Archive for the ‘Pollination’ Category
Many beginner gardeners start off with a bang and are excited and encouraged when their seeds germinate and their started plants take off and grow. But then the weeds begin to show more vigor than the desired veggies.
Even experienced gardeners, who know that you cannot let the weeds even get a couple day’s advantage, sometimes lose the garden to weeds, when there’s several days of rain and it becomes too muddy to get into the garden.
It’s pretty dismaying when you have trouble finding your plants among all the weeds. You can wind up spending many hours of catch-up work, and still find that your plants were severely set back, both by the competition with weeds, and the damage you did to their roots when you pulled up the weeds.
It’s been several years now, since I basically solved the weed problem. Sure, there’s weeds in my garden, but they are few and far between, compared with what they used to be. I find that just a few minutes a week is sufficient to pull up the weeds, and keep my own veggies growing without competition.
There are three basic reasons why the weed problem mostly disappeared:
1. I no longer till my garden. Every time you turn over the earth, you expose new weed seeds to sunlight and air. Weed seeds can lie dormant in the soil for many years, then suddenly germinate when you’ve given them ideal conditions to grow.
I’ve been able to pretty much eliminate tilling because all my gardening now is in raised beds. I was forced to go to raised beds, because our land is as flat as it can be, and we are subject here in coastal South Carolina to occasional heavy rains. These rains would flood my garden and pretty much spoil it. Few of our garden veggies can stand in water without dying or getting riddled with disease.
The raised beds took a lot of work to set up, but once they are up and running, the work forever afterwards is minimal. I started with a mix of about 40% sandy loam topsoil, 40% well rotted compost, 10% crushed coquina (for lime and minerals), and 10% crushed charcoal (to help prevent leaching when those heavy rains come).
These raised beds are in production year around. As soon as one crop is finished, I start with another. About the only disturbance to the soil is when I pull a deep rooted plant like tomatoes, or a root veggie like carrots or turnips. With smaller plants like beans or peas, I just snip them at the soil surface and leave the roots in the ground.
2. When planting or setting out a new crop, I topdress it with about an inch of fresh compost. This compost has very few weed seeds, as it reaches a high temperature during its formation.
My soil remains soft; I can easily plunge my hand up to the wrist into the soil, just by wriggling my fingers and pushing. The soil smells sweet and it’s full of worms and insects, unlike most agricultural soils in the area, which are quite barren of life. I always figure that the worms are tilling the soil for me, as much as it needs and in a very natural way.
3. I don’t let the weeds go to seed. By having raised beds, I never walk directly on my garden. I have more-or-less permanent walkways between the beds. This means that I can always pull weeds, even if it’s very muddy. The weeds never get a chance to get ahead of me.
I can’t take very much credit for this system of weed supression. Actually it came as a pleasant surprise. And I had to study it a bit to come to an understanding of why there are so few weeds.
I recently received an e-mail from “Solutions from Science” that promotes a system of seed sprouting for emergencies.
Now the concept is good. We grow sprouts ourselves, and they are easy to do and highly nutritious.
But I get suspicious when I see that hype and misinformation are used to promote a high-priced product (and it is very high priced).
I have two questions for these folks – “Why can’t you tell the truth?” and “Why do your prices seem like a real rip-off?
I’ll leave the reader to judge further about the price. You can go to their site, if you want to see their comercial at: http://www.survivalsproutbank.com/
But here’s what they said in their e-mail with reference to the pollinator crisis:
“If only it was [sic] the weather. Unfortunately, it’s something much more insidious and much less understood than climate changes. It’s called “Colony Collapse Disorder.”
With Colony Collapse Disorder, you have entire hives of bees dying off, and no one has been able to ascertain why or pinpoint a cause.
You may wonder how this affects your garden.Look out the window. Do you have beautiful tomato plants… with no tomatoes? Are your squash plants leafy and vibrant… with no squash? Are you looking at a luscious green garden with little or no produce to show for it? That’s what a dearth of honey bees will do. You have to have bees to pollinate in order to make many vegetables and fruits.”
Tomatoes – honey bees? Nope! It’s true that honeybees will work tomato plants – when they reach a saturation point where little else is available and honey bees are desperate. And they may accomplish a little bit of pollination.
