Resource library

Every free source the course relies on, grouped by module, with who publishes it and what it provides. Links were checked on the date stated below.

Most of these are published by Cooperative Extension, the outreach arm of each state's land-grant university, and by federal agencies. Your own state's extension service is the best source for your climate, soil and pests: use Find Extension in Your State to reach it. Nothing here is an advertisement, and no link carries a referral or tracking parameter.

Paid courses we compared (references only)

• Vegetable Gardening. Oklahoma State University Extension. Course page: price, length, 12-module list.
• Vegetable Gardening Online Course (Master Gardener Short Course Series). Oregon State University PACE. Course page: price, length, learning objectives; no module list.
• Fundamentals of Home Gardening. UConn Extension. Course page: four-course structure and price.
• Organic Vegetable Gardening. joegardener Online Gardening Academy. Course page: module list and supplements.
• Beginning Gardener Fundamentals. joegardener Online Gardening Academy. Course page: price, module list.
• No Dig Gardening, Online Course. Charles Dowding. Course page: price, 6 modules and 17 lessons.

Listed so you can see what paid courses cover. We receive nothing from them and do not recommend buying any course. Prices change; check the course page.

Site, sun and climate (Modules 1, 2)

• Planning a Garden (HGIC 1256). Clemson Cooperative Extension Home & Garden Information Center. Sun minimum and site basics.
• An educator's guide to vegetable gardening (EM 9032). Oregon State University Extension. Sun hours by crop type; site pitfalls.
• Growing Leafy Greens in a Home Garden. University of Maryland Extension. Greens tolerate 4 to 6 hours of direct light.
• 2023 USDA Plant Hardiness Zone Map. USDA Agricultural Research Service. Official zone lookup; zones are the average annual extreme minimum winter temperature in 10 °F zones and 5 °F half zones.
• How to Use the Maps. USDA ARS. What the map leaves out (wind, soil, moisture, snow, summer heat, timing of cold); microclimates.
• USDA Unveils Updated Plant Hardiness Zone Map. USDA ARS. 2023 map uses 1991 to 2020 data from 13,412 stations; about half the country shifted a half zone warmer.
• When to Plant. University of Illinois Extension. Most vegetables are annuals, so zones mostly apply to landscape plants; planting dates come from frost dates and days to maturity; median and 1-in-10 dates.
• Interpreting Freeze/Frost Probabilities from the National Centers for Environmental Information (AG-873). NC State Extension. Frost 36 °F, freeze 32 °F, hard freeze 28 °F; 50 percent is the median; choose the 90, 50 or 10 percent date by risk tolerance.
• Interactive map: Average date of last spring freeze across the United States. NOAA Climate.gov. The mapped date is when the chance of a freeze falls below 50 percent, from 1991 to 2020 Normals; Normals also give 40, 30, 20 and 10 percent dates.
• When to Expect Your Last Spring Freeze. NOAA National Centers for Environmental Information. NCEI freeze-date entry point; 32 °F threshold; actual years vary widely.

Soil (Modules 3, 4, 9)

