Past Questions and Answers | July 2006
This month's questions concern:
Yellow Sweet Onions
Can Cucumbers and Pumpkins Cross Pollinate
Rose of Sharon
Willow Tree Propagation
Please scroll down to read the answers.
Question #1: Red Japanese Maple
We recently moved into a home with an established landscape. As new gardeners, we have some questions. One is that we have two Red Japanese Maple trees growing, and they seem to be growing green leafy tree-like things out the sides. Is this normal? They are not very attractive-can I cut them off?
Deborah Price, Everett, WA
ANSWER: Hi Deborah - Yes, you can, and should, definatly cut them off. From your description, it sounds like your maples are producing suckers.
Occasionally, a maple will grow sucker sprouts, and these are excessively vigorous shoots. Such sprouts should be pruned out as soon as they are recognized, because they only take away energy from the regular growth.
They also, as you mentioned, don't look good either. But overall, Japanese Maples are beautiful trees, and they will do even better when you remove the unwanted growth.
Question #2: Avocado Problems
Hi, my avocado tree is in a large pot, facing south, and I have fed it with avocado - citrus food, and the leaves are turning black and curling up and drying out.......what is happening? The tree was a gift and is about 6 to 7 ft. high.....thank you,
Pam Roth, Rancho Dominguez, CA
ANSWER: Pam, it sounds like your avocados could be suffering from too much water. While Avocados do grow well in containers, they require excellent drainage. They don't like "wet feet" so to speak.
They are very susceptible to Phytophthora root rot and must have good drainage to thrive. Phytophthora is a fungus that kills roots and also gets into the crowns of plants.
Plants that are suffering from Phytophthora will wilt, their leaves discolor, the growth becomes stunted and you can see leaf drop.
To help your avocado, let it dry out, and try and improve its drainage. You could also try a soil drench of fungicide or some neem oil as well. Good luck!
Question #3: Yellow Sweet Onions
Hi Hilary, I am growing sweet yellow onions and the stalks are getting very thick and the top of the onion is peeking out of the soil. Should I cover this up and let the onion continue to mature?
Tracey Lee, Atascadero, CA
ANSWER: Hi Tracey, sounds like your onions are doing great. I wouldn't do a thing to them, except thin a few out to allow the others more "shoulder room" to grow and expand.
I wouldn't cover them up, because you don't want to rot the bulb. Just let them grow, and when the tops have died back, they are done and ready to harvest. But you can harvest onions just about anytime, they are always good!
Question #4: Cross Pollination Possible?
Hello, Can you tell me if it's safe to plant cucumbers near pumpkin plants, because of crossbreeding?
ANSWER: Hi Colleen. That is a really interesting question because all vine crops belong to the Cucurbitaceae family. To know how plants will cross pollinate, though, you need to look at a couple other factors.
Pumpkins, squashes, and most gourds belong to the genus Cucurbita.
Cucumbers belong to the genus Cucumis and thus will not pollinate with pumpkins, squashes, gourds and watermelons, since they are of a different genus.
Also, cucumbers will not cross with other melons of the same genus, because cucumbers belong to a different species known as sativus
It gets kind of confusing doesn't it? But the bottom line, plant away.
Question #5: Gardenia Plants
I've bought several Griffith's Select Gardenia plants this year. Over the past month I've noticed several of the leaves on all the plants are turnning yellow and falling off. Any way I can stop this from happening?
Steve, Richmond, VA
ANSWER: Hi Steve. Well I applaud you for getting a Gardenia. They are one of those plants that can be difficult to grow. They require certain conditions to be perfect, or you will experience problems.
Gardenias are a like like Ficus plants in that when they get upset, they drop leaves. Here are a couple of reasons Gardenia foliage becomes yellow:
1. It can be because your water is too high in lime. Use only lime-free water and apply some iron every 2 weeks for a couple of months.
2. The other reason the leaves are yellowing and falling is that the plant is in too much shade. Gardenias like very bright light, but no direct hot light. They like cool conditions around 60 - 65 degrees F.
They also like high humidity and to be feed every few weeks with half-strength acid plant food.
If it were my plant, I would check its location, temperature, light, humidity, and make sure it was getting its acid fertilizer regularly. Then I would tweak the environment until I got the combination right.
I hope I haven't made you feel you need to get rid or your gardenia! Once you find the right spot, and can make it happy, they are the most beautiful, fragrant, and rewarding plants to have in your home.
Let me know how it goes, I know you can do it!
Question #6: Rose of Sharon
I have 94 rose of sharon bushes some of the leaves are turning yellow is it because to much water or not enough?
Kimmissi, Saucier, MS
ANSWER: Hi Kimmissi, well, fist of all, I can't believe you counted all 94 of them! That's great!
To your problem: it could be a couple of things. First, Rose of Sharon, Hibiscu syriacus, are a relatively easy shrub to grow. They take the heat, and some drought, so it is better to underwater them a bit than over water.
I don't know how much or often you are watering, or how regularly you feed them, but here is what I would do.
Water your plants deeply and infrequently. Meaning, give them a good drink and then allow them to dry out before you water them again.
When I say dry out, I mean that you can dig down a couple inches and the top soil has dried out. When that has happened, give them another good drink. In time you will see a pattern start to develop. At certain times of the year the soil will dry out in a certain amount of time.
You also need to feed your shrubs regularly, with a complete fertilizer like a 20-20-20 or a hydrolized fish fertilizer, either one will work wonders.
