Hydrangeas are gorgeous shrubs with show-stopping flowers. Easy to grow, they will generally thrive if you plant them in early spring or the fall, well before you expect the first frost.
Our new planting guide will help you grow hydrangeas that will be the envy of your neighborhood.
How do you know when it’s the right time to plant hydrangeas in your garden? The very best time to plant is in early fall before the threat of frost. Otherwise, plant in early spring when it’s cool and they will be protected from heat stress. You want them to establish healthy roots before they flower.
If you live in a region where the ground freezes in winter, make sure you plant your hydrangeas at least six weeks before you expect the first frost. The best time of the day to plant is early in the morning or late in the afternoon.
When the plants are in the ground, cover the ground around the plants with about two inches of mulch. This will help to insulate the roots and promote healthy growth.
PLANTING HYDRANGEAS IN DIFFERENT CLIMATES
Because both frost and heat are important issues when growing hydrangeas, the climatic conditions in your part of the world are extra important.
You don’t get the distinctly different temperature changes in the tropics that you get in other parts of the world.
In a tropical climate, it’s always warm because the tropics get more exposure to the sun.
If you live in a tropical climate, the important issue is where you plant rather than when you plant.
Frost will never be a problem, but full sun will.
In areas that have a dry climate, there are big seasonal temperature variations. There are even enormous differences day-to-day during one season.
Generally, winter days are cool in the morning, warm during the day, and cool in the evening. In summer temperatures are usually very hot, even at night, and the air tends to be dry.
Another factor is that water tends to escape and so it is important to have draining soils. This means that watering is vital whenever you plant.
Conditions are mostly mild in temperate-climate regions, but winters are distinctly cold.
Frost will be more of a problem than heat if you are hoping for beautiful flowers on your hydrangea bushes.
Like other climatic areas, the best time to plant is in early spring and early autumn.
A continental climate is typified by very hot summers and very cold winters. It is also quite dry.
Some areas have enormous differences in their average winter and summer temperatures.
Plant in early spring or autumn, and make sure you keep the young plants watered.
Areas that have a polar climate are just plain cold. While some types of hydrangeas do well in colder climates, in polar regions they will need protection.
It’s best to plant them in pots and keep them indoors, at least during the winter months. If you do this it won’t matter when you plant them, but early summer is probably the optimum time either way.
CHOOSING HYDRANGEA SEEDS
The basic choice of hydrangea seeds is between those you buy online or from a garden center or other high street shop, and those that you harvest yourself from your hydrangea flowers, or a friend’s. Either way, the choice is huge.
You can choose seed according to species, color, size, flower-head shape, even suitability for growing in certain climatic regions. You might even opt for mixed seeds that will surprise you!
If you buy seed packets, there will be guidelines on the packet for sowing, spacing, and thinning.
Other plant facts will include plant height to maturity, days until your hydrangea bloom, and their habit of growth, upright or spreading for example.
If you decide to harvest your own seeds you might get a plant with hydrangea flowers that are similar to the mother plant. But, unlike cuttings that are a clone of the mother plant, seeds often propagate something a little different.
Of course, you will also have to collect your seeds if you don’t choose a commercial product.
TYPES OF HYDRANGEAS
Whichever seed types you choose, you will also have a choice of the types of hydrangeas to grow. There are several types including the universally popular bigleaf or French Hydrangea macrophylla and smooth species.
Oakleaf hydrangeas and panicle hydrangeas are also very popular. And most types are available as standard-size shrubs, taller tree-type plants, and/or smaller dwarf varieties.
Oakleaf hydrangeas are perfect for warmer areas while smooth hydrangeas do well in cold climatic conditions. Panicle hydrangeas will grow up to 15 feet tall.
French hydrangeas make good cut flowers.
COLLECTING HYDRANGEA SEEDS
Wait until your hydrangea flowers have begun to fade and dry out. Cut off the flower heads and pop them into brown paper bags to continue drying out.
After three to seven days, shake the bags to release the tiny little seeds. Carefully remove the old flower heads, scrape up as many seeds as possible, and place them in a sealed container or plastic bank bag.
