Contributed by C. Skema and O. Plume

If you are not working on the front line during this pandemic (and a big thanks to everyone who is!), you may be spending more time than ever before observing your yard, nearest green space, or even cracks in the sidewalk. Perhaps you’ve wondered “What plant is that?” while doing so. If that’s the case, this article is for you. We will cover some common, spontaneous (meaning not cultivated) plants occurring in and around the yards of Philadelphia at this time of year. We cover 9 families, 17 genera, and 21 species – all seen on a walk to the mailbox! And that is just what’s in flower or fruit presently. Pretty impressive diversity for a run-of-the-mill yard, right?

A great way to get a handle on the >350,000 plants on our planet is to learn plant families. Knowing key characteristics of families helps organize all that diversity in your head and gives you some orientation for where to start looking up or keying out a particular species you want to identify. For this reason, we’ll present the plants we cover by family, with family characteristics listed where useful. Each plant description will appear as follows:

Scientific name (common name; native area): key characteristics

Images show the plant's habit and highlight key characteristics. Click on any plant image to see it in its entirety. We use the word “widespread” to describe the native area when a plant occurs in multiple large areas (e.g., continents), but its nativity is unclear or currently debated. Also, if you ever want help with a plant ID, feel free to contact The Plant Clinic at Morris Arboretum (email images to This email address is being protected from spambots. You need JavaScript enabled to view it.).

Asparagaceae: A difficult family to characterize, but the plants covered here both occur in the subfamily Scillioideae (sometimes considered as family Hyacinthaceae), which is described here: bulbous herbs; leaves basal (all coming from base of plant), linear, arising directly from a bulb (no stem); inflorescence a raceme (flowers attached to a single axis by stems), tepals (undifferentiated sepals and petals) 6, stamens 6; ovary superior (sitting above the tepals and stamens); fruit a capsule

Ornithogalum umbellatum (star-of-bethlehem; Europe): bulbous herb; leaves often with lighter midrib; raceme inflorescence nearly flat-topped due to long pedicels (floral stems) on lower flowers; flowers of 3+3 tepals, each white with wide green stripe on underside

Muscari botryoides (common grape-hyacinth; Europe): bulbous herb; flowers purple with tepals fused in globe-shape

Ornithogalum_flowers
Flowers of Ornithogalum umbellatum (star-of-bethlehem). Note the wide green stripe on the underside of the tepals (undifferentiated sepals and petals) on flower in back.
Ornithogalum umbellatum (star-of-bethlehem) in flower.
The inflorescence (collection of flowers) of Muscari botryoides (common grape-hyacinth).
 

Caryophyllaceae: herbs; leaves opposite (or whorled), nodes often swollen (nodes are where the leaves meet the stem -- here, think carnations), sepals/petals in parts of 4’s or 5’s, ovary superior with 2-5 fused carpels (units of the pistil), styles often distinct (=not fused)

Face view of flowers of Stellaria media (left, common chickweed) and Cerastium glomeratum (right, mouse-ear chickweed).
Fruits (developing fruit on right and open fruit on left) of each of Stellaria media (left, common chickweed) and Cerastium glomeratum (right, mouse-ear chickweed). Note the six teeth at the opening of the fruit of the Stellaria and the ten teeth at the opening of the fruit of the Cerastium.

Cerastium glomeratum (mouse-ear chickweed; Eurasia): annual herb, moderately hairy on all parts; leaves opposite, without stipules; stamens 10; styles 5; fruit a capsule opening by 10, minute teeth

Stellaria media (common chickweed; Europe): annual herb; leaves opposite, short (<3 cm), about as long as wide, with petioles but no stipules, on weak stems; petals 5, deeply notched (can appear as 10); stamens 3; styles 3; fruit a capsule opening by 6, minute teeth

 
Cerastium glomeratum (mouse-ear chickweed) in flower.
The flowers of Stellaria media (common chickweed).
Stellaria media (common chickweed) in flower.
 

Violaceae: herbs; flowers bilaterally symmetrical (can be divided in half by only one line, like a heart), usually with a spur enveloping nectaries; sepals, petals and stamens each 5-parted; ovary superior, 3-parted with 1 style; fruit a capsule

Viola sororia (common blue violet; eastern North America): perennial herb; stemless (all leaves arising from one point at base of plant); leaves as long as broad, heart-shaped, serrate (with a margin like a saw's teeth); flowers with side petals with long, thread-like hairs on inside

Leaf and flower of Viola sororia (common blue violet).
Face view of open flower of Viola sororia (common blue violet). Note long, thread-like hairs on inside of side petals.
Viola sororia (common blue violet) in flower, purple color form.
Side view of flower of Viola sororia (common blue violet). Note nectary spur formed by lower petal extending out of the back of the flower (at left, below flower stalk).
Viola sororia (common blue violet) in flower, white with purple markings color form.
 

