Healthy tibouchina stems can be pruned
Q: The top of a tibouchina in our landscape was damaged by the cold. How far can the shrub be pruned back?
A:
Like many cold-sensitive plants tibouchina, also known as the princess flower plants, were damaged in some landscapes by the recent freeze. These shrubs or tree forms can be pruned way down to near the ground if needed. Really cold weather won’t be over for a few more weeks, so you might wait to determine the extent of damage and then prune at least a few inches below where the injury stops. If you want to renew this tibouchina shrub, the healthy stems can be pruned to within a foot or two of the ground and be expected to recover.
Q: Mushrooms are popping up in an area where two
diseased oak trees were removed over the last five years. Will they affect nearby oak trees planted in recent years?
A:
Mushrooms are a sign the old roots of your tree are being used as food for these fungal growths and decomposing. Regretfully, the mushrooms in an emailed picture appear to be from the Armillaria or mushroom root rot fungus. This is not the best news, but it may not be so bad either. The fungus is known to live among oak tree roots and cause no harm. But if the oak trees are weakened, possibly by age, the fungus can contribute to their further decline and death. Don’t be in a hurry to replace the new trees. Allow the new trees to continue growth and provide good watering and maybe a fertilizer application or two each year for the first few years. This can keep them vigorous and resistant to the fungus. Trees you might use as replacements are likely to be susceptible to the fungus, but some reported with degrees of tolerance include bald cypress, crape myrtle, southern magnolia, red maple, sweetgum and sycamore.
Q: We had to remove a favorite navel orange tree due to the greening disease. We would like to plant a new one. What should we do?
A:
Greening disease affects all types of citrus trees and is caused by a bacterium spread by the Asian citrus psyllid. If there is any good news, it’s the bacterium only lives in live plant tissue. So, once your tree is removed, a new one can be planted at the same site or nearby. Of course, all roots and maybe some soil would have to be removed if planted at the same site. What you need to determine is if there are other citrus trees nearby that might be infected with the disease. These would be a source of the bacteria that could be spread to your new tree by psyllids in those trees. Even if other trees are not observed in the area, a good care program, including sprays to eliminate the psyllids during times of new foliage growth, would be needed. Also, a good fertilizer, minor nutrient and water program should be followed.
Q: We want to grow tomatoes in containers. What size is best, and is there a special soil?
A:
Bigger the better is best when it comes to containers for tomatoes. Ones between 15 and 25 gallons would be fine. You might consider using nursery pots that once contained trees or shrubs. Plastic containers that resemble half whisky barrels or similar are also ideal when fitted with drainage holes. Use one of the good potting mixtures found at local garden centers. Find one that contains more than just peat moss. Good ones usually have perlite, bark and similar ingredients to help provide drainage and aeration.
Q: We are thinking of purchasing petunias for our hanging baskets. If planted now, how long might they last?
A:
Expect your new petunia plantings to last through May and maybe into June if given good care. One to three plants are all you need per hanging basket as they quickly grow to fill the empty spaces. Keeping the soil moist is going to be your big job as the plants grow to full size and fill the containers with roots. Also, apply a slow-release fertilizer at planting to feed the petunias for the next two to three months. A second application may be needed to get them into May or June. Do prune off old blooms and trim stems back as they become lanky.
Q: It was below freezing a few weeks ago, and it appears my Gold Mound Duranta has damaged tips on its branches. I thought these plants were hardy. Was I misinformed?
A:
Being a hardy plant may only mean your Gold Mound Durantas are survivors. The foliage and stems are sensitive to temperatures at or below freezing, as indicated by the browning of the ends of the branches. You may continue to notice more decline over the next month or two. Gold Mound Duranta are normally survivors and, when frozen, can come back from buds near the ground. For some, this would be hardy plants. Actually, the dieback after a freeze might not be bad as Mother Nature does the pruning that you and I might be reluctant to do. Just prune out all dead and reshape your plants around mid to late February.
Q: After I start seeds for transplants, the seedlings often rot in the containers. What can I use to prevent the decline?
A:
Seedling rot problems are normally culturally related. As soon as the seeds begin germinating, give them the light required for growth and a warm location. A full sun exposure all day is the best spot for most seedlings. Next, keep the soil moist but not wet. Too moist a soil encourages rot organisms. Wait until the surface soil starts to dry to water. Lastly, find a warm spot with good air movement to keep the seedlings dry. If needed, use a fan to provide a light breeze. Fungicides are available but costly and only work if you cure cultural problems.