Dry gardening community science

How can you grow tomatoes and melons in a home garden with limited water?

By Ann B., Master Gardener Volunteer

Volunteers measure a soil core to see if the soil is deep enough for dry gardening. Credit: Benton County Master Gardener Association

OSU Extension, with Amy Garrett, has been developing the protocols and plants to garden without irrigation.  Not only will this allow gardening in the ever-increasing years of drought, but it also can save on water bills.   So, a project was started at the Master Gardener volunteer demonstration garden to determine whether vegetables can be grown in the home garden without watering. 

First we used an auger to remove a soil core from our plot to determine if we had at least 4-6 feet of soil.  Our soil was deep enough and contained clay as well.  Organic-rich soils with some clay content have more water-holding capacity.  Shallow or sandy soils are not amenable to dry farming.  Before planting, the soil was tilled, some organic fertilizer and organic matter was added and the area was soaked.    Plants were placed at least twice as far apart as usually indicated.  We planted ours 6 feet apart.  The soil was gently packed around the transplants and 2-3″ mulch was placed on top.  During the summer we did not water at all, removed weeds regularly and did not walk on the area so that the soil was not compacted.  Despite having a very warm summer (above 100F for a week), we harvested lovely Early Girl tomatoes.  Subsequent years we harvested Dirty Girl tomatoes and melons. 

Volunteers install tomato plants for dry gardening experiment. Credit: Benton County Master Gardener Association

During our first summer we noticed that one plant was much bigger than the other two.  We had several theories of what caused it, from it getting less wind to being a hybrid planted by mistake.  In the fall, at the end of the season, when we were removing the dead plants, we solved the mystery.  This was a very clever plant.  It grew a very long thick root that grew over about 6 ft. to a nearby bed that was watered.  Therefore it was not really participating in the experiment!  In subsequent years we did not irrigate that near-by bed. 

Amy Garrett, OSU Extension Service, has run experiments on many other plants.  These are some that she has determined do well with dry farming: Stupice and Perfect Rogue tomatoes, Beefy Resilient beans, Sweet Freckels melon, Eel River  and Christmas watermelon, Zeppelin and Delicata winter squash, Dark Star and Costa Romanesco zucchini.  And there are varieties of potato, dry beans, and grapes that will flourish.  Although we did not do this, using a cover crop over winter, especially a legume such as crimson clover, will add organic matter and increase nitrogen availability.

Growing tomatoes with dry gardening system. Credit: Benton County Master Gardener Association

Tips for success

  • Don’t plant where there is competition for water from trees or other plants.
  • Don’t plant on a slope.
  • Raised beds are not ideal as they dry out faster; sunken beds work the best.
  • Try to find a place protected from wind, which causes plants to lose water quicker.
  • Use plants as indicators of where you have the most water. Notice which plants are still green and lush in August. They’re telling you where deep soil with water-holding capacity exists.
  •  Maintain a neutral pH of 6.5 to 7. Most soils in the Willamette Valley will need an application of lime.
  •  Timing is key. Plant when is not too wet or too dry. It’s tricky, but the important thing to remember is to plant when there’s still moisture in the top profile of soil.
  • It’s possible to use little or no water and have a productive garden. It’s an important technique when you’re trying to save resources, and water is one of the biggest issues.

Resources

  • OSU Extension- Small Farms Dry Farming Demonstration: http://smallfarms.oregonstate.edu/dry-farming-demonstration
  • Runsten, D. and Mamen, K- Introduction to Dry Farming Organic Vegetables.
  • CA Agricultural Water Stewardship Initiative 10 Nov 2014 http://agwaterstewards.org/index.php/practices/dry farming
  • Solomon, Steve- “Gardening Without Irrigation: or without much anyway”, 2013
  • Widtsoe, John-“The Better Days Books Origiganic Guide to Dry-Farming: A Complete System for Achieving Bountiful Harvests Where Rain is Scarce, and Without Irrigation”, Nov. 2008
  • Widtsoe, John- “Dry Farming: A Guide for Farming Crops Without Irrigation in Climates with Low Rainfall and Drought”, 2018

Less water, successful veggies

By Diane Hyde, OSU Extension Master Gardener Volunteer

Credit: Markus Spiske. Indeterminate (vine) tomatoes, especially earlier-producing small cherry varieties, produce flavorful fruit in a dry garden.

