Gardening with Gary




Gardening Advice from an Expert

Hibiscus

Q. I have a large Hibiscus plant that I will have had three summers this summer. It is about four feet tall, but only on one side. It is very healthy, and is very happy in front of the window, where I have it. My question is, the tall side is all new growth, the short side hasn't started to make new shoots. Should I cut the tall side down to the level of the short side, and do the flowers bloom on old wood or new wood? I will put it out in the spring, if spring ever comes. I am in zone 5. Thank you for your help.

A. I would like you to help nature and even the shrub out. Prune back some of the tall front growth so that the bare rear will get more light. It sounds as if it is being smothered, and this can lead to damage to the entire plant.

The flowers will come out on the new growth, but you will suffer a bit of a loss this spring, for the good of the plant. The rear will hardly ever bloom in its present state. Give it a deep feeding as soon as the new growth starts. A 20-20-20 or similar garden fertilizer would be good, then switch to one with a higher middle number for the blooms.

Continue to trim out stems after the blooming is done. Take out any weak or dying branches so that the center and back of the shrub will get more light.

Next year at this time, you will see an improved plant!

Q. Can I grow my hibiscus indoors and have it bloom? Can I water it if I have drainage holes in the bottom of the pot?

A. Hibiscus are not well-suited to indoor gardening. They need high humidity for best growth and bloom. The indoors does not supply this.

Give it excellent sunlight all day long, protecting it only from the harshest of afternoon suns. They drink lots of water, so have the drainage holes you mentioned plus a saucer of pebbles underneath the pot. Allow water to sit in the saucer at all times as long as you do not have the pot down into the water, as then the roots will rot.

Give it good fertilizer, like Peters, Miracle-Gro, Schultz, or Optimara at one teaspoon per gallon water every two weeks. Remove all dead or yellow leaves.

If you could at all place it outdoors for the summer, not allowing it to get cold, then the plant would be much happier and bloom more.

Q. As soon as the weather permits I will be trying to grow Hibiscus from seeds. I need to know how to mix a good starter. I have Sphagnum peat moss, Perlit, Vermiculite and Schultz potting soil.

A. You can start them inside in small trays or flats right now. Then, when the weather has warmed so that there will be no more frost, which is pretty close for most in the US, you can transplant them outside into a worked-up garden bed with lots of sun. They do not do well with less than 1/2 day of full sunlight.

Mix:
one part peat moss
one part perlite
one part vermiculite

I would not use any potting mix, as it is heavy, stays wet, and can lead to damping off and rot of the seedlings. Mix the three well, moisten, and then lay the seeds on top of the mix, one inch apart. Cover lightly with fine peat moss, crumbled in your hands, laid on top just to cover the seed.

Cover with plastic wrap or glass pane and turn it into a little greenhouse. Grow in a good window with no direct light. If steamy, prop open to allow air to dry it out. Never let the mix go dry as the seedlings will die off. Do not feed them until they are about 3" tall.

Q. We have a potted hibiscus that has bloomed well indoors over the winter. The branches now seem to be getting long. There are a couple new bloom buds showing. Is it OK to trim this plant anytime and how much?

A. If you have not already, I recommend that you move the plant outside now for the entire summer. They enjoy the fresh air and will use the sunlight to produce much needed food for growth and flowering. Be sure not to place into direct light until it has been acclimated.

I would not trim any stems right now. Even though it may be partly spindly, that is to be expected after a low light winter of stress indoors. If you prune, there will be no more flowers for quite a while.

Let the stems bear the flowers which they like. Then, when all blossoming is through, trim the branches back all at once. Shape the tree so it is even all around. Take out any weak, yellow or brown stems. Cut back to a good healthy bud, as that is where the vegetative growth will arise. The amount to trim out depends upon how the tree looks, but you could cut out as much as 1-2' if needed to leave only the best, strongest and healthiest green foliage.

Maintain good light and watering at this point. Give it fertilizer, once every two weeks. MirAcid is particularly good, as hibiscus like a slightly acid soil. Look over it for any sign of aphids, mealybugs or whitefly. Spray accordingly at first sign.

Planting a Hibiscus Tree:

Q. What is the correct way to plant a hibiscus tree? I live in zone 5 in the USA. Can it be next to other trees? Any hints will help.

