Category Archives: Botany

Passion Flower and the Bees

I’ve never grown a passion flower plant before but at the end of the season, a local gardening center had the passion flower “Incense” at a great price so I decided to give it a try.

Passion Flower Incense

Passion Flower Incense

The plant didn’t do much for the first month; it just sat there in the garden, working to get established.

But now it’s starting to grow and is becoming filled with flowers.

Yesterday I noticed something about the way a bee interacts with a passion flower. It’s clear that the bee wants to get to the nectar and the nectar appears to be found in the center of the flower. But in making its way to the center, something interesting happens.

The male reproductive organ of the flower – the stamen – has two parts: the filament and the anther. The filament is simply the stalk that supports the anther. The anther is what produces pollen.

Passion flowers have five anthers and each of them open facing down. That means that when the bee crawls into the center of the flower, its back gets coated with pollen from the anthers.

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The female part of the flower is the pistil and the end of the pistil, the stigma, is where the pollen needs to land in order for the flower to be fertilized. The way the passion flower is set up makes it hard for the pollen to get to the stigma; that is, unless a bee is present.

After digging around in the center of the flower, the bee is coated in pollen. When the bee takes flight or lands on another passion flower, there’s a good chance that it might bump into one of the three stigmas of the flower with its pollen covered body. And when it does, fertilization takes place.

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I’m liking the passion flower plant. The flowers are interesting and seeing the bees pollination them is even more interesting!

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A Lackluster Spring

(To those who follow my blog,  I apologize for being away for so long. Late summer, fall and winter was a time of some health issues that took my focus from writing. But I’m thankful for those who still view the site (100 or more views a day) and I’m back!)

This has been a terrible year for spring flowers.

In December we had temperatures in the 70’s and this caused the lilacs to start to bud. But the cold of January brought an end to the budding and the lilacs this year are a bust.

March was a warm month and all of the shrubs and bulbs started to grow. It looked like it was going to be a great season of early blooms but then came April with nighttime temperatures in the lower 20’s. Anything that had started to blossom was damaged and only the toughest of the daffodils survived the cold. The magnolia bush had started to bloom but the cold destroyed them.

peonyThe plant that I find the most interesting throughout this weird weather is the tree peony. By late March the plant was filled with leaves and buds. When the freezing nights of April came, I thought the plant would never recover but it did. A few of the buds opened but all of the rest of them just stayed there in a state of suspended animation.

It’s now the middle of May and the peony is green, bushy and heathy and still covered with buds that have yet to open. Recently I pulled a few of the buds off and cut them in half to see what was going on.

IMG_2222When cut open, I could see the stamens (male reproductive organs) and the pistil (female reproductive organ) of the peony but instead of being firm and health, they were soft and damaged. It’s clear that the cold weather injured these parts of the flower. Since the development of the flower depends on plant growth regulators that are produced by these organs, their impairment meant that flowering wasn’t going to happen. A few buds escaped the damage but most weren’t so lucky.

Yes, this spring was a bust. The weird weather caused all sorts of chaos for the flowering shrubs and bulbs. Flowers are one of the most fragile parts of a plant and this year was too much for them. The good news is that the plants are all fine and will live on to reproduce again another year. I have hope of seeing lilacs, magnolia, tree peonies and spring bulbs all flowering again – next year.

Thanksgiving Cacti – It’s All About the Temperature

cactusA few years ago I wrote a post entitled  Things I Learned About My “Christmas Cactus.”  In that post, I explained how I’d learned that the so-called “Christmas cacti” that you find in stores around the holidays are really Thanksgiving cacti (Schlumbergera truncate).

I also learned that while darkness can make the cactus bloom, temperature is even a stronger force causing this plant to want to reproduce. That made sense given the way that my cacti blossom. I never worry about light and darkness yet they bloom every year.

But right now I have proof that temperature really is a strong factor in getting this plant to blossom.

I have a pot with four different Thanksgiving cacti in it. I have it hanging on a curtain rod in a west-facing window. The plant blossomed well around the holidays and since then, I’ve basically forgotten about it. I’ve watered it when I think of it, but that’s all the care it’s received.

