Gardening resources: Extension services, plant ID, books, soil testing

Everything I rely on for primary research, soil testing, plant identification, and disease diagnosis. Most are free. The links to books are Amazon affiliate links - I earn a small commission if you buy through them, at no extra cost to you (see affiliate disclosure).

Cooperative Extension - the most underused free resource

Every US state has a Cooperative Extension service through its land-grant university. They publish growing guides, do soil testing (usually $10-25), identify pest and disease specimens, and answer questions by phone or email. Most home gardeners have no idea this exists.

• Cornell Cooperative Extension - my local resource for Long Island
• Penn State Extension - excellent for turfgrass, vegetables, pest management
• NC State Extension - the Extension Gardener Handbook is one of the best general references in print
• Missouri Botanical Garden Plant Finder - cultivar database for thousands of plants
• Clemson HGIC - Home and Garden Information Center; excellent searchable factsheets
• UC IPM (Integrated Pest Management) - the authoritative pest identification and treatment resource
• UMass Extension Greenhouse, Floriculture, and Landscape - particularly strong on greenhouse and ornamental disease
• University of Minnesota Extension - reliable for cold-climate gardening
• Texas A&M AgriLife Extension - particularly strong on turfgrass and warm-climate vegetables
• Oregon State University Extension - excellent for Pacific Northwest
• UC ANR (Agriculture & Natural Resources) - California's Extension network

Find your local Extension office: USDA NIFA Extension Locator.

Plant identification

• PlantNet - free AI plant ID from photos. The plant identifier tool on this site uses the PlantNet API.
• iNaturalist - photo upload + community identification + observation records.
• Cornell Lab of Ornithology Merlin - not plants but excellent for bird ID (because you'll want to know who's eating your blueberries).

Disease diagnosis

• Cornell Plant Disease Diagnostic Clinic
• Oregon State Plant Disease Diagnostic
• Penn State Plant Disease Clinic

Most Extension services offer mail-in plant disease diagnosis for $20-50. Often the most efficient way to figure out what's killing your plant.

Pollinator references

• Xerces Society - the authoritative source on native pollinator conservation
• Pollinator Partnership ecoregional guides - region-specific pollinator plant lists
• Lady Bird Johnson Wildflower Center - native plant database with regional filters
• USDA Plants Database - native range and characteristics for every plant in the US

Books worth owning

These are the references I actually pull off my shelf:

• The Well-Tempered Garden by Christopher Lloyd - the best garden writing in English
• Bringing Nature Home by Doug Tallamy - the case for native plants in suburban yards
• The New Sunset Western Garden Book - the definitive reference for western US gardeners
• Armitage's Garden Perennials by Allan Armitage - cultivar-level information for hundreds of perennials
• The Vegetable Gardener's Bible by Edward C. Smith - the standard vegetable reference for home growers
• Manual of Woody Landscape Plants by Michael Dirr - the standard reference for trees and shrubs (used by every horticulture program)
• What Bug Is That? - any of the regional Field Guides to Pests of the Northeast (or your region) is worth $30

Soil testing

Send a soil test through your county Extension office. Most states charge $10-25 and return: pH, organic matter, P, K, Mg, Ca, micronutrients. Far better than the chemical color-change kits at the hardware store.

• Penn State Soil Testing Lab - $9-15 standard test
• Cornell Soil Health Lab - more comprehensive ($45-60)
• UMass Soil Testing Lab - $15-20

Seed and plant suppliers

Specialty seed companies with quality control good enough that university researchers buy from them:

• Johnny's Selected Seeds - vegetable seeds, with detailed growing guides that are themselves a reference
• Fedco Seeds - cooperative; cold-hardy varieties for the Northeast
• Hudson Valley Seed Company - heirloom and open-pollinated varieties
• Botanical Interests - widely available retail seeds with excellent germination
• Park Seed - established mail-order house

My other site

• IndoorPlantCare.com - the same approach for houseplants. If you have an outdoor garden, you probably have indoor plants too.

Questions, corrections, suggestions

I read everything sent to thomas at outdoorplantcare dot com. If I have something wrong, tell me - I'll fix it and credit you. If a resource I missed should be on this list, send it.