A. There are some species which are hardy in your clime. The Rose of Sharon is, and my grandparents had one huge for years in Ohio...what a fantastic show! Others need a milder climate with no frost. So, I am unsure how yours will do. If you have a name on it, get back to me.

They do very well in Florida and California and points in between, needing lots of sun and heat, with a slightly acid, well-drained soil. Provide plenty of water and food. MirAcid is very good for them, also for azaleas, gardenias, rhodies, hydrangeas and camellias.

Pick an area at least 8 feet from the branches of any other tree. Dig a big hole, 1/2 again as big as the root ball. Work up the soil, add some dried compost and clear of any stems and rocks. Fill back some soil and plant the tree, maintaining the same soil level as before at the trunk. If balled, open and spread out the roots in a circle to encourage outward lateral growth. Water in slowly, very well, and stake if need be. A tall tree in a slightly breezy area may need support for the first couple months until the roots take hold.

After flowering, prune out weak or dead stems, and shape up. Propagation is by either seed or stem cuttings. Watch for aphids, mealy bugs and whitefly. Eradicate with an insecticide, such as an Ortho product, from your nursery.

Repotting:

Q. I have received great answers to questions from you and have another one. I have this hibiscus tree as a house plant, but put it outside in the summer. It is about double its size now or more, and I am wondering if it would be advisable to repot it into a larger pot. I see small white roots at the top of the pot and am wondering if it is potbound and whether this is good or if it needs more room to grow. Also the leaves turn brown on the edges, eventually turn yellow and fall off.

A. Glad to have been a help. Hibiscus love to spend the summers outdoors when the weather is mild and not too hot. Make sure that you are providing protection for the plant, as the foliage is tender, having been inside for so long., This can lead to burning and leaf drop, as can change in environment, humidity, light, water and food.

Seeing some fine roots on the soil surface is OK. But, if the plant has not been repotted for a couple years, if you see roots coming out of the bottom, if the soil seems to be swelling at the top, or if the proportion of the plant to pot size looks odd, then please do repot. Buy some new, fresh potting soil and amend it with perlite and some leaf mold or peat moss. Buy a pot only a size or two larger, that is, if it is in a 8" pot, place it up into a 9-10" pot. make sure you have a large saucer underneath.

Maintain the same soil line as before. Keep protected for several weeks until it can acclimate to the move. Keep watered well, but only when it feels dry. Do not overwater or give it too much light, and no fertilizer. Start feeding it again in about a month, every 3-4 weeks.

Please do not take my words to mean to grow this plant in total shade. They like light, lots of it, especially the AM light, but keep out of direct rays. Glad your bugs are gone, but keep a wary eye all summer long. You may have to re-treat it before moving back inside.

Member Beve writes~
I have a Hibiscus in a large pot that was a gift. May I leave it outdoors in the winter, or do I have to bring it inside? I live in southwestern Pennsylvania, zone 5 or 6, I believe.

A. Hibiscus are frost-hardy in your zone. The problem here is that you have it in a container and the pot is above the ground. If the bush were planted right into the ground, its roots would be kept much warmer. You do run the risk of its death in an unprotected container.

I suggest that you place the pot as close to a building as possible. There is quite a lot of heat given off from buildings, especially a heated home. Keep it out of the wind and direct weather. A north or east wall is best, and provide an overhang if possible. You could also drape with mesh material and fasten, to keep snow and sleet off the bush. Do not trim any growth at this mid-September date. It is too late to harden new sprouts. Prune in the spring after the buds have broken and you can see which limbs survived the winter.

Carol writes~
I have these two hibiscus plants, [well one is almost a tree, having three entwined trunks together] and the other one is a single plant. I have been battling mealy bugs for over a year and cannot get rid of them. They keep coming up from the dirt. What I would like to know is what would happen if I cleaned all the dirt off the roots and replanted them. That is the only solution I can come up with. I have sprayed and sprayed and it seemed to get rid of them for a while but they keep coming back. For a while I would just use a brush and sweep them off the leaves and trunks but am getting tired of doing that.

A. What a horrible dilemma you are facing. I sure cannot figure why the mealies will not be eradicated. I would use a systemic insecticide, one where you mix it and drench the soil. The poison goes right up the stems and spreads throughout the foliage. Any bug which sucks into the tissue ingests the killer and dies. They are applied once every 4-8 weeks, depending upon what the label says. We use them all the time for nasty houseplant pests.