Thanksgiving Cactus - 1/2 in bloom

Thanksgiving Cactus – only on side in bloom

One day when I was watering I was surprised to see that half of the pot was filled with buds while the other half wasn’t. What caused this strange phenomenon? Temperature. The half of the pot with buds was the part closest to the window. We’ve had a cold winter so those stems have been kept very cool, especially at night. The part of the pot that had no buds was the side facing the room.

The other interesting thing is that whatever factors cause the cactus to bloom, they appear to stay localized. Branches of a cactus that were close to the window are blooming while other branches of the same plant that were facing the room aren’t blooming. That seems to show that whatever causes the plant to bloom isn’t some chemical that translocates throughout the plant. Instead, the factors that cause the plant to bloom only affect the areas that are exposed to the cooler temperatures.

While days are getting longer and the intensity of sunlight is increasing, the cool temperatures close to the window were enough to get this cactus to re-bloom – well, at least half of it. I will admit it’s a little strange to see a pot with only half in bloom but it just goes to show that when it comes to getting Thanksgiving cacti to bloom, temperature trumps all!

 

Cucumber Beetle Resistant Parthenocarpic Zucchini – Say What?!?!

Partenon Hybrid Zucchini (Park Seeds)

Partenon Hybrid Zucchini
(Park Seeds)

If there’s one plant I’m really looking forward to growing in the vegetable garden this year it’s Partenon hybrid summer squash. I found this new zucchini in the Park Seed catalog. The two things about this squash that caught my eye are that it is cucumber beetle resistance and parthenocarpic.

One of the constant struggles I have with zucchini is dealing with cucumber beetles. While these beetles cause leaf damage to the plants, the real problem is that they’re vectors for bacterial wilt. Bacterial wilt is caused by the bacterium Erwinia tracheiphila. When a cucumber beetle chew on a leaf, if it carries this bacterium in its intestinal tract, it’ll transmit Erwinia tracheiphila to the squash plant through the tissue damaged by its feeding on it. The bacteria multiplies in the xylem (the vascular tissue of a plant that transports water from the roots to the rest of the plant). In time, the xylem clogs and the plant wilts and dies.

While I haven’t had as much of a problem with bacterial wilt as I have in the past, it’s still a problem. Sprays, traps, row covers and silver plastic mulch are all ways to limit the problem of cucumber beetles but none of them are fool-proof. The idea of a squash that resists the beetle sounds like a good idea to me.

The other cool thing about this squash is that it’s parthenocarpic. Parthenocarpic comes from two Greek words: parthenos meaning virgin and karpos meaning fruit. Parthenocarpy is the formation of fruit without fertilization and a parthenocarpic plant produces fruit without fertilization.

Squash plants produce male and female flowers. In order for a squash to form, a pollinator (usually a bee) has to take pollen from the male flower and transfer it to the female flower. This usually isn’t a problem but if the weather is cool and/or rainy or if the pollinator population is low, the fruit set might be diminished due to lack of pollination/fertilization.

A parthenocarpic plant solves these problem. The fruit will form and mature without pollination so any variables to pollination that would affect fruit set in a normal squash are gone. Also, if you’ve ever let a zucchini get a little large, you know how the center of the squash is full of seeds. In the case of parthenocarpic squash there are no seeds because it wasn’t fertilized. It’s a “virgin fruit!”

It should be interesting to see how this cucumber beetle resistant parthenocarpic zucchini does in the garden. I’ll still plant some other varieties of zucchini but this is the one I’ll be watching closely.

Blooming Petioles!?!?

If you look at most plants, the stalk that supports the flowers (peduncle) emerges from somewhere on the stem. Sometimes the flowers grows at the end of the stems and other times them develop along the stem, particularly at the place where the petiole of the leaves (the stalk that supports the leaf) meets the stem.

Streptocarpus

Streptocarpus

Since this is the norm, I was surprised when I was looking at the streptocarpus hybrids that I have growing in the house. The plants have started to come into full bloom but where those blooms develop surprised me.

Streptocarpus hybrids leaves grow in a rosette. Instead of large spaces between the leaves (internodes) like tomatoes or peas, in plants with a rosette growth pattern, the internodes are very short. This cause the plants to grow their leaves in a tight circular pattern. Some plants that have this rosette form of growth are dandelions, agave and african violets. In these plants the flowers still emerge from the stem, short and compact as it might be.