In all my years as a beekeeper and flower observer, I’ve seen honeybees on a tomato blossom maybe a half dozen times. Now I’ve seen bumblebees many thousands of times, and even seen sweat bees a whole lot more often than honeybees.
I love my honey bees and I maintain a few hives in my back yard. But it would be a phony argument for me to ascribe my tomato pollination to them. I have two species of bumblebees that consistently visit my tomato blossoms. And that’s the truth!
Squash? Again, it’s not a favored plant for honey bees. In a garden setting, which is what these folks refer to, honeybees aren’t likely to even visit squash blossoms. They are beat to the draw by squash bees, bumble bees and sweat bees.
Now in a large field, where there is little competition from other flowers (and there are few squash bees), honey bees are brought in to pollinate the squash. And they do a fine job, with a little help from bumble bees.
They go on to say: “According to the U.S. Department of Agriculture, about a third of our food comes from pollinated plants, and the honeybee is responsible for 80 percent of that pollination. Larger bumblebees cannot pollinate as effectively (if at all) as the smaller honeybee. Today, wild populations of bees are nearly gone. Instead, the bee has become dependent on the human population to insure its survival, and beekeepers struggle to maintain vibrant bee colonies.”
Struggle? I’m not struggling to keep my honey bees alive. They are doing fine, thank you – as long as my neighbors obey label directions in using pesticides, I’m confident they will continue to do fine!
Bumblebees not pollinators? HA! A bumble bee is about three times more effective in pollinating cucumbers than a honey bee!
And many flowers are almost exclusively pollinated by bumblebees. Now in an agricultural setting, honey bees are more important, partly because they have 30,000 hive members as opposed to around 100 for bumblebees, and honey bees are portable and manageable.
But to question bumble bees’ ability to pollinate? That’s the biggest one yet!
What bothers me (and I see this a lot, particularly when someone is selling something) is the mixture of fact and fiction. When that happens we wind up with “myth” or “hype.”
And I’m not going to buy anything from those who play fast and lose with the truth!
It’s time for a short course in cucumber pollination. On Internet gardening groups and mailing lists, this question keeps coming up, over and over: “Why are my cucumbers falling off, or becoming deformed?”
To answer the question, we have to go back to some basics, because many new gardeners don’t understand them.
First off, cucumbers have separate male and female flowers. They are produced on the same plant – and the plants are basically self-fertile, although there is evidence that pollination is improved when there is cross pollination between separate plants.
Pollen must be transferred from the male blossoms to the female blossoms. It’s amazing to me that many people assume that this heavy, sticky pollen will just jump from one to another all by itself. Believe me, it does not jump – it would take a gale wind to move pollen from the male – and that kind of wind would destroy the plant.
Some plants are wind pollinated – corn, grasses, pecan and hickory trees, ragweed – but these make light, fluffy pollen grains that are produced by the billions.
Bees are the workhorse pollinators for cukes - basically honey bees and bumble bees; with occasional minor help from other bee species. Some will also say some beetles, ants, and other insects can tranfer pollen – but these are negligible.
A brawny and fuzzy bee is the best possible pollinator. They are totally equipped with branched hairs and strong electrostatic charges to carry pollen. A bee pushes its way through the flower structures and picks up large quantities of pollen on its body.
Now a bumble bee has been shown by studies, to transfer about three times as much pollen per flower visit than a honey bee. But honey bees make up in numbers what they cannot do in comparison to bumble bees. A typical bumble bee colony is about 100 workers, while a honey bee colony may have 20,000 to 30,000 workers.
Many gardeners assume that when a bee goes to a flower, that it is instantly pollinated. While this can be true for a fruit with a single seed (like a peach), it is not true of multi-seeded fruits like cucumbers. Many grains of pollen have to be delivered – and this takes numerous visits by bees.
If no or very little pollen is delvered, the fruit simply aborts. There may well be spoilage, starting from the blossom end. This is due to an opportunistic fungus, but no fungicide will fix poor pollination.
Well suppose then, that a few more grains get delivered to the flower – and some seeds get fertilized by those pollen grains.
The fruit may grow, instead of abort, but it will be slow growing and can be highly deformed.
The only portion of the cuke that developed was the portion where the seeds were – which is on the outer curve of the cucumber. On the inner curve there are NO seeds, so the flesh didn’t develop in this area at all. Also note that on the top end, there were very few seeds that formed, so the top end is also undersized.
