Tulip poplars are fast-growing trees that can reach 20 feet...

Tulip poplars are fast-growing trees that can reach 20 feet tall in as little as six years. This seedling was found growing wild in reader Adam Strickland's Sayville garden. Credit: Handout

I have beautiful African violets that bloom all year. The pots now seem overcrowded, and the leaves are losing color. I do not know what to do as far as repotting and starting new plants. I am afraid I might do something that will cause them to die. Any advice will be so appreciated. Thanks. -- Lorraine Lloyd

If the leaves are yellowing or becoming pale, it's possible the plants got too much sunlight over the summer. So during spring and summer keep them near a window but behind a curtain; then from about October through the end of February, give them direct light (sunlight in winter is not as strong as in spring and summer). But if the leaves are spotted, it's likely they came into contact with cold water. Use only room-temperature water on these plants.

Fertilize them with 20-20-20 products labeled for African violets. Use a tablespoon diluted in a gallon of water about every two to three months except during the winter, when you should use just 1/2 tablespoon to a gallon of water.

Also, this is a plant that should be planted with its crown slightly above the soil, so keep that in mind when repotting your crowded plant: Potting African violets too deep can lead to rot.

We are in desperate need of advice. It appears that we have an infestation of fungus gnats in our nine houseplants. Five of the plants are in one room, where the infestation seems most prevalent. Can you recommend anything to get rid of them? We've tried "bombing" the room with Raid House & Garden, which says it won't harm plants. We are also spraying the plants and the top of the soil directly with Safer Houseplant Insect Killing Soap. And we're watering the plants with a solution of 1 gallon of water with 2 teaspoons of liquid dishwashing soap. At this writing, nothing seems to be working. Anything you might suggest? Thanks! -- Frank and Susan Galan

Fungus gnats are living in the soil, not on the plants, so the best thing to do would be to repot all your plants.

Take them outside and remove them from their pots. Discard the soil and wash pots with a 10 percent bleach solution. Rinse well. Then rinse the plants - foliage and roots - with a very gentle stream of water and replant in new sterile potting mix.

To kill any flying adults in the house, use a product containing pyrethrum or tetramethrum, or use flypaper.

Update: After e-mailing my response to the Galans, they tried out my suggestion and reported back immediately:

Just to let you know, we repotted all the plants last weekend in fresh soil and new pots, washed the roots and foliage, and it seems (so far) to have done the trick! Haven't seen one bug flying or on the flypaper since. Your advice was extremely helpful. Thanks so much! -- The Galans

So glad to have helped!

Wondering if you can help me with a question on mums. Usually I plant some mums in early fall and pull them out before winter, never to use them again. This year they're still in the ground. Can I just cut them down to ground level to keep them for next year? -- Tony G.

 

Yes, Tony, Chrysanthemums are perennials. They'll come back every year if you let them. Just cut them back after they've gone dormant - it's OK to wait until spring, if you prefer - and you'll notice new growth next May.

What plant is this? (photo sent via e-mail) -- Adam Strickland, Sayville

Looks like you have a tulip poplar (Liriodendron tulipifera), a fast-growing tree that can reach 20 feet tall in as little as six years. If you don't want to keep it where it's growing now, move it in early spring. When established, it will become covered in springtime flowers that resemble tulips - hence, the name - and foliage will put on a bright yellow show in fall. It's also the state tree of Kentucky.