I tried growing a couple of the big types of pumpkins this year in July. I worked mushroom compost and cow manure into the soil and planted them in IRT \"green\" plastic mulch watered with drip tape.
Well they set fruit and the fruit reached about thirty pounds after two weeks. Then the plants got powdery mildew and died quickly. The pumpkins did keep all of the way until Halloween, but they were not what I was hoping for size wise.
When would you recommend planting giant pumpkins down here in Southern California? How would you recommend fertilizing them? What would you recommend to fight the fungus problems (I'm not opposed to using inorganic methods with pumpkins planned for jack-o-lanterns). Is there a systemic, that despite being unsafe for food production, would help me get huge pumpkins?!
Your approach can work. I assume your drip tape is under the plastic(?). Since the plastic precludes using a granular fertilizer, inject a high-quality liquid bloom formula into the water supply once per month -- those nutrients are also needed to grow larger fruit. I recommend Dyna-Gro Bloom formula.
For gardeners without a plastic cover (this can work too), I recommend Gro-Power Flower & Bloom formula, initially 1/2 cup around each plant where the water will hit it, then 1 cup per month per plant thereafter.
In all cases remove new blossoms after a suitable amount of fruit has set. Also keep the runners to a maximum of 5 feet.
If you grow from seed, you'll need to start in early April. In most parts of San Diego, you will need bottom warmth with a vented, transparent cover to keep the extra moisture out and the sunlight in. Inside a south-facing enclosed patio can work, but inside a house in my experience is too dry compared to the later adventure outdoors.
All squashes will develop mildew on their leaves in coastal environments. The best fungicide on the market (here) is Spectracide Immunox. If you limit your sprayings as directed, most crops can be eaten. Sulphur sprays are partially effective with squash (will kill your eggplant though). The best product I've seen is Lily Miller Polysul -- use the \"summer spray\" dosage. By the way, rabbits and most humans hate the smell of it. When mildew on a large leaf *starts* to get out of control, remove it.
Rich, it sounds like you have plenty of earthworms. However, the plastic keeps most of the bacteria associated with the earthworms from killing the mold.
Insects can also bring mold and in coastal San Diego they often do. The Bayer Powerforce (don't let that scare you) insecticide that contains Cyfluthrin is actually environment friendly. When there is daily morning dew (or one day of rain) it won't have a lot of staying power for more than a few days. Malathion is one step up but at the risk of killing some of your positive agents in the soil.
Once the fruit has set, you need to put something under it so it doesn't rot. Competitive growers use a coated pallet.
Variety matters a lot. Accumulated warmth (Citrus growers call it degree-days, or heat units) is also very important. These plants (not seedlings) should be in the ground by mid- to late-May.
I hope this helps!
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