That’s why I was so amazed with where the flowers develop on a streptocarpus. Instead of developing from the stem, in this plant the flowers develop along the base of the petiole. Usually there are two or three inflorescences that grow from each petiole, the first emerging closest to the stem and the subsequent ones developing further along the petiole away from the stem.

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As one who’s always looking closely at where and how the various parts of a plant grow, this is something I’ve never seen before. I’m sure there are other plants whose flowers grow from the petiole but I don’t know of any other than the streptocarpus.

This is just one more example of the amazing variety of plant morphology. Who knows what the evolutionary advantage is in having blooming petioles? All I know is that streptocarpus hybrids have them and it’s a difference from other plants that’s pretty cool!

Mycorrhizal Inoculants – Help or Hype?

v1764While I was exploring what mycorrhizae are, I found that they’re available not only in potting mix. Park Seeds sells “Myco Blast” which is touted as a probiotic for your plants – the plant version of Bifidus Regularis®  in Activia yogurt! Territorial Seeds has “Myco-Edge Endo Myco.” I typed “mycorrhizae” into Amazon and found all sorts of mycorrhizal supplements.

All of this made we wonder if I’d missed an important component of gardening for all the years I’ve been growing plants. Is this the new frontier of gardening? Do I need to get these formulas in order to grow a good garden?

After exploring it, I’ve come to the conclusion, that for me, the answer is no!

(The only plants for which mycorrhizae are necessary for their survival are trees and shrubs that have endomycorrhizae such as pine trees. If you purchase a pine tree to plant in your yard, it already has the necessary mycorrhizae or it wouldn’t have grow to the size of a transplant. Also all of the inoculants that I found for sale were for ectomycorrhizae.)

A lot of organic gardening sites purport that tilling of the soil and the use of inorganic fertilizers and various pesticides have reduced the amount of zygomycete spores in the soil and therefore limit the number of mycorrhizae that can form in plants. That might be true though I have to admit that I have a some doubts about this claim – fungi spores are not only ubiquitous but also tough. I have a hard time believing that the ones that produce ectomycorrhizae don’t already exist in most soil.

But there are other reasons that cause me to question the use of these various formulas of “mycorrhizae.”

The first is that a number of common plants in the vegetable garden don’t form mycorrhizae even if the soil is full of zygomycete spores. Plants of the goosefoot family (Chenopodiaceae) and cruciferous plants (Brassicaceae) never form mycorrhizae. For me, that’s a large part of my vegetable garden, including spinach, beets, chard, broccoli, cabbage, radishes and more. Using a mycorrhizae inoculant on these plants will do nothing because they don’t form mycorrhizae.

But the biggest reason why I don’t think I’ll be using these products is because of something that research has found. Mycorrhizae help to extract water and nutrients from the soil and are particularly helpful when the soil is marginally fertile. But it’s been shown that plants which in the wild form ectomycorrhizae don’t form them if the soil is fertile.

That makes perfect sense. This mycorrhizal symbiotic relationship does cost the plant some energy in the form of carbohydrates that the plant provides to the fungi. When fertility is low, this cost to the plant is offset by the benefit of nutrients that the fungi are able to extract from the soil (particularly phosphorus). But when the soil is fertile, mycorrhizae offer the plant no benefit so they don’t form.

I fertilize my vegetable and flower beds so there’s plenty of nutrients in the soil for the plant to absorb. The odds are pretty good that even if I added mycorrhizae inoculant, mycorrhizae wouldn’t form because the plants don’t need it. Also most of the plants that grow in the vegetable and flower garden aren’t bred to live in marginal conditions where mycorrhizae show their greatest benefit. They grow best in fertile soil, the very conditions that limit the formation of mycorrhizae.

If I was planting a field of wildflowers that I never planned to fertilize – a native, natural garden – it might be of benefit to add one of the mycorrhizae inoculants to the soil. But then again, there would probably be all of the necessary fungi spores already in the soil.

All of these mycorrhizae products certainly don’t hurt anything and they might help. They’re also fairly inexpensive so it won’t break the bank to give them a try. But I can’t help but think that a lot of the so-called benefits from these products are little more than the placebo effect. You can say you added mycorrhizae to the soil and your plants grew better but without a microscope you can’t see the mycorrhizal associations so any “benefits” from these products can’t be proven to be the result of mycorrhizae.

I might learn more over time that’ll change my mind but for now, I’m glad to know about mycorrhizae but I don’t think it’s something with which I need to concern myself in the vegetable and flower garden.