When a full complement of pollen is delivered and evenly distributed across the stickly stigma of the female flower, the finished cucumber will look like the top one. It will grow rapidly, and be crisp and good flavord.
If some pollen is missing – and some seeds do not get fertilized the deformation of the fruit in the area of the missing seeds will show up in the shape of the fruit, as in the lower example in the photo above. The fruit forms a “neck” on the right side, due to missing fertilized seeds.
Cucumbers need to grow fast to be of good quality. Lack of water, excessive heat or cold, fertility, or plant disease can slow down growth. This makes the flesh tougher and dryer – and it can be bitter as well.
Anything that slows growth can cause bitterness – and this includes inadequate pollination. A poorly pollinated cucumber of the same size as a well pollinated one will usually be a day or two older. It will be tougher, and is more apt to be bitter.
Another problem with poor pollination is that the deformed area is the first place that spoilage will occur, if the grower tries to store, or send to market his or her cukes.
All in all, we see that good bee populations are critical to obtaining the perfect cuke.
Now, it is possible to hand pollinate cukes – yes, we can do the bee’s job, and we’ll talk about that in future articles. But, if you have more than a few plants that you are trying to hand pollinate, you’ll quickly come to appreciate the tremendous service the bees do for us!
Some have commented to me that I seem to spend an inordinate amount of my blog on the topic of pollination, and have asked why.
There are several answers. One is that good pollination information is hard to find, though there are many sources of inadequate, or just plain wrong information online. And a lot of garden and farming literature simply ignores pollination completely.
I was just looking around on the Internet at various Extension publications about watermelon culture, both for those who sell them and those who just raise them for home use. It’s surprising to me how many of them say nothing about pollination. To me, this is a disservice when a serious Extension publication purports to teach growers, yet assumes pollination will just take care of itself.
I have seen entire fields of watermelons, squash and other crops that were unharvestable or had to be severely culled, because of pollination failure. Pollination is a vital input in agriculture today, but it’s the least understood of all inputs.
So, as you can see, I am working on an article on watermelon pollination. If you don’t understand watermelon pollination, you don’t understant the plant!
A second reason that I concentrate on pollination is that this was my livelihood and specialty for my career. Although I am now retired from active duty in the contract pollination field, I figure it’s my responsibility to make sure I share the things I have learned in years of experience, observation, and study.
A third reason, is that I have available the many years of photos that I’ve taken, so I can usually well illustrate the points I make – and this makes it more interesting and clear for my readers.
You could say, this is the payment of dues for my spot on this earth. And I hope it does help!
Many gardeners, especially new ones, are dismayed to find that the luscious ears of sweet corn that they expected look more like this:
Only a few kernals are present on the cob! All that hard work, fertilizer, watering, and all is just wasted!
(Please note that all the illustrations of corn pollination are with field corn, as I do not currently have room for sweet corn in our garden – a problem I’m working on – but the illustrations will work fine; all the principles are exactly the same.)
There are two main reasons why we have failure to pollinate: one is that the pollen is dead, and the other is that the pollen just did not reach the female flowers.
Dead pollen is common in years of extreme heat and drought during the pollen shed time for corn. Corn is rather unique among plants in that it is on an exact schedule from the day it is planted until the day it is harvested. When pollination time comes, whatever will happen will happen, and it only lasts a few days, after which the opportunity is gone. The corn will go on doing its thing, but all the inputs of the farmer or gardener are wasted if pollination doesn’t occur.
Corn is generally wind pollinated. Lack of wind can be a big factor in corn pollination. When one sultry day follows after another, corn pollination can fail.
A morning thunderstorm can do an immense amount of pollination in that first rush of wind before the rain starts. There is normally a flush of pollen shed in the morning just after the dew dries, and there may be another smaller discharge in the evening as the air cools. The male flower is the tassel at the top of the stalk.
An acquaintance of mine had a charter helicopter service in Illinois, and he was kept busy during the corn pollen shed, by contracting with farmers to provide wind for pollination. He would hover over the fields, moving up and down the rows – and got paid for it, because it was a valuable service for the farmers.
