How can I make lettuce head?
Lettuce heads form best when the weather is cooler. If your area is experiencing unusually warm weather, this can delay or even prevent head formation. You can help to reduce the stress on the plant and encourage head formation by keeping the roots cool. Mulching the roots and regular watering will help and you can also try setting up a sun shade with an opaque piece of cloth. This will allow the light to get through but will keep some of the warmer rays of sun from heating the plants too much.
How many types of lettuces are there?
While there are literally hundreds of individual varieties of lettuce, all of them actually derive from 5-6 main categories or groups. These include: Butterhead, Chinese lettuce (Stem lettuce), Crisphead (which includes Iceberg), Looseleaf (Bunching), Romaine, and Summer crisp (this one is not always named).
Does a possibly poisonous mushroom contaminate lettuce growing beside it?
No, not at all. The mushroom just indicates you have really good soil. You can pull it out and eat the lettuce as usual. Just don't eat the mushroom! :)
The plants vary from tomato to lettuce and also my roses, but only the leaves. Anything that has green leaves is with holes and brown to yellow color. Most of them are eaten too. There is just the stem of the plant. I would like to know what it has and how to treat it.
It sounds like you have a fungus and the weakened plants are also attracting pests. Treat the plants with both a fungicide and a pesticide. Neem oil is a good choice as it is both. It is also organic and safe for people and pets so can be used on food crops.
When do you harvest green leaf lettuce?
Leaf lettuce is harvested when the plants get large enough to use. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/lettuce/harvesting-leaf-lettuce.htm
I noticed that there are tiny black egg-like things all over my lettuce plants, and whatever left these behind appear to also be feasting on my lettuce. I also noticed what I believe to be a cabbage worm on one of the plants, so I am speculating that this is the culprit. Any advice, or tips on what I can do about these pests? Are my plants done for and/or should I remove them from the bed, as not to infect the other veggies I have in the same box? Help!?!? Thank you kindly!
It is likely the frass from a pest of some kind rather than egg. Since you have seen what you believe to be the pest, we would recommend neem oil, which we have found to be very effective against almost all harmful pests in the garden, including a variety of worms. This article has more information:
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
For additional help in detecting the culprit or for other control ideas, these articles should help: https://www.gardeningknowhow.com/edible/vegetables/cabbage/protecting-your-cabbages-from-cabbage-maggot-cabbageworm-and-cabbage-moth.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/prevent-caterpillars.htm
I have a garden and the lettuce is starting to have brown rims. Does that mean to harvest? I can't taste it because my dad put chemicals in all of my plants and vegetables.
The time to harvest lettuce depends on the type of lettuce. Head lettuce is ready when the head becomes firm. Leaf lettuce is harvested when the plants get large enough to use. Here is an article or two that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/lettuce/harvesting-lettuce-heads.htm
https://www.gardeningknowhow.com/edible/vegetables/lettuce/harvesting-leaf-lettuce.htm