Summers are getting hotter and drier while water is getting more expensive. Some vegetables can produce acceptable yields successfully with no supplemental irrigation with some careful planning. Not all vegtables are suitable for dry gardening, and not all locations will support gardens without water. Dry farming has been done for millennia, and knowledge of the practice has been passed on in a few farming families and cultures.

Oregon State University Extension Dry Farming Project has focused on management strategies to grow with little or no irrigation. Yields may be 25% to 50% less than irrigated crops because plants are spaced out farther apart. Each plant can still have good yield, so a family dry garden might take more space to provide as much produce. Produce grown without irrigation has often been judged to be more better in color, texture and sweetness in taste comparisons. 

Successful dry gardening requires soil that will retain spring rain water. Clay soils and organic humus will hold seasonal moisture, but if the underlying ground has rock that drains well then water will not be available for the summer. Four feet of moisture-retentive soil is recommended. Shallow, rocky or sandy soils may not hold enough water for decent crop yields. The climate should have a wet period, like ours, that provides lots of moisture prior to the dry period. The dry garden area should have no competing trees, shrubs or turf sucking up the water before the vegetables can get it.

Sloped land holds less water than flat land. South-facing gardens lose more water to evaporation than north-facing gardens. A windy garden site will lose water from plant leaf evapotranspiration. A site that grows good weeds or healthy blackberries with no irrigation may be a good place to transform into a dry garden. 

To dry garden in summer, plant as early in Spring as possible to take advantage of seasonal rain. Soil in our area can often be prepared as early as February to April, but frost dates and soil temperatures limit which veg will grow that early. Seeds need to be planted in wet soil, deeper that the seed packet recommends if the surface has dried. Pre-soaking seeds 24 hours before planting helps them germinate and establish more quickly. Transplants may need to have all but the top leaves removed and the stems buried as deep as possible. Mudding in the plants at planting, filling the hole with water, will get the roots started well so they can deal with no more irrigation. 

Roots will reach deeper and wider in a dry garden, so more space per plant will be required, probably at least twice the space recommended on the seed packet. Because there is less water applied to dissolve ground minerals, lime applied to the soil before planting helps prevent blossom end rot in tomatoes, squashes, peppers and other veg that require more calcium. Mulches applied deeply after the plants are established will retain more moisture and keep the soil cooler. 

Indeterminate (vine) tomatoes, especially earlier-producing small cherry varieties, produce flavorful fruit in a dry garden if they are started well. Peppers, potatoes, winter squash, zucchini, melons, dry beans and corn are commonly dry-farmed. Beets, carrots, chard, kale, leeks, rutabagas will grow without irrigation, but will do better with occasional water. Fall-planted garlic, fava beans, root crops and leafy greens establish in the rainy season and mature without irrigation in early summer. Fall-planted broccoli, kale and other cool-season crops can grow through winter but bolt and flower quickly when warmer weather arrives. Spring-planted onions, celery, radishes and greens require irrigation to be productive. Choosing varieties with shorter growing periods listed on the seed packets means they might complete their growing cycle before the water dries up. 

For more information about dry vegetable gardening and a list of resources visit http://center for small farms.oregonstate.edu/dry farm.

Extension publication “Intro to Dry Farming Organic Vegetables” is available for free download at catalog.extension.oregonstate.edu/EM9229. 

Start your garden with these five resources you can access from home

Birdseye view of person and dog at outdoor table in a garden, working on a laptop.
  1. Start with a research-based introduction to growing food at home. Our favorite is Growing Your Own from OSU Extension. Learn when to plant, how to prepare your growing space, stopping pests and more: https://catalog.extension.oregonstate.edu/em9027
  2. Where can you get garden supplies? Plant Something Oregon has a list of suppliers that offer a range of options for safer shopping. Find them here: https://plantsomethingoregon.com/coronavirus/
  3. Where to get your soil tested? Master Gardener volunteers are not currently able to test soil pH, so gardeners will need to send samples to soil testing labs found in Analytical Laboratories Serving Oregon: https://catalog.extension.oregonstate.edu/em8677

These labs can provide a variety of services. Most home gardeners who are growing plants in the ground will want to check soil pH as well as levels of nitrogen, potassium and phosphorus. Many labs offer the option to request recommendations for amending soil when ordering their tests. Learn how to take a good soil sample to achieve the most accurate results with A Guide to Collecting Soil Samples for Farms and Gardens: https://catalog.extension.oregonstate.edu/ec628

