The Plant Lady: Here are tips to get the best out of your colorful hydrangeas

Growing up in San Diego I assumed hydrangeas were weeds — the purple-and-blue, nonstop-flowering beauties were everywhere. Fast forward to living in the Central Valley and … it can be more of a struggle in warm, dry locations to achieve this look.

There are a few different types of hydrangeas — Mophead (hydrangea macrophylla), Lacecap (hydrangea macrophylla), Oakleaf (hydrangea quercifolia) and hydrangea paniculata. Hydrangeas are best planted in fall and spring, when temperatures are mild and roots have a chance to develop before frost or heat occurs. Don’t fret if the foliage dies down after planting. Most often the rootball is still alive, so keep the soil moist until new growth occurs. They prefer moist but good-draining soil. If planting in a heavy clay spot, amend the ground with compost or plant on a raised mound. Hydrangeas grow great in pots but keep in mind they can get larger than 6 feet, depending on the cultivar.

Here are answers to some of the more common hydrangea questions I get.

Why are my leaves browning?

Hydrangeas do best in climates with morning sun and protection from the afternoon direct sun. Too much shade will result in poor blooms, whereas too much sun in hot locations will scorch leaves and flowers. They can also be stressed due to poor water quality, such as high boron content. Typically, this will manifest later in the season. Discoloration can also be caused by leaf spot and bacterial disease. Leaf spot usually corrects itself when temperatures warm up, however if it continues into the season, apply sulfur spray.

Why are my Hydrangeas not blooming?

When Hydrangeas are in too much shade they may not bloom. Other potential culprits are excessive nitrogen fertilizer, crowded plants and pruning at the incorrect time (see below).

When can I prune my hydrangeas and how?

The only pruning that needs to be done on hydrangeas is removing the dead canes and thinning them out when they get crowded. Hydrangea macrophylla (lacecap and mophead), as well as Oakleaf cultivars, should not be cut back in spring, but instead directly after they bloom in late summer/fall. Since they flower on old growth, pruning too late in spring can result in lack of blooms. Of course, I have had gardeners tell me they prune their plants back every spring and without fail they flower that year.

The panicle type hydrangeas (paniculata) bloom on new wood, so it is best to prune in spring, if needed. Removing dead flowers (deadheading) can be done anytime the flowers fade. Simply cut off above the growth point below the flower cluster.

Hydrangeas can be divided as well. This is best done in spring. Cut into the rootball with a shovel and dig up a section. You can also dig the entire plant up and use a serrated saw to divide.

How can I make my flowers blue?

Keep in mind not all hydrangeas have the ability to change flower color. Only the hydrangea macrophylla (Lacecap and Mopheads) are able to do so, and even then some cultivars won’t change color (especially white). If you have alkaline soil/water (with a pH above 7), you may be disappointed if you were expecting blue flowers. However, all hope is not lost. One way of dropping the pH is to apply soil sulfur or aluminum sulfate in spring and fall. Patience is required, as it can take several months for color change to occur. If your goal is to achieve more pink blooms, then apply lime to the soil to raise pH.

Why are my flowers not opening up all the way?

Hydrangeas have two types of flowers, sterile and fertile. The sterile flowers (no reproductive structures) are the showy, larger flowers. The fertile flowers are much smaller and found in the center of the plant. On most hybrid Mophead types there is a complete lack of fertile flowers, with only the showier sterile ones existing. On Lacecap type varieties there is an outer ring of showy sterile flowers, with a cluster of smaller fertile ones in the center. If growing for pollinators is a goal, then it is best to choose Lacecap varieties or the Oakleaf hydrangea.

How can I propagate my Hydrangeas?

Hydrangeas can be easily propagated via stem cuttings taken in spring.

▪ Take a stem section of newer growth about 4-to-8-inches long and with at least three growth points (nodes).

▪ Place the cuttings in a pot of wet perlite.

▪ Rooting hormone is not necessary if taking actively growing new growth.

▪ If concerned about rot, then dust with sulfur or even cinnamon.

▪ At least one node needs to be below the soil media and one node needs to be above.

▪ Remove all but one set of leaves on the cutting.

▪ Keep the cuttings misted or cover with a plastic bag to create a greenhouse environment.

▪ Place in a bright but shady area.

▪ When roots form in a few weeks pot each plant up individually in all-purpose potting soil.

▪ Dividing is also an option for larger specimens (as explained in the pruning section).

This story was originally published August 31, 2020 at 10:25 AM.