How to Grow Hollyhock From Seed
Spring and fall are the best times to start the wonderful hollyhock (Alcea rosea) from seed. The entire process, from sowing to transplanting seedlings, takes about nine weeks.
This growing and maintenance guide will cover the following topics for this biennial:
- Prepping seeds for germination
- Sprouting and growing seedlings
- Transplanting seedlings
- Getting hollyhock to bloom
- Collecting seeds
- Saving hollyhock seeds
How to Prep Hollyhock Seed for Germination
Water treatments are commonly used on seeds with hard shells. The water softens the seed casing, breaking the dormancy of the embryo inside and encouraging germination.
Because hollyhock seeds are large and have fairly tough seed coats, soaking them in warm water or hot water prior to sowing increases the percentage of seed that germinates. It also causes those that do sprout to do so more quickly.
Warm Water Treatment
Prior to sowing, give hollyhock seeds a warm water treatment by soaking them in water that is approximately 113°F (45°C) for roughly 12 hours.
Hot Water Treatment
Rushed for time? Try a hot water treatment. In the late 1960s, botanists at the National Botanic Gardens in Lucknow, India found that soaking hollyhock seeds in hot water anywhere from 60–70°C for 30 minutes greatly improved their germination rate.
When to Soak Hollyhock Seeds
Giving hollyhock seeds a water treatment is a good idea if you're using store-bought seed or seed that you've collected, dried, and stored.
If you sow them by breaking and scattering dried seed pods outdoors at the end of the growing season, there's no need to soak the seed beforehand. The rains, snows, frosts, and thaws of autumn, winter, and spring are all the water treatment the seed needs to prep it for germination.
Sowing Hollyhock Seeds in Spring
Here's how to sow your hollyhock seeds in the springtime.
To start hollyhock seed indoors in the spring, begin in late winter, about nine weeks before the last predicted spring frost in your area. It's best to start the seed in individual pots, as hollyhocks (even seedlings) can develop long taproots that don't transplant well.
If possible, sow hollyhock seed in biodegradable containers, such as peat pots, newsprint pots, or paper towel and toilet tissue rolls (cut into 3-inch lengths). Although some gardeners recommend biodegradable egg cartons or even eggshell halves, they probably aren't deep enough to give hollyhock seedlings a good start.
Sow the seed in seed-starting mix with a little sand mixed in. Cover it lightly with soil, as the seed needs light in order to germinate. Place the pots on a sunny windowsill—under grow lights or in a cold frame—and keep the soil slightly moist throughout the germination process.
Hollyhock seed also may be directly sown outdoors in early spring.
Scatter seeds where you want the hollyhocks to grow, preferably by a doorway, along a fence, or at the back of a flowerbed. (Remember, hollyhocks are tall! And they don't transplant well, so be sure to sow them where you want them to grow.)
When temperatures reach anywhere from 59–68°F, the seed will germinate. The resulting plants, however, probably won't blossom for another year.
Sowing Hollyhock Seeds in Fall
The best time (and the easiest time) to sow hollyhock seed is in autumn.
Simply sprinkle the seed onto soil that's been amended with lots of rich compost and cover it very, very lightly with soil. (As noted above, hollyhock seeds need light in order to germinate.)
In spring, the seed will sprout. And because it will have experienced bouts of winter cold—unlike spring-sown hollyhock—the plants will likely produce flowers in the first growing season.
Unlike perennial hollyhocks (Alcea pallida and A. rugosa), biennial hollyhocks A. ficifolia and A. rosea require two periods of cold weather before they will flower.
The first year, biennial hollyhocks grow vegetatively; that is, they produce only stalks, stems, and leaves—no flowers. They bloom the following year, unless brutal winter weather kills them.
To force biennial hollyhocks to flower the first year, treat them with gibberellic acid, a flower inducer that takes the place of a cold period. Planting them in fall may also induce hollyhocks to bloom the first year.
How to Transplant Hollyhock Seedlings
- It's best to plant hollyhock seedlings outdoors when they're small, before they develop long taproots that don't transplant well.
- As recommended previously, for good transplanting results, sow the seeds in individual pots so that transplanting causes less distress to the roots.
