I have always planted marigolds around my tomatoes... don't know if it has actually helped them, but it certainly doesn't seem to have hurt them at all. My tomatoes have been trouble-free except for late blight during last year's wet summer. I love companion planting; it makes for a beautiful garden and attracts lots of pollinators and beneficial insects, if nothing else. Sometimes my N of 1 finds good results from something I try... like the nasturtiums acting as a very effective trap crop for aphids, or the squash interplanted with flowering radishes which were untouched by SVB while the others were all hit. Coincidence? Maybe, but it certainly didn't hurt anything, and might have helped!

It could be that they are different varieties. Not all marigolds have the same germination time or maturity date. Depending on the variety, they can pop up in just a few days and take up to a couple weeks to start popping. It could also be a problem with low vitality on the homegrown. Do a sprout test. Take an amount of seed, I like to do 10 or 25 depending on how much seed I got. It's easier to see how many sprout with a sprout test rather than when the seed gets kind of lost in soil.

In order to save seeds, I grow only one variety of each species of annual such as marigolds, and I select and save seeds from the ones that grow well or have a color or features that I like. So for marigolds, I select for bright saffron-orange color and pull out those that bloom brown, so now almost all that come up have the color I like. I haven't found the companion planting thing to work at all for repelling pests: pests go straight to the plant they like and don't mind what other plants are nearby. I do still plant polycultures, growing a mix of flowers, herbs and salad greens all around the garden next to other plants, but for other reasons. 1) Biodiversity makes a more resilient ecosystem, so the desirable pest predators and pollinators have something to eat and somewhere to stay at all different times of the season, and also if one crop fails, 15 others do fine. 2) The flowers, herbs and salad greens self-seed so I thin them out and occasionally transplant them to a better spot, but mostly let them grow, and they grow earlier than what I plant. 3) At least the herbs and salad greens tend to produce and be finished by the time big things like tomatoes or cucurbits need the space. Flowers like marigolds can be less accommodating, getting big and starting to bloom just when the major plants need the space, so I've been trying to plan and give them more space. The flowers I've been allowing to self-seed or keeping seed from are: cornflowers / bachelors buttons, marigolds, calendula, cosmos (I'm growing only a bicolor variety), snapdragons, edible chrysanthemums (I'm selecting for the bicolor white and yellow ones), and zinnias (selecting for red to purple ones), and Dracocephalum moldavica (also a culinary herb). The edibles I've been allowing to self seed or collecting seed from are: red butter lettuce, green leaf lettuce, rocket/arugula, red orach, mustard green, claytonia, dill, coriander/cilantro, summer savory, and probably others that I'm not thinking of at the moment. Basil hasn't self-seeded for me so I plant it, and parsley can be aggressive (deep roots) so I plant only one in a place where it can stay all year.

Mike, anyone having seen and sampled these marigolds in my garden were in for a pleasant surprise, taste tests have usually result in a "WOW!" I'm down to only three seedling, an oversight upon watering and several perished, just means I'll attempt to take cuttings when these establish. Debra, I think floral either requires a flamethrower, a sledgehammer or a searing pan of garlic butter and mushroom caps, LOL. :)