• Soil Texture Analysis "The Jar Test" (HGIC 1656). Clemson HGIC. Jar test steps; read sand at 1 minute, silt at 2 hours, clay at 48 hours; percent = layer height / total x 100; texture triangle.
• Improving garden soils with organic matter (EC 1561). Oregon State University Extension. Texture explained; organic matter benefits; 1 in of material over 200 sq ft is 0.6 cu yd; do not add sand to clay.
• Soil and Plant Nutrient Testing Laboratory. UMass Amherst. Example lab; routine test reports pH, lime requirement, nutrients and recommendations; metals test is separate.
• Sampling Instructions for Routine Soil Analysis. UMass Amherst. Sample 6 to 8 in deep, 12 or more subsamples, about one cup air-dried, not within 6 to 8 weeks of lime or fertilizer.
• Soil Fertility Testing. Penn State Agricultural Analytical Services Lab. What a standard report includes (pH, lime requirement, P, K, Mg, Ca, crop recommendations); organic matter optional.
• Soil Sampling Instructions. Penn State AASL. At least 13 places, 6 in deep, composite, air dry without heat, send 1 cup.
• Fertilizers for Vegetables in Home Gardens (G945). University of Nebraska-Lincoln Extension. PH 6.5 ideal for most vegetables; lime and sulfur rates depend on a test; lime can take 1 to 3 years to peak.
• Healthy Gardening Practices to Reduce Exposure to Lead-Contaminated Soil. U.S. EPA. Actions by soil lead level (near 200 ppm good practices; 200 to 400 ppm raised beds of clean soil, mulch, peel roots; over 400 ppm do not use existing soil, raised beds with at least 16 in of clean soil on fabric, or containers); keep pH 6.5 to 7.5; wash produce and hands; testing through extension or health departments.
• Residential Soil Lead Directive for CERCLA Sites and RCRA Hazardous Waste Cleanup Facilities. U.S. EPA. October 16, 2025 cleanup directive; supersedes the January 2024 guidance for those programs; 200 ppm residential screening level; does not address gardening.
• Soil Lead Screening: Understanding Your Results and Next Steps. New York Soil Health / Cornell. Stricter tiers than EPA (under 63 ppm background; 63 to 99 consider no root crops; 100 to 199 raised beds, favor fruiting crops; 200 to 399 raised beds only); dated November 2024, it reports EPA's January 2024 cleanup guidance, since superseded by the October 2025 directive above.
• Sources and Types of Contaminants. Cornell Healthy Soils, Healthy Communities. Lead sources (old paint, busy roads, old orchards, industry, treated lumber); research site history.
• Healthy Soils, Healthy Communities. Cornell Cooperative Extension NYC. Research background (900+ soil samples, NYC gardens) and practices list.

Growing space: raised beds, containers, fill (Module 4)

• Growing Vegetables in Raised Beds. University of Maryland Extension. Beds 2 to 4 ft wide, 2 to 12 in tall; on hard surfaces 8 in for greens and beans, 12 to 24 in for tomatoes and squash; CCA discontinued for residential use in 2004; MCA common; raised beds dry faster.
• Soil to Fill Raised Beds. University of Maryland Extension. Compost to topsoil 1:2 or 1:1; hard surfaces compost and soilless mix 1:1; pH 6.2 to 6.8; ask topsoil sellers for test results.
• Raised bed gardens. University of Minnesota Extension. Width 2.5 ft from one side, 5 ft from both; 27 in comfortable for wheelchair users; avoid old lumber, CCA and railroad ties; some metal beds sold online found to contain lead; 2/3 topsoil and 1/3 compost or half and half; potting soil dries too fast for beds.
• Pressure-treated wood for raised bed construction in Oregon (EM 9879). Oregon State University Extension. Study of CA-C treated beds; soil copper rose only within 1 in of the board, within natural range; no increase in vegetables; CCA not sold to the public for over 20 years.
• Types of Containers for Growing Vegetables. University of Maryland Extension. Container size by crop (large crops 8 to 10 gal, 12 to 16 in deep; medium 4 to 6 gal; small 1 to 3 gal; potatoes 30 gal); drainage holes required; gravel does not improve drainage.
• Container Vegetable Gardening: Four Keys to Success. Penn State Extension. Tomato pot at least 20 in wide, peppers 14 in; soilless mix; water at least daily in hot months; slow-release then soluble fertilizer every 2 to 4 weeks.
• How to use compost in gardens and landscapes (EM 9308). Oregon State University Extension. New beds 3 to 4 in of compost into the top 8 to 12 in; existing beds 1/4 to 1 in a year; up to 25 percent compost in raised beds; cubic yards = cubic feet / 27; bags typically 1 to 2 cu ft; a 1 cu ft bag covers 12 sq ft at 1 in.
• NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement. National Institute of Standards and Technology. 27 cu ft = 1 cu yd; 1 gal = 231 cu in; 1 cu ft = 7.480519 gal.
• Miracle-Gro Organic Raised Bed & Garden Soil. Scotts Miracle-Gro. One example bag size (1.5 cu ft) and the maker's fill claim, which implies about 50 percent more product than geometric volume.

