Gardening with Gary

Gardening Advice from an Expert

Hydrangeas

Q. I love Hydrangeas, but I live on the West coast of Florida, near the Tampa area. Can you tell me if the conditions here are all right for them to grow? Also how about Lilacs...? Appreciate any help.

A. Hydrangeas are well-suited for parts of Florida. They like moist tropical zones and many originate from South America. But, if growing in a hot location, they must be shaded, so that they are cool, and moist. The soil must be rich in humus, too, and well-drained. Do not allow to sit in the hot, dry sun, or they will scorch.

Pruning is best done right after flowering, with vegetative cuttings used for propagation. Watch for powdery mildew, aphids, red spider mite and scale.

If you want your hydrangea flowers to be more blue, incorporate enough ammonium sulfate into the soil to reach a pH of 5.0. And if you would like a pink color, add lime to the soil to raise the pH above 7.0.

Unfortunately, I cannot recommend lilacs to you. They need the cold winter temperatures to bloom properly [at least two good frosts], so you would be wasting your time, since if you did get any flowers, they would be sporadic at best.

Q. I am growing a hydrangea that was blue but is now pink! Can I grow plants here in Southern California which come from the North?

A. Yes, you can, but first about the hydrangeas. The flowers start out greenish white and then develop according to the pH of the soil in which they are growing. If you have acidic soil [low pH] then you will see more blue flowers. Pink flowers are found in soils more toward the alkaline, above 7 on the pH scale of 14 [7 is called neutral]. You can buy a soil testing kit and measure your soil, regulate with additives to get the color you wish.

You can grow many plants from various climates, being in So Cal. We up here can, too. What we have to be aware of are two main ideas:

Some of the tropical plants thrive, but if we have a weird cold snap, they can be hit by frost and either damaged or killed. We lost 1000s of palm trees up here about 10 years ago during such a spell. So, protect the tender plants in the winter when the reporters warn of low night temps.

Secondly, we can grow so many plants from the northern regions. But some of them do require a cold winter to continue to perform well. The spring bulbs need cold to initiate flowers for the next season. That is why we must replant the bulbs each fall, or cold treat in a refrigerator over the winter, for 12 weeks. Lilacs do not bloom well without cold weather...I could go on. But, experiment and see how your choices perform in your area!

Q. Are you familiar with a successful way to grow hydrangeas?

A. Hydrangeas prefer partial shade. Morning sun and afternoon shade is perfect in inland areas, while on the coast, no shade is required. Give them moist, well-drained soil. Avoid planting them in hot and dry spots.

Incorporate compost or well-rotted manure thoroughly into the top 8-12" of soil. Organic matter holds nutrients and water in the soil and helps prevent stress from changes in soil moisture. As with any other shrub, plant the root ball level with the soil surface, and water thoroughly immediately after transplanting.

Don't fertilize Hydrangeas at all until they are well-established. This will be 4 to 8 weeks after transplanting. Then, feed with an all-purpose gardening fertilizer. Hydrangeas are water-demanding. Avoiding wilting when rain is lacking. This is particularly important during the spring months when the flower heads are forming, so be sure to monitor the soil moisture around your hydrangeas during dry weather.

You can change the color of their flowers! Lots of aluminum makes them blue, while no aluminum makes pink. Rather than treat or not with aluminum, most gardeners change the pH of their soil to achieve the color they desire [lower=blue, higher=pink].

To make flowers pink, add dolomite lime and water into the soil. Areas with naturally alkaline soils will have pink Hydrangeas. To make flowers blue, add wetable sulfur and water to the soil. Areas with naturally acid soil will have naturally blue hydrangeas. It may take a year to see a noticeable change in flower color from this treatment.

Hydrangeas sometimes fail to bloom. Here are several reasons...

Frost damage to flower buds
Pruning in late summer
Too much shade
Too much high-nitrogen fertilizer
Plant is not old enough yet.

Hydrangeas form their flower buds in late summer for the following year, so pruning in late summer, fall and winter will remove potential flowers. Prune when the flower heads begin to fade. Snip back other shoots to encourage branching and fullness.

For further info, check:

American Hydrangea Society
The AHS is devoted to increasing knowledge of the genus hydrangea for gardeners of all abilities. [publish quarterly newsletter] dir.gardenweb.com/directory/ahs2

Q. A neighbour of mine has asked to get your views about Hydrangeas [you helped me greatly with my fuchsias!] that are not flowering. Any tips would be appreciated

A. My guess is too much fertilizer. Hydrangeas don't need much more than a fresh layer of organic compost applied every spring and maybe two to three shots of fertilizer [higher in the middle number [P], acidic, as MirAcid] during the season. Otherwise all you will get is wonderful foliage.

