The Artistry of Seedbox

Winter is the perfect time to see Seedbox (Ludwigia alternifolia) in fruit, and to understand how this plant got its name.

Seedbox (Ludwigia alternifolia) with fruit capsules

Attached along the length of the standing stems of this plant are fruit capsules that look like perfectly carved wooden boxes, each with a convex top and rounded bottom, and with elaborate designs that appear to be carved on the cube’s lid.

Seedbox (Ludwigia alternifolia) fruit capsules

These tiny decorative fruit capsules are often visible throughout winter, splitting open at the seams when ripe to release the many tiny seeds inside.  Before the fruit capsule opens, the seeds may rattle, giving this plant another common name, Rattlebox.

How is this perfectly shaped fruit capsule produced?  Who is responsible for the beautiful carvings on the lid? (Could it be tiny flower elves?  Maybe there is a less magical explanation.)

Seedbox typically blooms in mid to late summer, usually July and August.  Let’s look at the flowers and buds for an explanation.

Seedbox (Ludwigia alternifolia) in bloom

In Seedbox buds, sepals are the outermost layer of flower parts. They are green and leaf-like, and play the role of bud scales, enclosing and protecting the other parts of the flower before it opens.  The photo below shows a flower bud, enclosed by the sepals. In the upper right of the photo, there is a notch in the sepals at the base of the bud, a narrowing of the structure, and a squarish impression in the leafy covering.  This covering is enclosing the flower’s ovary, the flower part destined to become the fruit capsule.  We can see two sides of the ovary, already hinting at the box-like fruit capsule to come.

Seedbox (Ludwigia alternifolia) flower bud. In the top right corner, note the square ovary with a leafy covering at the base of the bud. The ovary will become the fruit capsule; its square shape is already in place.

The purpose of the flowers is to attract visitors to assist with cross-pollination. The most effective pollinator will have a tongue long enough to reach the nectaries on the face of the ovary below, while brushing its body on the flower’s reproductive parts, including the Sweat Bee in the photo below, and some Bumble Bees.  Other bees and beetles are known to visit the flowers for nectar and pollen, while flies, wasps, and butterflies only partake of the nectar.

Seedbox (Ludwigia alternifolia) flower with a visiting Sweat Bee. Her tongue is long enough to reach the nectaries while her body brushes against the flower’s reproductive parts, dropping off and picking up pollen.

The bee is rewarded for her pollination assistance with nectar and pollen for herself, and she will also carry some back to provision her nest for her larvae.

Seedbox (Ludwigia alternifolia) flower with a visiting Sweat Bee. Notice the pollen she has packed on her hind legs to bring back to her nest for her larvae.

Let’s look at an open flower.

Seedbox (Ludwigia alternifolia) in flower.

Working from the outer ring of flower parts layer by layer towards the center, each flower has four sepals, four yellow petals, four stamens (male reproductive parts) and one pistil (female reproductive part).  The pistil consists of a stigma at its tip, where the pollen must be deposited in order for pollination to take place, the style, which positions the stigma and through which the pollen must travel to get to the ovary, which is at the pistil’s base. Seedbox stigmas look like miniature pompoms perched at the top of their pedestal-like styles.  As the ovary ripens to a fruit capsule, if the pollen successfully reaches and fertilizes the ovules in the ovary, seeds will be produced.

Seedbox (Ludwigia alternifolia) in flower. The green sepals are peeking out from behind the yellow petals. The petals, stamens and style of the pistil are attached to the top of the ovary, while the sepals are appressed to the four sides of the ovary.

If we look at the very center of the flower, we can see the petals, stamens and pistil attached to the square top of the ovary, with the sepals appressed to the four straight sides around the ovary’s outside edges.

The flower parts that made pollination possible eventually wither and drop off, leaving their mark on the face of the ripening fruit capsule.

The petals drop off after about a day, leaving tiny scars that can be seen at each corner of the developing fruit capsule’s topside.  As the stamens drop off, each leaves a mark midway between the corners, just slightly in from the edge of the square.

Developing Seedbox (Ludwigia alternifolia) fruit capsule. Notice the scars left by the petals and stamens which have withered and dropped off. The stigma, style and sepals are still present.

Eventually the pistil’s stigma and style, positioned at the center of the flower above the ovary, drop off, leaving a round scar as a reminder of their role in the flower’s reproduction strategy.

Developing Seedbox (Ludwigia alternifolia) fruit capsule. The stigma and style have dropped off. The sepals are still present.

Finally the sepals are gone, leaving the bare woody ‘seedbox’.

Seedbox (Ludwigia alternifolia) fruit capsules

The face of a Seedbox fruit capsule records the history of its pollination story. The four large-ish evenly spaced ovals in each quadrant on the top of the fruit capsule were the nectaries, the source of the beverage that enticed the flower’s visitors.

Seedbox (Ludwigia alternifolia) fruit capsules. The scars from the petals and stamens are visible near the edges of the fruit capsule’s top, the round scar in the center marks the spot where the style was attached, and the four ovals are the flower’s nectaries.

Seedbox prefers moist soil, and can be found growing in wet meadows, prairies and woods, as well as in drainage ditches. It is native in Quebec and Ontario provinces in Canada, and in the United States from Vermont west to Wisconsin, southwest to Colorado, then south as far as Texas and the Florida panhandle. It is a member of the Evening-primrose (Onagraceae) family.

If you’re looking for something to do while waiting for spring, look for Seedbox!

Dedication:  Pam, this is for you!

Related Posts

Evening Primrose

Resources

Illinois Wildflowers

Illinois Wildflowers Flower Visiting Insects

Missouri Botanical Garden

USDA NRCS Plant Database