The pollen is produced inside the anthers:
Gardeners generally have pollination problems for the second reason – pollen doesn’t reach the female flowers at the right time:
The silk is the female flower which can be seen at the tip of the incipient ears on the side of the cornstalk. Each thread connects to a single incipient kernal on the ear. When it is green and tender, it is receptive, but it will turn brown in just a few days and the opportunity to pollinate is gone.
When a grain of pollen falls and sticks to one of the silks, it begins to grow a pollen tube down inside the silk strand, right to the incipient seed, which it then fertilizes.
The problem with garden pollination is that there are usually few plants; not a whole field; there is a limited amount of pollen available – and it may blow the wrong way. New gardeners are frequently advised to use four short rows, rather than one long row, for this reason. Corn planted in blocks does pollinate a bit better.
For even more pollination insurance, do it by hand – it only takes a minute. When tassels first appear, pollen shed is only a day or two away. If you look at the tassels in early morning light, you can see the pollen, if you look toward the sun. If you shake a tassel there will be a visible dust from it, if it’s ready. If you shake it too hard, of course you’ll shake loose the anthers themselves.
So, when the tassels are ready, in the morning just after dew is mostly dry, bend a tassel over the silk (on another plant) and shake it.
Or you can snip a tassel and go down the row, “dusting” each silk. If you do it gently, focusing as much of the pollen on the silks as possible, you can do 10-15 ears for each tassel.
On bigger patches, you can simply walk the rows with your elbows out, so you give the stalks a bit of a jar, which will shake loose the pollen.
Some gardeners claim the process works better if you play soft music (but that may be a myth).
Corn is considered a wind pollinated plant. It’s pollen is tiny, and millions of grains are produced; only a small portion of them falling onto the female flowers.
Some falls on the leaves, some on the ground, and some will fall on your car hood, if you are downwind of a corn field.
Because the grains are small and have very little protein, they are not a priority pollen for bees to gather to feed their brood. However, many times corn pollen shed is during a general time of pollen dearth; on these occasions honey bees and bumble bees will vigorously gather corn pollen.
In the process of gathering, they will shake loose quite a bit also – and this can fall on adjacent plant silks. So, while corn is basically a wind pollinated plant, bees can be significant in pollination, particularly if there is no wind.
I have *almost* no insect pests in my garden.
I’m not bragging so much as wishing to share some wonderful principles that I have learned.
I like to browse the Internet garden groups, and am seeing large numbers of gardeners who are losing all or a major part of their garden crop to aphids, grasshoppers, tomato worms, flea beetles, squash bugs — you name it, and somebody, somewhere has a major problem with it.
If these are a problem year after year, something is wrong. We often treat our gardens as if we are fighting a fire. We stamp out a spot fire here, and another pops up there. We are in constant damage-control mode. A garden should be a symphony, not a battle zone.
Here are some of the important principles to consider:
1. Learn to work alongside Nature instead of fighting her. Simply by tilling the soil, we are altering Nature a great deal. Then we plant monocultures, add herbicides, spray poisons for pests, add extremely concentrated nutrients, and generally totally disrupt Nature’s balance in multiple ways. How can we reduce our impact and get things back into balance?
My garden is no longer tilled. The only soil that’s disturbed is the spot where I put a seed or a plant. Minimal! I don’t pack it down either. All my gardening is in raised beds that I can reach without walking on it. I let the worms till it, the natural way. I can wiggle my fingers and easily dig six inches into the soil.
2. Feed the soil. Our southeastern soils are naturally heavily leached, so they are mineral poor. They tend to be higly acid. Organic matter is near zero because of burning of crop residues and scorching of the sun. I add about an inch of compost each spring on the top. The worms till it. Then I use lots of leaves and grass clipping for mulch around the growing plants. This cools the soil, preserves moisture, and promotes biological diversity in the life of the soil.
Yes, plants grow much better when the soil is teeming with life – much of it too small for you to see. These organisms feed the plants. Plants grow sturdy and resistant to pests. If used at all, fertilizer is used sparingly. We don’t want an artificial growth spurt, especially one from overuse of nitrogen, which actually makes plants more susceptible to insect pests and disease.
