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Archive for June, 2011

Evaluating squash pollination

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.

Well pollinated squash

A perfect squash resulting from almost every incipient seed fertilized.

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.

Squash fruit abortion due to inadequate pollination

Squash fruit abortion due to inadequate pollination

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.

Poorly pollinated zucchini

Poorly pollinated zucchini: the fruit starts to grow, then shrivels and aborts.

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:

Deformed squash fruit from inadequate pollination

Deformed squash fruit from inadequate pollination

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.

Partly and fully pollinated squash

Partly and fully pollinated squash: the upper one did not have enough pollen for fertilization of all the seeds.

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.

Live and learn department

The squash borers got a couple more squash, including one I had done surgery to, to remove the borer, whom I thought was a loner. But the post mortem revealed that he had four siblings.

Tomato variety trials – some notes so far

We are testing some tomato varieties to see how well they do in our unique environment. Many varieties that do well in the northland are pretty poor producers here. In Coastal South Carolina, heat is a killer; already in June we have hit 101 and have been in the mid to high 90s for the first half of the month. Humidity is also very high, though we are prone to drought – which we have right now. My tomatoes are all in raised beds, and are watered as needed – with rainwater if I have it; when that runs out we use town water.

The soil is a mix of about 40% fine sandy loam, 40% compost, 10% crushed coquina, and 10% crushed charcoal. Some of these beds are in their second year and were amended with about one inch of new compost. The soil has been stirred as little as possible.

On all tomato varieties the lower leaves and lower suckers are removed. No leaves are allowed to touch the soil. No chemicals have been used, although we are considering the use of some mild ones for the future to see if we can retard early blight.

Biological control by the many paper wasps and assassin bugs apparently is keeping tomato worms out of the picture. Marigolds are also planted around the raised beds. These are reputed to be helpful in repelling insects, but we don’t know if it is a factor for any tomato pests.

Pollination is ensured by abundant bumble bees on our wild bee refuge, and the bumbles are often seen “buzzing” the flowers. This is called sonication, or buzz pollination, which releases great quantities of pollen with resonant vibrations.

Two varieties have already been sufficiently tried to say they’ve passed the taste test with flying colors. These are the large red cherry and the Abe Lincoln. For others, we have not harvested or we are wanting more samples to give a fair test.

One variety has a serious weakness – Super Sioux:

Super Sioux BER

Super Sioux BER

This one is close to being disqualified for further tests, with blossom end rot (BER) spoiling about 20% of the early harvest. If all the rest of the production comes clean, MAYBE, I’ll try it again.

Another one that’s pretty sorry is Homestead, which is supposed to be a heat tolerant variety. But this is the third year of testing for me; the plants are puny and they aren’t very heavily loaded with fruit, nor is the fruit sizing up well. They are also highly infected with early blight. I see no reason to continue testing this, especially with the limited amount of space I have.

Marion has proved the opposite of Homestead, though they are supposed to be related.

Marion tomato

Marion tomato

This variety produced large stocky plants that set a large quanty of tomatoes that are sizing up very well. They have some early blight on the lower branches, but the harvest appears to be outracing the disease. Only the taste test awaits to see if these get the thumbs up.

Abe Lincoln is already a winner, having proven its taste as excellent. The plants are extremely stocky, vigorous, and deep green, with no sign of any disease whatsoever. They are heavily loaded and already yielding ripe tomatoes.

Abe Lincoln tomato

Abe Lincoln tomato

Rio Grande looks very good, with a very good set, and no disease. It has not yet produced a ripe tomato.

Rio Grande tomato

Rio Grande tomato

Cherokee Purple also looks good, with good set and large tomatoes. None have ripened yet for tasting.

Cherokee Purple tomato

Cherokee Purple tomato

Black Plum is supposed to be more of a sauce tomato, but we find it to be excellent in taste. It has some early blight, but the yield should be good before the blight takes over.

Black Plum tomato

Black Plum tomato

One surprise for us is Verja’s Paradajz. It was tried last year and it just didn’t set enough fruit to really test it. This year, perhaps with our much higher bumblebee population, it set fairly well and the tomatoes are very large. It also has no disease evident at all.

Verja's Paradajz tomato

Verja's Paradajz tomato

And finally, besides the heirlooms, we have two hybrids this year – Park’s Whopper and Big Boy.  I am cutting back on hybrids, partly because I want to save seeds from at least some varieties. But these two are long respected as heavy producers, so I continued to try them. I must say that Big Boy is out of the running at this point. I won’t be growing it again. It is full of early blight, and I think some of the later tomato set is just not going to make it. There won’ be enough leaf surface to feed the fruit. We will get some of the early fruit, and that’s it.

Whopper is doing well, though it also has some early blight. But I expect we’ll get a very good crop before the blight gets these plants. I’ve grown Park’s Whopper several times over the years, and it has proven to be a very reliable producer. The flavor is also quite good.

Park's Whopper tomato

Park's Whopper tomato

We’ll return to this topic soon with more comments and photos.

Bubba, you’ve got a home here as long as you live!