4. Use research-based resources to find garden solutions. OSU Extension offers straightforward tested resources to build resiliency for by growing gardens in this amazing virtual collection: https://extension.oregonstate.edu/gardening

5. Connect with real gardeners to get help! Though our offices may be closed, OSU Extension Master Gardeners are still available to answer your gardening questions by phone or email. Please leave us a detailed voicemail and a callback number. We’re also checking email! Share your photos of plant or insect problems with us. Master Gardeners will research your question and give you a call back or send an email. In Benton County: (541) 713-5000 or email: bentonmg@oregonstate.edu In Linn County: (541) 967-3871 or email: linn.mg@oregonstate.edu

Before Reaching for Pesticides, Get to Know Beneficials – The Good Guys!

By Judi Di Bord, Master Gardener Volunteer

Did you know there is an alternative to controlling pests in your garden by using a pesticide?  Attracting beneficial insects, like lady beetles, green lacewings, praying mantis and dragonflies can help control insects that feed on your plants.  Beneficials don’t just help control pests. Some beneficials are also important pollinators! 

Ladybug (Coccinella septempunctata) on an Common Yarrow's umbel (Achillea millefolium)
Ladybug (Coccinella septempunctata) on an Common Yarrow’s umbel (Achillea millefolium). By Hélène Rival on Wikimedia Commons.

How can you attract beneficials to your garden?  One way is to purchase them at a local garden center and release them into your garden.  You can also attract them to your garden by growing plants to provide an enticing habitat for them.  If you are able to dedicate some space to growing these habitat plants, the rest of your garden can reap the rewards.

Following are some recommendations from the Penn State Extension Service:

  • Carrot Family (Apiaceae)  Plants in the carrot family are especially attractive to small parasitic wasps and flies. Interplant them in your vegetable garden and flower beds. Plants in this family include: caraway (Carum carvi); coriander/cilantro (Coriandrum sativum); dill (Anethum graveolens); fennel (Foeniculum vulgare); Bishop’s flower (Ammi majus); Queen Anne’s Lace (Daucus carota); and toothpick ammi (Ammi visnaga).
  • Aster Family (Asteraceae)  Attractive to larger predators such as lady beetles and soldier beetles. Incorporate into the vegetable garden and flower beds. Plants in this family include: blanketflower (Gaillardia spp.); coneflower (Echinacea spp.); coreopsis (Coreopsis spp.); cosmos (Cosmos spp.); golden marguerite (Anthemis tinctoria); goldenrod (Solidago spp.); signet marigold (Tagetes tenuifolia); sunflower (Helianthus spp.); tansy (Tanacetum vulgare); and yarrow (Achillea spp.).
  • Legumes (Fabaceae)  Generally grown as cover crops and attractive to many beneficials. Plants in this family include: alfalfa (Medicago sativa); fava bean (Vicia fava); hairy vetch (Vicia villosa); and sweet clover (Melilotus spp.).
  • Mustard Family (Brassicaceae)  Attractive to beneficials that are parasites and predators of the insect pests of the mustard family (broccoli, Brussels sprouts, cabbage, cauliflower, kohlrabi, mustard greens). Be sure to plant these away from the garden rather than in the garden since these plants attract pests as well as beneficials. Some are common weeds, such as yellow rocket and wild mustard. Plants in this family include: basket-of-gold alyssum (Aurinia saxatilis); mustards (Brassica spp.); sweet alyssum (Lobularia maritima); yellow rocket (Barbarea vulgaris); and wild mustard (Brassica kaber).
  • Verbena Family (Verbenaceae)  Attractive to a variety of beneficial insects. Many plants in this family are favorite garden flowers. They include: lantana (Lantana camera); Buenos Aires verbena (Verbena bonariensis); hybrid verbena (Verbena x hybrida); and lilac vervain (Verbena rigida).

Beneficial insects also need a source of water. Shallow containers such as ceramic pot saucers with pebbles for the beneficials to rest on are best.

Suggested OSU Extension publications:

PNW550: Encouraging Beneficials in Your Garden

For kids:

EC1601: The Wildlife Garden: Dragonfly

EC1604: The Wildlife Garden: Lady Beetle

EC1605: The Wildlife Garden: Praying Mantis

Suggested websites:

National Pesticide Information Center, Beneficial Insects.

Penn State Extension, Attracting Beneficial Insects