Planning, spacing and rotation (Module 5)

• Intensive Gardening Methods (426-335). Virginia Cooperative Extension. Equidistant spacing for 19 of the 21 crops (garlic and basil absent); interplanting average; succession and relay definitions.
• Virginia's Home Garden Vegetable Planting Guide: Recommended Planting Dates and Amounts to Plant (426-331). Virginia Cooperative Extension. Planting windows by Virginia zone (an example of a regional calendar); spacing and plants per person; row covers extend 2 to 4 weeks; children need about half the adult amount.
• Vegetable Planting Calendar (G6201). University of Missouri Extension. Feet of row per person, spacing, depth, days to harvest.
• Vegetable Garden Planting Guide (MF315). K-State Research and Extension. Days to harvest, germination temperature, spacing, frost resistance, amount per person; the statement that 100 sq ft can produce a good portion of a family of four's vegetables (quoted as the publisher's claim only).
• Crop Rotation in the Vegetable Garden. Iowa State University Extension and Outreach. Rotate 3 to 4 years (5 or more if possible); family lists with current names.
• Rotating crops for a more resilient garden. University of Illinois Extension. 3 to 4 years between the same family.
• Using Crop Rotation in Home Vegetable Gardens. WSU Extension Snohomish County. Older family names (Chenopodiaceae, Alliaceae) a learner will meet; changing families every year still helps.
• Catalog Code. University of Illinois Extension. Seed catalog codes (V, F, N, TMV for tomato; CMV, PM, DM for cucumber; F1; AAS).
• Square Foot Gardening Method. Square Foot Gardening Foundation. The 4 x 4 ft grid and its soil mix as one practitioner's method.

Timing and the planting calendar (Module 6, calendar tool)

• Vegetable Planting Guide (CMG GardenNotes #720). Colorado State University Extension. Spring planting by frost-tolerance class (hardy 2 to 4 weeks before the average last frost; semi-hardy 0 to 2 weeks before; tender around the date; very tender 2 or more weeks after); per-crop germination temperatures, spacing, depth, days to harvest and transplant age.
• Indiana Vegetable Planting Calendar (HO-186-W). Purdue Extension. A second set of class windows (hardy 4 to 6 weeks before, semi-hardy 2 to 4 before, tender after, very tender 2 or more weeks after); cool-season fall crops 4 to 8 weeks before first frost; soil at least 60 °F for warm-season crops; 10 and 50 percent frost map statement; propagation codes.
• Suggested Vegetable Planting Dates for Utah. Utah State University Extension. Groups A to D relative to the last frost with a worked example.
• Vegetable Planting Guide (Hort 52). Cornell Cooperative Extension Rockland County. Indoor starts by weeks before last frost (onions 10 to 12; brassicas, lettuce, kale, eggplant, pepper 6 to 8; tomato 4 to 6; cucurbits under 4); fall rule of adding 2 weeks before counting back.
• Vegetable Gardening: Keep Your Garden Growing. University of Maine Cooperative Extension, Cumberland County. Weeks to sow indoors before last frost per crop (a third set to show disagreement).
• Planting the vegetable garden. University of Minnesota Extension. Soil temperature for early and warm-season sowing; says radish, carrot and beet do not tolerate transplanting (qualified by the farm guidance below).
• Reducing tillage intensity in vegetable crops. University of Minnesota Extension. Farm-scale guidance; notes growers transplanting beets from paper pots and that transplanting carrots is uncommon.
• Soil temperature conditions for vegetable seed germination. Oregon State University Extension. Minimum, optimum range, optimum and maximum germination temperatures; days to emergence by soil temperature.
• The Fall Vegetable Garden (HO-66-W). Purdue Extension. Frost tolerance classes; the 50 percent chance on the average first frost date and 10 percent two weeks before; last feasible fall plantings for Indiana.
• Fall Vegetable Gardening (G1343). Nebraska Extension. The fall planting formula (days to harvest + seed-to-transplant days if growing your own + harvest period + 14-day fall factor + 14-day frost-tender factor for corn, beans, cucumbers, tomatoes and squash = days to count back from the first fall frost); semi-hardy and hardy fall lists.
• Fall Vegetable Gardening (426-334). Virginia Cooperative Extension. The same formula.
• Succession Planting Charts for Vegetables. Johnny's Selected Seeds. Succession intervals and last sowing relative to first frost.
• Succession Planting. University of Kentucky Cooperative Extension, Franklin County. 7, 10, 14, 21 and 30-day interval groups (credited to Johnny's).
• Planting and Growing Garlic. University of Illinois Extension. Plant in fall 4 to 6 weeks before the ground freezes; depth and spacing; straw mulch; harvest when about half the leaves yellow; cure 4 to 6 weeks.