- For the best results, sow seeds in individual biodegradable containers. That way, you can plant hollyhock seedlings in their containers outdoors without disturbing the roots at all.
- Be sure to transplant hollyhock plants into fertile, well-composted soil in a sunny location.
- Because hollyhocks are tall, they are excellent plants for the back of a border or flowerbed. They are also traditionally grown along fences, by gates, and next to doorways.
How to Care for Hollyhock
- After transplanting seedlings into fertile soil in a sunny spot in the garden, keep the young plants moist. After a few weeks, when their roots are established, the hollyhock plants will need little care.
- If blooms develop the first growing season, the stalks may need to be staked to prevent them from falling over under the weight of the plant's full, heavy flowers.
- To keep hollyhock growing from year to year, allow established plants to self-seed, or scatter the seed yourself in autumn at the end of the growing season. (See directions for harvesting and saving hollyhock seed below.)
How to Harvest and Save Hollyhock Seeds
Collecting and saving hollyhock flower seeds is a simple process. In fact, it's so easy that it's an ideal garden activity for children.
Hollyhock seed pods are big and fuzzy, the seeds themselves thick and large—and very easy for little fingers to handle.
To collect and store the seeds, you'll need:
- brown paper bag(s)
- paper towels
- empty seed packets or envelopes
- resealable glass jar(s)
Allow the Flowers to Go to Seed Before Harvesting
Hollyhock flowers "go to seed" when they are left on the plant. As the flowers die, the petals fall. Pods form, dry, and begin to open. At this point, they are ready to harvest. Because they're dry, the pods easily break away from the plant.
First, allow the hollyhock flowers to "go to seed."
When the flowers have devolved into large, brown pods, snap them off and drop them into an ordinary paper sack, such as a brown lunch bag, for safe keeping. While in the sack, they'll dry out further.
After a few days, remove the hollyhock pods, breaking them open onto sheets of paper towels. The seeds inside the pod will be stuck together, so you'll have to break them apart as well.
Almost every year, I pick the most mature green seed pods and bring them inside to dry. If the pods are spread out on a flat surface in a warmish room for a few weeks, the seeds can easily be removed from the pods. I have found that seeds from green pods dried this way have an astounding germination rate, even after several years of storage.
Place the individual seeds flat on the paper towels, removing the chaff with your fingers or with tweezers. Unlike snapdragon seeds, which are black and fine, hollyhock seeds are large and course. So you'll have little trouble differentiating bits of stem, pod, and other chaff from them.
Be sure to remove as much chaff as you can. Not only does chaff retain moisture, which could cause seed to rot, but it may also harbor fungal spores and viruses.
Drying and Storing Hollyhock SeedsClick thumbnail to view full-size
- Seeds contain plant embryos that must be kept alive in order for them to germinate.
- As a general rule, fresher seed is more likely to germinate than older seed, because the embryos in them are more likely to be alive. Conversely, older seeds are less likely to contain living embryos and are therefore less likely to sprout.
- If purchasing hollyhock seed, check the date on the packet in order to select the freshest seed available.
- To keep the embryos of seeds that you collect alive longer, store dry seeds in air-tight glass containers in a cool place, such as the refrigerator or freezer. Before refrigerating or freezing them, either place the seeds in small glass jars or place packets of seed in a large, sealable glass container.
- Make sure the seeds are completely dry before storing them, as they have a tendency to mildew.
- Adding a packet of silica gel to the container—like the desiccating packets found in new leather shoes and purses—will absorb any residual dampness in the seed and prevent it from molding. A teaspoon of powdered milk wrapped in Kleenex or a paper towel will do the same.
How to Propagate Hollyhock by Division
Hollyhocks can be propagated by division as well as by seed.
In winter, spring, or fall (when the hollyhocks are not blooming), loosen the ground around established plants. Then gently pull stalks out of the ground—retaining their long roots—and place them in a bucket of water.
Once you've collected all of the rooty stalks you intend to collect, immediately transplant them into your garden. As when sowing hollyhock seed, be sure to choose a sunny, rich-soil location that's right for a tall, tall plant.
Will you grow hollyhocks (or any other flower) from seed this spring?
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
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© 2013 Jill Spencer