While watering my flower beds, I noticed a hole next to the house foundation. I wondered what creature was accessing the crawl space. Could it be a rat, a snake?

I don’t get bent out of shape too much about wild critters. Most mean us no harm, and actually will help us. But rats and mice are certainly not welcome. And poisonous snakes would not be either, though I am happy for non-poisonous ones.

On a whim I tried filling the hole with water from the hose. In a moment this little guy popped out:

Bufo terrestris - Southern garden toad

Bufo terrestris - Southern garden toad

I don’t think he minded the water; he doesn’t like his skin too dry, so he goes underground when the sun gets hot.

But I told him he’s welcome to stay; my house is your house, as they say!

He’ll make a meal of many a pest insect (slugs too). Maybe he’ll eat a few of the good guys too, but on balance he does far more good than harm.

Here’s more info on toads, and how to care for them in winter:

http://www.nwf.org/News-and-Magazines/National-Wildlife/Gardening/Archives/2006/Backyard-Houses-for-Toads.aspx

 

Time for emergency surgery!

All of the various squashes are prone to suddenly wilt and die, just when we think we will have a bumper crop. It’s all due to a reddish moth that looks like a wasp to the uninitiated, that has a larva (grub) that eats the inside of the squash stems.

Squash borer adult

Squash borer adult

If you see this mama flitting around your squash, be prepared for trouble!  And you can see that she’s already been there. Note the holes and the damage to the main stem.

Squash borer adult - closeup

Squash borer adult - closeup

She’s not going to hold still very long to get the camera focused, but here you see the coloration that identifies her as an adult squash borer.

Once you see damage on the stems, just above ground level, that plant is not long for the world, unless you intervene. Soon, as it munches away, you will see gelatinous pellets of frass alongside the hole. The larva is growing.

We are going to try to catch this one young. We hope we can save the plant.

Squash borer frass

Squash borer frass

So we will carefully slit the stem, parallel to its length. This won’t hurt the stem, at least not near as much as the borer will!

Careful cut to find squash borer

Careful cut to find squash borer

Found ya! You little parasite!  You are dead meat!

Found squash borer!

Found squash borer!

We’ve saved this plant. Time to cover the wound with some moist soil, so it can heal.

One can try a less intrusive form of surgery by poking a sharp toothpick or a stiff wire straight into the stem every quarter inch or so above the entry hole. But this poses a risk of missing the larva.

Here’s one that was too late to save; the borer has already eaten out all the plant’s plumbing, and has grown to large size.

Squash borer from killed plant

Squash borer from killed plant

The squash borer is a serious pest of all kinds of squashes. Some try to kill it with pesticides, but this is fraught with problems. You must kill the adult in the brief time it comes to lay eggs – or the freshly hatched egg just before it bores into the stem.

Once it is inside the stem, it’s pretty well protected. But using an insecticide on squash that is blooming may contaminate the nectar and pollen that feeds the pollinators. Kill the pollinators – and you bite the hand that feeds you!

So I would personally rule out pesticides for borers. Most years, you can get a harvest before the borers arrive.

Some use aluminum foil around the stem to either confuse or prevent the moth from egg laying. Some wrap the stems in pieces of old pantyhose.

One technique that I have used for vining squash is to cover the stem with dirt every couple feet. The plant will put out new roots at that point. If the main stem is destroyed by a borer, the plant will still live and produce from its alternative roots.

What has worked for you?

It’s all my mother’s fault!

When I was four years old, my mother handed me two packets of seeds and pointed to a row in the garden.

“That’s your own row now. You can plant your seeds there just like I do.”

The pictures on the packages made their contents plain. The one held radish seed. I was sophisticated enough, having watched her do gardening, to realize that you had to put the seeds in the ground and wait for them to grow.

I liked radishes, so that was a hit with me. The second one had a picture of a pretty blue flower on it. I didn’t want to do flowers. I wanted things to eat.

But my mother insisted. “These are bachelor buttons. You are a bachelor, so they are appropriate for you to grow.”

Bumble bee on Bachelor Button

Bumble bee on Bachelor Button

I had no idea what she was talking about; her wry humor was not apparent to me until years later. But I guess she impressed me with her big words and I went along with her.

She helped me, of course. I learned to hand weed, to hoe, to water the plants – all the sorts of things that gardeners do. Both radishes and bachelor buttons were failsafe, and they did well.

The next year I got a bigger section and more responsibility. She gave me some tomato plants, and ever since then, gardening has been mostly about tomatoes.  I soon acquired the habit of carrying a salt shaker to the garden with me during tomato season.

I don’t recall ever growing any flowers again until my “mature” years.

I began planting flowers around and among my veggies when I retired. I was looking for beauty, but moreso for plants for the bees and for biodiversity.

Then, I planted some bachelor buttons. As they came into bloom, and I (and the bees) enjoyed their beauty, I began to be immersed in the memory of those bygone years with my late Mama.

She knew, of course that she’d infected me with the gardening bug; that was pretty obvious.

But I wish I could tell her now, how special and beautiful was that row of bachelor buttons!

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