I’d rather spend the money that these mycorrhizal products cost on good fertilizer to boost the fertility of the soil. I know that’ll benefit my plants!

Mycorrhizae… Wait, Myco-what?

A few weeks ago I needed some potting soil. When I got the bag of Pro Mix home, I noticed that it said it contained mycorrhizae. I knew that mycorrhizae had something to do with fungus and roots, but that was about it. So I did some research online and it’s led me on a journey of discovery about fungus, roots, water absorption and the latest hype targeted at gardeners.

IMG_1484aLet me start off by saying that the label on the bag of potting mix is a little misleading. The word mycorrhizae (pronouned mīkəˈrīzə) comes from two Greek words – mykós  meaning fungus and  riza meaning root. Mycorrhizae  is the symbiotic relationship between certain kinds of fungi and the roots of some plants. Since the term described the relationship between fungi and roots, it’s impossible for a bag of soil to contain mycorrhizae; what it contains are spores of the various fungi that, in the presence of roots, can form mycorrhizae.

OK, enough of my word usage obsession! What I’ve learned is that often in nature, the mycelium of some fungi (the vegetative parts of a fungi that’s made up of thread-like hyphae) can become interconnected with the roots of plants in order to help the plant absorb water and nutrients. This association is what’s called a mycorrhiza. Just as root hairs increase the surface area of the root, when the roots of plant become connected with the mycelium of fungi, suddenly the entire mycelium of the fungus becomes surface area for the plant to absorb water. While the fungi of mycorrhizae aid the plant, the plant provides the fungi with carbohydrates that the fungi can’t produce because they’re not photosynthetic. This is why mycorrhizae are symbiotic – both parties are benefiting from their association.

Ectomycorrhizal Sheath (from http://en.wikipedia.org)

Ectomycorrhizal Sheath
(from http://en.wikipedia.org)

There are two major types of mycorrhizae found in nature: edomycorrhizae and ectomycorrhizae. Ectomycorrhizae are less common in nature but are associated with members of the beech, willow and pine family. Many of these mycorrhizae fungi are in the class basidiomycetes, the fungi that we associate with toadstools and mushrooms. In ectomycorrhizae the fungi forms a sheath around the fine roots of the plant and the mycelium extends out into the soil to aid in the transfer of nutrients and water to the plant. Many of these plants have evolved along with the fungi and don’t produce any root hairs – they don’t need them since the mycorrhizae substitutes for the root hairs.

While ectomycorrhizae may not be a huge concern for the home gardener, they’re very important to the gourmet cook. Many of the mushrooms that are prized by chefs are the fruiting bodies of the fungi of ectomycorrhizae. Truffles, morels, chanterelles and others are all edible mycorrhizal fungi. Because of the complex relationship between tree roots and fungi which produce these mushrooms, cultivating truffles or morels is difficult if not impossible. These mushrooms grow in the wild and their prices reflect this fact.

Endomycorrhizae  (from http://sdhydroponics.com)

Endomycorrhizae
(from http://sdhydroponics.com)

Endomycorrhizae are far more common and occur in about 80% of all plants. Instead of forming a sheath around the root, in endomycorrhizae, the hyphae of the fungi penetrate between the cell walls and also penetrate the cells of the root, forming coils and branched structures. There are only about 30 kinds of fungi that form endomycorrhizae and all of them are from the class zygomycete, the fungi class that causes black bread mold. In endomycorrhizae, the fungi along with root hairs aid in transferring water and nutrients from the soil to the plant.

In the natural world, the fungi that can create mycorrhizae are ubiquitous and most plants growing in a natural environment have mycorrhizae. While you can see the sheath of ectomycorrhizae, the hyphae of endomycorrhizae are too small to be seen with the naked eye.

It’s clear that mycorrhizae are very important in the life of plants; in fact, it appears that this has always been the case. Paleobotanists have shown that endomycorrhizae are present in the fossils of early vascular plants. This symbiotic relationship between green plants and fungi appears to be vital to plants and their growth.

But does potting mix for house plants need to have the spores of zygomycetes mixed into it? Should gardeners rush out and buy some of the “mycorrhizae” inoculants that are on the market? Are mycorrhizae something that the home gardeners needs to think about?

Those questions are for the next post!