Systemics work so superiorly to contact sprays which you have been using. The ones you miss with the spray survive, but this cannot happen with systemics. Consider trying one before the upheaval of washing the roots.

Yes, you could wash the soil. If they are coming up from the ground, they are not the foliar type but the soil ones. Both are very nasty and pesky. The eggs can be found in the soil and when hatched, the adults climb upwards.

Washing the soil will not eradicate them, but cut their number greatly. I trust you do not have freezes there, as that would finish them off completely each year and they do not overwinter.

Bill writes~ I'm in Louisville, KY. For the last 2 years, I bought hibiscus plants and put them in the garden, but they never come back the following year. Am I in the wrong area for this to be a perennial plant. I buy them at Home Depot and they told me that they will survive in this area. I know that it is just March, but it looks like a dead plant to me. I have the same problem with ornamental grass. Can you recommend a grass for my area?

A. I have grown hibiscus in Ohio and Michigan and they always survived the harsh winter after they were established. I did lose one or two after the first winter, so maybe that is what is happening to yours.

I want you to protect them this coming winter. Put a foot of dried leaves [oak is very good and acidic] and a small fence or border around the bushes to keep the mulch resting. Do not do any pruning after August, so that there is no young, fresh growth. Prune right after flowering this summer.

Were you fertilizing them last year? I know this sounds unrelated, but if they were insufficiently fed, then their resistance to cold is greatly reduced. Give them 20-20-20, like Rapid-Grow every 3-4 weeks starting right after bud break until the end of September.

What about water? Stressed bushes again are not ready to face cold temperatures. Drought has been a problem recently and quite possibly the bushes did not receive sufficient moisture to make a very good root system necessary to survive the winter dormancy.

I will tell you that I found an excellent document on ornamental grasses for Kentucky. Can you imagine that? Go to:

http://www.ca.uky.edu/agc/pubs/ho/ho79/ho79.htm

There are lists of grasses by height and amount of sunlight. Rather than attempt to copy all the information and care here, I refer to the University of Kentucky publication: ORNAMENTAL GRASSES FOR KENTUCKY LANDSCAPES by Lenore J. Nash, Mary L. Witt, Linda Tapp and A. J. Powell, Jr.

Carole writes~
I have two hibiscus plants. I brought them in the house over the winter. Now they are outside. However, they have gotten very long and stringy. I did not know I should cut them back. Now I have done so. I know it may take a while to come back, but what else can I do to ensure good growth? Does the plant require certain food?

A. Pruning is used to shape future growth, invigorate old plants, manage plant size and get rid of diseased and dead wood. While hibiscus can be pruned any time, the ideal is the earliest where resulting tender new growth will be safe from cold damage. For shaping purposes, some growers will prune the longest third of the branches and return in 4 to 6 weeks and prune the next longest third. Only sharp, clean shears should be used. A clean cut should be just above and angled down and away from an "eye" or node. (A node is the junction of a leaf and the stem. There is a small bud in this junction that is activated after pruning.) Cutting above outward pointing "eyes" will encourage growth in that direction. The new growth resulting from pruning invigorates the plant and will provide a source for many new blooms.

Hibiscus are good performers, both in the garden and in bright areas inside the house. If they receive just a small amount of care they reward us with many magical blooms throughout the year. Here, in short, is what they need:

Most important, a warm place where their tropical origins are respected. It is often said that hibiscus like much the same conditions as people and with temperature, that is pretty much true. For best results and lots of blooms, hibiscus should be located where the temperature remains between 60 and 90F most of the time. Short periods of either hot or cold will not injure them though they may show their displeasure by shedding a few leaves or dropping some developing flower buds.

If temperatures routinely drop below 50F, particularly at night, most growth and blooming will stop until it warms up again. Flower size will become much smaller and the occasional blooms may also be misshapen.

Temperatures below freezing will injure hibiscus. Factors such as how cold and for how long, the age of the plant, and whether it is dehydrated determine how extensive the damage. Under 30F for many hours will most likely kill the plant entirely. Such temperatures must be avoided.