Seeds and transplants (Module 7)

• Start Your 2020 Victory Garden, section 5: planting. Montana State University Extension, Powder River County. Definition of days to maturity (from the day seeds or transplants go in the garden; an average); what a seed packet carries; counting back from a transplant date.
• Read Your Seed Packet. Penn State Extension Master Gardeners of Pike County. Packet checklist.
• Vegetable Garden Seed Storage and Germination Requirements (G2090). Nebraska Extension. Seed longevity by crop in cool, dry storage; paper towel germination test (25 or 50 seeds, 70 to 75 °F, count at 2 to 3 weeks).
• Testing Seed Viability. University of Wisconsin-Madison Extension, Dane County. Viability years (some differ from [UNL-G2090]); 10-seed roll test; below 40 percent buy fresh seed.
• Starting seeds indoors. University of Minnesota Extension. Weeks indoors per crop; 12 to 16 hours of light with lights 2 to 4 in above seedlings; air above 60 °F; soilless mix; harden off about 2 weeks.
• Starting Vegetable Seeds Indoors: IV. Seedling Culture and Transplanting. Utah State University Extension. Night 60 to 65 °F; 12 to 14 or more hours of light, lights 2 to 3 in above; window light insufficient in most situations; half-strength weekly feeding; seed depth 2 to 3 times diameter; harden off at least 2 weeks.
• Hardening Off Vegetable Seedlings for the Home Garden. University of Maryland Extension. 1 to 2 weeks; start in shade; not below 45 °F.
• Harden Your Transplants Prior To Planting Your Garden. South Dakota State University Extension. 7 to 14 days, day-by-day schedule starting at 3 to 4 hours.
• Growing basil in home gardens. University of Minnesota Extension. Sow indoors 6 to 8 weeks before planting out; direct sow after frost danger; tender annual; space 6 to 12 in.

Water and mulch (Module 8, water calculator)

• Watering the vegetable garden. University of Minnesota Extension. About 1 inch of water a week; 62 gallons per 100 sq ft; sandy soil twice a week at 1/2 in; water when dry 2 in down; time a 5-gallon pail and multiply by 12 for 62 gallons.
• Residential Rain Water Catchment Systems: Useful Information. University of Arizona Water Wise / Cochise County Extension. Gallons = area (sq ft) x inches x 0.623; screen containers against mosquitoes; drip needs 15 to 20 psi.
• Water Q&A: How much water falls during a storm? U.S. Geological Survey. 1 in of rain on 1 acre is 27,154 gallons (0.623 per sq ft is our arithmetic from that figure).
• Drip Irrigation Fundamentals: The Math Behind the Drip (FSA6174). University of Arkansas Division of Agriculture. Drip rate (in/hr) = emitter gph x 231.1 / (emitter spacing in x bed width in); maximum single run by soil.
• Determining How Long to Run Drip Irrigation Systems for Vegetables. Penn State Extension. Vegetables need 1 to 1.5 in a week; subtract rainfall.
• Landscape Irrigation Equipment Part 2: Drip Irrigation (HGIC 1811). Clemson HGIC. Emitters typically 0.5, 1 or 2 gph; pressure 20 to 30 psi, regulator above 40; filter required.
• How Long to Run Drip Irrigation. UC Master Gardeners, Solano and Yolo. Tablespoon test (1 gph emitter fills one in 14 seconds); wet 12 to 18 in deep.
• Rain Barrels Part IV: Testing and Applying Harvested Water to Irrigate a Vegetable Garden (FS1218). Rutgers Cooperative Extension. First flush carries the most contaminants; apply to soil, not leaves; morning watering; not drinking water under New Jersey law.
• Wood chips for mulch?. Oregon State University Extension. Sawdust ties up more nitrogen than large chips, and chips mixed into soil more than chips on the surface; chips suit paths and the soil surface.
• Using Mulch in the Garden. Iowa State University Extension. 2 to 4 in; straw, shredded leaves, dried clippings, compost; newspaper or cardboard under organic mulch.
• Mulching Vegetables (Circular 984). University of Georgia Cooperative Extension. 3 to 4 in; shred leaves; benefits (moisture, cooler soil, weeds, less splash and fruit rot).
• Composting At Home. U.S. EPA. Browns to greens 2 to 3 : 1; what to exclude (meat, dairy, pet waste, diseased plants); mix 2 to 4 in into the top 6 to 9 in; 3 in as mulch kept off stems.

