I have some apple tree seedlings that I started as an experiment. I simply placed them in a pot with some potting soil and they came up. The seedlings are about 2 inches high, and I noticed that 2 of them have brown areas on the stem and are not able to stand upright from these areas.
There is one very important aspect to know when propagating apple trees from seeds. The apple trees you purchase in a nursery are produced by grafting because apple seeds are very unreliable. The seeds found in the apple are the result of cross pollination between two different species or varieties of apples. This makes each seedling a genetically unique individual with unpredictable traits; for example, seedlings sprouted from your ‘Macintosh’ apple might produce tiny red crab apples. You will have years invested in these seedlings before finding out if they will produce an edible or flavorful apple.
That being said, experimenting with growing different kinds of trees from seed can be fun and it is a great project for kids as well. It’s a good way to get them connected with the origins of the food they eat.
To begin dry the seeds out. Next sow them about 1/2 inch deep in sterile potting soil. Be sure your containers are
sterile as well. Place the seed pots in a sunny location. Keep the soil moist and at temperatures above 60 degrees.
Tree seedlings require full intensity light. If you cannot place them outdoors, consider using a grow light. They need 18 hours of artificial light per day.
The browning you see on your seedlings is probably a fungus caused by either by overwatering the plants, seed pots that were not sterile or too much warmth. To correct this you will need to start over with seeds sown in sterile containers that have drainage holes in the bottom and use fresh potting soil. Water them only when you can stick your finger in the soil about an inch and it feels dry to the touch.
Once your seedlings outgrow their seed pots you can transplant them to larger containers and move them outdoors.
They can be planted in the garden when they are large enough to not get stepped on or mistaken for a weed.
Be sure to plant your trees in areas of full sun in well-drained, slightly acidic soil.
One last tip. Because the traits of your trees are unknown, the mature height and width are hard to predict. Be sure to plant them in an area where they will have plenty of room to grow.