3. Aim for as much biodiversity as possible. Mix it up. Yes, plant your flowers intermixed with your veggies. If you choose your flowers well, you can have nectar and pollen sources that run continously through the garden season. Some folks do this for pollinators – and this is good – but most don’t realize that you also gain pest control. Many pollinators, soldier beetles for example, in their adult stages are voraceous predators in their younger life.
4. Don’t freak out when you see a pest, and go to battle to eradicate it! Identify it. Learn about its life cycle; its food preferences; its enemies. The more you know, the better you are prepared to deal with it.
A lot of folks dust their garden at the first sign of any insect. This is very bad policy; first the insect may well be a friend. And second, using a pesticide that’s not labeled for an identified pest is a violation of the label (pesticide misuse), and it may well be ineffective or add risks that you don’t need.
5. Learn to accept some damage and the sight of a few pest insects. Ten years ago, we had a plague of Japanese beetles. Today, I can count on my fingers the number I see each year. The reason – we are practically overrun by assassin bugs, who love to eat Japanese beetles.
Now when I see an occasional Japanese beetle here or there, I am glad. I don’t want a pest to die out completely – as its control may then also die or leave the area. I just want to keep them in balance.
A critical, but often overlooked or misunderstood part of growing squash is pollination. Some folks have a vague notion that bees are good – that bees have to visit the squash blossoms – and they assume bees will come.
In these days of pollinator decline, this is not a valid assumption. To grow squash sucessfully, one must ensure good pollination. And pollination is not just an on/off switch, where a bee just visits the flower and pollination is accomplished.
Pollination is a progressive thing with any multi-seeded fruit. You can have many stages, from no pollination at all, to full pollination. This is because many grains of pollen must be delivered to the sticky stigma of the female flower – two pollen grains for each incipient seed. And these pollen grains must be evenly spread across the surface of the stigma.
The perfect squash in the photo above results from almost every incipient seed being fertilized. The act of fertilization stimulates the development of the flesh of the fruit.
Female squash blossoms have an ovary – the incipient fruit – at the base of the flower. If no pollen grains are delivered, the ovary will simply shrivel and dry up. If you touch it, it will fall off.
But, if a few grains are delivered, the fruit may actually start to grow. This fools some people into thinking that it’s pollinated.
The fruit will stop growing, shrivel up and often rot at the blossom end. This is not blossom end rot. Blossom end rot is a calcium metabolism problem; it shows up in fully-formed fruit; and it is much more common in tomatoes than squash.
There is a fungus involved here, but it is opportunistic; no amount of fungicide will prevent this fruit from aborting.
Zucchini (courgette) and other squashes all will exhibit the same kind of response to inadequate pollination.
Let’s suppose a few more incipient seeds are fertilized, but still nowhere near the full quota of seeds. This is what you get:
The fruit may actually size up somewhat, but it still will be wrinkled and poor quality. It will also grow much slower than a well pollinated fruit.
The poorly pollinated squash on the top is actually 2 days older than the well pollinated one on the bottom.
When I was in the pollination business, a farmer called me. He was just about in tears. He had planted 75 acres of yellow squash for market. During the winter, he had given me an order for bees to place on the fields, and he gave me the date he expected to need them. But he planted his squash much earlier than planned – taking a risk with frost – but he figured he’d win big if he had the first on the market.
Unfortunately he forgot to call and tell me he needed the bees earlier. Now his harvest crew was on the first picking, and they were throwing away almost the entire picking. They looked just like the upper squash in the above photo. I went straight to his farm that morning, and bees were notably absent from his fields.
The bees were delivered that night, and the rest of his harvest was very good. The problem: The day of the first picking, there was very little squash on the market – and it was bringing $18 a box. If he’d had a normal picking, it would have brought a small fortune. But the price dropped rapidly, and by the fourth picking only brought him $4 per box. There was no 5th picking, as the market price of $2 a box would not pay the picking cost.
The lesson is clear: we need to pay much more attention to the bees. Pollination is a critical part of growing squash, whether for the garden or the farm. And commercial growers cannot assume wild bees will do the job!
Pollination failure can occasionally happen from a rainy day. In small plantings, you sometimes have crazy plants that have all female and no male flowers. And extreme heat can kill squash pollen. So there are other possible reasons for pollination failure. But persistent pollination problems usually stem from a lack of bees.
In an upcoming post, we’ll talk about the kinds of bees that do squash pollination.
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