Oxalidaceae: herbs (or trees, vines); most species (Oxalis) with leaves alternate, trifoliate and leaflets cordate (=heart-shaped) with entire margins

Oxalis corniculata (creeping yellow wood sorrel; widespread): creeping, annual herb; leaves (often purple-tinted) with stipules on creeping stems that root at the nodes; flowers yellow

Oxalis stricta (common yellow wood sorrel; widespread): annual (or short-lived perennial) herb; leaves without stipules on creeping stems that root at the nodes; flowers yellow

Oxalis corniculata (creeping yellow wood sorrel) in flower.
Nodes (where the leaf stalk meets the stem) of Oxalis corniculata (creeping yellow wood sorrel). Note stipule at leaf base (white arrow).
Oxalis corniculata (left, creeping yellow wood sorrel) and Oxalis stricta (right, common yellow wood sorrel).
 

Rosaceae (Rose Family): trees, shrubs or herbs, armed or not; leaves alternate, usually serrate and stipulate; flowers radially symmetrical (can be divided in half by many lines, like a pie), 5-parted

Potentilla indica (Indian-strawberry; Asia): creeping, perennial herb; alternate, trifoliate leaves; leaflets serrate; flowers solitary; five green, three-lobed bractlets below five green, triangular sepals below five yellow petals; fruit like a strawberry (= swollen, red receptacle) but neither sweet nor edible

Developing fruit of Potentilla indica (Indian strawberry). Working from the outside of the flower in, you can see five 3-lobed bractlets, five triangular sepals, a ring of spent stamens, and many brown styles at the center.
Flower of Potentilla indica (Indian strawberry).
The leaf of Potentilla indica (Indian strawberry).
 

Brassicaceae (Mustard Family): herbs; leaves alternate; flowers white for those covered here (other colors occur in family); sepals and petals 4 in number; stamens 6 (typically 4 long + 2 short); fruits capsules, typically divided into siliques (>3x longer than wide) versus silicles (<3x longer than wide); all the species covered here have multiple seeds per locule (ovary chamber)

A lot of Brassicaceae flower and fruit in early spring, so this is a good family to get to know now. If you’ve never been pelted by scores of tiny Cardamine seeds exploding out of their capsular fruit as you walk across your yard, well, you are probably much more on top of yard maintenance than we are.

Alliaria petiolata (garlic mustard, Europe): biennial herb; smelling strongly of garlic; leaves basal (coming from base of plant) and along stem, kidney-shaped to heart-shaped, with palmate venation (leaf veins all radiating from where the leaf base meets the stem); fruits siliques, round in cross section

Capsella bursa-pastoris (shepherd’s purse, Eurasia): annual herb; basal leaves widest above the midpoint, subentire to pinnately divided, leaves along stem sessile and auriculate (with small lobes at base), fruit silicles, heart-shaped at the top and tapering to base

Cardamine hirsuta (hairy bittercress, Eurasia): annual herb; many basal leaves with few leaves along stem, all pinnately compound; fruits siliques, opening explosively

 
Leaf and flower of Alliaria petiolata (garlic mustard) in flower. Note the kidney-shaped to heart-shaped leaves.
Alliaria petiolata (garlic mustard) flowers.
Capsella bursa-pastoris (shepherd's purse) in fruit.
Cardamine hirsuta (hairy bittercress) in fruit (with a few flowers remaining at top).
 

Microthlaspi perfoliatum (pennycress, Eurasia): annual herb; leaves basal and along stem, those along stem auriculate; fruits inflated silicles, briefly winged at the top with notch and persistent style

Thlaspi arvense (field pennycress, Eurasia): annual herb; leaves along stem, upper leaves auriculate; fruits flattened silicles, winged along entire margin

 
Microthlaspi perfoliatum (left, pennycress) and Thlaspi arvense (right, field pennycress).
Top view of fruits of Microthlaspi perfoliatum (left, pennycress) and Thlaspi arvense (right, field pennycress).
Side view of fruits of Microthlaspi perfoliatum (left, pennycress) and Thlaspi arvense (right, field pennycress).
 

Plantaginaceae (Plantain Family): This is one family where learning the family characteristics isn’t much of a shortcut. It’s best just to learn the major components of the family separately as there isn’t much that holds them together beyond molecular data. Nonetheless, there are various lovely members of Plantaginaceae in bloom around Philly right now.

Cymbalaria muralis (Kenilworth ivy; Mediterranean): trailing annual herb, often found in rock wall crevices; leaves alternate, palmately lobed and veined; petals fused, violet with yellow patch, with spur

Cymbalaria muralis (Kenilworth ivy) in flower in its typical habitat, a rock wall crevice.
Side view of Cymbalaria muralis (Kenilworth ivy) flower.
 

With their unique and diminutive 4-parted blue/purple flowers and heart-shaped fruits, speedwells (Veronica) are easy to identify to genus; the trick lies in telling the species apart. It’s a worthy task though – who would’ve thought you had so many species of them in your yard? Veronica has opposite leaves, but those beneath flowers can be alternate in these species. Another common species you may see, Veronica arvensis (not covered here), can be differentiated from the three species below by its very short pedicel (flower stalk), which is typically 1 mm or less in length.