Temperatures over 95F will often cause most flower buds to drop off. Hibiscus can survive temperatures even as high as 115F, provided they have adequate water. When the weather is hot, it is best to maintain a steady supply of water to the plant, rather than have it go through wet/dry cycles.

Watering is divided into two areas - cold weather watering and hot weather watering. In hot weather hibiscus will use lots of water and prefer a steady supply of it. Avoid flooding the roots or allowing the plant to stand in a saucer full of water for an extended time. Hibiscus will develop droopy leaves in hot weather if they do not have enough water. The cure is simple, provide some water and the leaves will regain their crispness.

In cold weather there is a danger of fungus disease attacking the roots of the hibiscus. Cold and wet conditions are what encourage this. Avoid this problem in colder weather by watering only as much as the plant needs. It is better to let it get too dry than to overwater it. This is one of the few things that will cause the early death of a hibiscus plant. If you can keep the roots warm you will have few problems with this.

In order to maintain a healthy hibiscus that blooms a lot, you must feed it. Purchase a good quality plant food (HVH Special Blend is the best available anywhere) and use it regularly according to directions on the container. Avoid those labeled SuperBloom. Look at the label for minor elements such as iron, copper, manganese, and other minerals as these are also good for hibiscus. Or, use a time-release product like Osmocote that can last for months with just one application. Worm Castings mixed into or placed on top of your potting or planting soil give a nutritional boost to your hibiscus.

Defend your hibiscus against insects as necessary. Many insects can be driven away simply by spraying the plant with a water hose or the highly recommended Bug Blaster or placing it in the shower for a few minutes. There are other safe treatments that a good nursery can advise you about, too.

Do not overpot or change the diameter pot size more than one inch or unit at a time. If the plant is in a 2 gallon pot the next step up should be a 3 gallon. Equally important is good potting soil with lots of drainage. If planting in the ground, be sure the hole and location are such that water will not build up around the roots of the plant.

Check out some outstanding new cultivars available below, especially one called 'Trademark':

http://www.trop-hibiscus.com/bfertins.html

http://www.exotic-hibiscus.com/care

Excellent**The Hibiscus Handbook** (96 pages with many color photographs) is an excellent source of hibiscus and general gardening information. It is available (US$13) from AHS Publications, 4170 Sussex Ave, Lake Worth, FL 33461-1721. Foreign orders add US$2 for ground or US$5 for air.

Barbara writes~
We have 10 hibiscus bushes which are pretty much growing like crazy. Most are big and bushy, very green. There is no more than the usual 1-2 occasion yellow leaves and there are no visible fungus, insects, etc., on the plants. They are covered in buds. However, 99% of the time before any of the buds open and bloom, they simply drop off the plant. A lot of times the entire little 3" stem just drops off its beautifully green bud before it opens. Any clue as to what is going on with these?

A. Hibiscus have a reputation of being somewhat finicky. If you over-fertilizer, they do not flower and when pruned they may take many months to bloom again. But if you are doing everything right and the buds just keep dropping it may not be the hibiscus's fault.

Hibiscus have a new pest affecting them: a gall midge. If your plants are green and growing properly but they will not hold their buds the insect may be the problem. The tiny fly-like insect lays eggs in the forming flowers. When the larva hatch, they feed in the buds and cause them to drop.

If you suspect plants are affected by the gall midge collect some of the fallen buds and place them in a clear plastic bag. In a day or two look for the very small yellowish worm-like larva on the plastic. When present a control is needed. Since bud drop can have many causes, use these tips not only to control the midge but to encourage good growth and decrease the blossom drop:

Control the midge affecting buds with Orthene sprays as needed.
Apply a blossom booster fertilizer in March, May and September if needed for growth.
Maintain a 3- to 4-inch mulch layer over the root system.
Water when the surface inch of soil begins to dry to the touch. Allowing to dry out, even
    slightly, leads to bloom dropping.
Remove older and declining stems as needed to encourage new flowering shoots.

Assistance from: Better Lawns/Gardens

Julia writes~
I have a hibiscus ornamental tree that I planted this summer in a large pot by my front door, which receives morning sun. I live in Charleston, SC and was wondering what would you recommend I do with it through the winter. My neighbor suggested bringing it inside and letting it go dormant, but I am not sure. What do you think?