Fertilizer (Module 9, fertilizer calculator)

• Fertilizing Vegetable Gardens. University of Maryland Extension. 2 lb N per 1,000 sq ft generally, 3 for heavy feeders; product math worked for three fertilizers; each 1 percent organic matter releases about 0.4 lb N per 1,000 sq ft; over-fertilizing effects; runoff.
• Reading A Fertilizer Label (HGIC 1228). Clemson HGIC. The three numbers are percent by weight of N, P2O5 and K2O; 100-lb bag example; ratio; slow-release definition.
• Home and Market Garden Fertilization (Guide H-120). New Mexico State University Extension. P to P2O5 x 2.29, K to K2O x 1.2; formula 100 / percent x pounds needed.
• Sidedressing Garden Vegetables. Kansas State University Extension. Side-dress timing by crop; crops that get no late nitrogen.

Problems: IPM, pests, disease, wildlife, weeds (Module 10)

• Integrated Pest Management (IPM) Principles. U.S. EPA. Action thresholds, monitoring and identification, prevention, least-risk control first.
• Home and Landscape. UC Statewide IPM Program. Hub for home garden IPM and Pest Notes.
• Plant problem diagnostic tool. UC IPM. Identification by plant, part and damage.
• Natural Enemies Gallery. UC IPM. Predators, parasitoids and pathogens.
• Tomato (Home and Landscape). UC IPM. Index of tomato pests, diseases and disorders including blossom end rot.
• Aphids (Pest Notes 7404). UC IPM. Check twice weekly; most established plants outgrow aphid damage; water spray; excess nitrogen favors aphids; natural enemies.
• Snails and Slugs (Pest Notes 7427). UC IPM. Night checks, board traps, copper barriers, habitat removal; some baits are poisonous to dogs and cats.
• Squash vine borers. University of Minnesota Extension. Life cycle, monitoring, row covers on and off at flowering, sanitation, less susceptible squash types.
• Imported Cabbageworm. UNH Cooperative Extension. Identification, row covers, handpicking, leave parasitoid cocoons.
• Caterpillar Pests of Brassica Vegetables. Utah State University Extension. Row covers just after planting; an action threshold for head-forming crops.
• Early blight in tomato and potato. University of Minnesota Extension. Conditions, target-ring spots, remove no more than one-third of leaves, mulch against splash, resistant varieties; tomatoes tolerate a lot of early blight.
• Powdery Mildew of Cucurbits. UConn Home & Garden Education Center. Conditions; sun, airflow, no excess fertilizer; resistant cultivars (list may be dated; not reproduced).
• Introduction to Pesticide Labels. U.S. EPA. Labels are legally enforceable; "the label is the law." Claim type: convention (legal).
• Signal Words Fact Sheet. National Pesticide Information Center. CAUTION, WARNING, DANGER describe acute toxicity only.
• National Pesticide Information Center. NPIC, Oregon State University and EPA. 1-800-858-7378 for product questions; reduced hours noted for 2026.
• Pesticide Home Remedies. NPIC. Home remedies are untested and unlabeled and can be hazardous.
• Storing Pesticides Safely. U.S. EPA. Locked, ventilated storage in original containers; child-resistant is not child-proof.
• Protecting Pollinators When Using Pesticides. University of Illinois Extension. Read the environmental hazards section; nothing bee-toxic on flowering plants.
• Lacewings. University of Maryland Extension. Identification of a common beneficial insect.
• Managing Critters in Vegetable Gardens. University of Arizona Cooperative Extension, Yavapai County. Deer fences at least 8 ft (or two low fences 38 in apart); rabbit and gopher barriers.
• Groundhogs. University of Maryland Extension. Strong 4-ft fence buried 12 in.
• Rabbits. University of Maryland Extension. 2-ft chicken wire secured at the bottom.
• Controlling Weeds by Cultivating and Mulching (HGIC 1253). Clemson HGIC. Weed young, hoe shallow, mulch; herbicides generally not needed in home gardens.
• Vegetable and Floriculture Diagnostics. UMass Amherst Extension. How to collect and send a plant sample (an example; fees and eligibility vary by state).

