Porterweed shrubs are easy to grow — with caution
By H. JEAN SHIELDS
Porterweed: Family Verbenaceae, Genuis: Stachytarpheta, Species;Jamaicensis.
We are writing about the several species of the Porterweed family. The first
One to be considered here is the blue Porterweed shrub (S. Jamaicensis) which is the only Florida native Porterweed, a low growing sub shrub.
There is a lot of confusion about these shrubs. Not all of them are the same style of shrub, not all of them are the same color.
All of them grow in the full sun and tolerate a light shade, are salt tolerant, and are great butterfly attractors. They do not require frequent fertilization or much water. A good xeriscaping plant.
They are all considered somewhat invasive due to their habit of rapid self seeding. Little babies can turn up 50 feet away from the mother plant. You can pull them out easily and transplant them to increase your own bed, or pot them up and gift them away.
You can also easily propagate them by stem cuttings that will show results in a couple of weeks.
I have a blue Porterweed I have had for about 8 years. It is about 12 feet tall. You will not see that height in any gardening material. I guess mine is too happy. I am about to destroy it, for several reasons, which will become clear as you read on about the phrase “native plant” did not mean much to me at all. Now that I am immersed in Garden Clubbing and keep running into Master Gardeners, I find I am fostering a non native, invasive monster.
I would not let all of the above deter me from growing something I really like, except the darn thing is very, very tall and is now very. very woody and is not blooming in its beautiful old way.
There is a lot of misconception about what is a native plant and what is not. I am not going to lecture about that right now. Enough said, that I understand.
Now that I have been enjoying a non-native Porterweed, (Stachytarpheta Uticifolia). I do understand that all Porterweed plants, except the S Jamaicensis, are exotics.
When I bought mine, I was looking for a butterfly attractor and was not caring about any plant families, or species. I still do not do well at that level of education. All of this plant knowledge does take the carefree fun out of shopping for something and looking only for the tag that says, sun or shade, low water tolerance, and a butterfly attractor picture.
Shopping for a Porterweed is doubly hard because you cannot trust just the pretty blue flowers on the thin slender spikes. I mean there is bright blue, soft blue and a violet blue. I am not even talking a red or pink species because the flowers look so alike I will have to consider does the tag say 2 feet or more high, or lower and more spread out.
The leaves themselves are an education, and the best way to tell what you are actually going to be growing. The S Jamaicensis has leaves that are a dull green. The leaf margins are coarsely serrated and the teeth are usually pointing toward the tip of the leaf. The leaves are smooth on top, slightly hairy on the underside, no quilt look. Several small blue/violet flowers will slowly appear along the slender spike. Each flower will last one day.
The flowers, however, bloom mostly year around. They do attract butterflies, maybe a few bees. They must be sweeter than my old non-native giant because I have never noticed any bees around. The S Jamiacensis will grow to about 2 feet and be more mounding, at least 3 feet.
The delicate flower spikes push up from this mounding form, swaying in the wind. This is the plant I do not have. The flowers do not cover the whole spike.
Stachytarpheta Uticifolia is mine. The leaves are a darker green kind of shiny with acute marginal teeth that are more numerous and are outward pointing.
These leaves also have a distinct raised area between the veins, causing a quilted look This one is definitely a background plant.
This tall, woody shrub, with a distinct trunk is fast becoming established in Florida as an escaped exotic.
There is that exotic word again. No wonder there are so many landscapers and Master Gardeners around. They must know something about Mother Nature that the rest of us do not.
Remember there are no red native Porterweeds. I mention that because I just brought home three nice red Porterweeds from a gardening friend. I care not that they are non-native, because they are hard to find and I covet them.
Red Porterweed: Stachytarpheta mutabilis var. Same family, same Genus as the above. The colors and the fact that they are more shade tolerant than the blues are the main difference. They grow in same conditions of climate and water. They attract butterflies and will self seed easily. These plants will be welcome gifts to fellow gardeners because they are hard to find. I am sure the nursery industry will soon wake up to the marketability of these colors.
Lets hope they do not call them Native. These plants are native to South America.
The blooms appear on the shaft just as on the blue Porterweed, however they do last a little longer. The pink can grow 6 feet tall and about 8 feet wide.
There is a red flowered Porterweed – Stachytarpheta miniaces, a native of Mexico. This one only grows 3 feet tall.
There is a rare pink and a red dwarf of the pink. In this grouping they do have a violet flowered variety. It is S mutabilis var. Violacea.
All of these shrubs are really pest free. Can be cut way back and will, especially if cut back in the early spring, do great. You do not need to fertilize every three months. I feed my tree about once a year. I did not plant it in any special soil mix, however it is not clay either.
In case you are now confused about choosing a Porterweed, choose the native plant, S jamiacensis. It will be smooth on top of leaf and the ragged edges of the leaf will be pointing toward the tip of the leaf. Flowers will be a violet blue.
If you covet a red or pink exotic Porterweed, and can find one, just buy it and enjoy. The seeds are in the long spike and you can cut them off and they will not go out into the world and you can control the new little plants as they show up.
Do you know what an exotic plant is? I will explain in a couple of weeks.
Happy Gardening until we meet again.
H. Jean Shields is past president of the Garden Club of Cape Coral.