Hydrangeas come in many varieties, and not all of them are the same! Some bloom on old wood, others bloom on new wood. It's always best to know what kind you have if you can find out somehow. There are also some that do best in light shade, and others that need direct sun, and the amount of sun that they need (or can tolerate) has a lot to do with how hot that sun is - in other words, what zone you're in. One should consider moving it to a sunnier spot.

I wouldn't fertilize anything without knowing the condition of the soil and the preferences of the plant. A big mistake that lots of gardeners make is that they fertilize everything and make no distinctions for soil conditions or plant types. This can result in overfertilization, underfertilization, and over-stress for some plants. It's like giving a sick person some "all purpose medicine" to help them get better - it just doesn't work that way. For hydrangeas, to be on the safe side, prune in the fall, not the spring (just in case they are some of the varieties that bloom on old wood). Cut down the fertilizer for a year, and do some research to figure out what varieties they are, so to know how best to provide care.

Most hydrangea blooms on old wood. By cutting them down to 6 inches in the spring, you're cutting away all the stems that would have produced flowers this year. Hydrangea arborescens Annabelle blooms on new wood. I think the plants need more sun and less fertilizer. Hydrangeas need to mature before putting on blooms. So, it could just be too young to bloom.

Do not prune too much or too late in the fall. You don't want to encourage a lot of new growth just before winter. Move them this fall if in too shady a spot. That and overfertilization sound like the problems without knowing the varieties and age.

Toni writes~
I was wondering if hydrangeas need to be cut down after blooming season. I have four of them about 3 years old now and my bushes have never flowered. What can I do to produce flowers on these beautiful plants? I live in Pennsylvania.

A. Here is the best answer for you, plus a link for much more info on hydrangeas, a marvelous garden flowering bush!

How Should Hydrangeas Be Pruned?

If you don't read any further than this sentence - the best advice for pruning hydrangeas is - "DON'T". However, pruning can be done quite successfully if a few things are kept in mind. Unless a hydrangea is quite old and the blooms have become small, it is not necessary to prune a hydrangea to maintain good health. But if pruning is necessary to revitalize it or to reduce it's size, the following guidelines should be considered (By the way, it is fine to cut the blooms off for arrangements or just to neaten the plant at any time.)

For pruning purposes, hydrangeas can be placed into two categories:

(1) those that bloom on new wood ("new wood" means branches that emerged on the shrub in Spring of the current year).

(2) those that bloom on old wood ("old wood" means branches that have been on the shrub throughout at least one summer and winter before Spring bloom).

HYDRANGEAS THAT BLOOM ON NEW WOOD
If a hydrangea blooms on new wood, it can be pruned almost any time of the year, as close to the ground as one wishes. It will still bloom at its normal time since blooms form on the current new growth.

Two popular hydrangeas that bloom on new wood, and thus can be pruned regularly, are Annabelle (H. arborescens 'Annabelle') and P.G. hydrangeas (H. paniculata grandiflora). Both bloom creamy white and are often referred to as "snowball bushes". Other H. paniculata varieties would also fall into this category.

HYDRANGEAS THAT BLOOM ON OLD WOOD
Most commonly grown hydrangeas bloom on old wood (last year's branches). Hydrangeas that bloom on old wood set their flower buds in late summer or early fall to bloom the following spring. It is very important that this type be pruned before the end of July to assure abundant bloom the following Spring. Do not prune "old-wood" types in the fall, winter or early spring, because most of the flower buds will be removed and few blooms will appear. (Cut blooms for arrangements or what-not, any time.)

The best-known species in this category is Hydrangea macrophylla. This group includes the commonly grown "mophead" or "hortensia" varieties with blooms of pink and blue and occasionally white. There are also many lovely "lacecaps" that are in this category. In addition, the following are old-wood-bloomers: H. quercifolia (Oakleaf hydrangeas), H. aspera, H. serrata (such as 'Grayswood' and 'Preziosa'), H. petiolaris and some other lesser known species.

How can one change the color of Hydrangeas?

Why won't my hydrangeas bloom?