Harvest, storage and food safety (Module 11)

• Harvesting and storing home garden vegetables. University of Minnesota Extension. Four storage groups by temperature and humidity; harvest cues; curing onions and potatoes; a home refrigerator runs about 40 °F and 50 to 60 percent humidity.
• When to Harvest Vegetables (Guide H-216). New Mexico State University Extension. Harvest indicators per crop.
• Using Manure in the Home Garden. Iowa State University Extension. 120 days before harvest for crops touching soil, 90 days for others; no cat, dog or pig manure; compost at 131 °F or more.
• Guidelines for Using Manure on Vegetable Gardens (Bulletin 2510). University of Maine Cooperative Extension. Ties the 90 and 120-day intervals to the USDA National Organic Program; never side-dress with raw manure.
• Five Steps to Food Safe Fruit and Vegetable Home Gardening. UConn Extension Master Gardener. Compost temperature and turning; pets out of the garden; food-grade containers; refrigerate at 40 °F or less.
• Selecting and Serving Produce Safely. U.S. FDA. Rinse home-grown produce under running water, no soap or produce wash; scrub firm produce; wash hands 20 seconds.
• Poisonous and non-poisonous plants: An illustrated list. National Capital Poison Center. Rhubarb leaves are poisonous; Poison Control 1-800-222-1222.
• Are sprouted potatoes safe to eat? National Capital Poison Center. Solanine and chaconine are highest in sprouts, leaves, flowers, eyes and green skin; cooking does not destroy them.

Season extension, cover crops, cleanup, records (Modules 1, 12)

• Extending the Season in the Garden. UConn Home & Garden Education Center. Row covers hold about 5 degrees; hoops; cold frames; vent on sunny days.
• Appendix E. Season Extenders and Greenhouses. Row covers and low tunnels give 4 to 5 °F of frost protection; vent above 90 °F; cold frame orientation and width.
• Tips for Planting Cover Crops in Home Gardens. Penn State Extension. Species, sowing windows and rates per 1,000 sq ft; turn under 2 to 3 weeks before planting.
• Cleaning up the vegetable garden in fall. University of Maryland Extension, Maryland Grows. Remove diseased plants and keep them out of home compost; cover beds with leaves or straw.
• Garden Journaling. Iowa State University Extension. What to record (dates, varieties, maps, rotation, pests, applications, weather, harvest).

Safety and local help (legal page, all modules)

• Preventing Tick Bites. CDC. Repellents, clothing, check for ticks after time in your own back yard, shower within 2 hours.
• About Heat and Your Health. CDC. Shade, breaks, cooler hours, water; higher risk at 65 and older.
• Heat-related Illnesses. CDC/NIOSH. Signs of heat stroke and heat exhaustion and first aid; call 911 for heat stroke.
• Reducing Risk for Skin Cancer. CDC. Broad-spectrum SPF 15 or higher; UV strongest 10 a.m. to 4 p.m.; hat.
• About Tetanus. CDC. Wounds with soil warrant a call to a provider; boosters every 10 years.
• Healthy Tips to Garden with Fewer Aches and Pains. Penn State Extension. Lifting with hips and knees, load close; change posture often; sharp tools.
• 811 Before you dig. Common Ground Alliance. 811 is free; contact a few business days before digging; planting a garden counts; lines can be inches deep.
• Find Extension in Your State. Extension Foundation. Links to every state's extension institution.
• Master Gardeners. American Horticultural Society. Master Gardener program directory by state and province.