A. Hibiscus ornamental is not cold hardy and is usually recommended for USDA zone 9b and above. In subtropical areas it can recover from very light frosts. There are species which are hardy to zone 5, read below:

WINTER PROTECTION

http://www.gardenguides.com/TipsandTechniques/winter.htm

WINTERIZING - POTS

http://instruct1.cit.cornell.edu/courses/hort400/graftage/hibiscus_growth.htm#Internet
http://www.trop-hibiscus.com/gindr.html
http://www.trop-hibiscus.com/svenska.html
http://www.trop-hibiscus.com/trop-hibiscus/mn.html
http://www.exotic-hibiscus.com/pages/hibiscus.htm
http://oakridger.com/stories/031998/gar_hibiscus.html
http://tiger.coe.missouri.edu/~hort1/gs/gs13.html

http://www.hibiscus.org

Julia writes~
I have a hibiscus ornamental tree that I planted this summer in a large pot by my front door, which receives morning sun. I live in Charleston, SC and was wondering what would you recommend I do with it through the winter. My neighbor suggested bringing it inside and let it go dormant, but I am not sure. What do you think?

A. Either way the plant must go dormant to fulfill its normal lifecycle. If you can furnish cool, low light in its pot inside, then this is fine. Otherwise you must keep in a protected an area away from deep frost, but outdoors is fine, too. Your choice, but trim the branches back severely to 10-12' long, reduce water and food and allow to start to grow again next spring as per the season.

Aron writes~
I got a Hibiscus tree that was brought back as a gift to me from Hawaii last year. It was packed and sealed in a plastic bag. When I got it, it was just a three inch trunk with roots and wax on the top. I planted it and scraped the wax off the top. Almost immediately it sprouted a small branch on the side. Since then the trunk hasn't grown a bit and the little branch has sprouted leaves and is probably ten times taller than the trunk. How do I get the trunk growing?

A. It seems that the trunk may have died in transport or shortly after planting. Train the new branch to become the new trunk. It can grow upright and become strong enough to handle the entire new tree growth. Since the old trunk has not sprouted after such a long time, it is useless to expect it to finally grow. Be happy that you have some healthy growth. It may need to be turned into a thick bush with pruning instead of a single-trunk tree. See what develops through the season, then make a decision.

Anthony writes~
I have several little dogwoods coming up around the bottom of the larger dogwood trees. They are around 2-4" tall babies. I would like to know the best way to go about transplanting them into containers without putting them into too much shock. I live in East Texas if that matters. Should I dip the tiny roots in a rooting hormone before putting in containers? I was thinking about putting some in a controlled environment under a grow light. Would that be too much light? Would I need to shade them? I can grow tomatoes and hot peppers indoors but never tried dogwoods or redbud trees.

A. Transplant while the tree is dormant. It should be small, generally 1" or less in diameter. Ideally, before transplanting, root-prune the tree 1 year before moving it. To root-prune, insert a sharp spade in the soil to cut the roots at the point 2-3" from where the tree will later be dug. When digging up the tree, dig a root ball that is a minimum of 12" in diameter for each inch caliper of tree measured 6" above the ground. After root-pruning, do not disturb the tree for 1 year. This will allow feeder roots to develop close to the tree, enabling the tree to get a better start when it is moved. Do not use a rooting hormone. Place burlap around the root ball to prevent the loss of any soil from the ball. Pin the burlap so it fits snugly around the root ball. Maintaining it after planting is essential for survival. Container and bareroot trees should be staked if they are planted in a high-traffic or windy area. Also, water and mulch dogwoods to promote a healthy tree. Check for disease and insects throughout the year. Do not prune or fertilize until the second year. Remove all support stakes and ties after the first year. When planting dogwoods, be certain to provide good drainage. The most favorable soil is moist, fertile loam, slightly acid to neutral (pH 5.5 to 6). The addition of peat or leaf-mold improves nearly all soils for the dogwood. A 3- to 4" layer of organic mulch, replenished occasionally, is beneficial as it keeps soil moist near the surface where the roots are most active, discourages weeds from growing, and most of all, offers protection to the trunk from mowers and other equipment. The optimum transplanting time is fall and winter. During the first year, protect them from harsh sunlight or wind, with a light aerated mesh-like draping. Do not attempt to grow under artificial light.