Physocarpus malvaceus, mallow ninebark

10/23/2014 9:14 AM

Physocarpus malvaceus, mallow ninebark; Roseaceae family

It is said that a woman, perhaps a teacher at Rogers High School, brought many plants into Drumheller Springs Park that are not native to the park but are native to its ecological type. These introductions are obvious in the northwest corner of the park with sagebrush, prickly pear, mountain mahogany and other plants in a rather small group that are found nowhere else in the park.

There are at least two other shrubs that have only one plant in the park. I suppose she brought these in, too.

One of these is Physocarpus malvaceus, mallow ninebark. The plant is just west of tall pine grove. It’s a low shrub and it doesn’t seem to be thriving.

April and I started our wildflower photographs in the 1991 burn, in Riverside State Park. There is a luxurious P. malvaceus there. Once again, there is only one plant in the region we searched.

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My primary resources have little to say about P. malvaceus. Neither Jepson Herbarium nor Flora of North America list it at all.

I have very few photographs and I don’t have good photographs.

It’s an interesting plant. It needs more attention.

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The shrub is just west of tall pine grove.

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Paul Slichter and the fire fighters say the inflorescence is a corymb. Burke and E-FLORA BC say it is a terminal cluster. E-FLORA BC says half round terminal cluster. Montana Plant Life says it’s a round cluster.

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[Corymb – a flower cluster whose lower stalks are proportionally longer so that the flowers form a flat or slightly convex head.]

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Burke says there are 2 pistils. Paul Slichter says 1 or 2 but could be 4 or 5. E-FLORA BC  and the fire fighters don’t comment on the pistils. Montana Plant Life says 2 pistils, sometimes 3.

I don’t have a photo that displays the pistils.

I don’t know what the greenish structure is that looks like an opened sphere in the front-view flower. Can it be 2 pistils? The side-view flower might have two styles that might be fused at the base.

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P. malvaceus is Rose family so it has an hypanthium. Here’s a definition of hypanthium that I’m comfortable with. I don’t think I have seen it put this concisely before: a cuplike or tubular enlargement of the receptacle of a flower, loosely surrounding the gynoecium or united with it.

However, this definition from Wikipedia:  The bases of the sepals, petals, and stamens are fused together to form a characteristic cup-like structure called a hypanthium.

Wikipedia’s Glossary of Botanical Terms refers us to ‘floral tube’: tube bearing the perianth and stamens, consisting of tissue derived from the receptacle and/or perianth and/or stamens; hypanthium.

And this from the on line Dictionary of Botany: The flat or cup-shaped receptacle found in perigynous flowers. It is joined to the ovary when the ovary is inferior.

Botany Word of the Day has this: Hypanthium: A cup shaped or tubular expansion of the receptacle of a flower. Formed by the fusion of the basal portions of sepals, petals and stamens from which the rest of the floral parts emanate. Referred to as corolla tube, floral cup, floral tube or Calyx tube.

There is no visible transition from stem to the base of the flower in the photo below. The stem obviously encloses the ovary. The sepals are attached at the top of the hypanthium, bent away from the petals.

We could say the sepals are lobes of the hypanthium. And we can see the hypanthium as a calyx, the sepals as the lobes of the calyx, the base of the sepals fused.

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Burke says there are stellate [star shaped] hairs [trichoms] all over the plant. Even on the petals.

I don’t have closeups that show the star shape of the trichomes but you can see trichomes [hairs] covering the stems and even some on the margin of the petal. 

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The leaves are alternate, that is, one to a node.

And there, ‘inside’ the attachment of the leaf is the stipule characteristic of Roseaceae family plants.

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P. malvaceae foliage has the maple leaf look.

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The fire fighters say the leaves turn brownish red in early autumn.

The tendril is winter vetch trying to strangle it.

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Several resources mention that the branches are angled so I suppose that’s important. I don’t have a photo showing branch angle.

The sources mention the shredding bark on the older branches. It is distinctive.

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Most of the sources say the fruit is a follicle. The fire fighters say it is a capsule. But a follicle is sort of a capsule … the number of chambers in the fruit is an issue.

I don’t know if these are buds getting ready to open or flowers in the process of becoming fruit. I’m assuming the blossom low and on the outside of the inflorescence is a late blossom and the rest have done their job and retired.

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The ‘flower’ in the upper left might be displaying two or more pistils.

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The fire fighters have an interest in P. malvaceus. Here are some of their facts:

Seeds stored in the soil are 11 percent viable, and germinate in partial shade on scarified soil

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FIRE ECOLOGY OR ADAPTATIONS : 

Mallow ninebark sprouts vigorously following fire.  Sprouts originate from horizontal rhizomes, of which a high proportion are situated in mineral soil. Mallow ninebark has 36 to 99 percent of its rhizomes buried in mineral soil, ensuring its potential for survival and sprouting following a fire. It has been ranked in the highest fire-survival category in a western Montana study

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Wikipedia has this caveat:

This shrub is a pioneer species that increases after disturbance and decreases as the overstory grows back and shades it out. It grows rapidly after events such as wildfire, sprouting up from its rhizomes. It is considered a "fire-resistant" plant. It survives fire and resprouts, becoming more common on burned sites than unburned.^[1]

This plant is known to hamper regeneration of forest habitat after disturbance such as fire or logging. It outcompetes new conifer seedlings. It is controlled with herbicide spray in some regions.^[1][2]