You’ll lose some, but it’s not an issue. Store in a cool place until spring or fall.
HOW TO PLANT HYDRANGEA SEEDS
You can plant hydrangea seeds directly in the ground or in seed trays, plant pots, or flower boxes. Wherever you decide to plant them you will need to thin them out once they germinate and start growing.
If you plant them in pots you will need a well-drained potting mix that you should keep moist while the seeds germinate. If you plant directly into the ground, be sure to amend the soil with compost to improve its quality.
Acidic soils are best if you are growing blue hydrangeas, or want to try and change the color to blue. Also, the soil pH should be low (5.2 to 5.5), while pink flowers grow happily in soil with a pH of about 6.0 to 6.2.
Whatever type or color you plant, you need a humid environment with lots of light. Just don’t try to grow your plants in full sun and avoid windy areas.
The ideal is an area that gets morning sun and afternoon shade.
Scatter the seeds over the surface of the soil and sprinkle them with a little water. It usually takes about two weeks for the seeds to germinate.
When transplanting hydrangeas (or planting cuttings or store-bought shrubs), dig holes that are about two or three times wider than the root ball. The plant should be level with, or a little higher than, the surrounding soil.
HOW TO WATER HYDRANGEAS
Hydrangeas have a shallow root system, so you need to water them regularly. You need to ensure that the plants are always in moist soil, but they mustn’t become waterlogged.
As a guide, water enough for it to penetrate about one inch during the growing season. Also, water deeply three times a week to encourage the roots to grow.
It’s best to water in the mornings especially on hot days, to stop the plants from wilting.
Once the plants are well established, it should be enough to give them a deep, thorough watering once a week. A thick layer of mulch around the base of the shrub will help to keep the soil moist.
HOW TO GROW HYDRANGEAS
Once you have planted your hydrangea seeds or cuttings you need to water and feed them and prune them once they have flowered.
Feeding is quite simple, and you can use a chemical or an organic fertilizer. It’s best to use a slow-release product that is formulated for shrubs and trees.
Since fertilizing will often stimulate new growth, wait until fall to fertilize. Be careful when you fertilize potted plants because there is always a danger it might burn the roots.
Pruning hydrangeas isn’t difficult, and they don’t normally need a major prune. All you need to do is remove dead flowers and woody stems.
Pruning hydrangeas will also help to improve the shape of the shrubs. Deadheading them, or cutting for the vase, will usually keep them blooming into fall.
Pests and diseases aren’t usually a problem when growing hydrangeas. But watch out for leaf spot, mildew, bud blight, and bacterial wilt, and treat immediately if necessary.
Also, keep an eye out for mites and aphids, and if you are growing oakleaf hydrangeas, for Japanese beetles.
In cold climates, you should protect all types of hydrangeas by covering with with straw, pine needles, or bark mulch. Ideally, also cover with a chicken wire or snow fencing cage.
HOW LONG DO HYDRANGEAS TAKE TO GROW?
If you are growing hydrangeas from seed, it usually takes about 14 days for them to germinate. Thereafter, their growth depends on the variety.
Hydrangeas are, though, classified as rapid growers and they will grow about two feet or more every year until the plant reaches maturity. The time this will take depends on the variety and how big it is likely to grow.
DO HYDRANGEAS SPREAD?
The height and spread of hydrangeas vary depending on species and type.
Some little ones only spread about three feet, and grow to about the same height. Others grow as tall as 15 feet and spread as much as 12 feet.
It’s important to take this into account when you decide which types of hydrangeas to grow.
Hydrangeas are unrivaled in the world of shrubs for their beautiful flowers. They are easy to propagate and grow, which makes them one of the most rewarding species for the home garden.
Our planting guide shows you how and when to grow hydrangeas from seeds. It has invaluable guidelines for watering, fertilizing, growing, and pruning hydrangeas.
Whether you want to grow them en-masse as a lush border or combined in beds with other shrubs and flowers, you can be sure that your efforts will bring great pleasure.