Free Tool
Plant Family Tree
Explore how 200+ garden crops are related through botanical family, genus, and species. Click any family to zoom in and see its members. Understanding these relationships is the foundation of effective crop rotation -- plants in the same family share pests, diseases, and nutrient needs.
Why Plant Families Matter
Shared pests and diseases
Plants in the same family are attacked by the same pests and pathogens. Late blight does not care whether it is on your tomato or your potato -- both are nightshades, and both are hosts. When you grow the same family in the same bed year after year, those pest populations accumulate in the soil. Rotation breaks the cycle by removing the host plant before populations can build to damaging levels.
The rotation principle
The simplest rotation plan groups your beds by plant family and moves each group to the next bed each year. A four-bed rotation might go: nightshades (bed 1) followed by legumes (bed 2) followed by brassicas (bed 3) followed by roots and alliums (bed 4). The legumes fix nitrogen that the nightshades depleted. The brassicas benefit from the nitrogen the legumes left behind. Each family gets a 3-year break before returning to the same soil.
Same species, different vegetables
Some of the most surprising relationships are within a single species. Broccoli, cauliflower, kale, cabbage, Brussels sprouts, and kohlrabi are all the same species -- Brassica oleracea -- selected over centuries for different plant parts. Beets and Swiss chard are both Beta vulgaris. This means they share not just family-level diseases but species-level vulnerabilities. The sunburst above shows these relationships clearly: click into a family to see how crops cluster by genus and species.
Beyond rotation: companion planting
Plant families also inform companion planting decisions. Aromatic herbs in the mint family (Lamiaceae) deter many pests when interplanted with vegetables. Carrot family flowers (Apiaceae) attract parasitic wasps and hover flies that prey on aphids. Legumes share nitrogen with neighboring plants through mycorrhizal networks. The companion planting guide explores these relationships crop by crop.
Common Questions
Why do plant families matter for gardening?
Plants in the same family share pests, diseases, and nutrient needs. Growing the same family in the same spot year after year lets pest populations build and diseases accumulate in the soil. Understanding families is the foundation of effective crop rotation.
How many years should I wait before replanting the same family?
Most families need 2-3 years. Brassicas and nightshades benefit from 3+ years because clubroot and late blight persist in soil. Legumes and herbs can rotate every 1-2 years. Click any family in the diagram above to see specific rotation guidance.
What are the most important families to know?
Six families cover most home garden vegetables: Solanaceae (tomato, pepper, potato), Brassicaceae (broccoli, kale, cabbage), Fabaceae (beans, peas), Cucurbitaceae (squash, cucumber), Apiaceae (carrot, parsley, dill), and Amaryllidaceae (onion, garlic). Learning these six gives you enough for effective rotation.
Are broccoli and kale really the same species?
Yes. Broccoli, cauliflower, kale, cabbage, Brussels sprouts, kohlrabi, and collard greens are all Brassica oleracea -- selected from the same wild ancestor for different edible parts over thousands of years.
Do herbs need to be rotated?
Most culinary herbs are in the mint family (Lamiaceae) and are perennial -- they stay in place. Annual herbs like basil benefit from rotation if you grow large amounts, mainly to manage Fusarium wilt. For home garden scale, herb rotation is less critical than vegetable rotation.
More Free Tools
Want a rotation plan built for your garden?
Understanding plant families is the first step. A site consultation helps you design a rotation plan that fits your specific beds, goals, and growing history.
Schedule a Consultation