How should hydrangeas be fertilized?

http://www.geocities.com/Paris/Parc/1003/index.html

www.geocities.com/Paris/Parc/1003/faqprunehyd.html
Site of J. A. King, South Carolina

Christina writes~ From No. Mississippi. zone 7. I am wanting to learn how to make cutting from plants to add to our Neighborhood Garden room which joins the back three yards together. Hydrangea's are #1 on my list. Also, this area is some sun, but mostly semi-shade. We have started the room last summer with pea gravel walkways, and now planting plants this year and last fall. Any suggestions?

A. Sounds like a super project! Cuttings are best taken in the spring when growth is young, fresh and vigorous. As soon as you have about 6" of good growth, cut them off and propagate them before they are planted in the beds, after they have produced a healthy root system. Keep well-watered especially on warm breezy days and possibly protect or cover them with light cheesecloth.

Here is a fine website with diagrams to assist you:

Take a cutting from a branch of the hydrangea shrub about 5-6" long. Most experts say the cutting will work best if taken from a branch that did not flower this year.

Remove the lower leaves of the bottom two leaf nodes. Cut largest leaves down to about half their size. Dip cuttings in rooting hormone (this is entirely optional) and insert into damp vermiculite or sterile soil.

Water pot well and allow to drain. Make sure soil is moist but not soggy. Cover cuttings and pot with plastic. Try to keep plastic from touching leaves by adding stakes.

TIPS: Place cuttings in bright light. NEVER PLACE NEW CUTTINGS IN THE SUN. They will cook in the plastic. And even if they are not in plastic, they should be placed in a bright shady area. Do not water again until top of soil begins to feel dry. Overwatering will cause cuttings to rot.

Expect cuttings to begin to form roots in 2-3 weeks depending on temperature (faster in warm weather) and humidity. Some cuttings root in as little as one week. If a tug on the cutting resists the pull, it is rooting.

Also, ground layering is a very easy method. I love it. However, one is limited to rooting only a small number of new plants at a time unless there are many hydrangeas.

Select a branch close to the ground (or several). Remove the leaves for about 5-6 inches at the spot where the branch touches the ground and scrape a little of the bark off the underside of the branch in this area. Make sure at least one leaf node will be under the ground. The leaf node is where a leaf comes out of the branch and most roots will form.

Do not cut the branch off the mother plant. Dig a little trench about 2 inches deep and lower the branch into it and cover generously with soil (potting soil would be nice but is entirely optional).

Put a brick or stone on the buried area so that it will stay under the soil. This also helps to hold the moisture around the branch. Keep it watered occasionally. When roots form, the branch can be removed from the mother plant, potted up and treated like a mature cutting.

Judith King, http://www.hydrangeashydrangeas.com/propagation.html

Betty and Wayne write~
Our neighbor just dug out a mature Hydrangea bush and gave it to us. I planted it and the leaves are drooping. I was wondering if we should prune it back or just leave it.

A. Your plant has undergone shock due to its size and that roots probably have been severed during the move. It is a natural repercussion of such a transplanting. If the plant does not respond slowly to light watering [do not go overboard with kindness and keep wet, as that will rot it], then a slight pruning is recommended. Cut off wilted portions and any brown or crisp foliage. Do not cut way back. Keep out of any direct sun rays, using a light covering as gauze. Gentle morning misting can be beneficial, but not evening as that may lead to mildew. If it does not respond within 2-3 weeks, a more severe pruning may be needed. There is no guarantee that the plant will recover from this shock. It is best to transplant new young plants from 4" pots, knocking them out, placing in a slightly larger well-worked hole, and thus not damaging the roots. It will take longer to get to a blooming size, but Hydrangeas are fast growing and hardy.

Buck & Sharon write~
I have a question about my hydrangea. It had started to get its leaves and we had cold weather that has now damaged them. Will it go ahead and get new leaves and bloom as usual?

A. Lack of Bloom on Hydrangeas

It is the Hydrangeas which bloom on last year's wood most worrisome when we experience wide temperature swings. They are quick to break dormancy so it only takes a couple warm days for their tender buds to begin swelling and do so at a very fast rate. As the weather warms, flower buds on the tips of the stems may start to swell and that tender new growth will probably be zapped by extended freeze. If the flower buds that formed last fall are all destroyed, no amount of fertilizer, water or anything else will coax them into bloom. But all may not be lost. There are additional flower buds on the sides of the stems below the tip [terminal] bud. If the damaged terminal bud is removed, the plant produces hormones that stimulate the side flower buds to mature. The flower buds on the sides of the stems are larger than the leaf buds. To prune, cut the stem 1/4" above a healthy flower bud. Hydrangeas damaged by quick frost may bloom after all with the side buds.