in soil that‘s rich
in organic matter (a minimum of 5%). You can improve soil by
adding compost, aged manure, and other amendments such as lime, bone meal, etc.,
(based on the results and recommendations of the soil test). Bags of compost can
be purchased at garden centers and nurseries, but that gets expensive quickly.
Some places offer compost in bulk; you can buy it by the truckload. In Maryland,
Pogo Organics offers this service. To save money,
build a compost pile of your own. Read the DC Urban Gardeners primer on
County Maryland residents can get a free basic compost bin from the Department
of Environmental Protection. If you don’t have a yard our outdoor space for a compost bin, consider setting
up an indoor vermicomposting ("worm composting") system to turn your food scraps
- Don’t want to dig up sod? Try Lasagna Gardening or Sheet Composting. Lay
down sheets of wet newspaper or cardboard followed by layers of other organic
materials (grass clippings, leaves, soil mix, straw). These layers will
eventually "smother" the existing vegetation where you want to plant.
- Build raised beds. Raised beds tend to have better drainage, and the soil
warms up faster in the spring so you can plant a little sooner.
When can I plant?
The District of Columbia is in
USDA Zone 7A. The average last frost is around April 15, and the first frost in
the fall is usually around October 15. Based on these dates, you can make a
- Many gardening books provide a basic month-by-month calendar of "what to
plant when." A good one is Rodale’s Almanac & Pest-Control Primer.
- A good online resource for planning is the Weekend Gardener Grow Guide.
- Washington Post online has a basic month-by-month gardening calendar.
- Washington Gardener E-News also provides monthly reminders. Sign up here for the newsletter.
- Maryland Cooperative Extension has a free fact sheet, "Planting Dates for
Vegetable Crops in Maryland".
- Cool season plants — peas (sow as early as February/March), radishes,
- Warm season plants — tomatoes, peppers, basil, eggplant — should only be
transplanted outside after all danger of frost. Usually after Mother’s Day, it’s
safe in our Zone 7A.
- Last season crops — in July plant seeds of lettuce, arugula, carrots,
beets, chard, kale. These do well in cool weather, and some plants overwinter in
- In October – plant garlic, onions. They’ll overwinter and you can harvest
them next summer.
- Extend the season by creating a cold frame to protect plants from
Where can I get seeds and
Purchase plants at local nurseries such as American Plant Food
Company and Behnke’s. They’re likely to have a better selection — and healthier
plants — than big-box stores such as Home Depot. Avoid plants that are getting
long and lanky or yellowish. For the best variety, and/or to save money, many
vegetable gardeners prefer to start plants from seed.
- Seed Exchanges and Plant Swaps. Check out Washington Gardener
magazine’s annual Seed Exchange (January). Neighborhood gardening clubs also
hold plant swaps occasionally (find a DC-area garden club here. Go online
to exchange seeds at Garden Web or use the Garden Online’s Seed Exchange. Ask your
neighbors for seeds or transplants. Post a message to your local Freecycling
group and see if anyone in your
neighborhood has the seeds/plants you’re looking for. Gardeners like to share!
- Seed Catalogs. Good ones for vegetables are Seed Savers Exchange, Seeds of
Change, Baker Creek Heirloom Seeds, Fedco Seeds, Vermont Bean Seeds Company.
They will send you a free catalog for the asking, or just place your order
- D. Landreth Seed Company has a good selection of seeds for patio gardeners.
- America the Beautiful Fund offers grants of free seeds to community groups.
What about plant pests and
Plants are susceptible to viruses, parasites, and diseases.
The following resources can help you determine what’s bugging your plants, and
what to do about it.
- Maryland Cooperative Extension answers plant and pest questions. Call their
free hotline, Monday – Friday, 8 am – 1pm, at 1-800-342-2507. Outside of
Maryland, call 1-410-531-1757.
- The Brooklyn Botanical Garden staffs a Gardener’s Resource Center to vet
questions. The hotline is 718-623-7270.
Start small, go easy! A single zucchini plant
can provide enough zucchinis for two people for an entire summer. It’s easy to
plant too much at first and then become overwhelmed with the chores of watering,
weeding, harvesting, soil amending, etc. Vegetable gardening takes effort, and
it’s extremely rewarding when you succeed. A great resource for determining
how much to plant (and how) is Mel Bartholomew’s Square Foot
Gardening. Also, consider starting with some of the easier-to-grow plants:
lettuce, Swiss chard, kale, radishes, squash, cucumbers, carrots, turnips,
beans, basil, thyme.
- DC’s 7th Street Garden offers clinics on growing vegetables.
Consider volunteering at the Washington Youth Garden, located in the
National Arboretum. They have a large piece of land under cultivation with all
kinds of different vegetables and people who can teach you the best
- The New Seed-Starters Handbook is an excellent book with information
on growing garden vegetables from seed, how to set up a cold frame to extend the
season, and how to save seeds from year to year.
- National Gardening Association publishes an online newsletter for urban and
small space gardeners and another on how to
grow edible landscaping.
- Kitchen Gardeners International has an online
forum and blog for food gardeners.