Plant Systems Citrus Study Bank Learn fruit, leaves, rootstocks, weeds, pests, diseases, disorders, pathogens, parasites, and predators.
Test me on Citrus Fruit & leaves ●
Sweet Orange Round to slightly oval fruit with a familiar sweet-orange flavor profile.
Compare overall fruit shape, peel texture, rind thickness, and leaf petiole. Do not rely on fruit color alone; maturity and cultivar can change appearance. Memory cue Orange = classic round citrus baseline.
Fruit & leaves ●
Grapefruit Typically larger fruit than most oranges, often with a broad round shape.
Use size together with peel, leaf, and internal fruit traits. Practice side-by-side comparisons rather than memorizing one photo. Memory cue Grapefruit = think bigger, broad, round.
Fruit & leaves ●
Lemon Often oblong fruit with a noticeable nipple at one or both ends.
Look for elongated shape and pointed ends. Leaves and petioles help when fruit is absent. Memory cue Lemon = longer fruit, pointed ends.
Fruit & leaves ●
Lime Usually smaller than a lemon and commonly round to oval.
Color is not enough because ripe fruit can yellow. Use fruit size, shape, peel and leaf clues together. Memory cue Lime = small citrus; never trust green alone.
Diseases & disorders ●
Citrus Greening (HLB) Look for blotchy, uneven mottling and declining tree vigor rather than a perfectly mirrored nutrient pattern.
HLB is associated with the Asian citrus psyllid vector. Compare leaf pattern, fruit development, and whole-tree symptoms before naming a disorder. Memory cue HLB = blotchy, uneven, whole-tree decline.
Diseases & disorders ●
Citrus Canker Raised corky lesions may appear on leaves, stems, and fruit, commonly surrounded by a yellow halo.
Focus on lesion texture and halo. Do not confuse every leaf spot with canker. Memory cue Canker = raised corky spot + halo.
Pests ●
Asian Citrus Psyllid Small sap-feeding insect strongly associated with citrus greening transmission.
Adults characteristically feed with the body angled upward. Nymphs are found on tender new flush. Memory cue Psyllid = tiny vector on new flush.
Rootstocks ●
Rootstock concept The rootstock supplies the root system; the scion is the desired fruiting variety grafted above it.
Rootstock choice can affect vigor, soil adaptation, disease response, and tree performance. Know the difference between rootstock and scion before memorizing named rootstocks. Memory cue Roots = rootstock; fruiting top = scion.