Fruits of Veronica hederifolia (left, ivy-leaved speedwell), Veronica polita (middle, speedwell), and Veronica persica (right, bird’s-eye speedwell).
Face view of flowers of Veronica polita (left, speedwell) and Veronia persica (right, bird’s-eye speedwell).
Pedicels (flower stalks, at white arrows) of flowers of Veronica polita (left, speedwell) and Veronica persica (right, bird’s-eye speedwell).
 

Veronica hederifolia (ivy-leaved speedwell; Eurasia): weak-stemmed annual herb; leaves wider than long with 3-5 lobes; flowers mostly white (with violet stripes) on stalk >1 cm long, fruit inflated and barely notched at top

Veronica persica (bird’s-eye speedwell; Eurasia): low-growing annual herb; leaves toothed (coarsely serrate) but not lobed; flowers white to blue with darker blue stripes, about 10 mm across width of petals; fruit strongly cordate (heart-shaped) and flatter than in V. polita

Veronica polita (speedwell; Eurasia): low-growing annual herb; leaves toothed (coarsely serrate) but not lobed; flowers white to blue with darker blue stripes, about 5 mm across width of petals; fruit strongly cordate (heart-shaped) and more inflated than in V. persica, with glandular hairs

 
Veronica hederifolia (ivy-leaved speedwell) in flower.
Flower of Veronica hederifolia (ivy-leaved speedwell).
Veronica persica (bird’s-eye speedwell) in flower.
Veronica polita (speedwell) in flower.
 

Lamiaceae (Mint Family): plants can be fragrant; stems often square; leaves opposite; petals often fused into bilabiate (two-lipped) corolla tube

Glechoma hederacea (gill-over-the-ground, Eurasia): evergreen perennial herb; leaves kidney-shaped to heart-shaped, crenate, palmately veined; flowers in axils of leaves; corolla distinctly two-lipped, with upper lip flattened; stamens 4, all anther-bearing, not extending beyond corolla tube

Glechoma hederacea (gill-over-the-ground) in flower.
 

Lamium amplexicaule (henbit, Eurasia): annual herb; leaves kidney-shaped to heart-shaped, crenate, palmately veined, smaller than in L. purpureum; inflorescence terminal (flowers gathered at end of stem); corolla dark pink to magenta, distinctly two-lipped, with upper lip hooded; stamens 4, all anther-bearing

Lamium purpureum (purple dead-nettle, Eurasia): annual herb; leaves kidney-shaped to heart-shaped, crenate, palmately veined, larger than in L. amplexicaule; inflorescence terminal (flowers gathered at end of stem); corolla light pink to lavender, distinctly two-lipped, with upper lip hooded; stamens 4, all anther-bearing

 
Lamium purpureum (left, purple dead-nettle) and Lamium amplexicaule (right, henbit).
Leaves of Lamium purpureum (left, purple dead-nettle) and Lamium amplexicaule (right, henbit).
Side view of the flowers of Lamium purpureum (left, purple dead-nettle) and Lamium amplexicaule (right, henbit).
 

Asteraceae (Sunflower Family): inflorescence is a capitulum (dense head) of florets (small flowers) that can mimic a single flower (think sunflower); florets typically of two types – disks, with petals fused into radially symmetric (see previous definition) tube, and rays, petals fused into bilaterally symmetrical (see previous definition) tube ending in a long, strap-shaped extension

Erigeron philadelphicus (Philadelphia fleabane, North America): short-lived perennial herb; leaves alternate, clasping the stem at the base; bracts around capitulum roughly in a single series (not overlapping); capitulum with disk and ray florets; sepals in the form of long bristles, rays >100, white to pink, with a strap <0.5 mm wide

Erigeron philadelphicus (Philadelphia fleabane) in flower.
Back of a leaf of Erigeron philadelphicus (Philadelphia fleabane). Note small lobes (auricles) at base of leaf.
 

Taraxacum officinale (common dandelion, Eurasia): biennial, glabrous (without hairs), with milky sap; leaves basal (all coming from base of plant), sessile (without stems), deeply pinnately divided; bracts around capitulum in two series; capitulum solitary on each stem, with only ray florets; sepals in the form of long bristles; rays yellow

Taraxacum officinale (common dandelion) in flower.
Longitudinal section through the capitulum (collection of flowers in a dense head) of Taraxacum officinale (common dandelion), with a single ray flower pulled out (on right). Note the milky latex oozing out where the cut on the capitulum was made. On the single flower, from left to right, note the small, white, inferior ovary, then the ring of fine bristles that are the pappus (modified sepals), then the white corolla tube with a long, yellow strap-like extension that are the modified petals.
Fruits of Taraxacum officinale (common dandelion) still attached to receptacle (some fruits removed). Fruits are brown, and minutely spiny at the top, with a long extended, white pappus (modified sepals) of bristles that form a "parachute" to help the fruits float in the air..