With 94 plants they will put on quite a show when they are looking their best.
Question #7: Dusting Insects
When is the best time to dust for bugs and what is the best dust to use?
Brenda Findley, Crab Orchard, TN
ANSWER: Hi Brenda. Well, I almost didn't include this question in the magazine because it is rather vague. But, I never want to shy away from a vague question!
Without knowing what kind of plants are being infested, or what the damage they are inflicting looks like, it is hard to give a solid answer.
I never like to randomly tell people to use any kind of pesticide, so here is what I want you to do. Write me back again with a bit more detail and I'll update this answer as soon as I hear from you? OK?
I look forward to your response.
Question #8: Willow Tree Propagation
I cut a branch of a friends willow tree and put it in water, it is now sprouting roots and I don' know when I can plant the tree in my yard. Is there a certain length the roots need to be before planting?
Samantha Dutcher, Hayward, WI
ANSWER: Hi Samantha. Great question. I love willow trees and I have propagated several myself. I'm not surprised your cutting is sprouting roots, the darn things love to live in water!
There is no certain length the roots need to be, but I would wait until it cools off. I would plant it out either in the fall, and let it go dormant. It will start to grow again in the spring. Or you can plant it out in the early spring while it is still cool, so it can get established before it gets too hot. Just make sure you keep it moist until it is growing well.
Actually in fall, when a willow has gone dormant, you can take cuttings and plant them directly into the ground. In the spring they will start growing. You can propagate a ton of them this way. They are regular weeds!
Question #9: Lilac Propagation
I was just wondering how to or if I even could start a lilac bush out of the trimmings of an already grown bush?
Gina West, West Allis, WI
ANSWER: Hi Gina. I just love lilacs, they remind me of my grandmother.
As far as propagating them, they are often grafted or layered. There are, however, two ways you can propagate them from cuttings.
1. You can propagate it from stem cuttings taken in the fall. Cut a good four-inch piece off the top part of a healthy, non-flowering shoot.
Cut it off at a very slanted angle and take a pruning shears or knife and score it just above and just below the buds. Lightly apply a rooting hormone to the base, Carefully tap the powdered edge of the cutting against the edge of the hormone container to remove any excess.
Plant your cutting in a mixture made up of half peat and half coarse sand. Plant it about half the depth of your cutting and insert the bottom half, making sure the base has good contact with the soil.
Fill any gaps in with soil, pat it down well and water it. I would plant mine in a pot so I could keep an eye on it. When it starts to grow in the spring, you can plant it out anywhere you want.
2. You can also take root cuttings. Now keep in mind, if you have a variety that was grafted on, you will be propagating the rootstock.
When the plant is fully dormant, so in December - February, dig up a couple young, vigorous roots about pencil thickness. Make sure to take about a 4 to 6 inch long piece.
Now, what is most important, and this may sound silly, but remember which end was pointing down, because you want to plant the root piece correctly! Cuttings should be planted vertically the correct way up because new roots always form at the distal end (the end farthest away from the plant).
Plant them so the proximal end (the end that was closest to the surface) is flush with the soil surface. Keep it moist until it sprouts new growth.
You will have success with either method, so give them both a try and see how you like results.
Enjoy your lilacs!
Question #10: Wilting Tomatoes
What can cause tomato plants to wilt?
Tonya Hare, Portsmouth, VA
ANSWER: Hi Tonya. Lots of things can make a tomato wilt. If I had to choose my top three, here is what I would pick.
1. Lack of consistent water. If your plant wilts, but then recovers when it is watered, you have a lack of water problem. Even out your watering so you don't stress the plant.
2. If the plants wilt and the leaves are yellow and curling, you have a fungal wilt. The only thing you can do is get rid of the dying plants. In the future, you'll want to allow the soil to dry out a bit between waterings, and grow resistant varieties.
3. If the plant wilts, but still sets some fruit, you have a root and stem rot. Again, you need to clean up the area, let the soil dry out and grow resistant varieties.
Lastly, don't plant your tomatoes in the same area every year. Rotate them around to different parts of the garden to keep the soil and plants healthy.
Question #11: Petunia Problems
I have twelve hanging baskets which contain an array of petunia's. Both the regular and wave variety. I water them regularly in the morning. I have noticed that in a few of the baskets the plants are turning a paler green shade, and the flowers are not as vibrant nor hardy as they are in the other baskets. These baskets are in the same locale (full-part sun), as the other baskets which contain to appear normal. Can you help me with this problem?
Melissa Palan, Carrollton, IL
ANSWER: Hi Melissa. I have experienced the same thing. I used to take care of a huge hotel-restaurant complex and we had hanging baskets all along the pool areas and walkways. Some did great, and every now and again, the odd one did poorly.
One thing about plants that you have to remember is that they are as individual as people. Some plants will thrive no matter what, others will need a bit more care, even within the same type of plants.
I would cut back to ones doing poorly to about 4 to 5 inches, and then feed your plants with a balanced fertilizer like a 20-20-20. Go ahead and feed all of them, not just the ones that are doing poorly. Some plants just react to the soil, location, depth of planting, etc. differently.
It isn't uncommon for the occasional plant that simply needs to be replaced. It has no reflection on your gardening skills!
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Nothing finishes off a flower bed like low, long flowering edging plants.
Alyssum, lobelia, and dianthus are great for just this purpose.
For good continual flowering, also fertilize every few weeks with a balanced fertilizer like a 15-15-15.